= LutaML Ruby modeller

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image:https://img.shields.io/gem/v/lutaml-model.svg[RubyGems Version]

== Purpose

Lutaml::Model is a lightweight library for serializing and deserializing Ruby
objects to and from various formats such as JSON, XML, YAML, and TOML. It uses
an adapter pattern to support multiple libraries for each format, providing
flexibility and extensibility for your data modeling needs.

NOTE: Lutaml::Model is designed to be mostly compatible with the data modeling
API of https://www.shalerb.org[Shale], an impressive Ruby data modeller.
Lutaml::Model is meant to address advanced needs not currently addressed by
Shale.

NOTE: Instructions on how to migrate from Shale to Lutaml::Model are provided in
<<migrate-from-shale>>.


== Data modeling in a nutshell

Data modeling is the process of creating a data model for the data to be stored
in a database or used in an application. It helps in defining the structure,
relationships, and constraints of the data, making it easier to manage and use.

Lutaml::Model simplifies data modeling in Ruby by allowing you to define models
with attributes and serialize/deserialize them to/from various serialization
formats seamlessly.


== Features

* Define models with attributes and types
* Serialize and deserialize models to/from JSON, XML, YAML, and TOML
* Support for multiple serialization libraries (e.g., `toml-rb`, `tomlib`)
* Configurable adapters for different serialization formats
* Support for collections and default values
* Custom serialization/deserialization methods
* XML namespaces and mappings

== Installation

Add this line to your application's Gemfile:

[source,ruby]
----
gem 'lutaml-model'
----

And then execute:

[source,shell]
----
bundle install
----

Or install it yourself as:

[source,shell]
----
gem install lutaml-model
----

== Data model class

=== Definition

==== General

There are two ways to define a data model in Lutaml::Model:

* Inheriting from the `Lutaml::Model::Serializable` class
* Including the `Lutaml::Model::Serialize` module

[[define-through-inheritance]]
==== Definition through inheritance

The simplest way to define a model is to create a class that inherits from
`Lutaml::Model::Serializable`.

The `attribute` class method is used to define attributes.

[source,ruby]
----
require 'lutaml/model'

class Kiln < Lutaml::Model::Serializable
  attribute :brand, :string
  attribute :capacity, :integer
  attribute :temperature, :integer
end
----

[[define-through-inclusion]]
==== Definition through inclusion

If the model class already has a super class that it inherits from, the model
can be extended using the `Lutaml::Model::Serialize` module.

[source,ruby]
----
require 'lutaml/model'

class Kiln < SomeSuperClass
  include Lutaml::Model::Serialize

  attribute :brand, :string
  attribute :capacity, :integer
  attribute :temperature, :integer
end
----


=== Comparison

A `Serialize` / `Serializable` object can be compared with another object of the
same class using the `==` operator. This is implemented through the
`ComparableModel` module.

Two objects are considered equal if they have the same class and all their
attributes are equal. This behavior differs from the typical Ruby behavior,
where two objects are considered equal only if they have the same object ID.

NOTE: Two `Serialize` objects will have the same `hash` value if they have the
same class and all their attributes are equal.

[source,ruby]
----
> a = Kiln.new(brand: 'Kiln 1', capacity: 100, temperature: 1050)
> b = Kiln.new(brand: 'Kiln 1', capacity: 100, temperature: 1050)
> a == b
> # true
> a.hash == b.hash
> # true
----



== Defining attributes

=== Supported attribute value types

==== General types

Lutaml::Model supports the following attribute types, they can be
referred by a string, a symbol, or their class constant.

Syntax:

[source,ruby]
----
attribute :name_of_attribute, {symbol | string | class}
----

|===
| String | Symbol | Class name | Actual value class

| `String` | `:string` | `Lutaml::Model::Type::String` | `::String`
| `Integer` | `:integer` | `Lutaml::Model::Type::Integer` | `::Integer`
| `Float` | `:float` | `Lutaml::Model::Type::Float` | `::Float`
| `Date` | `:date` | `Lutaml::Model::Type::Date` | `::Date`
| `Time` | `:time` | `Lutaml::Model::Type::Time` | `::Time`
| `DateTime` | `:date_time` | `Lutaml::Model::Type::DateTime` | `::DateTime`
| `TimeWithoutDate` | `:time_without_date` | `Lutaml::Model::Type::TimeWithoutDate` | `::Time`
| `Boolean` | `:boolean` | `Lutaml::Model::Type::Boolean` | `Boolean`
| `Decimal` (optional) | `:decimal` | `Lutaml::Model::Type::Decimal` | `::BigDecimal`
| `Hash` | `:hash` | `Lutaml::Model::Type::Hash` | `::Hash`

|===

.Defining attributes with supported types via symbol, string and class
[example]
====
[source,ruby]
----
class Studio < Lutaml::Model::Serializable
  # The following are equivalent
  attribute :location, :string
  attribute :potter, "String"
  attribute :kiln, :string
end
----

[source,ruby]
----
> s = Studio.new(location: 'London', potter: 'John Doe', kiln: 'Kiln 1')
> # <Studio:0x0000000104ac7240 @location="London", @potter="John Doe", @kiln="Kiln 1">
> s.location
> # "London"
> s.potter
> # "John Doe"
> s.kiln
> # "Kiln 1"
----
====

==== (optional) Decimal type

The `BigDecimal` class is no longer part of the standard Ruby library from Ruby
3.4 onwards, hence the `Decimal` type is only enabled when the `bigdecimal`
library is loaded.

This means that the following code needs to be run before using (and parsing)
the `Decimal` type:

[source,ruby]
----
require 'bigdecimal'
----

If the `bigdecimal` library is not loaded, usage of the `Decimal` type will
raise a `Lutaml::Model::TypeNotSupportedError`.


=== Attribute as a collection

Define attributes as collections (arrays or hashes) to store multiple values
using the `collection` option.

`collection` can be set to:

`true`:::
The attribute contains an unbounded collection of objects of the declared class.

`{min}..{max}`:::
The attribute contains a collection of objects of the declared class with a
count within the specified range.
If the number of objects is out of this numbered range,
`CollectionCountOutOfRangeError` will be raised.
+
[example]
====
When set to `0..1`, it means that the attribute is optional, it could be empty
or contain one object of the declared class.
====
+
[example]
====
When set to `1..` (equivalent to `1..Infinity`), it means that the
attribute must contain at least one object of the declared class and can contain
any number of objects.
====
+
[example]
====
When set to 5..10` means that there is a minimum of 5 and a maximum of 10
objects of the declared class. If the count of values for the attribute is less
then 5 or greater then 10, the `CollectionCountOutOfRangeError` will be raised.
====


Syntax:

[source,ruby]
----
attribute :name_of_attribute, Type, collection: true
attribute :name_of_attribute, Type, collection: {min}..{max}
attribute :name_of_attribute, Type, collection: {min}..
----

.Using the `collection` option to define a collection attribute
[example]
====
[source,ruby]
----
class Studio < Lutaml::Model::Serializable
  attribute :location, :string
  attribute :potters, :string, collection: true
  attribute :address, :string, collection: 1..2
  attribute :hobbies, :string, collection: 0..
end
----

[source,ruby]
----
> Studio.new
> # address count is `0`, must be between 1 and 2  (Lutaml::Model::CollectionCountOutOfRangeError)
> Studio.new({ address: ["address 1", "address 2", "address 3"] })
> # address count is `3`, must be between 1 and 2  (Lutaml::Model::CollectionCountOutOfRangeError)
> Studio.new({ address: ["address 1"] }).potters
> # []
> Studio.new({ address: ["address 1"] }).address
> # ["address 1"]
> Studio.new(address: ["address 1"], potters: ['John Doe', 'Jane Doe']).potters
> # ['John Doe', 'Jane Doe']
----
====


[[attribute-enumeration]]
=== Attribute as an enumeration

An attribute can be defined as an enumeration by using the `values` directive.

The `values` directive is used to define acceptable values in an attribute. If
any other value is given, a `Lutaml::Model::InvalidValueError` will be raised.

Syntax:

[source,ruby]
----
attribute :name_of_attribute, Type, values: [value1, value2, ...]
----

The values set inside the `values:` option can be of any type, but they must
match the type of the attribute. The values are compared using the `==` operator,
so the type must implement the `==` method.

.Using the `values` directive to define acceptable values for an attribute (basic types)
[example]
====
[source,ruby]
----
class GlazeTechnique < Lutaml::Model::Serializable
  attribute :name, :string, values: ["Celadon", "Raku", "Majolica"]
end
----

[source,ruby]
----
> GlazeTechnique.new(name: "Celadon").name
> # "Celadon"
> GlazeTechnique.new(name: "Raku").name
> # "Raku"
> GlazeTechnique.new(name: "Majolica").name
> # "Majolica"
> GlazeTechnique.new(name: "Earthenware").name
> # Lutaml::Model::InvalidValueError: Invalid value for attribute 'name'
----
====

The values can be Serialize objects, which are compared using the `==`
and the `hash` methods through the Lutaml::Model::ComparableModel module.


.Using the `values` directive to define acceptable values for an attribute (Serializable objects)
[example]
====
[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :firing_temperature, :integer
end

class CeramicCollection < Lutaml::Model::Serializable
  attribute :featured_piece,
            Ceramic,
            values: [
              Ceramic.new(type: "Porcelain", firing_temperature: 1300),
              Ceramic.new(type: "Stoneware", firing_temperature: 1200),
              Ceramic.new(type: "Earthenware", firing_temperature: 1000),
            ]
end
----

[source,ruby]
----
> CeramicCollection.new(featured_piece: Ceramic.new(type: "Porcelain", firing_temperature: 1300)).featured_piece
> # Ceramic:0x0000000104ac7240 @type="Porcelain", @firing_temperature=1300
> CeramicCollection.new(featured_piece: Ceramic.new(type: "Bone China", firing_temperature: 1300)).featured_piece
> # Lutaml::Model::InvalidValueError: Invalid value for attribute 'featured_piece'
----
====

Serialize provides a `validate` method that checks if all its attributes have
valid values. This is necessary for the case when a value is valid at the
component level, but not accepted at the aggregation level.

If a change has been made at the component level (a nested attribute has
changed), the aggregation level needs to call the `validate` method to verify
acceptance of the newly updated component.

.Using the `validate` method to check if all attributes have valid values
[example]
====
[source,ruby]
----
> collection = CeramicCollection.new(featured_piece: Ceramic.new(type: "Porcelain", firing_temperature: 1300))
> collection.featured_piece.firing_temperature = 1400
> # No error raised in changed nested attribute
> collection.validate
> # Lutaml::Model::InvalidValueError: Invalid value for attribute 'featured_piece'
----
====


=== Attribute value default

Specify default values for attributes using the `default` option.
The `default` option can be set to a value or a lambda that returns a value.

Syntax:

[source,ruby]
----
attribute :name_of_attribute, Type, default: -> { value }
----


.Using the `default` option to set a default value for an attribute
[example]
====
[source,ruby]
----
class Glaze < Lutaml::Model::Serializable
  attribute :color, :string, default: -> { 'Clear' }
  attribute :temperature, :integer, default: -> { 1050 }
end
----

[source,ruby]
----
> Glaze.new.color
> # "Clear"
> Glaze.new.temperature
> # 1050
----
====

=== Attribute as raw string

An attribute can be set to read the value as raw string for XML, by using the `raw: true` option.

Syntax:

[source,ruby]
----
attribute :name_of_attribute, :string, raw: true
----

.Using the `raw` option to read raw value for an XML attribute
[example]
====
[source,ruby]
----
class Person < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :description, :string, raw: true
end
----

For the following xml
[source,xml]
----
<Person>
  <name>John Doe</name>
  <description>
    A <b>fictional person</b> commonly used as a <i>placeholder name</i>.
  </description>
</Person>
----

[source,ruby]
----
> Person.from_xml(xml)
> # <Person:0x0000000107a3ca70
    @description="\n    A <b>fictional person</b> commonly used as a <i>placeholder name</i>.\n  ",
    @element_order=["text", "name", "text", "description", "text"],
    @name="John Doe",
    @ordered=nil,
    @validate_on_set=false>
----
====

== Serialization model mappings

=== General

Lutaml::Model allows you to translate a data model into serialization models of
various serialization formats including XML, JSON, YAML, and TOML.

Depending on the serialization format, different methods are supported for
defining serialization and deserialization mappings.

Serialization model mappings are defined under the `xml`, `json`, `yaml`, and
`toml` blocks.

.Using the `xml`, `json`, `yaml`, and `toml` blocks to define serialization mappings
[source,ruby]
----
class Example < Lutaml::Model::Serializable
  xml do
    # ...
  end

  json do
    # ...
  end

  yaml do
    # ...
  end

  toml do
    # ...
  end
end
----

=== XML

==== Setting root element name

The `root` method sets the root element tag name of the XML document.

If `root` is not given, then the snake-cased class name will be used as the
root.

[example]
Sets the tag name for `<example>` in XML `<example>...</example>`.

Syntax:

[source,ruby]
----
xml do
  root 'xml_element_name'
end
----

.Setting the root element name to `example`
[example]
====
[source,ruby]
----
class Example < Lutaml::Model::Serializable
  xml do
    root 'example'
  end
end
----

[source,ruby]
----
> Example.new.to_xml
> #<example></example>
----
====

==== Mapping elements

The `map_element` method maps an XML element to a data model attribute.

[example]
To handle the `<name>` tag in `<example><name>John Doe</name></example>`.
The value will be set to `John Doe`.

Syntax:

[source,ruby]
----
xml do
  map_element 'xml_element_name', to: :name_of_attribute
end
----

.Mapping the `name` tag to the `name` attribute
[example]
====
[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :name, :string

  xml do
    root 'example'
    map_element 'name', to: :name
  end
end
----

[source,xml]
----
<example><name>John Doe</name></example>
----

[source,ruby]
----
> Example.from_xml(xml)
> #<Example:0x0000000104ac7240 @name="John Doe">
> Example.new(name: "John Doe").to_xml
> #<example><name>John Doe</name></example>
----
====

If an element is mapped to a model object with the XML `root` tag name set, the
mapped tag name will be used as the root name, overriding the root name.

.The mapped tag name is used as the root name
[example]
====
[source,ruby]
----
class RecordDate < Lutaml::Model::Serializable
  attribute :content, :string

  xml do
    root "recordDate"
    map_content to: :content
  end
end

class OriginInfo < Lutaml::Model::Serializable
  attribute :date_issued, RecordDate, collection: true

  xml do
    root "originInfo"
    map_element "dateIssued", to: :date_issued
  end
end
----

[source,ruby]
----
> RecordDate.new(date: "2021-01-01").to_xml
> #<recordDate>2021-01-01</recordDate>
> OriginInfo.new(date_issued: [RecordDate.new(date: "2021-01-01")]).to_xml
> #<originInfo><dateIssued>2021-01-01</dateIssued></originInfo>
----
====

==== Mapping attributes

The `map_attribute` method maps an XML attribute to a data model attribute.

Syntax:

[source,ruby]
----
xml do
  map_attribute 'xml_attribute_name', to: :name_of_attribute
end
----

.Using `map_attribute` to map the `value` attribute
[example]
====
The following class will parse the XML snippet below:

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :value, :integer

  xml do
    root 'example'
    map_attribute 'value', to: :value
  end
end
----

[source,xml]
----
<example value="12"><name>John Doe</name></example>
----

[source,ruby]
----
> Example.from_xml(xml)
> #<Example:0x0000000104ac7240 @value=12>
> Example.new(value: 12).to_xml
> #<example value="12"></example>
----

The map_attribute method does not inherit the root element's namespace. If you need to specify a namespace for an attribute,
you must explicitly declare the namespace and prefix in the map_attribute method.
[example]
====
The following class will parse the XML snippet below:

[source,ruby]
----
class Attribute < Lutaml::Model::Serializable
  attribute :value, :integer

  xml do
    root 'example'
    map_attribute 'value', to: :value, namespace: "http://www.tech.co/XMI", prefix: "xl"
  end
end
----

[source,xml]
----
<example xl:value="20" xmlns:xl="http://www.tech.co/XMI"></example>
----

[source,ruby]
----
> Attribute.from_xml(xml)
> #<Attribute:0x0000000109436db8 @value=20>
> Attribute.new(value: 20).to_xml
> #<example xmlns:xl=\"http://www.tech.co/XMI\" xl:value=\"20\"/>
----
====


==== Mapping content

Content represents the text inside an XML element, inclusive of whitespace.

The `map_content` method maps an XML element's content to a data model
attribute.

Syntax:

[source,ruby]
----
xml do
  map_content to: :name_of_attribute
end
----

.Using `map_content` to map content of the `description` tag
[example]
====
The following class will parse the XML snippet below:

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :description, :string

  xml do
    root 'example'
    map_content to: :description
  end
end
----

[source,xml]
----
<example>John Doe is my moniker.</example>
----

[source,ruby]
----
> Example.from_xml(xml)
> #<Example:0x0000000104ac7240 @description="John Doe is my moniker.">
> Example.new(description: "John Doe is my moniker.").to_xml
> #<example>John Doe is my moniker.</example>
----
====



==== Example for mapping

[example]
====
The following class will parse the XML snippet below:

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :description, :string
  attribute :value, :integer

  xml do
    root 'example'
    map_element 'name', to: :name
    map_attribute 'value', to: :value
    map_content to: :description
  end
end
----

[source,xml]
----
<example value="12"><name>John Doe</name> is my moniker.</example>
----

[source,ruby]
----
> Example.from_xml(xml)
> #<Example:0x0000000104ac7240 @name="John Doe", @description=" is my moniker.", @value=12>
> Example.new(name: "John Doe", description: " is my moniker.", value: 12).to_xml
> #<example value="12"><name>John Doe</name> is my moniker.</example>
----
====


==== Namespaces

[[root-namespace]]
===== Namespace at root

The `namespace` method in the `xml` block sets the namespace for the root
element.

Syntax:

.Setting default namespace at the root element
[source,ruby]
----
xml do
  namespace 'http://example.com/namespace'
end
----

.Setting a prefixed namespace at the root element
[source,ruby]
----
xml do
  namespace 'http://example.com/namespace', 'prefix'
end
----


.Using the `namespace` method to set the namespace for the root element
[example]
====
[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, :string

  xml do
    root 'Ceramic'
    namespace 'http://example.com/ceramic'
    map_element 'Type', to: :type
    map_element 'Glaze', to: :glaze
  end
end
----

[source,xml]
----
<Ceramic xmlns='http://example.com/ceramic'><Type>Porcelain</Type><Glaze>Clear</Glaze></Ceramic>
----

[source,ruby]
----
> Ceramic.from_xml(xml_file)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze="Clear">
> Ceramic.new(type: "Porcelain", glaze: "Clear").to_xml
> #<Ceramic xmlns="http://example.com/ceramic"><Type>Porcelain</Type><Glaze>Clear</Glaze></Ceramic>
----
====

.Using the `namespace` method to set a prefixed namespace for the root element
[example]
====
[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, :string

  xml do
    root 'Ceramic'
    namespace 'http://example.com/ceramic', 'cer'
    map_element 'Type', to: :type
    map_element 'Glaze', to: :glaze
  end
end
----

[source,xml]
----
<cer:Ceramic xmlns='http://example.com/ceramic'><cer:Type>Porcelain</cer:Type><cer:Glaze>Clear</cer:Glaze></cer:Ceramic>
----

[source,ruby]
----
> Ceramic.from_xml(xml_file)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze="Clear">
> Ceramic.new(type: "Porcelain", glaze: "Clear").to_xml
> #<cer:Ceramic xmlns="http://example.com/ceramic"><cer:Type>Porcelain</cer:Type><cer:Glaze>Clear</cer:Glaze></cer:Ceramic>
----
====


===== Namespace on attribute

If the namespace is defined on a model attribute that already has a namespace,
the mapped namespace will be given priority over the one defined in the class.

Syntax:

[source,ruby]
----
xml do
  map_element 'xml_element_name', to: :name_of_attribute,
    namespace: 'http://example.com/namespace',
    prefix: 'prefix'
end
----

`namespace`:: The XML namespace used by this element
`prefix`:: The XML namespace prefix used by this element (optional)

.Using the `namespace` option to set the namespace for an element
[example]
====
In this example, `glz` will be used for `Glaze` if it is added inside the
`Ceramic` class, and `glaze` will be used otherwise.

[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, Glaze

  xml do
    root 'Ceramic'
    namespace 'http://example.com/ceramic'

    map_element 'Type', to: :type
    map_element 'Glaze', to: :glaze, namespace: 'http://example.com/glaze', prefix: "glz"
  end
end

class Glaze < Lutaml::Model::Serializable
  attribute :color, :string
  attribute :temperature, :integer

  xml do
    root 'Glaze'
    namespace 'http://example.com/old_glaze', 'glaze'

    map_element 'color', to: :color
    map_element 'temperature', to: :temperature
  end
end
----

[source,xml]
----
<Ceramic xmlns='http://example.com/ceramic'>
  <Type>Porcelain</Type>
  <glz:Glaze xmlns='http://example.com/glaze'>
    <color>Clear</color>
    <temperature>1050</temperature>
  </glz:Glaze>
</Ceramic>
----

[source,ruby]
----
> # Using the original Glaze class namespace
> Glaze.new(color: "Clear", temperature: 1050).to_xml
> #<glaze:Glaze xmlns="http://example.com/old_glaze"><color>Clear</color><temperature>1050</temperature></glaze:Glaze>

> # Using the Ceramic class namespace for Glaze
> Ceramic.from_xml(xml_file)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze=#<Glaze:0x0000000104ac7240 @color="Clear", @temperature=1050>>
> Ceramic.new(type: "Porcelain", glaze: Glaze.new(color: "Clear", temperature: 1050)).to_xml
> #<Ceramic xmlns="http://example.com/ceramic"><Type>Porcelain</Type><glz:Glaze xmlns="http://example.com/glaze"><color>Clear</color><temperature>1050</temperature></glz:Glaze></Ceramic>
----
====

[[namespace-inherit]]
===== Namespace with `inherit` option

The `inherit` option is used at the element level to inherit the namespace from
the root element.

Syntax:

[source,ruby]
----
xml do
  map_element 'xml_element_name', to: :name_of_attribute, namespace: :inherit
end
----

.Using the `inherit` option to inherit the namespace from the root element
[example]
====
In this example, the `Type` element will inherit the namespace from the root.

[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, :string
  attribute :color, :string

  xml do
    root 'Ceramic'
    namespace 'http://example.com/ceramic', 'cera'
    map_element 'Type', to: :type, namespace: :inherit
    map_element 'Glaze', to: :glaze
    map_attribute 'color', to: :color, namespace: 'http://example.com/color', prefix: 'clr'
  end
end
----

[source,xml]
----
<cera:Ceramic
  xmlns:cera='http://example.com/ceramic'
  xmlns:clr='http://example.com/color'
  clr:color="navy-blue">
  <cera:Type>Porcelain</cera:Type>
  <Glaze>Clear</Glaze>
</cera:Ceramic>
----

[source,ruby]
----
> Ceramic.from_xml(xml_file)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze="Clear", @color="navy-blue">
> Ceramic.new(type: "Porcelain", glaze: "Clear", color: "navy-blue").to_xml
> #<cera:Ceramic xmlns:cera="http://example.com/ceramic"
  # xmlns:clr='http://example.com/color'
  # clr:color="navy-blue">
  #  <cera:Type>Porcelain</cera:Type>
  #  <Glaze>Clear</Glaze>
  # </cera:Ceramic>
----
====

[[mixed-content]]
==== Mixed content

In XML there can be tags that contain content mixed with other tags and where
whitespace is significant, such as to represent rich text.

[example]
====
[source,xml]
----
<description><p>My name is <bold>John Doe</bold>, and I'm <i>28</i> years old</p></description>
----
====

To map this to Lutaml::Model we can use the `mixed` option in either way:

* when defining the model;
* when referencing the model.

NOTE: This feature is not supported by Shale.


To specify mixed content, the `mixed: true` option needs to be set at the
`xml` block's `root` method.

Syntax:

[source,ruby]
----
xml do
  root 'xml_element_name', mixed: true
end
----

.Applying `mixed` to treat root as mixed content
[example]
====
[source,ruby]
----
class Paragraph < Lutaml::Model::Serializable
  attribute :bold, :string, collection: true # allows multiple bold tags
  attribute :italic, :string

  xml do
    root 'p', mixed: true

    map_element 'bold', to: :bold
    map_element 'i', to: :italic
  end
end
----

[source,ruby]
----
> Paragraph.from_xml("<p>My name is <bold>John Doe</bold>, and I'm <i>28</i> years old</p>")
> #<Paragraph:0x0000000104ac7240 @bold="John Doe", @italic="28">
> Paragraph.new(bold: "John Doe", italic: "28").to_xml
> #<p>My name is <bold>John Doe</bold>, and I'm <i>28</i> years old</p>
----
====

TODO: How to create mixed content from `#new`?

[[xml-schema-location]]
==== Automatic support of `xsi:schemaLocation`

The
https://www.w3.org/TR/xmlschema-1/#xsi_schemaLocation[W3C "XMLSchema-instance"]
namespace describes a number of attributes that can be used to control the
behavior of XML processors. One of these attributes is `xsi:schemaLocation`.

The `xsi:schemaLocation` attribute locates schemas for elements and attributes
that are in a specified namespace. Its value consists of pairs of a namespace
URI followed by a relative or absolute URL where the schema for that namespace
can be found.

Usage of `xsi:schemaLocation` in an XML element depends on the declaration of
the XML namespace of `xsi`, i.e.
`xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"`. Without this namespace
LutaML will not be able to serialize the `xsi:schemaLocation` attribute.

NOTE: It is most commonly attached to the root element but can appear further
down the tree.

The following snippet shows how `xsi:schemaLocation` is used in an XML document:

[source,xml]
----
<cera:Ceramic
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:cera="http://example.com/ceramic"
  xmlns:clr='http://example.com/color'
  xsi:schemaLocation=
    "http://example.com/ceramic http://example.com/ceramic.xsd
     http://example.com/color http://example.com/color.xsd"
  clr:color="navy-blue">
  <cera:Type>Porcelain</cera:Type>
  <Glaze>Clear</Glaze>
</cera:Ceramic>
----

LutaML::Model supports the `xsi:schemaLocation` attribute in all XML
serializations by default, through the `schema_location` attribute on the model
instance object.

.Retrieving and setting the `xsi:schemaLocation` attribute in XML serialization
[example]
====
In this example, the `xsi:schemaLocation` attribute will be automatically
supplied without the explicit need to define in the model, and allows for
round-trip serialization.

[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, :string
  attribute :color, :string

  xml do
    root 'Ceramic'
    namespace 'http://example.com/ceramic', 'cera'
    map_element 'Type', to: :type, namespace: :inherit
    map_element 'Glaze', to: :glaze
    map_attribute 'color', to: :color, namespace: 'http://example.com/color', prefix: 'clr'
  end
end

xml_content = <<~HERE
<cera:Ceramic
  xmlns:cera="http://example.com/ceramic"
  xmlns:clr="http://example.com/color"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  clr:color="navy-blue"
  xsi:schemaLocation="
    http://example.com/ceramic http://example.com/ceramic.xsd
    http://example.com/color http://example.com/color.xsd
  ">
  <cera:Type>Porcelain</cera:Type>
  <Glaze>Clear</Glaze>
</cera:Ceramic>
HERE
----

[source,ruby]
----
> c = Ceramic.from_xml(xml_content)
=>
#<Ceramic:0x00000001222bdd60
...
> schema_loc = c.schema_location
#<Lutaml::Model::SchemaLocation:0x0000000122773760
...
> schema_loc
=>
#<Lutaml::Model::SchemaLocation:0x0000000122773760
 @namespace="http://www.w3.org/2001/XMLSchema-instance",
 @original_schema_location="http://example.com/ceramic http://example.com/ceramic.xsd http://example.com/color http://example.com/color.xsd",
 @prefix="xsi",
 @schema_location=
  [#<Lutaml::Model::Location:0x00000001222bd018 @location="http://example.com/ceramic.xsd", @namespace="http://example.com/ceramic">,
   #<Lutaml::Model::Location:0x00000001222bcfc8 @location="http://example.com/color.xsd", @namespace="http://example.com/color">]>
> new_c = Ceramic.new(type: "Porcelain", glaze: "Clear", color: "navy-blue", schema_location: schema_loc).to_xml
> puts new_c
# <cera:Ceramic
#   xmlns:cera="http://example.com/ceramic"
#   xmlns:clr="http://example.com/color"
#   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
#   clr:color="navy-blue"
#   xsi:schemaLocation="
#     http://example.com/ceramic http://example.com/ceramic.xsd
#     http://example.com/color http://example.com/color.xsd
#   ">
#   <cera:Type>Porcelain</cera:Type>
#   <cera:Glaze>Clear</cera:Glaze>
# </cera:Ceramic>
----
====

NOTE: For details on `xsi:schemaLocation`, please refer to the
https://www.w3.org/TR/xmlschema-1/#xsi_schemaLocation[W3C XML standard].



=== Key value data models

==== General

Key-value data models like JSON, YAML, and TOML all share a similar structure
where data is stored as key-value pairs.

Lutaml::Model works with these formats in a similar way.

==== Mapping

The `map` method is used to define key-value mappings.

Syntax:

[source,ruby]
----
json | yaml | toml do
  map 'key_value_model_attribute_name', to: :name_of_attribute
end
----

.Using the `map` method to define key-value mappings
[example]
====
[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :value, :integer

  json do
    map 'name', to: :name
    map 'value', to: :value
  end

  yaml do
    map 'name', to: :name
    map 'value', to: :value
  end

  toml do
    map 'name', to: :name
    map 'value', to: :value
  end
end
----

[source,json]
----
{
  "name": "John Doe",
  "value": 28
}
----

[source,ruby]
----
> Example.from_json(json)
> #<Example:0x0000000104ac7240 @name="John Doe", @value=28>
> Example.new(name: "John Doe", value: 28).to_json
> #{"name"=>"John Doe", "value"=>28}
----
====


==== Nested attribute mappings

The `map` method can also be used to map nested key-value data models
by referring to a Lutaml::Model class as an attribute class.

[example]
====
[source,ruby]
----
class Glaze < Lutaml::Model::Serializable
  attribute :color, :string
  attribute :temperature, :integer

  json do
    map 'color', to: :color
    map 'temperature', to: :temperature
  end
end

class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, Glaze

  json do
    map 'type', to: :type
    map 'glaze', to: :glaze
  end
end
----

[source,json]
----
{
  "type": "Porcelain",
  "glaze": {
    "color": "Clear",
    "temperature": 1050
  }
}
----

[source,ruby]
----
> Ceramic.from_json(json)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze=#<Glaze:0x0000000104ac7240 @color="Clear", @temperature=1050>>
> Ceramic.new(type: "Porcelain", glaze: Glaze.new(color: "Clear", temperature: 1050)).to_json
> #{"type"=>"Porcelain", "glaze"=>{"color"=>"Clear", "temperature"=>1050}}
----
====

[[separate-serialization-model]]
=== Separate serialization model

The `Serialize` module can be used to define only serialization mappings for a
separately defined model (a Ruby class).

Syntax:

[source,ruby]
----
class Foo < Lutaml::Model::Serializable
  model {DataModelClass}

  # ...
end
----

[example]
.Using the `model` method to define serialization mappings for a separate model
====
[source,ruby]
----
class Ceramic
  attr_accessor :type, :glaze

  def name
    "#{type} with #{glaze}"
  end
end

class CeramicSerialization < Lutaml::Model::Serializable
  model Ceramic

  xml do
    map_element 'type', to: :type
    map_element 'glaze', to: :glaze
  end
end
----

[source,ruby]
----
> Ceramic.new(type: "Porcelain", glaze: "Clear").name
> # "Porcelain with Clear"
> CeramicSerialization.from_xml(xml)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze="Clear">
> Ceramic.new(type: "Porcelain", glaze: "Clear").to_xml
> #<Ceramic><type>Porcelain</type><glaze>Clear</glaze></Ceramic>
----
====


=== Rendering empty attributes and collections

By default, empty attributes and collections are not rendered in the output.

To render empty attributes and collections, use the `render_nil` option.

Syntax:

[source,ruby]
----
xml do
  map_element 'key_value_model_attribute_name', to: :name_of_attribute, render_nil: true
end
----

[source,ruby]
----
json | yaml | toml do
  map 'key_value_model_attribute_name', to: :name_of_attribute, render_nil: true
end
----

.Using the `render_nil` option to render empty attributes
[example]
====
[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, :string

  xml do
    map_element 'type', to: :type, render_nil: true
    map_element 'glaze', to: :glaze
  end

  json do
    map 'type', to: :type, render_nil: true
    map 'glaze', to: :glaze
  end
end
----

[source,ruby]
----
> Ceramic.new.to_json
> # { 'type': null }
> Ceramic.new(type: "Porcelain", glaze: "Clear").to_json
> # { 'type': 'Porcelain', 'glaze': 'Clear' }
----

[source,ruby]
----
> Ceramic.new.to_xml
> # <Ceramic><type></type></Ceramic>
> Ceramic.new(type: "Porcelain", glaze: "Clear").to_xml
> # <Ceramic><type>Porcelain</type><glaze>Clear</glaze></Ceramic>
----
====

.Using the `render_nil` option to render empty attribute collections
[example]
====
[source,ruby]
----
class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glazes, :string, collection: true

  xml do
    map_element 'type', to: :type, render_nil: true
    map_element 'glazes', to: :glazes, render_nil: true
  end

  json do
    map 'type', to: :type, render_nil: true
    map 'glazes', to: :glazes, render_nil: true
  end
end
----

[source,ruby]
----
> Ceramic.new.to_json
> # { 'type': null, 'glazes': [] }
> Ceramic.new(type: "Porcelain", glazes: ["Clear"]).to_json
> # { 'type': 'Porcelain', 'glazes': ['Clear'] }
----

[source,ruby]
----
> Ceramic.new.to_xml
> # <Ceramic><type></type><glazes></glazes></Ceramic>
> Ceramic.new(type: "Porcelain", glazes: ["Clear"]).to_xml
> # <Ceramic><type>Porcelain</type><glazes>Clear</glazes></Ceramic>
----
====



=== Advanced attribute mapping

==== Attribute mapping delegation

Delegate attribute mappings to nested objects using the `delegate` option.

Syntax:

[source,ruby]
----
xml | json | yaml | toml do
  map 'key_value_model_attribute_name', to: :name_of_attribute, delegate: :model_to_delegate_to
end
----

.Using the `delegate` option to map attributes to nested objects
[example]
====
The following class will parse the JSON snippet below:

[source,ruby]
----
class Glaze < Lutaml::Model::Serializable
  attribute :color, :string
  attribute :temperature, :integer

  json do
    map 'color', to: :color
    map 'temperature', to: :temperature
  end
end

class Ceramic < Lutaml::Model::Serializable
  attribute :type, :string
  attribute :glaze, Glaze

  json do
    map 'type', to: :type
    map 'color', to: :color, delegate: :glaze
  end
end
----

[source,json]
----
{
  "type": "Porcelain",
  "color": "Clear"
}
----

[source,ruby]
----
> Ceramic.from_json(json)
> #<Ceramic:0x0000000104ac7240 @type="Porcelain", @glaze=#<Glaze:0x0000000104ac7240 @color="Clear", @temperature=nil>>
> Ceramic.new(type: "Porcelain", glaze: Glaze.new(color: "Clear")).to_json
> #{"type"=>"Porcelain", "color"=>"Clear"}
----
====

NOTE: The corresponding keyword used by Shale is `receiver:` instead of
`delegate:`.


==== Attribute serialization with custom methods

===== General

Define custom methods for specific attribute mappings using the `with:` key for
each serialization mapping block for `from` and `to`.


===== XML serialization with custom methods

Syntax:

.XML serialization with custom methods
[source,ruby]
----
xml do
  map_element 'element_name', to: :name_of_element, with: {
    to: :method_name_to_serialize,
    from: :method_name_to_deserialize
  }
  map_attribute 'attribute_name', to: :name_of_attribute, with: {
    to: :method_name_to_serialize,
    from: :method_name_to_deserialize
  }
  map_content, to: :name_of_content, with: {
    to: :method_name_to_serialize,
    from: :method_name_to_deserialize
  }
end
----

.Using the `with:` key to define custom serialization methods for XML
[example]
====
The following class will parse the XML snippet below:

[source,ruby]
----
class CustomCeramic < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :size, :integer
  attribute :description, :string

  xml do
    map_element "Name", to: :name, with: { to: :name_to_xml, from: :name_from_xml }
    map_attribute "Size", to: :size, with: { to: :size_to_xml, from: :size_from_xml }
    map_content with: { to: :description_to_xml, from: :description_from_xml }
  end

  def name_to_xml(model, parent, doc)
    el = doc.create_element("Name")
    doc.add_text(el, "XML Masterpiece: #{model.name}")
    doc.add_element(parent, el)
  end

  def name_from_xml(model, value)
    model.name = value.sub(/^XML Masterpiece: /, "")
  end

  def size_to_xml(model, parent, doc)
    doc.add_attribute(parent, "Size", model.size + 3)
  end

  def size_from_xml(model, value)
    model.size = value.to_i - 3
  end

  def description_to_xml(model, parent, doc)
    doc.add_text(parent, "XML Description: #{model.description}")
  end

  def description_from_xml(model, value)
    model.description = value.join.strip.sub(/^XML Description: /, "")
  end
end
----

[source,xml]
----
<CustomCeramic Size="15">
  <Name>XML Masterpiece: Vase</Name>
  XML Description: A beautiful ceramic vase
</CustomCeramic>
----

[source,ruby]
----
> CustomCeramic.from_xml(xml)
> #<CustomCeramic:0x0000000108d0e1f8
   @element_order=["text", "Name", "text", "Size", "text"],
   @name="Masterpiece: Vase",
   @ordered=nil,
   @size=12,
   @description="A beautiful ceramic vase",
   @validate_on_set=false>
> puts CustomCeramic.new(name: "Vase", size: 12, description: "A beautiful vase").to_xml
# <CustomCeramic Size="15">
#   <Name>XML Masterpiece: Vase</Name>
#   XML Description: A beautiful vase
# </CustomCeramic>
----
====


===== Key-value data model serialization with custom methods

.Key-value data model serialization with custom methods
[source,ruby]
----
json | yaml | toml do
  map 'attribute_name', to: :name_of_attribute, with: {
    to: :method_name_to_serialize,
    from: :method_name_to_deserialize
  }
end
----

.Using the `with:` key to define custom serialization methods
[example]
====
The following class will parse the JSON snippet below:

[source,ruby]
----
class CustomCeramic < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :size, :integer

  json do
    map 'name', to: :name, with: { to: :name_to_json, from: :name_from_json }
    map 'size', to: :size
  end

  def name_to_json(model, doc)
    doc["name"] = "Masterpiece: #{model.name}"
  end

  def name_from_json(model, value)
    model.name = value.sub(/^Masterpiece: /, '')
  end
end
----

[source,json]
----
{
  "name": "Masterpiece: Vase",
  "size": 12
}
----

[source,ruby]
----
> CustomCeramic.from_json(json)
> #<CustomCeramic:0x0000000104ac7240 @name="Vase", @size=12>
> CustomCeramic.new(name: "Vase", size: 12).to_json
> #{"name"=>"Masterpiece: Vase", "size"=>12}
----
====


[[attribute-extraction]]
==== Attribute extraction (for key-value data models only)

NOTE: This feature is for key-value data model serialization only.

The `child_mappings` option is used to extract results from a key-value data
model (JSON, YAML, TOML) into a `Lutaml::Model` collection.

The values are extracted from the key-value data model using the list of keys
provided.

Syntax:

[source,ruby]
----
json | yaml | toml do
  map 'key_value_model_attribute_name', to: :name_of_attribute,
    child_mappings: {
      key_attribute_name_1: <1>
        {path_to_value_1}, <2>
      key_attribute_name_2:
        {path_to_value_2},
      # ...
    }
end
----
<1> The `key_attribute_name_1` is the attribute name in the model. The value of
this attribute will be assigned the key of the hash in the key-value data model.

<2> The `path_to_value_1` is an array of keys that represent the path to the
value in the key-value data model. The keys are used to extract the value from
the key-value data model and assign it to the attribute in the model.

The `path_to_value` is in a nested array format with each value a symbol, where
each symbol represents a key to traverse down. The last key in the path is the
value to be extracted.

.Determining the path to value in a key-value data model
[example]
====
The following JSON contains 2 keys in schema named `engine` and `gearbox`.

[source,json]
----
{
  "components": {
    "engine": {
      "manufacturer": "Ford",
      "model": "V8"
    },
    "gearbox": {
      "manufacturer": "Toyota",
      "model": "4-speed"
    }
  }
}
----

The path to value for the `engine` schema is `[:components, :engine]` and for
the `gearbox` schema is `[:components, :gearbox]`.
====

In `path_to_value`, the `:key` and `:value` are reserved instructions used to
assign the key or value of the serialization data respectively as the value to
the attribute.

[example]
====
In the following JSON content, the `path_to_value` for the object keys named
`engine` and `gearbox` will utilize the `:key` keyword to assign the key of the
object as the value of a designated attribute.

[source,json]
----
{
  "components": {
    "engine": { /*...*/ },
    "gearbox": { /*...*/ }
  }
}
----
====

If a specified value path is not found, the corresponding attribute in the model
will be assigned a `nil` value.

.Attribute values set to `nil` when the `path_to_value` is not found
[example]
====
In the following JSON content, the `path_to_value` of `[:extras, :sunroof]` and
`[:extras, :drinks_cooler]` at the object `"gearbox"` would be set to `nil`.

[source,json]
----
{
  "components": {
    "engine": {
      "manufacturer": "Ford",
      "extras": {
        "sunroof": true,
        "drinks_cooler": true
      }
    },
    "gearbox": {
      "manufacturer": "Toyota"
    }
  }
}
----
====


.Using the `child_mappings` option to extract values from a key-value data model
[example]
====
The following JSON contains 2 keys in schema named `foo` and `bar`.

[source,json]
----
{
  "schemas": {
    "foo": { <1>
      "path": { <2>
        "link": "link one",
        "name": "one"
      }
    },
    "bar": { <1>
      "path": { <2>
        "link": "link two",
        "name": "two"
      }
    }
  }
}
----
<1> The keys `foo` and `bar` are to be mapped to the `id` attribute.
<2> The nested `path.link` and `path.name` keys are used as the `link` and
`name` attributes, respectively.

A model can be defined for this JSON as follows:

[source,ruby]
----
class Schema < Lutaml::Model::Serializable
  attribute :id, :string
  attribute :link, :string
  attribute :name, :string
end

class ChildMappingClass < Lutaml::Model::Serializable
  attribute :schemas, Schema, collection: true

  json do
    map "schemas", to: :schemas,
                   child_mappings: {
                     id: :key,
                     link: %i[path link],
                     name: %i[path name],
                   }
  end
end
----

The output becomes:

[source,ruby]
----
> ChildMappingClass.from_json(json)
> #<ChildMappingClass:0x0000000104ac7240
 @schemas=
  [#<Schema:0x0000000104ac6e30 @id="foo", @link="link one", @name="one">,
   #<Schema:0x0000000104ac58f0 @id="bar", @link="link two", @name="two">]>
> ChildMappingClass.new(schemas: [Schema.new(id: "foo", link: "link one", name: "one"), Schema.new(id: "bar", link: "link two", name: "two")]).to_json
> #{"schemas"=>{"foo"=>{"path"=>{"link"=>"link one", "name"=>"one"}}, {"bar"=>{"path"=>{"link"=>"link two", "name"=>"two"}}}}
----

In this example:

* The `key` of each schema (`foo` and `bar`) is mapped to the `id` attribute.

* The nested `path.link` and `path.name` keys are mapped to the `link` and
`name` attributes, respectively.
====


== Validation

=== General

Lutaml::Model provides a way to validate data models using the `validate` and
`validate!` methods.

* The `validate` method sets an `errors` array in the model instance that
contains all the validation errors. This method is used for checking the
validity of the model silently.

* The `validate!` method raises a `Lutaml::Model::ValidationError` that contains
all the validation errors. This method is used for forceful validation of the
model through raising an error.

Lutaml::Model supports the following validation methods:

* `collection`:: Validates collection size range.
* `values`:: Validates the value of an attribute from a set of fixed values.

[example]
====
The following class will validate the `degree_settings` attribute to ensure that
it has at least one element and that the `description` attribute is one of the
values in the set `[one, two, three]`.

[source,ruby]
----
class Klin < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :degree_settings, :integer, collection: (1..)
  attribute :description, :string, values: %w[one two three]

  xml do
    map_element 'name', to: :name
    map_attribute 'degree_settings', to: :degree_settings
  end
end

klin = Klin.new(name: "Klin", degree_settings: [100, 200, 300], description: "one")
klin.validate
# => []

klin = Klin.new(name: "Klin", degree_settings: [], description: "four")
klin.validate
# => [
#      #<Lutaml::Model::CollectionSizeError: degree_settings must have at least 1 element>,
#      #<Lutaml::Model::ValueError: description must be one of [one, two, three]>
#    ]

e = klin.validate!
# => Lutaml::Model::ValidationError: [
#      degree_settings must have at least 1 element,
#      description must be one of [one, two, three]
#    ]
e.errors
# => [
#     #<Lutaml::Model::CollectionSizeError: degree_settings must have at least 1 element>,
#     #<Lutaml::Model::ValueError: description must be one of [one, two, three]>
#   ]
----
====

=== Custom validation

To add custom validation, override the `validate` method in the model class.
Additional errors should be added to the `errors` array.

[example]
====
The following class validates the `degree_settings` attribute when the `type` is
`glass` to ensure that the value is less than 1300.

[source,ruby]
----
class Klin < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :type, :string, values: %w[glass ceramic]
  attribute :degree_settings, :integer, collection: (1..)

  def validate
    errors = super
    if type == "glass" && degree_settings.any? { |d| d > 1300 }
      errors << Lutaml::Model::Error.new("Degree settings for glass must be less than 1300")
    end
  end
end

klin = Klin.new(name: "Klin", type: "glass", degree_settings: [100, 200, 1400])
klin.validate
# => [#<Lutaml::Model::Error: Degree settings for glass must be less than 1300>]
----
====


== Adapters

=== General

Lutaml::Model uses an adapter pattern to support multiple libraries for each
serialization format.

You will need to specify the configuration for the adapter you want to use. The
easiest way is to copy and paste the following configuration into your code.

The configuration is as follows:

[source,ruby]
----
require 'lutaml/model'
require 'lutaml/model/xml_adapter/nokogiri_adapter'
require 'lutaml/model/json_adapter/standard_json_adapter'
require 'lutaml/model/toml_adapter/toml_rb_adapter'
require 'lutaml/model/yaml_adapter/standard_yaml_adapter'

Lutaml::Model::Config.configure do |config|
  config.xml_adapter = Lutaml::Model::XmlAdapter::NokogiriAdapter
  config.yaml_adapter = Lutaml::Model::YamlAdapter::StandardYamlAdapter
  config.json_adapter = Lutaml::Model::JsonAdapter::StandardJsonAdapter
  config.toml_adapter = Lutaml::Model::TomlAdapter::TomlRbAdapter
end
----

You can also provide the adapter type by using symbols like

[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  config.xml_adapter_type = :nokogiri # can be one of [:nokogiri, :ox, :oga]
  config.yaml_adapter_type = :standard_yaml
  config.json_adapter_type = :standard_json # can be one of [:standard_json, :multi_json]
  config.toml_adapter_type = :toml_rb # can be one of [:toml_rb, :tomlib]
end
----

NOTE: By default `yaml_adapter_type` and `json_adapter_type` are set to `:standard_yaml` and `:standard_json` respectively.

=== XML

Lutaml::Model supports the following XML adapters:

* Nokogiri (default)
* Oga (optional, plain Ruby suitable for Opal/JS)
* Ox (optional)

.Using the Nokogiri XML adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/xml_adapter/nokogiri_adapter'
  config.xml_adapter = Lutaml::Model::XmlAdapter::NokogiriAdapter
end
----

.Using the Oga XML adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/xml_adapter/oga_adapter'
  config.xml_adapter = Lutaml::Model::XmlAdapter::OgaAdapter
end
----

.Using the Ox XML adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/xml_adapter/ox_adapter'
  config.xml_adapter = Lutaml::Model::XmlAdapter::OxAdapter
end
----


=== YAML

Lutaml::Model supports only one YAML adapter.

* YAML (default)

.Using the YAML adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/yaml_adapter/standard_yaml_adapter'
  config.yaml_adapter = Lutaml::Model::YamlAdapter::StandardYamlAdapter
end
----



=== JSON

Lutaml::Model supports the following JSON adapters:

* JSON (default)
* MultiJson (optional)

.Using the JSON adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/json_adapter/standard_json_adapter'
  config.json_adapter = Lutaml::Model::JsonAdapter::StandardJsonAdapter
end
----

.Using the MultiJson adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/json_adapter/multi_json_adapter'
  config.json_adapter = Lutaml::Model::JsonAdapter::MultiJsonAdapter
end
----

=== TOML

Lutaml::Model supports the following TOML adapters:

* Toml-rb (default)
* Tomlib (optional)

.Using the Toml-rb adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  require 'lutaml/model/toml_adapter/toml_rb_adapter'
  config.toml_adapter = Lutaml::Model::TomlAdapter::TomlRbAdapter
end
----

.Using the Tomlib adapter
[source,ruby]
----
require 'lutaml/model'

Lutaml::Model::Config.configure do |config|
  config.toml_adapter = Lutaml::Model::TomlAdapter::TomlibAdapter
  require 'lutaml/model/toml_adapter/tomlib_adapter'
end
----


== Comparison with Shale

Lutaml::Model is a serialization library that is similar to Shale, but with some
differences in implementation.

[cols="a,a,a,a",options="header"]
|===
| Feature | Lutaml::Model | Shale | Notes

| Data model definition
|
3 types:

* <<define-through-inheritance,Inherit from `Lutaml::Model::Serializable`>>
* <<define-through-inclusion,Include `Lutaml::Model::Serialize`>>
* <<separate-serialization-model,Separate serialization model class>>
|
2 types:

* Inherit from `Shale::Mapper`
* Custom model class
|

| Value types
| `Lutaml::Model::Type` includes: `Integer`, `String`, `Float`, `Boolean`, `Date`, `DateTime`, `Time`, `Decimal`, `Hash`.
| `Shale::Type` includes: `Integer`, `String`, `Float`, `Boolean`, `Date`, `Time`.
| Lutaml::Model supports additional value types `Decimal`, `DateTime` and `Hash`.

| Configuration
| `Lutaml::Model::Config`
| `Shale.{type}_adapter`
| Lutaml::Model uses a configuration block to set the serialization adapters.

| Custom serialization methods
| `:with`, on individual attributes
| `:using`, on entire object/document
| Lutaml::Model uses the `:with` keyword for custom serialization methods.

| Serialization formats
| XML, YAML, JSON, TOML
| XML, YAML, JSON, TOML, CSV
| Lutaml::Model does not support CSV.

| Validation
| Supports collection range, fixed values, and custom validation
| Requires implementation
|

| Adapter support
| XML (Nokogiri, Ox, Oga), YAML, JSON (JSON, MultiJson), TOML (Toml-rb, Tomlib)
| XML (Nokogiri, Ox), YAML, JSON (JSON, MultiJson), TOML (Toml-rb, Tomlib), CSV
| Lutaml::Model does not support CSV.

4+h| XML features

| <<root-namespace,XML default namespace>>
| Yes. Supports `<root xmlns='http://example.com'>` through the `namespace` option without prefix.
| No. Only supports `<root xmlns:prefix='http://example.com'>`.
|

| XML mixed content support
| Yes. Supports the following kind of XML through <<mixed-content,mixed content>> support.

[source,xml]
----
<description>My name is
<bold>John Doe</bold>,
and I'm <i>28</i>
years old</description>
----
| No. Shale's `map_content` only supports the first text node.
|

| XML namespace inheritance
| Yes. Supports the <<namespace-inherit,`inherit`>> option to inherit the
namespace from the root element.
| No.
|

| Support for `xsi:schemaLocation`
| Yes. Automatically supports the <<xml-schema-location,`xsi:schemaLocation`>>
attribute for every element.
| Requires manual specification on every XML element that uses it.
|

4+h| Attribute features

| Attribute delegation
| `:delegate` option to delegate attribute mappings to a model.
| `:receiver` option to delegate attribute mappings to a model.
|

| Enumerations
| Yes. Supports enumerations as value types through the
<<attribute-enumeration,`values:` option>>.
| No.
| Lutaml::Model supports enumerations as value types.

| Attribute extraction
| Yes. Supports <<attribute-extraction,attribute extraction>> from key-value
data models.
| No.
| Lutaml::Model supports attribute extraction from key-value data models.

|===


[[migrate-from-shale]]
== Migration steps from Shale

The following sections provide a guide for migrating from Shale to Lutaml::Model.

=== Step 1: Replace inheritance class

`Lutaml::Model` uses `Lutaml::Model::Serializable` as the base inheritance class.

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  # ...
end
----

[NOTE]
====
`Lutaml::Model` also supports an inclusion method as in the following example,
which is not supported by Shale. This is useful for cases where you want to
include the serialization methods in a class that already inherits from another
class.

[source,ruby]
----
class Example
  include Lutaml::Model::Serialize
  # ...
end
----
====

Shale uses `Shale::Mapper` as the base inheritance class.

[source,ruby]
----
class Example < Shale::Mapper
  # ...
end
----

Actions:

* Replace mentions of `Shale::Mapper` with `Lutaml::Model::Serializable`.
* Potentially replace inheritance with inclusion for suitable cases.


=== Step 2: Replace value type definitions

Value types in `Lutaml::Model` are under the `Lutaml::Model::Type` module,
or use the LutaML type symbols.

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :length, :integer
  attribute :description, :string
end
----

[NOTE]
====
`Lutaml::Model` supports specifying predefined value types as strings or
symbols, which is not supported by Shale.

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :length, Lutaml::Model::Type::Integer
  attribute :description, "String"
end
----
====

Value types in Shale are under the `Shale::Type` module.

[source,ruby]
----
class Example < Shale::Mapper
  attribute :length, Shale::Type::Integer
  attribute :description, Shale::Type::String
end
----

Action:

* Replace mentions of `Shale::Type` with `Lutaml::Model::Type`.
* Potentially replace value type definitions with strings or symbols.


=== Step 3: Configure serialization adapters

`Lutaml::Model` uses a configuration block to set the serialization adapters.

[source,ruby]
----
require 'lutaml/model/xml_adapter/nokogiri_adapter'
Lutaml::Model::Config.configure do |config|
  config.xml_adapter = Lutaml::Model::XmlAdapter::NokogiriAdapter
end
----

The equivalent for Shale is this:

[source,ruby]
----
require 'shale/adapter/nokogiri'
Shale.xml_adapter = Shale::Adapter::Nokogiri
----


Here are places that this code may reside at:

* If your code is a standalone Ruby script, this code will be present in your code.
* If your code is organized in a Ruby gem, this code will be specified somewhere referenced by `lib/your_gem_name.rb`.
* If your code contains tests or specs, they will be in the test setup file, e.g. RSpec `spec/spec_helper.rb`.

Actions:

* Replace the Shale configuration block with the `Lutaml::Model::Config`
configuration block.

* Replace the Shale adapter with the `Lutaml::Model` adapter.



=== Step 4: Rewrite custom serialization methods

There is an implementation difference between Lutaml::Model and Shale for custom
serialization methods.

Custom serialization methods in `Lutaml::Model` map to individual attributes.

For custom serialization methods, Lutaml::Model uses the `:with` keyword
instead of the `:using` keyword used by Shale.

[source,ruby]
----
class Example < Lutaml::Model::Serializable
  attribute :name, :string
  attribute :size, :integer
  attribute :color, :string
  attribute :description, :string

  json do
    map "name", to: :name, with: { to: :name_to_json, from: :name_from_json }
    map "size", to: :size
    map "color", to: :color,
                 with: { to: :color_to_json, from: :color_from_json }
    map "description", to: :description,
                       with: { to: :description_to_json, from: :description_from_json }
  end

  xml do
    root "CustomSerialization"
    map_element "Name", to: :name,
                        with: { to: :name_to_xml, from: :name_from_xml }
    map_attribute "Size", to: :size
    map_element "Color", to: :color,
                         with: { to: :color_to_xml, from: :color_from_xml }
    map_content to: :description,
                with: { to: :description_to_xml,
                        from: :description_from_xml }
  end

  def name_to_json(model, doc)
    doc["name"] = "JSON Masterpiece: #{model.name}"
  end

  def name_from_json(model, value)
    model.name = value.sub(/^JSON Masterpiece: /, "")
  end

  def color_to_json(model, doc)
    doc["color"] = model.color.upcase
  end

  def color_from_json(model, value)
    model.color = value.downcase
  end

  def description_to_json(model, doc)
    doc["description"] = "JSON Description: #{model.description}"
  end

  def description_from_json(model, value)
    model.description = value.sub(/^JSON Description: /, "")
  end

  def name_to_xml(model, parent, doc)
    el = doc.create_element("Name")
    doc.add_text(el, "XML Masterpiece: #{model.name}")
    doc.add_element(parent, el)
  end

  def name_from_xml(model, value)
    model.name = value.sub(/^XML Masterpiece: /, "")
  end

  def color_to_xml(model, parent, doc)
    color_element = doc.create_element("Color")
    doc.add_text(color_element, model.color.upcase)
    doc.add_element(parent, color_element)
  end

  def color_from_xml(model, value)
    model.color = value.downcase
  end

  def description_to_xml(model, parent, doc)
    doc.add_text(parent, "XML Description: #{model.description}")
  end

  def description_from_xml(model, value)
    model.description = value.join.strip.sub(/^XML Description: /, "")
  end
end
----

Custom serialization methods in Shale do not map to specific attributes, but
allow the user to specify where the data goes.

[source,ruby]
----
class Example < Shale::Mapper
  attribute :name, Shale::Type::String
  attribute :size, Shale::Type::Integer
  attribute :color, Shale::Type::String
  attribute :description, Shale::Type::String

  json do
    map "name", using: { from: :name_from_json, to: :name_to_json }
    map "size", to: :size
    map "color", using: { from: :color_from_json, to: :color_to_json }
    map "description", to: :description, using: { from: :description_from_json, to: :description_to_json }
  end

  xml do
    root "CustomSerialization"
    map_element "Name", using: { from: :name_from_xml, to: :name_to_xml }
    map_attribute "Size", to: :size
    map_element "Color", using: { from: :color_from_xml, to: :color_to_xml }
    map_content to: :description, using: { from: :description_from_xml, to: :description_to_xml }
  end

  def name_to_json(model, doc)
    doc['name'] = "JSON Masterpiece: #{model.name}"
  end

  def name_from_json(model, value)
    model.name = value.sub(/^JSON Masterpiece: /, "")
  end

  def color_to_json(model, doc)
    doc['color'] = model.color.upcase
  end

  def color_from_json(model, doc)
    model.color = doc['color'].downcase
  end

  def description_to_json(model, doc)
    doc['description'] = "JSON Description: #{model.description}"
  end

  def description_from_json(model, doc)
    model.description = doc['description'].sub(/^JSON Description: /, "")
  end

  def name_from_xml(model, node)
    model.name = node.text.sub(/^XML Masterpiece: /, "")
  end

  def name_to_xml(model, parent, doc)
    name_element = doc.create_element('Name')
    doc.add_text(name_element, model.street.to_s)
    doc.add_element(parent, name_element)
  end
end
----

NOTE: There are cases where the Shale implementation of custom methods work
differently from the Lutaml::Model implementation. In these cases, you will need
to adjust the custom methods accordingly.

Actions:

* Replace the `using` keyword with the `with` keyword.
* Adjust the custom methods.


== About LutaML

The name "LutaML" is pronounced as "Looh-tah-mel".

The name "LutaML" comes from the Latin word for clay, "Lutum", and "ML"
for "Markup Language". Just as clay can be molded and modeled into beautiful and
practical end products, the Lutaml::Model gem is used for data modeling,
allowing you to shape and structure your data into useful forms.



== License and Copyright

This project is licensed under the BSD 2-clause License.
See the link:LICENSE.md[] file for details.

Copyright Ribose.