# encoding: utf-8
require 'active_support'
require 'active_support/core_ext/hash/indifferent_access'
require 'active_support/core_ext/string/inflections'

module SchemaTools
  module Modules
    module Hash

      # Create a Hash with the available (api)object attributes defined in the
      # according schema properties. This is the meat of the
      # object-to-api-markup workflow
      #
      # === Example
      #
      #  obj = Invoice.new(:title =>'hello world', :number=>'4711')
      #
      #  obj_hash = SchemaTools::Hash.from_schema(obj)
      #   => { 'invoice' =>{'title'=>'hello world', 'number'=>'4711' } }
      #
      #  obj_hash = Schema.to_hash_from_schema(obj, fields: ['title'])
      #   => { 'invoice' =>{'title'=>'hello world' } }
      #
      #  obj_hash = Schema.to_hash_from_schema(obj, class_name: :document)
      #   => { 'document' =>{'title'=>'hello world' } }
      #
      # @param [Object] obj returned as hash
      # @param [Hash{Symbol=>Mixed}] opts additional options
      # @options opts [String|Symbol] :class_name used as hash key. Should be
      # a lowercase underscored name and it MUST have an existing schema file.
      # Use it to override the default, which is obj.class.name. Only used for
      # top-level object NOT nested objects
      # @options opts [Array<String>] :fields to return. If not set all schema
      # properties are used.
      # @options opts [String] :path of the schema files overriding global one
      # @options opts [String] :base_url used in all links
      # @options opts [Boolean] :links if set the object hash gets its _links
      # array inline.
      #
      # @return [Hash{String=>{String=>Mixed}}] The object as hash:
      #   { 'invoice' => {'title'=>'hello world', 'number'=>'4711' } }
      #
      def from_schema(obj, opts={})
        # get objects class name without inheritance
        real_class_name = obj.class.name.split('::').last.underscore
        class_name = opts[:class_name] || real_class_name
        # get schema
        inline_schema = opts.delete(:schema) if opts[:schema].present?
        schema =  inline_schema || SchemaTools::Reader.read(class_name, opts[:path])

        # iterate over the defined schema fields
        data = parse_properties(obj, schema, opts)
        if opts[:links]
          links = parse_links(obj, schema, opts)
          links && data['_links'] = links
        end
        data
      end

      private

      # @param [Object] obj from which to grab the properties
      # @param [Hash] schema
      # @param [Hash] opts
      def parse_properties(obj, schema, opts)
        # only allow fields for first level object.
        # TODO collect . dot separated field names and pass them on to the recursive calls e.g nested object, ary
        fields = opts.delete(:fields)
        data = {}
        schema['properties'].each do |field, prop|
          next if fields && !fields.include?(field)
          if prop['type'] == 'array'
            # ensure the nested object gets its own class name
            opts.delete(:class_name)
            data[field] = parse_list(obj, field, prop, opts)
          elsif prop['type'] == 'object' # a singular related object
            opts.delete(:class_name)
            data[field] = parse_object(obj, field, prop, opts)
          else # a simple field is only added if the object knows it
            next unless obj.respond_to?(field)
            raw_val = obj.send(field)
            # convert field to schema type if set
            conv_val = if raw_val.nil?
                         raw_val
                       elsif prop['type'] == 'string'  # rely on .to_s for format from date/datetime
                         "#{raw_val}"
                       elsif prop['type'] == 'integer'
                         raw_val.to_i
                       else # bool / number rely on .to_s in json lib
                         raw_val
                      end
            data[field] = conv_val
          end
        end
        data
      end

      # Parse the link section of the schema by replacing {id} in urls
      # @param [Object] obj object being parsed
      # @param [Hash] schema
      # @param [Hash] opts
      # @options opts [String] :base_url prepended to link href, WATCH possible double //
      # @return [Array<Hash{String=>String}> | Nil]
      def parse_links(obj, schema, opts={})
        links = []
        schema['links'] && schema['links'].each do |link|
          href = link['href'].dup
          # placeholders: find all {xy}, create replacement ary with
          # values, than replace
          matches = href.scan(/{(\w+)}/) #{abc} => abc
          replaces = []
          matches.each do |match|
            obj_val = obj.send(match[0]) if obj.respond_to?(match[0])
            replaces << ["{#{match[0]}}", obj_val] if obj_val
          end
          replaces.each {|r| href.gsub!(r[0], "#{r[1]}")}
          href = "#{opts[:base_url]}/#{href}" if opts[:base_url]

          links << { 'rel' => link['rel'],
                     'href' => href }
        end
        links.uniq
        # return links only if not empty
        links.empty? ? nil : links
      end

      # Parse a nested array property.
      # @param [Object] obj the object in question
      # @param [String] field name
      # @param [Hash] prop fields schema properties
      # @param [Hash] opts to_schema options
      # @return [Array<Hash{String=>String}>]
      def parse_list(obj, field, prop, opts)
        res = []
        # TODO should we raise errors if one of those is missing?
        return nil if !obj.respond_to?( field )
        return nil if !prop['items']

        rel_objects = obj.send( field )
        # force an empty array if values are not present
        return res if !rel_objects

        if prop['items'].is_a?(Hash) || prop['items'].is_a?(ActiveSupport::HashWithIndifferentAccess)
          # array of plain values e.g number, strings e.g
          # "items": { "type": "string" },
          # should we convert the values? according to the type?
          if SCHEMA_BASE_TYPES.include?(prop['items']['type'])
            res = rel_objects
          elsif prop['items']['type'] == 'object'
            rel_objects.each { |rel_obj| res << from_schema(rel_obj, opts) }
          end
        end

        if prop['items'].is_a?(Array)
          #TODO recurse
          # res << rel_objects.each { |rel_obj| parse_list(rel_obj, field, prop opts) }
        end
        res
      end

      # Parse a nested object property.
      # @param [Object] obj the object in question
      # @param [String] field name
      # @param [Hash] prop fields schema properties
      # @param [Hash] opts to_schema options
      # @return [Array<Hash{String=>String}>]
      def parse_object(obj, field, prop, opts)
        return if !obj.respond_to?( field )
        rel_obj = obj.send( field )
        return if !rel_obj

        res = if prop['properties']
                opts[:schema] = prop
                from_schema(rel_obj, opts)
              elsif prop['oneOf']
                # auto-detects which schema to use depending on the rel_object type
                # Simpler than detecting the object type or $ref to use inside the
                # oneOf array
                from_schema(rel_obj, opts)
              end
        res
      end

    end
  end
end