# Would like to support other database adapters so no more hard dependency on Active Record.
require "flag_shih_tzu/validators"

module FlagShihTzu
  # taken from ActiveRecord::ConnectionAdapters::Column
  TRUE_VALUES = [true, 1, "1", "t", "T", "true", "TRUE"]

  DEFAULT_COLUMN_NAME = "flags"

  def self.included(base)
    base.extend(ClassMethods)
    base.class_attribute :flag_options unless defined?(base.flag_options)
    base.class_attribute :flag_mapping unless defined?(base.flag_mapping)
    base.class_attribute :flag_columns unless defined?(base.flag_columns)
  end

  # TODO: Inherit from StandardException
  class IncorrectFlagColumnException < Exception; end
  class NoSuchFlagQueryModeException < Exception; end
  class NoSuchFlagException < Exception; end
  class DuplicateFlagColumnException < Exception; end

  module ClassMethods
    def has_flags(*args)
      flag_hash, opts = parse_flag_options(*args)
      opts =
        {
          named_scopes: true,
          column: DEFAULT_COLUMN_NAME,
          flag_query_mode: :in_list, # or :bit_operator
          strict: false,
          check_for_column: true
        }.update(opts)
      if !valid_flag_column_name?(opts[:column])
        warn %[FlagShihTzu says: Please use a String to designate column names! I see you here: #{caller.first}]
        opts[:column] = opts[:column].to_s
      end
      colmn = opts[:column]
      if opts[:check_for_column] && (active_record_class? && !check_flag_column(colmn))
        warn(
          %[FlagShihTzu says: Flag column #{colmn} appears to be missing!
To turn off this warning set check_for_column: false in has_flags definition here: #{caller.first}]
        )
        return
      end

      # options are stored in a class level hash and apply per-column
      self.flag_options ||= {}
      flag_options[colmn] = opts

      # the mappings are stored in this class level hash and apply per-column
      self.flag_mapping ||= {}
      # If we already have an instance of the same column in the flag_mapping,
      #   then there is a double definition on a column
      if opts[:strict] && !self.flag_mapping[colmn].nil?
        raise DuplicateFlagColumnException
      end
      flag_mapping[colmn] ||= {}

      # keep track of which flag columns are defined on this class
      self.flag_columns ||= []
      self.flag_columns << colmn

      flag_hash.each do |flag_key, flag_name|
        unless valid_flag_key?(flag_key)
          raise ArgumentError,
                %[has_flags: flag keys should be positive integers, and #{flag_key} is not]
        end
        unless valid_flag_name?(flag_name)
          raise ArgumentError,
                %[has_flags: flag names should be symbols, and #{flag_name} is not]
        end
        # next if method already defined by flag_shih_tzu
        next if flag_mapping[colmn][flag_name] & (1 << (flag_key - 1))
        if method_defined?(flag_name)
          raise ArgumentError,
                %[has_flags: flag name #{flag_name} already defined, please choose different name]
        end

        flag_mapping[colmn][flag_name] = 1 << (flag_key - 1)

        class_eval <<-EVAL, __FILE__, __LINE__ + 1
          def #{flag_name}
            flag_enabled?(:#{flag_name}, "#{colmn}")
          end
          alias :#{flag_name}? :#{flag_name}

          def #{flag_name}=(value)
            FlagShihTzu::TRUE_VALUES.include?(value) ?
              enable_flag(:#{flag_name}, "#{colmn}") :
              disable_flag(:#{flag_name}, "#{colmn}")
          end

          def not_#{flag_name}
            !#{flag_name}
          end
          alias :not_#{flag_name}? :not_#{flag_name}

          def not_#{flag_name}=(value)
            FlagShihTzu::TRUE_VALUES.include?(value) ?
              disable_flag(:#{flag_name}, "#{colmn}") :
              enable_flag(:#{flag_name}, "#{colmn}")
          end

          def #{flag_name}_changed?
            if colmn_changes = changes["#{colmn}"]
              flag_bit = self.class.flag_mapping["#{colmn}"][:#{flag_name}]
              (colmn_changes[0] & flag_bit) != (colmn_changes[1] & flag_bit)
            else
              false
            end
          end

        EVAL

        if active_record_class?
          class_eval <<-EVAL, __FILE__, __LINE__ + 1
            def self.#{flag_name}_condition(options = {})
              sql_condition_for_flag(
                :#{flag_name},
                "#{colmn}",
                true,
                options[:table_alias] || table_name
              )
            end

            def self.not_#{flag_name}_condition
              sql_condition_for_flag(:#{flag_name}, "#{colmn}", false)
            end

            def self.set_#{flag_name}_sql
              sql_set_for_flag(:#{flag_name}, "#{colmn}", true)
            end

            def self.unset_#{flag_name}_sql
              sql_set_for_flag(:#{flag_name}, "#{colmn}", false)
            end

            def self.#{colmn.singularize}_values_for(*flag_names)
              values = []
              flag_names.each do |flag_name|
                if respond_to?(flag_name)
                  values_for_flag = send(:sql_in_for_flag, flag_name, "#{colmn}")
                  values = if values.present?
                    values & values_for_flag
                  else
                    values_for_flag
                  end
                end
              end

              values.sort
            end
          EVAL

          # Define the named scopes if the user wants them and AR supports it
          if flag_options[colmn][:named_scopes]
            if ActiveRecord::VERSION::MAJOR == 2 && respond_to?(:named_scope)
              class_eval <<-EVAL, __FILE__, __LINE__ + 1
                named_scope :#{flag_name}, lambda {
                  { conditions: #{flag_name}_condition }
                }
                named_scope :not_#{flag_name}, lambda {
                  { conditions: not_#{flag_name}_condition }
                }
              EVAL
            elsif respond_to?(:scope)
              # Prevent deprecation notices on Rails 3
              #   when using +named_scope+ instead of +scope+.
              # Prevent deprecation notices on Rails 4
              #   when using +conditions+ instead of +where+.
              class_eval <<-EVAL, __FILE__, __LINE__ + 1
                scope :#{flag_name}, lambda {
                  where(#{flag_name}_condition)
                }
                scope :not_#{flag_name}, lambda {
                  where(not_#{flag_name}_condition)
                }
              EVAL
            end
          end

        end

        if colmn != DEFAULT_COLUMN_NAME
          class_eval <<-EVAL, __FILE__, __LINE__ + 1

            def all_#{colmn}
              all_flags("#{colmn}")
            end

            def selected_#{colmn}
              selected_flags("#{colmn}")
            end

            def select_all_#{colmn}
              select_all_flags("#{colmn}")
            end

            def unselect_all_#{colmn}
              unselect_all_flags("#{colmn}")
            end

            # useful for a form builder
            def selected_#{colmn}=(chosen_flags)
              unselect_all_flags("#{colmn}")
              chosen_flags.each do |selected_flag|
                enable_flag(selected_flag.to_sym, "#{colmn}") if selected_flag.present?
              end
            end

            def has_#{colmn.singularize}?
              not selected_#{colmn}.empty?
            end

            def chained_#{colmn}_with_signature(*args)
              chained_flags_with_signature("#{colmn}", *args)
            end

            def as_#{colmn.singularize}_collection(*args)
              as_flag_collection("#{colmn}", *args)
            end

          EVAL
        end

        # Define bang methods when requested
        if flag_options[colmn][:bang_methods]
          class_eval <<-EVAL, __FILE__, __LINE__ + 1
            def #{flag_name}!
              enable_flag(:#{flag_name}, "#{colmn}")
            end

            def not_#{flag_name}!
              disable_flag(:#{flag_name}, "#{colmn}")
            end
          EVAL
        end

      end

    end

    def check_flag(flag, colmn)
      unless colmn.is_a?(String)
        raise ArgumentError,
              %[Column name "#{colmn}" for flag "#{flag}" is not a string]
      end
      if flag_mapping[colmn].nil? || !flag_mapping[colmn].include?(flag)
        raise ArgumentError,
              %[Invalid flag "#{flag}"]
      end
    end

    # Returns SQL statement to enable/disable flag.
    # Automatically determines the correct column.
    def set_flag_sql(flag, value, colmn = nil, custom_table_name = table_name)
      colmn = determine_flag_colmn_for(flag) if colmn.nil?
      sql_set_for_flag(flag, colmn, value, custom_table_name)
    end

    def determine_flag_colmn_for(flag)
      return DEFAULT_COLUMN_NAME if flag_mapping.nil?
      flag_mapping.each_pair do |colmn, mapping|
        return colmn if mapping.include?(flag)
      end
      raise NoSuchFlagException.new(
        %[determine_flag_colmn_for: Couldn't determine column for your flags!]
      )
    end

    def chained_flags_with(column = DEFAULT_COLUMN_NAME, *args)
      if (ActiveRecord::VERSION::MAJOR >= 3)
        where(chained_flags_condition(column, *args))
      else
        all(conditions: chained_flags_condition(column, *args))
      end
    end

    def chained_flags_condition(colmn = DEFAULT_COLUMN_NAME, *args)
      %[(#{table_name}.#{colmn} in (#{chained_flags_values(colmn, *args).join(",")}))]
    end

    def flag_keys(colmn = DEFAULT_COLUMN_NAME)
      flag_mapping[colmn].keys
    end

    private

    def flag_value_range_for_column(colmn)
      max = flag_mapping[colmn].values.max
      Range.new(0, (2 * max) - 1)
    end

    def chained_flags_values(colmn, *args)
      val = flag_value_range_for_column(colmn).to_a
      args.each do |flag|
        neg = false
        if flag.to_s.match /^not_/
          neg = true
          flag = flag.to_s.sub(/^not_/, "").to_sym
        end
        check_flag(flag, colmn)
        flag_values = sql_in_for_flag(flag, colmn)
        if neg
          val = val - flag_values
        else
          val = val & flag_values
        end
      end
      val
    end

    def parse_flag_options(*args)
      options = args.shift
      add_options = if args.size >= 1
                      args.shift
                    else
                      options.
                      keys.
                      select { |key| !key.is_a?(Fixnum) }.
                      inject({}) do |hash, key|
                        hash[key] = options.delete(key)
                        hash
                      end
                    end
      [options, add_options]
    end

    def check_flag_column(colmn, custom_table_name = table_name)
      # If you aren't using ActiveRecord (eg. you are outside rails)
      #   then do not fail here
      # If you are using ActiveRecord then you only want to check for the
      #   table if the table exists so it won't fail pre-migration
      has_ar = (!!defined?(ActiveRecord) && respond_to?(:descends_from_active_record?))
      # Supposedly Rails 2.3 takes care of this, but this precaution
      #   is needed for backwards compatibility
      has_table = has_ar ? connection.tables.include?(custom_table_name) : true
      if has_table
        found_column = columns.detect { |column| column.name == colmn }
        # If you have not yet run the migration that adds the 'flags' column
        #   then we don't want to fail,
        #   because we need to be able to run the migration
        # If the column is there but is of the wrong type,
        #   then we must fail, because flag_shih_tzu will not work
        if found_column.nil?
          warn(
            %[Error: Column "#{colmn}" doesn't exist on table "#{custom_table_name}". Did you forget to run migrations?]
          )
          return false
        elsif found_column.type != :integer
          raise IncorrectFlagColumnException.new(
            %[Table "#{custom_table_name}" must have an integer column named "#{colmn}" in order to use FlagShihTzu.]
          )
        end
      else
        # ActiveRecord gem may not have loaded yet?
        warn(
          %[FlagShihTzu#has_flags: Table "#{custom_table_name}" doesn't exist.  Have all migrations been run?]
        ) if has_ar
        return false
      end

      true
    end

    def sql_condition_for_flag(flag, colmn, enabled = true, custom_table_name = table_name)
      check_flag(flag, colmn)

      if flag_options[colmn][:flag_query_mode] == :bit_operator
        # use & bit operator directly in the SQL query.
        # This has the drawback of not using an index on the flags colum.
        %[(#{custom_table_name}.#{colmn} & #{flag_mapping[colmn][flag]} = #{enabled ? flag_mapping[colmn][flag] : 0})]
      elsif flag_options[colmn][:flag_query_mode] == :in_list
        # use IN() operator in the SQL query.
        # This has the drawback of becoming a big query
        #   when you have lots of flags.
        neg = enabled ? "" : "not "
        %[(#{custom_table_name}.#{colmn} #{neg}in (#{sql_in_for_flag(flag, colmn).join(",")}))]
      else
        raise NoSuchFlagQueryModeException
      end
    end

    # returns an array of integers suitable for a SQL IN statement.
    def sql_in_for_flag(flag, colmn)
      val = flag_mapping[colmn][flag]
      flag_value_range_for_column(colmn).select { |bits| bits & val == val }
    end

    def sql_set_for_flag(flag, colmn, enabled = true, custom_table_name = table_name)
      check_flag(flag, colmn)
      full_name = "#{custom_table_name}.#{colmn}"
      "#{full_name} = #{full_name} #{enabled ? "| " : "& ~" }#{flag_mapping[colmn][flag]}"
    end

    def valid_flag_key?(flag_key)
      flag_key > 0 && flag_key == flag_key.to_i
    end

    def valid_flag_name?(flag_name)
      flag_name.is_a?(Symbol)
    end

    def valid_flag_column_name?(colmn)
      colmn.is_a?(String)
    end

    # Returns the correct method to create a named scope.
    # Use to prevent deprecation notices on Rails 3
    #   when using +named_scope+ instead of +scope+.
    def named_scope_method
      # Can't use respond_to because both AR 2 and 3
      #   respond to both +scope+ and +named_scope+.
      ActiveRecord::VERSION::MAJOR == 2 ? :named_scope : :scope
    end

    def active_record_class?
      ancestors.include?(ActiveRecord::Base)
    end
  end

  # Performs the bitwise operation so the flag will return +true+.
  def enable_flag(flag, colmn = nil)
    colmn = determine_flag_colmn_for(flag) if colmn.nil?
    self.class.check_flag(flag, colmn)

    set_flags(flags(colmn) | self.class.flag_mapping[colmn][flag], colmn)
  end

  # Performs the bitwise operation so the flag will return +false+.
  def disable_flag(flag, colmn = nil)
    colmn = determine_flag_colmn_for(flag) if colmn.nil?
    self.class.check_flag(flag, colmn)

    set_flags(flags(colmn) & ~self.class.flag_mapping[colmn][flag], colmn)
  end

  def flag_enabled?(flag, colmn = nil)
    colmn = determine_flag_colmn_for(flag) if colmn.nil?
    self.class.check_flag(flag, colmn)

    get_bit_for(flag, colmn) == 0 ? false : true
  end

  def flag_disabled?(flag, colmn = nil)
    colmn = determine_flag_colmn_for(flag) if colmn.nil?
    self.class.check_flag(flag, colmn)

    !flag_enabled?(flag, colmn)
  end

  def flags(colmn = DEFAULT_COLUMN_NAME)
    self[colmn] || 0
  end

  def set_flags(value, colmn = DEFAULT_COLUMN_NAME)
    self[colmn] = value
  end

  def all_flags(colmn = DEFAULT_COLUMN_NAME)
    flag_mapping[colmn].keys
  end

  def selected_flags(colmn = DEFAULT_COLUMN_NAME)
    all_flags(colmn).
      map { |flag_name| self.send(flag_name) ? flag_name : nil }.
      compact
  end

  # Useful for a form builder
  # use selected_#{column}= for custom column names.
  def selected_flags=(chosen_flags)
    unselect_all_flags
    chosen_flags.each do |selected_flag|
      if selected_flag.present?
        enable_flag(selected_flag.to_sym, DEFAULT_COLUMN_NAME)
      end
    end
  end

  def select_all_flags(colmn = DEFAULT_COLUMN_NAME)
    all_flags(colmn).each do |flag|
      enable_flag(flag, colmn)
    end
  end

  def unselect_all_flags(colmn = DEFAULT_COLUMN_NAME)
    all_flags(colmn).each do |flag|
      disable_flag(flag, colmn)
    end
  end

  def has_flag?(colmn = DEFAULT_COLUMN_NAME)
    not selected_flags(colmn).empty?
  end

  # returns true if successful
  # third parameter allows you to specify that `self` should
  #   also have its in-memory flag attribute updated.
  def update_flag!(flag, value, update_instance = false)
    truthy = FlagShihTzu::TRUE_VALUES.include?(value)
    sql = self.class.set_flag_sql(flag.to_sym, truthy)
    if update_instance
      if truthy
        enable_flag(flag)
      else
        disable_flag(flag)
      end
    end
    if (ActiveRecord::VERSION::MAJOR <= 3)
      self.class.
        update_all(sql, self.class.primary_key => id) == 1
    else
      self.class.
        where("#{self.class.primary_key} = ?", id).
        update_all(sql) == 1
    end
  end

  # Use with chained_flags_with to find records with specific flags
  #   set to the same values as on this record.
  # For a record that has sent_warm_up_email = true and the other flags false:
  #
  #     user.chained_flags_with_signature
  #     => [:sent_warm_up_email,
  #         :not_follow_up_called,
  #         :not_sent_final_email,
  #         :not_scheduled_appointment]
  #     User.chained_flags_with("flags", *user.chained_flags_with_signature)
  #     => the set of Users that have the same flags set as user.
  #
  def chained_flags_with_signature(colmn = DEFAULT_COLUMN_NAME, *args)
    flags_to_collect = args.empty? ? all_flags(colmn) : args
    truthy_and_chosen =
      selected_flags(colmn).
        select { |flag| flags_to_collect.include?(flag) }
    truthy_and_chosen.concat(
      collect_flags(*flags_to_collect) do |memo, flag|
        memo << "not_#{flag}".to_sym unless truthy_and_chosen.include?(flag)
      end
    )
  end

  # Use with a checkbox form builder, like rails' or simple_form's
  # :selected_flags, used in the example below, is a method defined
  #   by flag_shih_tzu for bulk setting flags like this:
  #
  #     form_for @user do |f|
  #       f.collection_check_boxes(:selected_flags,
  #         f.object.as_flag_collection("flags",
  #             :sent_warm_up_email,
  #             :not_follow_up_called),
  #         :first,
  #         :last)
  #     end
  #
  def as_flag_collection(colmn = DEFAULT_COLUMN_NAME, *args)
    flags_to_collect = args.empty? ? all_flags(colmn) : args
    collect_flags(*flags_to_collect) do |memo, flag|
      memo << [flag, flag_enabled?(flag, colmn)]
    end
  end

  private

  def collect_flags(*args)
    args.inject([]) do |memo, flag|
      yield memo, flag
      memo
    end
  end

  def get_bit_for(flag, colmn)
    flags(colmn) & self.class.flag_mapping[colmn][flag]
  end

  def determine_flag_colmn_for(flag)
    self.class.determine_flag_colmn_for(flag)
  end

end