/* global fetch */
/* global Headers */
import {blob as createBlob, readAsArrayBuffer } from 'pouchdb-binary-utils';

function wrappedFetch() {
  var wrappedPromise = {};

  var promise = new Promise(function (resolve, reject) {
    wrappedPromise.resolve = resolve;
    wrappedPromise.reject = reject;
  });

  var args = new Array(arguments.length);

  for (var i = 0; i < args.length; i++) {
    args[i] = arguments[i];
  }

  wrappedPromise.promise = promise;

  Promise.resolve().then(function () {
    return fetch.apply(null, args);
  }).then(function (response) {
    wrappedPromise.resolve(response);
  }).catch(function (error) {
    wrappedPromise.reject(error);
  });

  return wrappedPromise;
}

function fetchRequest(options, callback) {
  var wrappedPromise, timer, response;

  var headers = new Headers();

  var fetchOptions = {
    method: options.method,
    credentials: 'include',
    headers: headers
  };

  if (options.json) {
    headers.set('Accept', 'application/json');
    headers.set('Content-Type', options.headers['Content-Type'] ||
      'application/json');
  }

  if (options.body &&
      options.processData &&
      typeof options.body !== 'string') {
    fetchOptions.body = JSON.stringify(options.body);
  } else if ('body' in options) {
    fetchOptions.body = options.body;
  } else {
    fetchOptions.body = null;
  }

  Object.keys(options.headers).forEach(function (key) {
    if (options.headers.hasOwnProperty(key)) {
      headers.set(key, options.headers[key]);
    }
  });

  wrappedPromise = wrappedFetch(options.url, fetchOptions);

  if (options.timeout > 0) {
    timer = setTimeout(function () {
      wrappedPromise.reject(new Error('Load timeout for resource: ' +
        options.url));
    }, options.timeout);
  }

  wrappedPromise.promise.then(function (fetchResponse) {
    response = {
      statusCode: fetchResponse.status
    };

    if (options.timeout > 0) {
      clearTimeout(timer);
    }

    if (response.statusCode >= 200 && response.statusCode < 300) {
      return options.binary ? fetchResponse.blob() : fetchResponse.text();
    }

    return fetchResponse.json();
  }).then(function (result) {
    if (response.statusCode >= 200 && response.statusCode < 300) {
      callback(null, response, result);
    } else {
      result.status = response.statusCode;
      callback(result);
    }
  }).catch(function (error) {
    if (!error) {
      // this happens when the listener is canceled
      error = new Error('canceled');
    }
    callback(error);
  });

  return {abort: wrappedPromise.reject};
}

function xhRequest(options, callback) {

  var xhr, timer;
  var timedout = false;

  var abortReq = function () {
    xhr.abort();
    cleanUp();
  };

  var timeoutReq = function () {
    timedout = true;
    xhr.abort();
    cleanUp();
  };

  var ret = {abort: abortReq};

  var cleanUp = function () {
    clearTimeout(timer);
    ret.abort = function () {};
    if (xhr) {
      xhr.onprogress = undefined;
      if (xhr.upload) {
        xhr.upload.onprogress = undefined;
      }
      xhr.onreadystatechange = undefined;
      xhr = undefined;
    }
  };

  if (options.xhr) {
    xhr = new options.xhr();
  } else {
    xhr = new XMLHttpRequest();
  }

  try {
    xhr.open(options.method, options.url);
  } catch (exception) {
    return callback(new Error(exception.name || 'Url is invalid'));
  }

  xhr.withCredentials = ('withCredentials' in options) ?
    options.withCredentials : true;

  if (options.method === 'GET') {
    delete options.headers['Content-Type'];
  } else if (options.json) {
    options.headers.Accept = 'application/json';
    options.headers['Content-Type'] = options.headers['Content-Type'] ||
      'application/json';
    if (options.body &&
        options.processData &&
        typeof options.body !== "string") {
      options.body = JSON.stringify(options.body);
    }
  }

  if (options.binary) {
    xhr.responseType = 'arraybuffer';
  }

  if (!('body' in options)) {
    options.body = null;
  }

  for (var key in options.headers) {
    if (options.headers.hasOwnProperty(key)) {
      xhr.setRequestHeader(key, options.headers[key]);
    }
  }

  if (options.timeout > 0) {
    timer = setTimeout(timeoutReq, options.timeout);
    xhr.onprogress = function () {
      clearTimeout(timer);
      if (xhr.readyState !== 4) {
        timer = setTimeout(timeoutReq, options.timeout);
      }
    };
    if (typeof xhr.upload !== 'undefined') { // does not exist in ie9
      xhr.upload.onprogress = xhr.onprogress;
    }
  }

  xhr.onreadystatechange = function () {
    if (xhr.readyState !== 4) {
      return;
    }

    var response = {
      statusCode: xhr.status
    };

    if (xhr.status >= 200 && xhr.status < 300) {
      var data;
      if (options.binary) {
        data = createBlob([xhr.response || ''], {
          type: xhr.getResponseHeader('Content-Type')
        });
      } else {
        data = xhr.responseText;
      }
      callback(null, response, data);
    } else {
      var err = {};
      if (timedout) {
        err = new Error('ETIMEDOUT');
        err.code = 'ETIMEDOUT';
      } else if (typeof xhr.response === 'string' && xhr.response !== '') {
        try {
          err = JSON.parse(xhr.response);
        } catch (e) {}
      }

      err.status = xhr.status;

      callback(err);
    }
    cleanUp();
  };

  if (options.body && (options.body instanceof Blob)) {
    readAsArrayBuffer(options.body, function (arrayBuffer) {
      xhr.send(arrayBuffer);
    });
  } else {
    xhr.send(options.body);
  }

  return ret;
}

function testXhr() {
  try {
    new XMLHttpRequest();
    return true;
  } catch (err) {
    return false;
  }
}

var hasXhr = testXhr();

function ajax(options, callback) {
  if (!process.env.FETCH && (hasXhr || options.xhr)) {
    return xhRequest(options, callback);
  } else {
    return fetchRequest(options, callback);
  }
}

export default ajax;