var Github = {
    params: {},

    setParams: function (params) {
        if (typeof params !== 'object') {
            return;
        }
        Github.params = params;
    },

    setProxy: function (HTTPProxy) {
        Github.HTTPProxy = HTTPProxy;
    },

    urlCheckFormat: function (url) {

        if (typeof url === 'string' && !url.endsWith('/')) {
            url += '/';
        }

        if (url.indexOf('http://') === -1 && url.indexOf('https://') === -1) {
            url = 'https://' + url;
        }

        return url;
    },

    createProblemURL: function (zabbix_url, triggerid, eventid, event_source) {
        var problem_url = zabbix_url;

        if (event_source === '0') {
            problem_url += 'tr_events.php?triggerid=' + triggerid + '&eventid=' + eventid;
        }

        return problem_url;
    },

    request: function (method, url, data) {
        ['token', 'user_agent'].forEach(function (field) {
            if (typeof Github.params !== 'object' || typeof Github.params[field] === 'undefined' || Github.params[field] === '') {
                throw 'Required Github param is not set: "' + field + '".';
            }
        });

        var response,
            request = new HttpRequest();

        request.addHeader('User-Agent: ' + Github.params.user_agent);
        request.addHeader('Accept: application/vnd.github.v3+json');
        request.addHeader('Authorization: token ' + Github.params.token);

        if (typeof Github.HTTPProxy !== 'undefined' && Github.HTTPProxy !== '') {
            request.setProxy(Github.HTTPProxy);
        }

        if (typeof data !== 'undefined') {
            data = JSON.stringify(data);
        }

        Zabbix.log(4, '[ Github Webhook ] Sending request: ' + url + ((typeof data === 'string')
            ? ('\n' + data)
            : ''));

        switch (method) {
            case 'post':
                response = request.post(url, data);
                break;

            case 'patch':
                response = request.patch(url, data);
                break;

            default:
                throw 'Unsupported HTTP request method: ' + method;
        }

        Zabbix.log(4, '[ Github Webhook ] Received response with status code ' +
            request.getStatus() + '\n' + response);

        if (response !== null) {
            try {
                response = JSON.parse(response);
            }
            catch (error) {
                Zabbix.log(4, '[ Github Webhook ] Failed to parse response received from Github');
                response = null;
            }
        }

        if (typeof response !== 'object') {
            throw 'Failed to process response received from Github. Check debug log for more information.';
        }

        if (request.getStatus() < 200 || request.getStatus() >= 300) {
            var message = 'Request failed with status code ' + request.getStatus();

            if (response.message) {
                message += ': ' + response.message;
            }

            throw message + ' Check debug log for more information.';
        }

        return response;
    }
};

try {
    var params = JSON.parse(value),
        github = {},
        url = '',
        data = {},
        comment_data,
        result = { tags: {} },
        required_params = [
            'alert_subject', 'alert_message', 'event_source', 'event_value',
            'event_update_status', 'event_recovery_value', 'event_severity',
            'event_id', 'trigger_id', 'zabbix_url',
            'github_token', 'github_url', 'github_user_agent'
        ],
        method = 'post',
        process_tags = true;

    Object.keys(params)
        .forEach(function (key) {
            if (key.startsWith('github_')) {
                github[key.substring(7)] = params[key];
            }
            else if (required_params.indexOf(key) !== -1 && params[key] === '') {
                throw 'Parameter "' + key + '" can\'t be empty.';
            }
        });

    if ([0, 1, 2, 3].indexOf(parseInt(params.event_source)) === -1) {
        throw 'Incorrect "event_source" parameter given: ' + params.event_source + '\nMust be 0-3.';
    }

    // Check {EVENT.VALUE} for trigger-based and internal events.
    if (params.event_value !== '0' && params.event_value !== '1'
        && (params.event_source === '0' || params.event_source === '3')) {
        throw 'Incorrect "event_value" parameter given: ' + params.event_value + '\nMust be 0 or 1.';
    }

    // Check {EVENT.UPDATE.STATUS} only for trigger-based events.
    if (params.event_update_status !== '0' && params.event_update_status !== '1' && params.event_source === '0') {
        throw 'Incorrect "event_update_status" parameter given: ' + params.event_update_status + '\nMust be 0 or 1.';
    }

    if (params.event_source !== '0' && params.event_recovery_value === '0') {
        throw 'Recovery operations are supported only for trigger-based actions.';
    }

    if (typeof params.zabbix_url !== 'string' || params.zabbix_url.trim() === '' || params.zabbix_url === '{$ZABBIX.URL}') {
        throw 'Field "zabbix_url" cannot be empty.';
    }

    // Check for backslash in the end of url and schema.
    github.url = Github.urlCheckFormat(github.url);
    params.zabbix_url = Github.urlCheckFormat(params.zabbix_url);

    // Default url for creating issue
    url = github.url + 'repos/' + github.repo + '/issues';

    data.title = params.alert_subject;
    data.body = params.alert_message;
    data.labels = [
        { name: "Zabbix" }
    ];

    // Adding label corresponding to trigger severity in Zabbix.
    if (params.event_severity !== 'undefined' && params.event_source === '0') {
        data.labels.push({ name: params.event_severity });
    }

    // In case of update or resolve event.
    if (params.event_source === '0' && (params.event_value === '0' || params.event_update_status === '1')) {
        process_tags = false;
        method = 'patch';
        url = github.url + 'repos/' + github.repo + '/issues/' + github.issue_number;
        comment_data = Object.assign({}, data);
        delete data.body;
    } else {
        problem_url = Github.createProblemURL(params.zabbix_url, params.trigger_id, params.event_id, params.event_source);
        data.body += '\nEvent details in Zabbix: [' + problem_url + '](' + problem_url + ')';
    }

    Github.setParams(github);
    Github.setProxy(params.HTTPProxy);

    var response = Github.request(method, url, data);

    // Leave a comment if comment_data present.
    if (typeof comment_data === 'object') {
        url = github.url + 'repos/' + github.repo + '/issues/' + github.issue_number + '/comments';
        Github.request("post", url, comment_data);
    }

    if (process_tags) {
        result.tags.__zbx_github_issue_number = response.number;
        result.tags.__zbx_github_repo = github.repo;
        result.tags.__zbx_github_link = response.html_url;
    }

    Zabbix.log(4, '[ Github Webhook ] Result: ' + JSON.stringify(result));
    return JSON.stringify(result);
}
catch (error) {
    Zabbix.log(4, '[ Github Webhook ] ERROR: ' + error);
    throw 'Sending failed: ' + error;
}