require 'uri'
require 'net/http'
require 'time'
require 'kconv'

$KCODE = 'UTF-8'

#
# = enokidu.rb
#
# Copyright; 2008 ODA Kaname [trashsuite@gmail.com]
# See also ; http://d.hatena.ne.jp/trashsuite/
#
# ウェブページ更新確認スクリプト
#
module Enokidu
  class UserAgent
    NAME    = 'Enokidu::Antenna'
    VERSION = '0.1.5'
  end

  class Antenna
    ERROR_CODE = {
      :connerr => 900,
      :noroute => 901,
      :sockerr => 902,
      :timeout => 903,
      :unknown => 999
    }

    def initialize(options = {})
      @timeout = options[:timeout] || 30
      @debug   = options[:debug] || false
      @request = Request.new(:timeout => @timeout, :debug   => @debug)
    end

    def detective(options = {})
      page    = options[:page]

      page.body ||= ''

      # タイトルを取得
      if page.title.empty?
        @request.get(page)
        page.last_modified_at = nil
      end

      # 初回は HEAD が使えるかどうか確認する
      page.method = 'HEAD' if page.last_modified_at.nil?

      page.updated = false
      case page.method
        when 'GET'  then @request.get(page)
        when 'HEAD' then @request.head(page)
        else             raise Request::InvalidMethod
      end
    rescue Request::Redirect
      retry
    rescue Request::InvalidHeadResponse
      page.method = 'GET'
      retry
    rescue Exception => exception
      case exception
        when Errno::ECONNREFUSED then page.code = ERROR_CODE[:connerr]
        when Errno::EHOSTUNREACH then page.code = ERROR_CODE[:noroute]
        when Timeout::Error      then page.code = ERROR_CODE[:timeout]
        when SocketError         then page.code = ERROR_CODE[:sockerr]
        else
          puts exception.class
          page.code = ERROR_CODE[:unknown]
      end
      page
    end
  end # Antenna

  class Request
    def initialize(options = {})
      @http_header = {'User-Agent' => Enokidu::UserAgent::NAME, 'Connection' => 'close'}
      @timeout = options[:timeout] || 30
      @debug   = options[:debug] || false
    end

    def get(page)
      page.method = 'GET'

      debug_print "sync by GET method"
      debug_print "initial sync"        if page.body.empty?
      debug_print "title #{page.title}" unless page.body.empty?

      uri  = URI.parse(page.uri)
      http = http_instance(uri)
      res  = nil

      # 更新状況を聞いてみる
      %w[If-Modified-Since, If-None-Match].each {|header|@http_header.delete header}
      if !page.title.empty? and !page.has_range?
        debug_print 'set If-Modified-Since'
        @http_header['If-Modified-Since'] = page.last_modified_at.httpdate if page.last_modified_at
        @http_header['If-None-Match']     = page.etag unless page.etag.empty?
      end

      timeout(@timeout) do
        res = http.get(mkpath(uri), @http_header)
      end

      page.code = res.code
      debug_print "Return code #{res.code}"

      # Redirect
      if res.code.match(/^30[12]$/)
        location = res['location'] || ''
        old_uri  = page.uri
        page.uri = location

        # ロケーションが空または不完全な場合
        if !location.empty? and !location.match(%r[^http://])
          uri = URI.parse(old_uri)
          path, query = location.split('?')
          uri.path  = path
          uri.query = query || ''
          page.uri  = uri.to_s
        end

        raise Redirect
      end

      # 親切な御仁に感謝しつつ終了
      if res.instance_of? Net::HTTPNotModified
        debug_print 'use If-Modified-Since'
        page.updated = false
        return page
      end

      # タイトルを抜き取る
      body = res.body.toutf8
      if page.title.empty?
        debug_print "get page title"
        page.title = body.scan(/<title>([^<]*)/im).to_s.strip
        page.title = 'no title' if page.title.empty?
      end

      body = if page.has_range?
        get_range(body, page.start_range, page.end_range)
      else
        body
      end.gsub(/<[^>]*>|\s|\n/, '')

      # 更新チェック
      debug_print "body size #{page.body.size} => #{body.size}"
      unless body.size == page.body.size
        page.last_modified_at = Time.now
        page.updated = true
      end

      page.body = body

      page
    end

    def head(page)
      page.method = 'HEAD'

      debug_print "sync by HEAD method"

      uri  = URI.parse(page.uri)
      http = http_instance(uri)
      res  = nil

      timeout(@timeout) do
        res = http.head(mkpath(uri), @http_header)
      end

      page.code = res.code
      debug_print "Return code #{res.code}"

      date = res['date']
      lm   = res['last-modified']
      etag = res['etag']

      # 初回は現在時刻をセット
      page.last_modified_at = Time.now if page.last_modified_at.nil?

      # Last-Modified で更新チェック
      raise InvalidHeadResponse if date == lm
      lm = Time.httpdate(lm).localtime if lm
      if lm and lm != page.last_modified_at.localtime
        page.last_modified_at = lm
        page.updated = true
      end

      # Etag で更新チェック
      if !lm and etag and page.etag != etag
        page.etag = etag
        page.last_modified_at = Time.now.localtime
        page.updated = true
      end

      # Last-Modified も Etag も使えない
      raise InvalidHeadResponse unless lm or etag

      page
    end

    private
    def mkpath(uri)
      uri.query ? [uri.path, uri.query].join('?') : uri.path
    end

    def http_instance(uri)
      http = Net::HTTP.new(uri.host, uri.port)
      http.use_ssl = true if uri.to_s.match(/^https/)
      http
    end

    def get_range(body, start_range, end_range)
      debug_print "use range"
      body.scan(/#{start_range}(.*)#{end_range}/im).to_s
    end

    def debug_print(content)
      puts content if @debug
    end

    class Redirect < StandardError; end
    class InvalidHeadResponse < StandardError; end
    class InvalidMethod < StandardError; end
  end # Request

  class Page
    PERMIT_OPTIONS = [:uri, :title, :method, :start_range, :end_range, :last_modified_at, :etag, :code, :body]
    PERMIT_OPTIONS.each {|opt|attr_accessor opt}
    attr_accessor :updated

    def initialize(options = {})
      @uri              = options[:uri] || ''
      @title            = options[:title] || ''
      @method           = options[:method] || 'GET'
      @start_range      = options[:start_range] || ''
      @end_range        = options[:end_range]   || ''
      @last_modified_at = options[:last_modified_at]
      @etag             = options[:etag] || ''
      @code             = options[:code] || 200
      @body             = options[:body] || ''

      raise ArgumentError if @uri.empty?
    end

    def code
      @code.to_i
    end

    def has_range?
      !start_range.empty? or !end_range.empty?
    end

    def updated?
      @updated || false
    end

    def valid?
      code == 200
    end
  end # Page
end # Enokidu