require 'thread'
require 'weakref'
require 'rest-core'

module RestCore::Client
  include RestCore

  Unserializable = [Proc, Method, IO]

  def self.included mod
    # honor default attributes
    src = mod.members.map{ |name|
      <<-RUBY
        def #{name}
          if (r = super).nil?
            self.#{name} = default_#{name}
          else
            r
          end
        end

        def default_#{name} app=app
          if self.class.respond_to?("default_#{name}")
            self.class.default_#{name}      # old class default style
          elsif app.respond_to?(:#{name})
            app.#{name}({})                 # middleware instance value
          elsif app.respond_to?(:app)
            default_#{name}(app.app)        # walk into next app
          else
            nil
          end
        end
        private :default_#{name}
      RUBY
    }
    accessor = Module.new
    accessor.module_eval(src.join("\n"), __FILE__, __LINE__)
    mod.const_set('Accessor', accessor)
    mod.send(:include, accessor)
  end

  attr_reader :app, :dry, :promises
  attr_accessor :error_callback
  def initialize o={}
    @app ||= self.class.builder.to_app # lighten! would reinitialize anyway
    @dry ||= self.class.builder.to_app(Dry)
    @promises = []  # don't record any promises in lighten!
    @mutex    = nil # for locking promises, lazily initialized
                    # for serialization
    @error_callback = nil
    o.each{ |key, value| send("#{key}=", value) if respond_to?("#{key}=") }
  end

  def attributes
    Hash[each_pair.map{ |k, v| [k, send(k)] }]
  end

  def inspect
    fields = if size > 0
               ' ' + attributes.map{ |k, v|
                 "#{k}=#{v.inspect.sub(/(?<=.{12}).{4,}/, '...')}"
               }.join(', ')
             else
               ''
             end
    "#<struct #{self.class.name}#{fields}>"
  end

  def lighten! o={}
    attributes.each{ |k, v| vv = case v;
                                   when  Hash; lighten_hash(v)
                                   when Array; lighten_array(v)
                                   when *Unserializable; nil
                                   else v
                                 end
                            send("#{k}=", vv)}
    initialize(o)
    @app, @dry = lighten_app(app), lighten_app(dry)
    self
  end

  def lighten o={}
    dup.lighten!(o)
  end

  def wait
    self.class.wait(promises, mutex)
    self
  end

  def url path, query={}, opts={}
    dry.call(build_env({
      REQUEST_PATH  => path,
      REQUEST_QUERY => query,
      DRY           => true}.merge(opts)), &Middleware.method(:request_uri))
  end

  def get    path, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :get   ,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  }.merge(opts), &cb)
  end

  def delete path, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :delete,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  }.merge(opts), &cb)
  end

  def head path, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :head  ,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  ,
       RESPONSE_KEY    => RESPONSE_HEADERS}.merge(opts), &cb)
  end

  def options path, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :options,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  ,
       RESPONSE_KEY    => RESPONSE_HEADERS}.merge(opts), &cb)
  end

  def post   path, payload={}, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :post  ,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  ,
       REQUEST_PAYLOAD => payload}.merge(opts), &cb)
  end

  def put    path, payload={}, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :put   ,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  ,
       REQUEST_PAYLOAD => payload}.merge(opts), &cb)
  end

  def patch  path, payload={}, query={}, opts={}, &cb
    request(
      {REQUEST_METHOD  => :patch ,
       REQUEST_PATH    => path   ,
       REQUEST_QUERY   => query  ,
       REQUEST_PAYLOAD => payload}.merge(opts), &cb)
  end

  def event_source path, query={}, opts={}
    self.class.event_source_class.new(self, path, query, opts)
  end

  def request env, app=app
    if block_given?
      request_full(env, app){ |response| yield(response[response_key(env)]) }
    else
      request_full(env, app)[response_key(env)]
    end
  end

  def request_full env, app=app, &k
    response = app.call(build_env({ASYNC => !!k}.merge(env))) do |res|
      (k || RC.id).call(request_complete(res))
    end

    give_promise(response)

    if block_given?
      self
    else
      response
    end
  end

  def give_promise response
    # under ASYNC callback, response might not be a response hash
    # in that case (maybe in a user created engine), Client#wait
    # won't work because we have no way to track the promise.
    if response.kind_of?(Hash) && response[PROMISE].kind_of?(Promise)
      weak_promise = WeakRef.new(response[PROMISE])
      self.class.give_promise(weak_promise)
      self.class.give_promise(weak_promise, promises, mutex)
    end

    response
  end

  def build_env env={}
    default_env.merge(
      Middleware.string_keys(attributes).merge(Middleware.string_keys(env)))
  end

  def default_env
    {REQUEST_METHOD  => :get,
     REQUEST_PATH    => '/' ,
     REQUEST_QUERY   => {}  ,
     REQUEST_PAYLOAD => {}  ,
     REQUEST_HEADERS => {}  ,
     FAIL            => []  ,
     LOG             => []  ,
     CLIENT          => self}
  end
  # ------------------------ instance ---------------------



  private
  def request_complete res
    if err = res[FAIL].find{ |f| f.kind_of?(Exception) }
      RC::Promise.set_backtrace(err) unless err.backtrace
      error_callback.call(err) if error_callback
      if res[ASYNC]
        if res[HIJACK]
          res.merge(RESPONSE_SOCKET => err)
        else
          res.merge(RESPONSE_BODY => err)
        end
      else
        raise err
      end
    else
      res
    end
  end

  def mutex
    @mutex ||= Mutex.new
  end

  def response_key opts
    opts[RESPONSE_KEY] ||
      if opts[HIJACK] then RESPONSE_SOCKET else RESPONSE_BODY end
  end

  def lighten_hash hash
    Hash[hash.map{ |(key, value)|
      case value
        when  Hash; lighten_hash(value)
        when Array; lighten_array(value)
        when *Unserializable; [key, nil]
        else [key, value]
      end
    }]
  end

  def lighten_array array
    array.map{ |value|
      case value
        when  Hash; lighten_hash(value)
        when Array; lighten_array(value)
        when *Unserializable; nil
        else value
      end
    }.compact
  end

  def lighten_app app
    members = if app.class.respond_to?(:members)
                app.class.members.map{ |key|
                  case value = app.send(key, {})
                    when  Hash; lighten_hash(value)
                    when Array; lighten_array(value)
                    when *Unserializable; nil
                    else value
                  end
                }
              else
                []
              end

    if app.respond_to?(:app) && app.app
      app.class.new(lighten_app(app.app), *members)
    else
      app.class.new(*members)
    end
  end
end