var _ = require('lodash');
var request = require('request');
var HttpStatus = require('http-status-codes');
var constants = require('./constants.js');

module.exports = function(
  logger,
  triggerDB,
  redisClient
) {
    this.module = 'utils';
    this.triggers = {};
    this.endpointAuth = process.env.ENDPOINT_AUTH;
    this.routerHost = process.env.ROUTER_HOST || 'localhost';
    this.worker = process.env.WORKER || "worker0";
    this.host = process.env.HOST_INDEX || 'host0';
    this.hostMachine = process.env.HOST_MACHINE;
    this.activeHost = 'host0'; //default value on init (will be updated for existing redis)
    this.redisClient = redisClient;
    this.redisHash = triggerDB.config.db + '_' + this.worker;
    this.redisKey = constants.REDIS_KEY;

    var retryAttempts = constants.RETRY_ATTEMPTS;
    var ddname = constants.DESIGN_DOC_NAME;
    var filter = constants.FILTER_FUNCTION;
    var utils = this;

    // Add a trigger: listen for changes and dispatch.
    this.createTrigger = function(dataTrigger) {
        var method = 'createTrigger';

        // both couch and cloudant should have their URLs in the username:password@host format
        var dbURL = `${dataTrigger.protocol}://${dataTrigger.user}:${dataTrigger.pass}@${dataTrigger.host}`;

        // add port if specified
        if (dataTrigger.port) {
            dbURL += ':' + dataTrigger.port;
        }

        try {
            var nanoConnection = require('nano')(dbURL);
            var triggeredDB = nanoConnection.use(dataTrigger.dbname);

            // Listen for changes on this database.
            var feed = triggeredDB.follow({since: dataTrigger.since, include_docs: false});
            if (dataTrigger.filter) {
                feed.filter = dataTrigger.filter;
            }
            if (dataTrigger.query_params) {
                feed.query_params = dataTrigger.query_params;
            }

            dataTrigger.feed = feed;
            utils.triggers[dataTrigger.id] = dataTrigger;

            feed.on('change', function (change) {
                if (utils.activeHost === utils.host) {
                    logger.info(method, 'Trigger', dataTrigger.id, 'got change from', dataTrigger.dbname);

                    var triggerHandle = utils.triggers[dataTrigger.id];
                    if (triggerHandle && (triggerHandle.maxTriggers === -1 || triggerHandle.triggersLeft > 0)) {
                        try {
                            utils.fireTrigger(dataTrigger.id, change);
                        } catch (e) {
                            logger.error(method, 'Exception occurred while firing trigger', dataTrigger.id, e);
                        }
                    }
                }
            });

            feed.follow();

            return new Promise(function(resolve, reject) {

                feed.on('error', function (err) {
                    logger.error(method,'Error occurred for trigger', dataTrigger.id, '(db ' + dataTrigger.dbname + '):', err);
                    reject(err);
                });

                feed.on('confirm', function (dbObj) {
                    logger.info(method, 'Added cloudant data trigger', dataTrigger.id, 'listening for changes in database', dataTrigger.dbname);
                    resolve(dataTrigger.id);
                });

            });

        } catch (err) {
            logger.info(method, 'caught an exception for trigger', dataTrigger.id, err);
            return Promise.reject(err);
        }

    };

    this.initTrigger = function(newTrigger) {
        var method = 'initTrigger';

        logger.info(method, 'create trigger', newTrigger.id, 'with the following args', newTrigger);

        var maxTriggers = newTrigger.maxTriggers || constants.DEFAULT_MAX_TRIGGERS;

        var trigger = {
            id: newTrigger.id,
            host: newTrigger.host,
            port: newTrigger.port,
            protocol: newTrigger.protocol || "https",
            dbname: newTrigger.dbname,
            user: newTrigger.user,
            pass: newTrigger.pass,
            apikey: newTrigger.apikey,
            since: newTrigger.since || "now",
            maxTriggers: maxTriggers,
            triggersLeft: maxTriggers,
            filter: newTrigger.filter,
            query_params: newTrigger.query_params
        };

        return trigger;
    };

    this.shouldDisableTrigger = function(statusCode) {
        return ((statusCode >= 400 && statusCode < 500) &&
            [HttpStatus.REQUEST_TIMEOUT, HttpStatus.TOO_MANY_REQUESTS].indexOf(statusCode) === -1);
    };

    this.disableTrigger = function(id, statusCode, message) {
        var method = 'disableTrigger';

        //only active/master provider should update the database
        if (utils.activeHost === utils.host) {
            triggerDB.get(id, function (err, existing) {
                if (!err) {
                    if (!existing.status || existing.status.active === true) {
                        var updatedTrigger = existing;
                        var status = {
                            'active': false,
                            'dateChanged': new Date().toISOString(),
                            'reason': {'kind': 'AUTO', 'statusCode': statusCode, 'message': message}
                        };
                        updatedTrigger.status = status;

                        triggerDB.insert(updatedTrigger, id, function (err) {
                            if (err) {
                                logger.error(method, 'there was an error while disabling', id, 'in database. ' + err);
                            }
                            else {
                                logger.info(method, 'trigger', id, 'successfully disabled in database');
                            }
                        });
                    }
                }
                else {
                    logger.error(method, 'there was an error while getting', id, 'from database', err);
                }
            });
        }
    };

    // Delete a trigger: stop listening for changes and remove it.
    this.deleteTrigger = function(triggerIdentifier) {
        var method = 'deleteTrigger';

        if (utils.triggers[triggerIdentifier].feed) {
            utils.triggers[triggerIdentifier].feed.stop();
        }

        delete utils.triggers[triggerIdentifier];
        logger.info(method, 'trigger', triggerIdentifier, 'successfully deleted from memory');
    };

    this.fireTrigger = function(triggerIdentifier, change) {
        var method = 'fireTrigger';

        var dataTrigger = utils.triggers[triggerIdentifier];
        var triggerObj = utils.parseQName(dataTrigger.id);

        var form = change;
        form.dbname = dataTrigger.dbname;

        logger.info(method, 'firing trigger', dataTrigger.id, 'with db update');

        var host = 'https://' + utils.routerHost + ':' + 443;
        var uri = host + '/api/v1/namespaces/' + triggerObj.namespace + '/triggers/' + triggerObj.name;
        var auth = dataTrigger.apikey.split(':');

        utils.postTrigger(dataTrigger, form, uri, auth, 0)
        .then(triggerId => {
            logger.info(method, 'Trigger', triggerId, 'was successfully fired');
            if (dataTrigger.triggersLeft === 0) {
                utils.disableTrigger(dataTrigger.id, undefined, 'Automatically disabled after reaching max triggers');
                logger.error(method, 'no more triggers left, disabled', dataTrigger.id);
            }
        }).catch(err => {
            logger.error(method, err);
        });
    };

    this.postTrigger = function(dataTrigger, form, uri, auth, retryCount) {
        var method = 'postTrigger';

        return new Promise(function(resolve, reject) {

            request({
                method: 'post',
                uri: uri,
                auth: {
                    user: auth[0],
                    pass: auth[1]
                },
                json: form
            }, function(error, response) {
                try {
                    logger.info(method, dataTrigger.id, 'http post request, STATUS:', response ? response.statusCode : response);
                    if (error || response.statusCode >= 400) {
                        logger.error(method, 'there was an error invoking', dataTrigger.id, response ? response.statusCode : error);
                        if (!error && utils.shouldDisableTrigger(response.statusCode)) {
                            //disable trigger
                            var message = 'Automatically disabled after receiving a ' + response.statusCode + ' status code when firing the trigger';
                            utils.disableTrigger(dataTrigger.id, response.statusCode, message);
                            reject('Disabled trigger ' + dataTrigger.id + ' due to status code: ' + response.statusCode);
                        }
                        else {
                            if (retryCount < retryAttempts ) {
                                var timeout = response && response.statusCode === 429 && retryCount === 0 ? 60000 : 1000 * Math.pow(retryCount + 1, 2);
                                logger.info(method, 'attempting to fire trigger again', dataTrigger.id, 'Retry Count:', (retryCount + 1));
                                setTimeout(function () {
                                    utils.postTrigger(dataTrigger, form, uri, auth, (retryCount + 1))
                                    .then(triggerId => {
                                        resolve(triggerId);
                                    }).catch(err => {
                                        reject(err);
                                    });
                                }, timeout);
                            } else {
                                reject('Unable to reach server to fire trigger ' + dataTrigger.id);
                            }
                        }
                    } else {
                        // only manage trigger fires if they are not infinite
                        if (dataTrigger.maxTriggers !== -1) {
                            dataTrigger.triggersLeft--;
                        }
                        logger.info(method, 'fired', dataTrigger.id, dataTrigger.triggersLeft, 'triggers left');
                        resolve(dataTrigger.id);
                    }
                }
                catch(err) {
                    reject('Exception occurred while firing trigger ' + err);
                }
            });
        });
    };

    this.initAllTriggers = function() {
        var method = 'initAllTriggers';

        logger.info(method, 'resetting system from last state');

        triggerDB.changes({ since: 0, include_docs: true, filter: ddname + '/' + filter, worker: utils.worker }, (err, changes) => {
            if (!err) {
                changes.results.forEach(function (change) {
                    var triggerIdentifier = change.id;
                    var doc = change.doc;

                    if (!doc.status || doc.status.active === true) {
                        //check if trigger still exists in whisk db
                        var triggerObj = utils.parseQName(triggerIdentifier);
                        var host = 'https://' + utils.routerHost + ':' + 443;
                        var triggerURL = host + '/api/v1/namespaces/' + triggerObj.namespace + '/triggers/' + triggerObj.name;
                        var auth = doc.apikey.split(':');

                        logger.info(method, 'Checking if trigger', triggerIdentifier, 'still exists');
                        request({
                            method: 'get',
                            url: triggerURL,
                            auth: {
                                user: auth[0],
                                pass: auth[1]
                            }
                        }, function (error, response) {
                            //disable trigger in database if trigger is dead
                            if (!error && utils.shouldDisableTrigger(response.statusCode)) {
                                var message = 'Automatically disabled after receiving a ' + response.statusCode + ' status code on init trigger';
                                utils.disableTrigger(triggerIdentifier, response.statusCode, message);
                                logger.error(method, 'trigger', triggerIdentifier, 'has been disabled due to status code:', response.statusCode);
                            }
                            else {
                                utils.createTrigger(utils.initTrigger(doc))
                                .then(triggerIdentifier => {
                                    logger.info(method, 'Trigger was added.', triggerIdentifier);
                                }).catch(err => {
                                    var message = 'Automatically disabled after receiving exception on init trigger: ' + err;
                                    utils.disableTrigger(triggerIdentifier, undefined, message);
                                    logger.error(method, 'Disabled trigger', triggerIdentifier, 'due to exception:', err);
                                });
                            }
                        });
                    }
                    else {
                        logger.info(method, 'ignoring trigger', triggerIdentifier, 'since it is disabled.');
                    }
                });
                utils.setupFollow(changes.last_seq);
            } else {
                logger.error(method, 'could not get latest state from database', err);
            }
        });
    };

    this.setupFollow = function(seq) {
        var method = 'setupFollow';

        try {
            var feed = triggerDB.follow({
                since: seq,
                include_docs: true,
                filter: ddname + '/' + filter,
                query_params: {worker: utils.worker}
            });

            feed.on('change', (change) => {
                var triggerIdentifier = change.id;
                var doc = change.doc;

                logger.info(method, 'got change for trigger', triggerIdentifier);

                if (utils.triggers[triggerIdentifier]) {
                    if (doc.status && doc.status.active === false) {
                        utils.deleteTrigger(triggerIdentifier);
                    }
                }
                else {
                    //ignore changes to disabled triggers
                    if (!doc.status || doc.status.active === true) {
                        utils.createTrigger(utils.initTrigger(doc))
                        .then(triggerIdentifier => {
                            logger.info(method, triggerIdentifier, 'created successfully');
                        }).catch(err => {
                            var message = 'Automatically disabled after receiving exception on create trigger: ' + err;
                            utils.disableTrigger(triggerIdentifier, undefined, message);
                            logger.error(method, 'Disabled trigger', triggerIdentifier, 'due to exception:', err);
                        });
                    }
                }
            });

            feed.on('error', function (err) {
                logger.error(method, err);
            });

            feed.follow();
        }
        catch (err) {
            logger.error(method, err);
        }
    };

    this.authorize = function(req, res, next) {
        var method = 'authorize';

        if (utils.endpointAuth) {

            if (!req.headers.authorization) {
                return utils.sendError(method, HttpStatus.BAD_REQUEST, 'Malformed request, authentication header expected', res);
            }

            var parts = req.headers.authorization.split(' ');
            if (parts[0].toLowerCase() !== 'basic' || !parts[1]) {
                return utils.sendError(method, HttpStatus.BAD_REQUEST, 'Malformed request, basic authentication expected', res);
            }

            var auth = new Buffer(parts[1], 'base64').toString();
            auth = auth.match(/^([^:]*):(.*)$/);
            if (!auth) {
                return utils.sendError(method, HttpStatus.BAD_REQUEST, 'Malformed request, authentication invalid', res);
            }

            var uuid = auth[1];
            var key = auth[2];

            var endpointAuth = utils.endpointAuth.split(':');

            if (endpointAuth[0] === uuid && endpointAuth[1] === key) {
                next();
            }
            else {
                logger.warn(method, 'Invalid key');
                return utils.sendError(method, HttpStatus.UNAUTHORIZED, 'Invalid key', res);
            }
        }
        else {
            next();
        }
    };

    this.sendError = function(method, code, message, res) {
        logger.error(method, message);
        res.status(code).json({error: message});
    };

    this.parseQName = function(qname, separator) {
        var parsed = {};
        var delimiter = separator || ':';
        var defaultNamespace = '_';
        if (qname && qname.charAt(0) === delimiter) {
            var parts = qname.split(delimiter);
            parsed.namespace = parts[1];
            parsed.name = parts.length > 2 ? parts.slice(2).join(delimiter) : '';
        } else {
            parsed.namespace = defaultNamespace;
            parsed.name = qname;
        }
        return parsed;
    };

    this.initRedis = function() {
        var method = 'initRedis';

        return new Promise(function(resolve, reject) {

            if (redisClient) {
                var subscriber = redisClient.duplicate();

                //create a subscriber client that listens for requests to perform swap
                subscriber.on("message", function (channel, message) {
                    if (message === 'host0' || message === 'host1') {
                        logger.info(method, message, "set to active host in channel", channel);
                        utils.activeHost = message;
                    }
                });

                subscriber.on("error", function (err) {
                    logger.error(method, 'Error connecting to redis', err);
                    reject(err);
                });

                subscriber.subscribe(utils.redisHash);

                redisClient.hgetAsync(utils.redisHash, utils.redisKey)
                .then(activeHost => {
                    return utils.initActiveHost(activeHost);
                })
                .then(resolve)
                .catch(err => {
                    reject(err);
                });
            }
            else {
                resolve();
            }
        });
    };

    this.initActiveHost = function(activeHost) {
        var method = 'initActiveHost';

        if (activeHost === null) {
            //initialize redis key with active host
            logger.info(method, 'redis hset', utils.redisHash, utils.redisKey, utils.activeHost);
            return redisClient.hsetAsync(utils.redisHash, utils.redisKey, utils.activeHost);
        }
        else {
            utils.activeHost = activeHost;
            return Promise.resolve();
        }
    };

};