# RETS4R Client
#
# Copyright (c) 2006 Scott Patterson <scott.patterson@digitalaun.com>
#
# This program is copyrighted free software by Scott Patterson.  You can
# redistribute it and/or modify it under the same terms of Ruby's license;
# either the dual license version in 2003 (see the file RUBYS), or any later
# version.
#
#  TODO: 1.0 Support (Adding this support should be fairly easy)
#  TODO: 2.0 Support (Adding this support will be very difficult since it is a completely different methodology)
#  TODO: Case-insensitive header

require 'digest/md5'
require 'net/http'
require 'uri'
require 'cgi'
require 'auth'
require 'client/dataobject'
require 'client/parsers/response_parser'
require 'thread'
require 'logger'

module RETS4R
  class Client
    COMPACT_FORMAT = 'COMPACT'

    METHOD_GET  = 'GET'
    METHOD_POST = 'POST'
    METHOD_HEAD = 'HEAD'

    DEFAULT_METHOD          = METHOD_GET
    DEFAULT_RETRY           = 2
    #DEFAULT_USER_AGENT      = 'RETS4R/0.8.2' # FIXME
    DEFAULT_USER_AGENT      = 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9b5) ' +
                                                            'Gecko/2008050509 Firefox/3.0b5'
    DEFAULT_RETS_VERSION    = '1.7'
    SUPPORTED_RETS_VERSIONS = ['1.5', '1.7']
    CAPABILITY_LIST   = [
            'Action',
            'ChangePassword',
            'GetObject',
            'Login',
            'LoginComplete',
            'Logout',
            'Search',
            'GetMetadata',
            'Update'
        ]

    # These are the response messages as defined in the RETS 1.5e2 and 1.7d6 specifications.
    # Provided for convenience and are used by the HTTPError class to provide more useful
    # messages.
    RETS_HTTP_MESSAGES = {
      '200' => 'Operation successful.',
      '400' => 'The request could not be understood by the server due to malformed syntax.',
      '401' => 'Either the header did not contain an acceptable Authorization or the ' +
                             'username/password was invalid. The server response MUST include a ' +
                             'WWW-Authenticate header field.',
      '402' => 'The requested transaction requires a payment which could not be authorized.',
      '403' => 'The server understood the request, but is refusing to fulfill it.',
      '404' => 'The server has not found anything matching the Request-URI.',
      '405' => 'The method specified in the Request-Line is not allowed for the resource ' +
                             'identified by the Request-URI.',
      '406' => 'The resource identified by the request is only capable of generating response ' +
                             'entities which have content characteristics not acceptable according to the accept ' +
                             'headers sent in the request.',
      '408' => 'The client did not produce a request within the time that the server was prepared to wait.',
      '411' => 'The server refuses to accept the request without a defined Content-Length.',
      '412' => 'Transaction not permitted at this point in the session.',
      '413' => 'The server is refusing to process a request because the request entity is larger than ' +
                             'the server is willing or able to process.',
      '414' => 'The server is refusing to service the request because the Request-URI is longer than ' +
                             'the server is willing to interpret. This error usually only occurs for a GET method.',
      '500' => 'The server encountered an unexpected condition which prevented it from fulfilling ' +
                             'the request.',
      '501' => 'The server does not support the functionality required to fulfill the request.',
      '503' => 'The server is currently unable to handle the request due to a temporary overloading ' +
                             'or maintenance of the server.',
      '505' => 'The server does not support, or refuses to support, the HTTP protocol version that ' +
                             'was used in the request message.',
    }

    attr_accessor :mimemap, :logger
    attr_reader   :format

    # Constructor
    #
    # Requires the URL to the RETS server and takes an optional output format. The output format
    # determines the type of data returned by the various RETS transaction methods.
    def initialize(url, format = COMPACT_FORMAT)
      @format   = format
      @urls     = {
                'Login' => URI.parse(url)
            }
      @nc       = 0
      @headers  = {
        'User-Agent'   => DEFAULT_USER_AGENT,
        'Accept'       => '*/*',
        'RETS-Version' => "RETS/#{DEFAULT_RETS_VERSION}",
        'RETS-Session-ID' => '0'
      }
      @request_method = DEFAULT_METHOD
      @semaphore      = Mutex.new

      @response_parser = RETS4R::Client::ResponseParser.new

      self.mimemap    = {
        'image/jpeg'  => 'jpg',
        'image/gif'   => 'gif'
      }

      if block_given?
        yield self
      end
    end

    # Assigns a block that will be called just before the request is sent.
    # This block must accept three parameters:
    # * self
    # * Net::HTTP instance
    # * Hash of headers
    #
    # The block's return value will be ignored.  If you want to prevent the request
    # to go through, raise an exception.
    #
    # == Example
    #
    #  client = RETS4R::Client.new(...)
    #  # Make a new pre_request_block that calculates the RETS-UA-Authorization header.
    #  client.set_pre_request_block do |rets, http, headers|
    #    a1 = Digest::MD5.hexdigest([headers["User-Agent"], @password].join(":"))
    #    if headers.has_key?("Cookie") then
    #      cookie = headers["Cookie"].split(";").map(&:strip).select {|c| c =~ /rets-session-id/i}
    #      cookie = cookie ? cookie.split("=").last : ""
    #    else
    #      cookie = ""
    #    end
    #
    #    parts = [a1, "", cookie, headers["RETS-Version"]]
    #    headers["RETS-UA-Authorization"] = "Digest " + Digest::MD5.hexdigest(parts.join(":"))
    #  end
    def set_pre_request_block(&block)
      @pre_request_block = block
    end

    # We only allow external read access to URLs because they are internally set based on the
    # results of various queries.
    def urls
      @urls
    end

    def set_header(name, value)
      if value.nil? then
        @headers.delete(name)
      else
        @headers[name] = value
      end

      logger.debug("Set header '#{name}' to '#{value}'") if logger
    end

    def get_header(name)
      @headers[name]
    end

    def set_user_agent(name)
      set_header('User-Agent', name)
    end

    def get_user_agent
      get_header('User-Agent')
    end

    def set_rets_version(version)
      if (SUPPORTED_RETS_VERSIONS.include? version)
        set_header('RETS-Version', "RETS/#{version}")
      else
        raise Unsupported.new("The client does not support RETS version '#{version}'.")
      end
    end

    def get_rets_version
      (get_header('RETS-Version') || "").gsub("RETS/", "")
    end

    def set_request_method(method)
      @request_method = method
    end

    def get_request_method
        # Basic Authentication
        #
      @request_method
    end

    # Provide more Ruby-like attribute accessors instead of get/set methods
    alias_method :user_agent=, :set_user_agent
    alias_method :user_agent, :get_user_agent
    alias_method :request_method=, :set_request_method
    alias_method :request_method, :get_request_method
    alias_method :rets_version=, :set_rets_version
    alias_method :rets_version, :get_rets_version

    #### RETS Transaction Methods ####
    #
    # Most of these transaction methods mirror the RETS specification methods, so if you are
    # unsure what they mean, you should check the RETS specification. The latest version can be
    # found at http://www.rets.org

    # Attempts to log into the server using the provided username and password.
    #
    # If called with a block, the results of the login action are yielded,
    # and logout is called when the block returns.  In that case, #login
    # returns the block's value. If called without a block, returns the
    # result.
    #
    # As specified in the RETS specification, the Action URL is called and
    # the results made available in the #secondary_results accessor of the
    # results object.
    def login(username, password) #:yields: login_results
      @username = username
      @password = password

      # We are required to set the Accept header to this by the RETS 1.5 specification.
      set_header('Accept', '*/*')

      response = request(@urls['Login'])

      # Parse response to get other URLS
      results = @response_parser.parse_key_value(response.body)

      if (results.success?)
        CAPABILITY_LIST.each do |capability|
          next unless results.response[capability]

          uri = URI.parse(results.response[capability])

          if uri.absolute?
            @urls[capability] = uri
          else
            base = @urls['Login'].clone
            base.path = results.response[capability]
            @urls[capability] = base
          end
        end

        logger.debug("Capability URL List: #{@urls.inspect}") if logger
      else
        raise LoginError.new(response.message + "(#{results.reply_code}: #{results.reply_text})")
      end

      # Perform the mandatory get request on the action URL.
      results.secondary_response = perform_action_url

      # We only yield
      if block_given?
        begin
          yield results
        ensure
          self.logout
        end
      else
        results
      end
    end

    # Logs out of the RETS server.
    def logout()
      # If no logout URL is provided, then we assume that logout is not necessary (not to
      # mention impossible without a URL). We don't throw an exception, though, but we might
      # want to if this becomes an issue in the future.

      request(@urls['Logout']) if @urls['Logout']
    end

    # Requests Metadata from the server. An optional type and id can be specified to request
    # subsets of the Metadata. Please see the RETS specification for more details on this.
    # The format variable tells the server which format to return the Metadata in. Unless you
    # need the raw metadata in a specified format, you really shouldn't specify the format.
    #
    # If called with a block, yields the results and returns the value of the block, or
    # returns the metadata directly.
    def get_metadata(type = 'METADATA-SYSTEM', id = '*')
      xml = download_metadata(type, id)

      result = @response_parser.parse_metadata(xml, @format)

      if block_given?
        yield result
      else
        result
      end
    end

    def download_metadata(type, id)
      header = {
        'Accept' => 'text/xml,text/plain;q=0.5'
      }

      data = {
        'Type'   => type,
        'ID'     => id,
        'Format' => @format
      }

      request(@urls['GetMetadata'], data, header).body
    end

    # Performs a GetObject transaction on the server. For details on the arguments, please see
    # the RETS specification on GetObject requests.
    #
    # This method either returns an Array of DataObject instances, or yields each DataObject
    # as it is created. If a block is given, the number of objects yielded is returned.
    def get_object(resource, type, id, location = 0) #:yields: data_object
      header = {
        'Accept' => mimemap.keys.join(',')
      }

      data = {
        'Resource' => resource,
        'Type'     => type,
        'ID'       => id,
        'Location' => location.to_s
      }

      response = request(@urls['GetObject'], data, header)
      results = block_given? ? 0 : []

      if response['content-type'].include?('text/xml')
        # This probably means that there was an error.
        # Response parser will likely raise an exception.
        rr = @response_parser.parse_object_response(response.body)
        return rr
      elsif response['content-type'].include?('multipart/parallel')
        content_type = process_content_type(response['content-type'])

#        TODO: log this
#        puts "SPLIT ON #{content_type['boundary']}"
        boundary = content_type['boundary']
        if boundary =~ /\s*'([^']*)\s*/
          boundary = $1
        end
        parts = response.body.split("\r\n--#{boundary}")

        parts.shift # Get rid of the initial boundary

#        TODO: log this
#        puts "GOT PARTS #{parts.length}"

        parts.each do |part|
          (raw_header, raw_data) = part.split("\r\n\r\n")

#          TODO: log this
#          puts raw_data.nil?
          next unless raw_data

          data_header = process_header(raw_header)
          data_object = DataObject.new(data_header, raw_data)

          if block_given?
            yield data_object
            results += 1
          else
            results << data_object
          end
        end
      else
        info = {
          'content-type' => response['content-type'], # Compatibility shim.  Deprecated.
          'Content-Type' => response['content-type'],
          'Object-ID'    => response['Object-ID'],
          'Content-ID'   => response['Content-ID']
        }

        if response['Transfer-Encoding'].to_s.downcase == "chunked" || response['Content-Length'].to_i > 100 then
          data_object = DataObject.new(info, response.body)
          if block_given?
            yield data_object
            results += 1
          else
            results << data_object
          end
        end
      end

      results
    end

    # Peforms a RETS search transaction. Again, please see the RETS specification for details
    # on what these parameters mean. The options parameter takes a hash of options that will
    # added to the search statement.
    def search(search_type, klass, query, options = false)
      header = {}

      # Required Data
      data = {
        'SearchType' => search_type,
        'Class'      => klass,
        'Query'      => query,
        'QueryType'  => 'DMQL2',
        'Format'     => format,
        'Count'      => '0'
      }

      # Options
      #--
      # We might want to switch this to merge!, but I've kept it like this for now because it
      # explicitly casts each value as a string prior to performing the search, so we find out now
      # if can't force a value into the string context. I suppose it doesn't really matter when
      # that happens, though...
      #++
      options.each { |k,v| data[k] = v.to_s } if options

      response = request(@urls['Search'], data, header)

      results = @response_parser.parse_results(response.body, @format)

      if block_given?
        yield results
      else
        return results
      end
    end

    def count(search_type, klass, query)
      header = {}
      data = {
        'SearchType' => search_type,
        'Class'      => klass,
        'Query'      => query,
        'QueryType'  => 'DMQL2',
        'Format'     => format,
        'Count'      => '2'
      }
      response = request(@urls['Search'], data, header)
      result = @response_parser.parse_count(response.body)
      return result
    end

    private

    # Copied from http.rb
    def basic_encode(account, password)
      'Basic ' + ["#{account}:#{password}"].pack('m').delete("\r\n")
    end

    # XXX: This is crap. It does not properly handle quotes.
    def process_content_type(text)
      content = {}

      field_start = text.index(';')

      content['content-type'] = text[0 ... field_start].strip
      fields = text[field_start..-1]

      parts = text.split(';')

      parts.each do |part|
        (name, value) = part.gsub(/\"/, '').split('=')

        content[name.strip] = value ? value.strip : value
      end

      content
    end

    # Processes the HTTP header
    #--
    # Could we switch over to using CGI for this?
    #++
    def process_header(raw)
      header = {}

      raw.each do |line|
        (name, value) = line.split(':')

        header[name.strip] = value.strip if name && value
      end

      header
    end

    # Given a hash, it returns a URL encoded query string.
    def create_query_string(hash)
      parts = hash.map {|key,value| "#{CGI.escape(key)}=#{CGI.escape(value)}"}
      return parts.join('&')
    end

    # This is the primary transaction method, which the other public methods make use of.
    # Given a url for the transaction (endpoint) it makes a request to the RETS server.
    #
    #--
    # This needs to be better documented, but for now please see the public transaction methods
    # for how to make use of this method.
    #++
    def request(url, data = {}, header = {}, method = @request_method, retry_auth = DEFAULT_RETRY)
      response = ''

      @semaphore.lock

      http = Net::HTTP.new(url.host, url.port)
      http.read_timeout = 600

      if logger && logger.debug?
        http.set_debug_output HTTPDebugLogger.new(logger)
      end

      http.start do |http|
        begin
          uri = url.path

          if ! data.empty? && method == METHOD_GET
            uri += "?#{create_query_string(data)}"
          end

          headers = @headers
          headers.merge(header) unless header.empty?

          @pre_request_block.call(self, http, headers) if @pre_request_block

          logger.debug(headers.inspect) if logger

          @semaphore.unlock

          post_data = data.map {|k,v| "#{CGI.escape(k.to_s)}=#{CGI.escape(v.to_s)}" }.join('&') if method == METHOD_POST
          response  = method == METHOD_POST ? http.post(uri, post_data, headers) :
                                              http.get(uri, headers)

          @semaphore.lock

          if response.code == '401'
            # Authentication is required
            raise AuthRequired
          elsif response.code.to_i >= 300
            # We have a non-successful response that we cannot handle
            @semaphore.unlock if @semaphore.locked?
            raise HTTPError.new(response)
          else
            cookies = []
            if set_cookies = response.get_fields('set-cookie') then
              set_cookies.each do |cookie|
                cookies << cookie.split(";").first
              end
            end
            set_header('Cookie', cookies.join("; ")) unless cookies.empty?
            set_header('RETS-Session-ID', response['RETS-Session-ID']) if response['RETS-Session-ID']
          end
        rescue AuthRequired
          @nc += 1

          if retry_auth > 0
            retry_auth -= 1
                      auth = Auth.authenticate(response,
                                                                         @username,
                                                                         @password,
                                                                         url.path,
                                                                         method,
                                                                         @headers['RETS-Request-ID'],
                                                                          get_user_agent,
                                                                         @nc)
            set_header('Authorization', auth)
            retry
          else
            @semaphore.unlock if @semaphore.locked?
            raise LoginError.new(response.message)
          end
        end

        logger.debug(response.body) if logger
      end

      @semaphore.unlock if @semaphore.locked?

      return response
    end

    # If an action URL is present in the URL capability list, it calls that action URL and returns the
    # raw result. Throws a generic RETSException if it is unable to follow the URL.
    def perform_action_url
      begin
        if @urls.has_key?('Action')
          return request(@urls['Action'], {}, {}, METHOD_GET)
        end
      rescue
        raise RETSException.new("Unable to follow action URL: '#{$!}'.")
      end
    end

    # Provides a proxy class to allow for net/http to log its debug to the logger.
    class HTTPDebugLogger
      def initialize(logger)
        @logger = logger
      end

      def <<(data)
        @logger.debug(data)
      end
    end

    #### Exceptions ####

    # This exception should be thrown when a generic client error is encountered.
    class ClientException < Exception
    end

    # This exception should be thrown when there is an error with the parser, which is
    # considered a subcomponent of the RETS client. It also includes the XML data that
    # that was being processed at the time of the exception.
    class ParserException < ClientException
      attr_accessor :file
    end

    # The client does not currently support a specified action.
    class Unsupported < ClientException
    end

    # The HTTP response returned by the server indicates that there was an error processing
    # the request and the client cannot continue on its own without intervention.
    class HTTPError < ClientException
      attr_accessor :http_response

      # Takes a HTTPResponse object
      def initialize(http_response)
        self.http_response = http_response
      end

      # Shorthand for calling HTTPResponse#code
      def code
        http_response.code
      end

      # Shorthand for calling HTTPResponse#message
      def message
        http_response.message
      end

      # Returns the RETS specification message for the HTTP response code
      def rets_message
        Client::RETS_HTTP_MESSAGES[code]
      end

      def to_s
        "#{code} #{message}: #{rets_message}"
      end
    end

    # A general RETS level exception was encountered. This would include HTTP and RETS
    # specification level errors as well as informative mishaps such as authentication being
    # required for access.
    class RETSException < RuntimeError
    end

    # There was a problem with logging into the RETS server.
    class LoginError < RETSException
    end

    # For internal client use only, it is thrown when the a RETS request is made but a password
    # is prompted for.
    class AuthRequired < RETSException
    end

    # A RETS transaction failed
    class RETSTransactionException < RETSException; end

    # Search Transaction Exceptions
    class UnknownQueryFieldException < RETSTransactionException; end
    class NoRecordsFoundException < RETSTransactionException; end
    class InvalidSelectException < RETSTransactionException; end
    class MiscellaneousSearchErrorException < RETSTransactionException; end
    class InvalidQuerySyntaxException < RETSTransactionException; end
    class UnauthorizedQueryException < RETSTransactionException; end
    class MaximumRecordsExceededException < RETSTransactionException; end
    class TimeoutException < RETSTransactionException; end
    class TooManyOutstandingQueriesException < RETSTransactionException; end
    class DTDVersionUnavailableException < RETSTransactionException; end

    # GetObject Exceptions
    class InvalidResourceException < RETSTransactionException; end
    class InvalidTypeException < RETSTransactionException; end
    class InvalidIdentifierException < RETSTransactionException; end
    class NoObjectFoundException < RETSTransactionException; end
    class UnsupportedMIMETypeException < RETSTransactionException; end
    class UnauthorizedRetrievalException < RETSTransactionException; end
    class ResourceUnavailableException < RETSTransactionException; end
    class ObjectUnavailableException < RETSTransactionException; end
    class RequestTooLargeException < RETSTransactionException; end
    class TimeoutException < RETSTransactionException; end
    class TooManyOutstandingRequestsException < RETSTransactionException; end
    class MiscellaneousErrorException < RETSTransactionException; end

    EXCEPTION_TYPES = {
      # Search Transaction Reply Codes
      20200 => UnknownQueryFieldException,
      20201 => NoRecordsFoundException,
      20202 => InvalidSelectException,
      20203 => MiscellaneousSearchErrorException,
      20206 => InvalidQuerySyntaxException,
      20207 => UnauthorizedQueryException,
      20208 => MaximumRecordsExceededException,
      20209 => TimeoutException,
      20210 => TooManyOutstandingQueriesException,
      20514 => DTDVersionUnavailableException,

      # GetObject Reply Codes
      20400 => InvalidResourceException,
      20401 => InvalidTypeException,
      20402 => InvalidIdentifierException,
      20403 => NoObjectFoundException,
      20406 => UnsupportedMIMETypeException,
      20407 => UnauthorizedRetrievalException,
      20408 => ResourceUnavailableException,
      20409 => ObjectUnavailableException,
      20410 => RequestTooLargeException,
      20411 => TimeoutException,
      20412 => TooManyOutstandingRequestsException,
      20413 => MiscellaneousErrorException

    }

  end
end