require 'json'
require 'openssl'
require 'net/http'
require 'net/https'
require 'time'
require 'stringio'
require 'zlib'
require 'uri'

require 'ddbcli/ddb-error'
require 'ddbcli/ddb-endpoint'

module DynamoDB
  class Client

    SERVICE_NAME = 'dynamodb'
    API_VERSION  = '2012-08-10'
    USER_AGENT   = "ddbcli/#{Version}"

    DEFAULT_TIMEOUT = 60

    attr_reader :region
    attr_accessor :timeout
    attr_accessor :retry_num
    attr_accessor :retry_intvl
    attr_accessor :debug

    def initialize(accessKeyId, secretAccessKey, endpoint_or_region)
      @accessKeyId = accessKeyId
      @secretAccessKey = secretAccessKey
      set_endpoint_and_region(endpoint_or_region)
      @timeout = DEFAULT_TIMEOUT
      @debug = false
      @retry_num = 3
      @retry_intvl = 10
    end

    def set_endpoint_and_region(endpoint_or_region)
      if endpoint_or_region.kind_of?(URI)
        @endpoint = endpoint_or_region
        @region = [@endpoint.host, @endpoint.port].join(':')
      else
        host, @region = DynamoDB::Endpoint.endpoint_and_region(endpoint_or_region)
        @endpoint = URI.parse("https://#{host}")
      end
    end

    def query(action, hash)
      retry_query do
        query0(action, hash)
      end
    end

    def query0(action, hash)
      if @debug
        $stderr.puts(<<EOS)
---request begin---
Action: #{action}
#{JSON.pretty_generate(hash)}
---request end---
EOS
      end

      req_body = JSON.dump(hash)
      date = Time.now.getutc

      headers = {
        'Content-Type'         => 'application/x-amz-json-1.0',
        'X-Amz-Target'         => "DynamoDB_#{API_VERSION.gsub('-', '')}.#{action}",
        'Content-Length'       => req_body.length.to_s,
        'User-Agent'           => USER_AGENT,
        'Host'                 => @endpoint.host,
        'X-Amz-Date'           => iso8601(date),
        'X-Amz-Content-Sha256' => hexhash(req_body),
        'Accept'               => '*/*',
        'Accept-Encoding'      => 'gzip',
      }

      headers['Authorization'] = authorization(date, headers, req_body)

      Net::HTTP.version_1_2
      http = Net::HTTP.new(@endpoint.host, @endpoint.port)

      if @endpoint.scheme == 'https'
        http.use_ssl = true
        http.verify_mode = OpenSSL::SSL::VERIFY_NONE
      end

      http.open_timeout = @timeout
      http.read_timeout = @timeout

      res_code = nil
      res_msg  = nil

      res_body = http.start do |w|
        req = Net::HTTP::Post.new('/', headers)
        req.body = req_body
        res = w.request(req)

        res_code = res.code.to_i
        res_msg  = res.message

        if res['Content-Encoding'] == 'gzip'
          StringIO.open(res.body, 'rb') do |f|
            Zlib::GzipReader.wrap(f).read
          end
        else
          res.body
        end
      end

      res_data = JSON.parse(res_body)

      if @debug
        $stderr.puts(<<EOS)
---response begin---
#{JSON.pretty_generate(res_data)}
---response end---
EOS
      end

      __type = res_data['__type']

      if res_code != 200 or __type
        errmsg = if __type
                   if @debug
                     "#{__type}: #{res_data['message'] || res_data['Message']}"
                   else
                     "#{res_data['message'] || res_data['Message']}"
                   end
                 else
                   "#{res_code} #{res_msg}"
                 end

        raise DynamoDB::Error.new(errmsg, res_data)
      end

      res_data
    end

    private

    def authorization(date, headers, body)
      headers = headers.sort_by {|name, value| name }

      # Task 1: Create a Canonical Request For Signature Version 4
      # http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html

      canonicalHeaders = headers.map {|name, value|
        name.downcase + ':' + value
      }.join("\n") + "\n"

      signedHeaders = headers.map {|name, value| name.downcase }.join(';')

      canonicalRequest = [
        'POST', # HTTPRequestMethod
        '/',    # CanonicalURI
        '',     # CanonicalQueryString
        canonicalHeaders,
        signedHeaders,
        hexhash(body),
      ].join("\n")

      # Task 2: Create a String to Sign for Signature Version 4
      # http://docs.aws.amazon.com/general/latest/gr/sigv4-create-string-to-sign.html

      credentialScope = [
        date.strftime('%Y%m%d'),
        @region,
        SERVICE_NAME,
        'aws4_request',
      ].join('/')

      stringToSign = [
        'AWS4-HMAC-SHA256', # Algorithm
        iso8601(date),      # RequestDate
        credentialScope,
        hexhash(canonicalRequest),
      ].join("\n")

      # Task 3: Calculate the AWS Signature Version 4
      # http://docs.aws.amazon.com/general/latest/gr/sigv4-calculate-signature.html

      kDate     = hmac('AWS4' + @secretAccessKey, date.strftime('%Y%m%d'))
      kRegion   = hmac(kDate, @region)
      kService  = hmac(kRegion, SERVICE_NAME)
      kSigning  = hmac(kService, 'aws4_request')
      signature = hexhmac(kSigning, stringToSign)

      'AWS4-HMAC-SHA256 Credential=%s/%s, SignedHeaders=%s, Signature=%s' % [
        @accessKeyId,
        credentialScope,
        signedHeaders,
        signature,
      ]
    end

    def iso8601(utc)
      utc.strftime('%Y%m%dT%H%M%SZ')
    end

    def hexhash(data)
      OpenSSL::Digest::SHA256.new.hexdigest(data)
    end

    def hmac(key, data)
      OpenSSL::HMAC.digest(OpenSSL::Digest::SHA256.new, key, data)
    end

    def hexhmac(key, data)
      OpenSSL::HMAC.hexdigest(OpenSSL::Digest::SHA256.new, key, data)
    end

    #def escape(str)
    #  CGI.escape(str.to_s).gsub('+', '%20')
    #end

    def retry_query
      retval = nil

      (@retry_num + 1).times do |i|
        begin
          retval = yield
          break
        rescue Errno::ETIMEDOUT => e
          raise e if i >= @retry_num
        rescue DynamoDB::Error => e
          if [/\bServiceUnavailable\b/i, /\bexceeded\b/i].any? {|i| i =~ e.message }
            raise e if i >= @retry_num
          else
            raise e
          end
        rescue Timeout::Error => e
          raise e if i >= @retry_num
        end

        wait_sec = @retry_intvl * (i + 1)

        if @debug
          $stderr.puts("Retry... (wait %d seconds)" % wait_sec)
        end

        sleep wait_sec
      end

      return retval
    end
  end # Client
end # DynamoDB