// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

library base_client;

import 'dart:async';
import 'dart:convert';
import 'dart:typed_data';

import 'base_request.dart';
import 'client.dart';
import 'exception.dart';
import 'request.dart';
import 'response.dart';
import 'streamed_response.dart';
import 'utils.dart';

/// The abstract base class for an HTTP client. This is a mixin-style class;
/// subclasses only need to implement [send] and maybe [close], and then they
/// get various convenience methods for free.
abstract class BaseClient implements Client {
  /// Sends an HTTP HEAD request with the given headers to the given URL, which
  /// can be a [Uri] or a [String].
  ///
  /// For more fine-grained control over the request, use [send] instead.
  Future<Response> head(url, {Map<String, String> headers}) =>
    _sendUnstreamed("HEAD", url, headers);

  /// Sends an HTTP GET request with the given headers to the given URL, which
  /// can be a [Uri] or a [String].
  ///
  /// For more fine-grained control over the request, use [send] instead.
  Future<Response> get(url, {Map<String, String> headers}) =>
    _sendUnstreamed("GET", url, headers);

  /// Sends an HTTP POST request with the given headers and body to the given
  /// URL, which can be a [Uri] or a [String].
  ///
  /// [body] sets the body of the request. It can be a [String], a [List<int>]
  /// or a [Map<String, String>]. If it's a String, it's encoded using
  /// [encoding] and used as the body of the request. The content-type of the
  /// request will default to "text/plain".
  ///
  /// If [body] is a List, it's used as a list of bytes for the body of the
  /// request.
  ///
  /// If [body] is a Map, it's encoded as form fields using [encoding]. The
  /// content-type of the request will be set to
  /// `"application/x-www-form-urlencoded"`; this cannot be overridden.
  ///
  /// [encoding] defaults to UTF-8.
  ///
  /// For more fine-grained control over the request, use [send] instead.
  Future<Response> post(url, {Map<String, String> headers, body,
      Encoding encoding}) =>
    _sendUnstreamed("POST", url, headers, body, encoding);

  /// Sends an HTTP PUT request with the given headers and body to the given
  /// URL, which can be a [Uri] or a [String].
  ///
  /// [body] sets the body of the request. It can be a [String], a [List<int>]
  /// or a [Map<String, String>]. If it's a String, it's encoded using
  /// [encoding] and used as the body of the request. The content-type of the
  /// request will default to "text/plain".
  ///
  /// If [body] is a List, it's used as a list of bytes for the body of the
  /// request.
  ///
  /// If [body] is a Map, it's encoded as form fields using [encoding]. The
  /// content-type of the request will be set to
  /// `"application/x-www-form-urlencoded"`; this cannot be overridden.
  ///
  /// [encoding] defaults to UTF-8.
  ///
  /// For more fine-grained control over the request, use [send] instead.
  Future<Response> put(url, {Map<String, String> headers, body,
      Encoding encoding}) =>
    _sendUnstreamed("PUT", url, headers, body, encoding);

  /// Sends an HTTP DELETE request with the given headers to the given URL,
  /// which can be a [Uri] or a [String].
  ///
  /// For more fine-grained control over the request, use [send] instead.
  Future<Response> delete(url, {Map<String, String> headers}) =>
    _sendUnstreamed("DELETE", url, headers);

  /// Sends an HTTP GET request with the given headers to the given URL, which
  /// can be a [Uri] or a [String], and returns a Future that completes to the
  /// body of the response as a String.
  ///
  /// The Future will emit a [ClientException] if the response doesn't have a
  /// success status code.
  ///
  /// For more fine-grained control over the request and response, use [send] or
  /// [get] instead.
  Future<String> read(url, {Map<String, String> headers}) {
    return get(url, headers: headers).then((response) {
      _checkResponseSuccess(url, response);
      return response.body;
    });
  }

  /// Sends an HTTP GET request with the given headers to the given URL, which
  /// can be a [Uri] or a [String], and returns a Future that completes to the
  /// body of the response as a list of bytes.
  ///
  /// The Future will emit an [ClientException] if the response doesn't have a
  /// success status code.
  ///
  /// For more fine-grained control over the request and response, use [send] or
  /// [get] instead.
  Future<Uint8List> readBytes(url, {Map<String, String> headers}) {
    return get(url, headers: headers).then((response) {
      _checkResponseSuccess(url, response);
      return response.bodyBytes;
    });
  }

  /// Sends an HTTP request and asynchronously returns the response.
  ///
  /// Implementers should call [BaseRequest.finalize] to get the body of the
  /// request as a [ByteStream]. They shouldn't make any assumptions about the
  /// state of the stream; it could have data written to it asynchronously at a
  /// later point, or it could already be closed when it's returned. Any
  /// internal HTTP errors should be wrapped as [ClientException]s.
  Future<StreamedResponse> send(BaseRequest request);

  /// Sends a non-streaming [Request] and returns a non-streaming [Response].
  Future<Response> _sendUnstreamed(String method, url,
      Map<String, String> headers, [body, Encoding encoding]) {
    return syncFuture(() {
      if (url is String) url = Uri.parse(url);
      var request = new Request(method, url);

      if (headers != null) request.headers.addAll(headers);
      if (encoding != null) request.encoding = encoding;
      if (body != null) {
        if (body is String) {
          request.body = body;
        } else if (body is List) {
          request.bodyBytes = body;
        } else if (body is Map) {
          request.bodyFields = body;
        } else {
          throw new ArgumentError('Invalid request body "$body".');
        }
      }

      return send(request);
    }).then(Response.fromStream);
  }

  /// Throws an error if [response] is not successful.
  void _checkResponseSuccess(url, Response response) {
    if (response.statusCode < 400) return;
    var message = "Request to $url failed with status ${response.statusCode}";
    if (response.reasonPhrase != null) {
      message = "$message: ${response.reasonPhrase}";
    }
    if (url is String) url = Uri.parse(url);
    throw new ClientException("$message.", url);
  }

  /// Closes the client and cleans up any resources associated with it. It's
  /// important to close each client when it's done being used; failing to do so
  /// can cause the Dart process to hang.
  void close() {}
}