require 'uri'
require 'cgi/util'
require 'webrick'

module Fluent::Plugin
  class ParseRequestBodyExtractor

    attr_reader :log

    def initialize(plugin, conf)
      @log = plugin.log

      if plugin.is_a?(Fluent::Plugin::Output)
        unless have_tag_option?(plugin)
          raise Fluent::ConfigError, "out_parse_request_body: At least one of remove_tag_prefix/remove_tag_suffix/add_tag_prefix/add_tag_suffix is required to be set."
        end
      end

      @key = plugin.key
      @only = plugin.only
      @except = plugin.except
      @discard_key = plugin.discard_key
      @add_field_prefix = plugin.add_field_prefix
      @permit_blank_key = plugin.permit_blank_key

      if @only
        @include_keys = @only.split(/\s*,\s*/).inject({}) do |hash, i|
          hash[i] = true
          hash
        end
      end

      if @except
        @exclude_keys = @except.split(/\s*,\s*/).inject({}) do |hash, i|
          hash[i] = true
          hash
        end
      end

      @map = {}
    # <record></record> directive
      conf.elements.select { |element| element.name == 'record' }.each { |element|
        element.each_pair { |k, v|
          element.has_key?(k) # to suppress unread configuration warning
          v = v[1..v.size-2] if quoted_value?(v)
          @map[k] = v
          validate_json = Proc.new {
            begin
              dummy_text = Yajl::Encoder.encode('dummy_text')
              Yajl::Parser.parse(v.gsub(REGEXP_PLACEHOLDER_SCAN, dummy_text))
            rescue Yajl::ParseError => e
              message = "parse_body: failed to parse '#{v}' as json."
              log.error message, error: e
              raise Fluent::ConfigError, message
            end
          }
          validate_json.call if json?(v.tr('\'"\\', ''))
        }
      }
    end

    def add_record_field(record)
      return record if @map.values.first.nil?
      @map.each do |record_key, value|
        record[record_key] = value
      end
      record
    end

    def add_query_params_field(record)
      return record unless record[@key]
      add_query_params(record[@key], record)
      record.delete(@key) if @discard_key
      record
    end

    private

    def have_tag_option?(plugin)
      plugin.remove_tag_prefix ||
        plugin.remove_tag_suffix ||
        plugin.add_tag_prefix    ||
        plugin.add_tag_suffix
    end

    def create_field_key(field_key)
      if add_field_prefix?
        "#{@add_field_prefix}#{field_key}"
      else
        field_key
      end
    end

    def add_field_prefix?
      !!@add_field_prefix
    end

    def permit_blank_key?
      @permit_blank_key
    end

    def add_query_params(body, record)
      return if body.nil?
      add_record_field(record)
      body.split('&').each do |pair|
        key, value = pair.split('=', 2).map { |i| CGI.unescape(i) }
        next if (key.nil? || key.empty?) && (!permit_blank_key? || value.nil? || value.empty?)
        key ||= ''
        value ||= ''

        new_key = create_field_key(key)
        if @only
          record[new_key] = value if @include_keys.has_key?(key)
        elsif @except
          record[new_key] = value if !@exclude_keys.has_key?(key)
        else
          record[new_key] = value
        end
      end
    end
  end
end