var irc = require('irc');
var express = require('express');
var bodyParser = require('body-parser');
var request = require('request');
var cheerio = require('cheerio');

var config = require('./config');

// Bind recipients to notifications.
var channels = [];
var hookToChannel = {};
for (var who in config.reports) {
    if (who.indexOf('#') === 0)
        channels.push(who);

    var hooks = config.reports[who];
    for (var i = 0; i < hooks.length; i++) {
        var hook = hooks[i];
        (hookToChannel[hook] = hookToChannel[hook] || []).push(who);
    }
}

// Sanitize projectUrl
if (typeof config.projectUrl !== 'undefined') {
    var url = '' + config.projectUrl;
    if (url[url.length - 1] !== '/') {
        url += '/';
    }
    config.projectUrl = url;
}

var client = new irc.Client(config.server, config.nick, {
    debug: config.debug || false,
    channels: channels,
    userName: config.userName,
    realName: config.realName,
    retryDelay: 120000
});

var app = express();

app.use(bodyParser.json()); // for parsing application/json
app.use(bodyParser.urlencoded({ extended: true })); // for parsing application/x-www-form-urlencoded

var shortenURL = function(url, callback) { callback(url); };

if (config.lstu) {
    if (config.lstu[config.lstu.length - 1] !== '/') {
        config.lstu += '/';
    }

    shortenURL = function shortenURL(url, callback) {
        request(config.lstu + 'a', { method: 'POST', form: { lsturl: url, format: 'json' } }, function (err, res, body) {
            try {
                body = JSON.parse(body);
            } catch(err) {
                body = {err: 'cant parse JSON'};
            }
            if (err || !body.success) {
                console.error("Error when shortening link: ",
                              res ? "(status: " + res.statusCode + ")" : "(no response)",
                              '\nerror:', err,
                              '\nfailure reason:', body.msg);
                callback(url);
            } else {
                callback(body.short);
            }
        });
    };
}

function conjugatePast(verb) {
    // Make action displayable (e.g., open -> opened, close -> closed, merge -> merged).
    return verb + (verb.substr(-1) === 'e' ? '' : 'e') + 'd';
}

var lastIssueActions = {};

var handlers = {

    push: function(body, say) {
        var user = body.user_username;
        var projectName = body.project.name;

        var commits = body.commits;
        var numCommits = body.total_commits_count;

        var branchName = body.ref.replace('refs/heads/', '');
        var found = false;
        for (var i = 0; i < config.branches.length; i++) {
            if (branchName === config.branches[i]) {
                found = true;
                break;
            }
        }
        if (!found)
            return;

        var msg = null;
        if (!numCommits) {
            // Special case: a branch was created or deleted.
            var action = 'created';
            if (body.after === '0000000000000000000000000000000000000000')
                action = 'deleted';
            msg = user + ' ' + action + ' branch ' + branchName + ' on ' + projectName + '.';
            say(msg);
        } else {
            var maybeS = numCommits === 1 ? '' : 's';
            var lastCommit = commits[commits.length - 1];
            var lastCommitMessage = lastCommit.message.trim().split('\n')[0].trim();
            shortenURL(lastCommit.url, function(shortUrl) {
                msg = user + ' pushed on ' + projectName + '@' + branchName + ': ';
                if (numCommits === 1) {
                    msg += lastCommitMessage + ' ' + shortUrl;
                } else {
                    msg += commits.length + ' commits (last: ' + lastCommitMessage + ') ' + shortUrl;
                }
                say(msg);
            });
        }
    },

    issue: function(body, say) {
        var user = body.user.username;
        var projectName = body.project.name;

        var issue = body.object_attributes;
        var issueNumber = issue.iid;
        var issueTitle = issue.title.trim();
        var issueState = issue.state;
        var url = issue.url;

        // Don't trigger the hook on issue's update;
        if (issue.action === 'update')
            return;

        // Don't trigger several close event.
        if (issue.action === lastIssueActions[issue.iid])
            return;
        lastIssueActions[issue.iid] = issue.action;

        var displayedAction = conjugatePast(issue.action);

        shortenURL(url, function(shortUrl) {
            var msg = user + ' ' + displayedAction + ' issue #' + issueNumber + ' ("' + issueTitle + '") on ' + projectName + ' ' + shortUrl;
            say(msg);
        });
    },

    merge_request: function(body, say) {
        var user = body.user.username;

        var request = body.object_attributes;

        var projectName = request.target.name;

        var from = request.source_branch;
        var to = request.target_branch;

        var id = request.iid;
        var title = request.title.trim();
        var url = request.url;
        var state = request.state;

        // Don't trigger the hook on mr's updates.
        if (request.action === 'update') {
            return;
        }

        var displayedAction = conjugatePast(request.action);

        shortenURL(url, function(shortUrl) {
            var msg = user + ' ' + displayedAction + ' MR !' + id + ' (' + from + '->' + to + ': ' + title + ') ' +
                      ' on ' + projectName + '; ' + shortUrl;
            say(msg);
        });
    },

    build: function(body, say) {

        var id = body.build_id;
        var status = body.build_status;

        var isFinished = body.build_finished_at !== null;
        var duration = body.build_duration;

        var projectName = body.project_name;
        var stage = body.build_stage;

        var msg = projectName + ': build #' + id + ' (' + stage + ') changed status: ' + status;
        if (isFinished)
            msg += ' (finished in ' + duration + ' seconds.)';

        say(msg);
    }

};

function makeSay(body) {
    var whom = hookToChannel[body.object_kind] || [];
    return function say(msgs) {
        if (!whom.length) {
            return;
        }
        if (msgs) {
            if (msgs instanceof Array) {
                for (var i = 0; i < msgs.length; i++)
                    client.say(whom, msgs[i]);
            } else {
                client.say(whom, msgs);
            }
        }
    };
}

app.post('/', function(req, res) {
    var body = req.body || {};

    var msgs = null;
    if (body.object_kind && handlers[body.object_kind])
        handlers[body.object_kind](body, makeSay(body));
    else
        console.log("Unexpected object_kind:", body.object_kind);

    res.sendStatus(200);
});

var chanMessageCounters = {};

var mentionCache = {};

function makeCacheKey(isIssue, id, chan) {
    return chan + '-' + (isIssue ? 'issue' : 'mr') + id;
}

function fetch_and_say(isIssue, id, from, chan) {
    var cacheKey = makeCacheKey(isIssue, id, chan);

    // Don't mention if it's been already mentioned in the last
    // config.cacheDuration messages.
    var mentionCounter = mentionCache[cacheKey];
    if (typeof mentionCounter !== 'undefined') {
        if (chanMessageCounters[chan] - mentionCounter <= config.cacheDuration) {
            return;
        }
    }

    var path, text_prefix;
    if (isIssue) {
        path = 'issues/';
        text_prefix = 'Issue #';
    } else {
        path = 'merge_requests/';
        text_prefix = 'Merge request !';
    }

    var to = chan === config.nick ? from : chan;

    var url = config.projectUrl + path + id;
    request(url, function(err, res, body) {
        if (res && res.statusCode === 200) {
            var title = cheerio.load(body)('head title').text();
            if (title.length) {
                client.say(to, title);
                client.say(to, url);
            } else {
                client.say(to, text_prefix + id + ": " + url);
            }
            mentionCache[cacheKey] = chanMessageCounters[chan];
        }
    });
}

var issueRegexp = /(?:\s|^)#(\d+)/g;
var mergeRequestRegexp = /(?:\s|^)!(\d+)/g;

function testIssueRegexp(r) {
    function test(input, expected) {
        var match = r.exec(input);
        var found = 0;
        while (match !== null) {
            if (match[1] !== expected[found].toString()) {
                throw new Error('should have found ' + expected[found]);
            }
            found++;
            match = r.exec(input);
        }
        if (expected.length !== found) {
            throw new Error('missing expected occurrences: ' + expected.length + 'vs expected ' + found);
        }
        r.lastIndex = 0;
    }

    test('hello #301 jeej', [301]);
    test('#302 lol', [302]);
    test('lol#303', []);
    test('lol #303', [303]);
    test('\t#304', [304]);
    test(' #305', [305]);
    test('hello#305 #306 jeej#42 #307 #lol # #308', [306, 307, 308]);
};

testIssueRegexp(issueRegexp);

app.listen(config.port, config.hostname, function() {
    console.log('gitlab-to-irc running.');

    client.on('message', function(from, chan, message) {
        chanMessageCounters[chan] = (chanMessageCounters[chan] || 0) + 1;

        var matches = null;
        while ((matches = issueRegexp.exec(message)) !== null) {
            var issueId = matches[1];
            fetch_and_say(true, issueId, from, chan);
        }

        while ((matches = mergeRequestRegexp.exec(message)) !== null) {
            var mrId = matches[1];
            fetch_and_say(false, mrId, from, chan);
        }
    });
});