function RemoGeoLocation () {
    this._remoteSvrUrl = 'https://webapi.amap.com/html/geolocate.html'

    this._callbackList = []

    this._seqBase = 1

    this._frameReady = 0

    this._watchIdMap = {}
}

RemoGeoLocation.prototype = {
    _getSeq: function () {
        return this._seqBase++
    },
    _onRrameReady: function (callback) {
        if (this._frameReady === 0) {
            if (!this._frameReadyList) {
                this._frameReadyList = []
            }

            this._frameReadyList.push(callback)

            this._prepareIframe()

            return
        }

        callback.call(this)
    },
    _prepareIframe: function () {
        if (this._iframeWin) {
            return
        }

        var ifrm = document.createElement('iframe')

        ifrm.src =
            this._remoteSvrUrl + (this._remoteSvrUrl.indexOf('?') > 0 ? '&' : '?')

        ifrm.width = '0px'
        ifrm.height = '0px'
        ifrm.style.position = 'absolute'
        ifrm.style.display = 'none'

        var self = this

        var timeoutId = setTimeout(function () {
            self._frameReady = false

            self._callbackFrameReadyList()
        }, 5000)

        ifrm.onload = function () {
            clearTimeout(timeoutId)

            self._frameReady = true

            self._callbackFrameReadyList()

            ifrm.onload = null
        }

        document.body.appendChild(ifrm)

        this._iframeWin = ifrm.contentWindow

        window.addEventListener(
            'message',
            function (e) {
                if (self._remoteSvrUrl.indexOf(e.origin) !== 0) {
                    return
                }

                self._handleRemoteMsg(e.data)
            },
            false
        )
    },
    _callbackFrameReadyList: function () {
        if (this._frameReadyList) {
            var list = this._frameReadyList
            this._frameReadyList = null

            for (var i = 0, len = list.length; i < len; i++) {
                list[i].call(this, this._frameReady)
            }
        }
    },
    _pickCallback: function (seqNum, keepInList) {
        var callbackList = this._callbackList

        for (var i = 0, len = callbackList.length; i < len; i++) {
            var cbkInfo = callbackList[i]

            if (seqNum === cbkInfo.seq) {
                if (!keepInList) {
                    callbackList.splice(i, 1)
                }

                return cbkInfo
            }
        }
    },
    _handleRemoteMsg: function (msg) {
        var seqNum = msg.seq

        var cbkInfo = this._pickCallback(seqNum, !!msg.notify)

        if (cbkInfo) {
            cbkInfo.cbk.call(null, msg.error, msg.result)
        } else {
            console.warn('Receive remote msg: ', msg)
        }
    },
    _postMessage: function (cmd, args, callback, seq) {
        this._prepareIframe()

        var msg = {
            cmd: cmd,
            args: args,
            seq: seq || this._getSeq()
        }

        this._callbackList.push({
            cbk: callback,
            seq: msg.seq
        })

        this._onRrameReady(function () {
            if (this._frameReady === true) {
                try {
                    this._iframeWin.postMessage(msg, '*')
                } catch (e) {
                    this._pickCallback(msg.seq)

                    callback(e)
                }
            } else {
                this._pickCallback(msg.seq)

                callback({
                    message: 'iFrame load failed!'
                })
            }
        })
    },
    getCurrentPosition: function (succHandler, errHandler, options) {
        this._postMessage('getCurrentPosition', [options], function (err, result) {
            if (err) {
                if (errHandler) {
                    errHandler(err)
                }
                return
            }
            if (succHandler) {
                succHandler(result)
            }
        })
    },
    watchPosition: function (succHandler, errHandler, options) {
        var watchKey = 'wk' + this._getSeq()
        var cmdSeq = this._getSeq()

        this._watchIdMap[watchKey] = {
            stat: 0,
            seq: cmdSeq
        }

        var self = this

        this._postMessage(
            'watchPosition',
            [options],
            function (err, result) {
                var id = null

                if (result) {
                    id = result.id
                }

                var watchInfo = self._watchIdMap[watchKey]

                watchInfo.id = id
                watchInfo.stat = 1

                if (watchInfo.callbackList) {
                    var list = watchInfo.callbackList
                    watchInfo.callbackList = null

                    for (var i = 0, len = list.length; i < len; i++) {
                        list[i].call(self, id)
                    }
                }

                if (err) {
                    if (errHandler) {
                        errHandler(err)
                    }
                    return
                }

                if (succHandler) {
                    succHandler(result.pos)
                }
            },
            cmdSeq
        )

        return watchKey
    },
    clearWatch: function (watchKey, callback) {
        if (!this._watchIdMap[watchKey]) {
            callback('Id not exists: ' + watchKey)
            return
        }

        var watchInfo = this._watchIdMap[watchKey]

        var self = this

        function clearId (id) {
            self._postMessage('clearWatch', [id], function (err, result) {
                if (!err) {
                    self._pickCallback(watchInfo.seq)

                    delete self._watchIdMap[watchKey]
                }

                if (callback) {
                    callback(err, result)
                }
            })
        }

        if (watchInfo.stat < 1) {
            if (!watchInfo.callbackList) {
                watchInfo.callbackList = []
            }

            watchInfo.callbackList.push(function (id) {
                clearId(id)
            })
        } else {
            clearId(watchInfo.id)
        }
    }
}

export default RemoGeoLocation