# encoding: utf-8

module XapianDb

  # A document blueprint describes the mapping of an object to a Xapian document
  # for a given class.
  # @example A simple document blueprint configuration for the class Person
  #   XapianDb::DocumentBlueprint.setup(:Person) do |blueprint|
  #     blueprint.attribute       :name, :weight => 10
  #     blueprint.attribute       :first_name
  #     blueprint.index           :remarks
  #   end
  # @example A document blueprint configuration with a complex attribute for the class Person
  #   XapianDb::DocumentBlueprint.setup(:Person) do |blueprint|
  #     blueprint.attribute       :complex, :weight => 10 do
  #       # add some logic here to evaluate the value of 'complex'
  #     end
  #   end
  # @author Gernot Kogler
  class DocumentBlueprint

    include XapianDb::Utilities

    # ---------------------------------------------------------------------------------
    # Singleton methods
    # ---------------------------------------------------------------------------------
    class << self

      attr_reader :blueprints

      # Configure the blueprint for a class.
      # Available options:
      # - adapter (see {#adapter} for details)
      # - attribute (see {#attribute} for details)
      # - index (see {#index} for details)
      def setup(klass_or_name, &block)
        name = class_name_from klass_or_name

        @blueprints ||= {}
        blueprint = DocumentBlueprint.new
        yield blueprint if block_given? # configure the blueprint through the block
        validate_type_consistency_on blueprint

        # Remove a previously loaded blueprint for this class to avoid stale blueprint definitions
        @blueprints.delete_if { |indexed_class, blueprint| indexed_class == name }
        @blueprints[name] = blueprint

        lazy_load_adapter_for blueprint, name

        @searchable_prefixes = @blueprints.values.map { |blueprint| blueprint.searchable_prefixes }.flatten.compact.uniq || []

        # We can always do a field search on the name of the indexed class
        @searchable_prefixes << "indexed_class"
        @attributes = @blueprints.values.map { |blueprint| blueprint.attribute_names}.flatten.compact.uniq.sort || []
        blueprint
      end

      # reset the blueprint setup
      def reset
        @blueprints = {}
      end

      # is a blueprint configured for the given name?
      # @return [Boolean]
      def configured?(name)
        @blueprints && @blueprints.has_key?(name.to_s)
      end

      # Get all configured classes
      # @return [Array<Class>]
      def configured_classes
        if @blueprints
          @blueprints.keys.map {|class_name| XapianDb::Utilities.constantize(class_name) }
        else
          []
        end
      end

      def dependencies_for(klass_name, changed_attrs)
        @blueprints.values.map(&:dependencies)
                          .flatten
                          .select{ |dependency| dependency.dependent_on == klass_name && dependency.interested_in?(changed_attrs) }
      end

      # Get the blueprint for a class
      # @return [DocumentBlueprint]
      def blueprint_for(klass_or_name)
        if @blueprints
          if klass_or_name.is_a?(Class)
            warn "xapian_db: blueprint_for(Class) is deprecated; use blueprint_for(Symbol) or blueprint_for(String) instead"
            key = klass_or_name.name
          else
            key = klass_or_name.to_s
          end
          while key != "Object" && key != "BasicObject"
            if @blueprints.has_key? key
              return @blueprints[key]
            else
              klass = XapianDb::Utilities.constantize key
              key = klass.superclass.name
            end
          end
        end
        return nil
      end

      # Get the value number for an attribute. Please note that this is not the index in the values
      # array of a xapian document but the valueno. Therefore, document.values[value_number] returns
      # the wrong data, use document.value(value_number) instead.
      # @param [attribute] The name of an attribute
      # @return [Integer] The value number
      def value_number_for(attribute)
        return 0 if attribute.to_sym == :indexed_class
        return 1 if attribute.to_sym == :natural_sort_order
        raise ArgumentError.new "attribute #{attribute} is not configured in any blueprint" if @attributes.nil?
        position = @attributes.index attribute.to_sym
        if position
          # We add 2 because slot 0 and 1 are reserved for indexed_class and natural_sort_order
          return position + 2
        else
          raise ArgumentError.new "attribute #{attribute} is not configured in any blueprint"
        end
      end

      # Get the type info of an attribute
      # @param [attribute] The name of an indexed method
      # @return [Symbol] The defined type or :untyped if no type is defined
      def type_info_for(attribute)
        return nil if @blueprints.nil?
        @blueprints.values.each do |blueprint|
          return blueprint.type_map[attribute] if blueprint.type_map.has_key?(attribute)
        end
        nil
      end

      # Return an array of all configured text methods in any blueprint
      # @return [Array<String>] All searchable prefixes
      def searchable_prefixes
        @searchable_prefixes || []
      end

      # Return an array of all defined attributes
      # @return [Array<Symbol>] All defined attributes
      def attributes
        @attributes || []
      end

      private

      def class_name_from(klass_or_name)
        if klass_or_name.is_a?(Class)
          warn "xapian_db: XapianDb::DocumentBlueprint.setup(Class) is deprecated; use XapianDb::DocumentBlueprint.setup(Symbol) or XapianDb::DocumentBlueprint.setup(String) instead"
          name = klass_or_name.name
        else
          name = klass_or_name.to_s
        end
      end

      def lazy_load_adapter_for(blueprint, klass_name)
        # lazy load the adapter
        unless defined? blueprint._adapter
          adapter_file = blueprint._adapter.name.split("::").last.downcase + "_adapter"
          require File.dirname(__FILE__) + "../adapters/#{adapter_file}"
        end

        # Needed to add class helper methods to indexed pure ruby classes
        if eval("defined?(#{klass_name}) && #{klass_name}.is_a?(Class)")
          blueprint._adapter.add_class_helper_methods_to XapianDb::Utilities.constantize(klass_name)
        end
      end

      def validate_type_consistency_on(blueprint)
        blueprint.type_map.each do |method_name, type|
          if type_info_for(method_name) && type_info_for(method_name) != type
            raise ArgumentError.new "ambigous type definition for #{method_name} detected (#{type_info_for(method_name)}, #{type})"
          end
        end
      end
    end

    # ---------------------------------------------------------------------------------
    # Instance methods
    # ---------------------------------------------------------------------------------

    attr_reader :type_map

    # Get the names of all configured attributes sorted alphabetically
    # @return [Array<Symbol>] The names of the attributes
    def attribute_names
      @attributes_hash.keys.sort
    end

    # Get the block associated with an attribute
    # @param [Symbol] attribute The name of the attribute
    # @return [Block] The block
    def block_for_attribute(attribute)
      @attributes_hash[attribute][:block]
    end

    # Get the names of all configured index methods sorted alphabetically
    # @return [Array<Symbol>] The names of the index_methods
    def indexed_method_names
      @indexed_methods_hash.keys.sort
    end

    # Get the options for an indexed method
    # @param [Symbol] method The name of the method
    # @return [IndexOptions] The options
    def options_for_indexed_method(method)
      @indexed_methods_hash[method]
    end

    # Return an array of all configured text methods in this blueprint
    # @return [Array<String>] All searchable prefixes
    def searchable_prefixes
      @searchable_prefixes ||= indexed_method_names
    end

    # Should the object go into the index? Evaluates an ignore expression,
    # if defined
    def should_index? obj
      return obj.instance_eval(&@ignore_expression) == false if @ignore_expression
      true
    end

    # Lazily build and return a module that implements accessors for each field
    # @return [Module] A module containing all accessor methods
    def accessors_module
      return @accessors_module unless @accessors_module.nil?
      @accessors_module = Module.new

      # Add the accessors for the indexed class and the score
      @accessors_module.instance_eval do

        define_method :indexed_class do
          self.values[0].value
        end

        define_method :score do
          @score
        end

        define_method :attributes do
          blueprint = XapianDb::DocumentBlueprint.blueprint_for indexed_class
          blueprint.attribute_names.inject({}) { |hash, attr| hash.tap { |hash| hash[attr.to_s] = self.send attr } }
        end
      end

      # Add an accessor for each attribute
      attribute_names.each do |attribute|
        index = DocumentBlueprint.value_number_for(attribute)
        codec = XapianDb::TypeCodec.codec_for @type_map[attribute]
        @accessors_module.instance_eval do
          define_method attribute do
            codec.decode self.value(index)
          end
        end
      end

      # Let the adapter add its document helper methods (if any)
      _adapter.add_doc_helper_methods_to(@accessors_module)
      @accessors_module
    end

    # ---------------------------------------------------------------------------------
    # Blueprint DSL methods
    # ---------------------------------------------------------------------------------

    attr_reader :lazy_base_query, :_natural_sort_order, :dependencies

    # Construct the blueprint
    def initialize
      @attributes_hash      = {}
      @indexed_methods_hash = {}
      @type_map             = {}
      @dependencies         = []
      @_natural_sort_order  = :id
      @autoindex            = true
      @indexer_preprocess_callback = nil
    end

    # Set the adapter
    # @param [Symbol] type The adapter type; the following adapters are available:
    #   - :generic ({XapianDb::Adapters::GenericAdapter})
    #   - :active_record ({XapianDb::Adapters::ActiveRecordAdapter})
    #   - :datamapper ({XapianDb::Adapters::DatamapperAdapter})
    def adapter(type)
      # We try to guess the adapter name
      @_adapter = XapianDb::Adapters.const_get("#{camelize(type.to_s)}Adapter")
    end

    # return the adpater to use for this blueprint
    def _adapter
      @_adapter || XapianDb::Config.adapter || XapianDb::Adapters::GenericAdapter
    end

    # Should objects for this blueprint be automatically reindexed?
    # @param [Boolean] boolean Yes or no?
    def autoindex(boolean)
      @autoindex = boolean
    end

    # Get the autoindex value
    # @return [Boolean] The autoindex value
    def autoindex?
      @autoindex
    end

    # Add an attribute to the blueprint. Attributes will be stored in the xapian documents an can be
    # accessed from a search result.
    # @param [String] name The name of the method that delivers the value for the attribute
    # @param [Hash] options
    # @option options [Integer] :weight (1) The weight for this attribute.
    # @option options [Boolean] :index (true) Should the attribute be indexed?
    # @option options [Symbol] :as should add type info for range queries (:date, :numeric)
    # @example For complex attribute configurations you may pass a block:
    #   XapianDb::DocumentBlueprint.setup(:IndexedObject) do |blueprint|
    #     blueprint.attribute :complex do
    #       if @id == 1
    #         "One"
    #       else
    #         "Not one"
    #       end
    #     end
    #   end
    def attribute(name, options={}, &block)
      raise ArgumentError.new("You cannot use #{name} as an attribute name since it is a reserved method name of Xapian::Document") if reserved_method_name?(name)
      do_not_index    = options.delete(:index) == false
      @type_map[name] = (options.delete(:as) || :string)

      if block_given?
        @attributes_hash[name] = {:block => block}.merge(options)
      else
        @attributes_hash[name] = options
      end
      self.index(name, options, &block) unless do_not_index
    end

    # Add a list of attributes to the blueprint. Attributes will be stored in the xapian documents ans
    # can be accessed from a search result.
    # @param [Array] attributes An array of method names that deliver the values for the attributes
    def attributes(*attributes)
      attributes.each do |attr|
        raise ArgumentError.new("You cannot use #{attr} as an attribute name since it is a reserved method name of Xapian::Document") if reserved_method_name?(attr)
        @attributes_hash[attr] = {}
        @type_map[attr] = :string
        self.index attr
      end
    end

    # Add an indexed value to the blueprint. Indexed values are not accessible from a search result.
    # @param [Array] args An array of arguments; you can pass a method name, an array of method names
    #   or a method name and an options hash.
    # @param [Block] &block An optional block for complex configurations
    # Avaliable options:
    # - :weight (default: 1) The weight for this indexed value
    # @example Simple index declaration
    #   blueprint.index :name
    # @example Index declaration with options
    #   blueprint.index :name, :weight => 10
    # @example Mass index declaration
    #   blueprint.index :name, :first_name, :profession
    # @example Index declaration with a block
    #   blueprint.index :complex, :weight => 10 do
    #     # add some logic here to calculate the value for 'complex'
    #   end
    def index(*args, &block)
      case args.size
        when 1
          @indexed_methods_hash[args.first] = IndexOptions.new(:weight => 1, :block => block)
        when 2
          # Is it a method name with options?
          if args.last.is_a? Hash
            options = args.last
            assert_valid_keys options, :weight, :prefixed, :no_split
            @indexed_methods_hash[args.first] = IndexOptions.new(options.merge(:block => block))
          else
            add_indexes_from args
          end
        else # multiple arguments
          add_indexes_from args
      end
    end

    # Add a block of code that evaluates if a model should not be indexed
    def ignore_if &block
      @ignore_expression = block
    end

    # Define a base query to select one or all objects of the indexed class. The reason for a
    # base query is to optimize the query avoiding th 1+n problematic. The base query should only
    # include joins(...) and includes(...) calls.
    # @param [expression] a base query expression
    # @example Include the adresses
    #   blueprint.base_query Person.includes(:addresses)
    def base_query(expression = nil, &block)
      if expression
        warn "xapian_db: directly passing a base query in a blueprint configuration is deprecated, wrap them in a block"
        block = lambda { expression }
      end
      @lazy_base_query = block
    end

    # Define the natural sort order.
    # @param [String] name The name of the method that delivers the sort expression
    # @param [Block] &block An optional block for complex configurations
    # Pass a method name or a block, but not both
    def natural_sort_order(name=nil, &block)
      raise ArgumentError.new("natural_sort_order accepts a method name or a block, but not both") if name && block
      @_natural_sort_order = name || block
    end

    def dependency(klass_name, when_changed: [], &block)
      @dependencies << Dependency.new(klass_name.to_s, when_changed, block)
    end

    # Set the indexer preprocess callback.
    # @param [Method] method a class method; needs to take one parameter and return a string.
    # @example
    #   class Util
    #     def self.strip_accents(terms)
    #       terms.gsub(/[éèêëÉÈÊË]/, "e")
    #     end
    #   end
    #
    #   XapianDb::DocumentBlueprint.setup(:IndexedObject) do |blueprint|
    #     blueprint.attribute :name
    #     blueprint.indexer_preprocess_callback Util.method(:strip_accents)
    #   end
    def indexer_preprocess_callback(method)
      @indexer_preprocess_callback = method
    end

    # Reader for indexer_preprocess_callback.
    # Returns the terms preprocessing method for this blueprint, the global method from config or nil.
    def preprocess_terms
      @indexer_preprocess_callback || XapianDb::Config.preprocess_terms
    end

    # Options for an indexed method
    class IndexOptions

      attr_reader :weight, :prefixed, :no_split, :block

      # Constructor
      # @param [Hash] options
      # @option options [Integer] :weight (1) The weight for the indexed value
      def initialize(options = {})
        @weight   = options[:weight] || 1
        @prefixed = options[:prefixed].nil? ? true : options[:prefixed]
        @no_split = options[:no_split]
        @block    = options[:block]
      end
    end

    class Dependency

      attr_reader :dependent_on, :trigger_attributes, :block

      # Constructor
      # @param [String] klass_name Name of the dependent class
      # @param [Array] trigger_attributes List of attributes to watch for changes (if empty, triggers on any change)
      # @option [Block] block Block that is called when changes are detected; the block must return an array of indexeable objects
      def initialize(klass_name, trigger_attributes, block)
        @dependent_on, @trigger_attributes, @block = klass_name, trigger_attributes.map(&:to_s), block
      end

      def interested_in?(changed_attrs)
        return true if @trigger_attributes.empty?
        (@trigger_attributes & changed_attrs).any?
      end
    end

    private

    # Add index configurations from an array
    def add_indexes_from(array)
      array.each do |arg|
        @indexed_methods_hash[arg] = IndexOptions.new(:weight => 1)
      end
    end

    # Check if the attribute name does not collide with a method name of Xapian::Document
    def reserved_method_name?(attr_name)
      @reserved_method_names ||= Xapian::Document.instance_methods
      @reserved_method_names.include?(attr_name.to_sym)
    end
  end
end