<?php
// The MIT License (MIT)
//
// Copyright (C) 2013 TrendSpottr
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

// DEBUG - change the first paramter to wherever you want your debug output to go.
$fp = fopen('/tmp/webHookReceiverLog.txt', "a");

// retrieve the request's body and parse it as JSON
$body = @file_get_contents('php://input');
$event = json_decode($body);

if (($error = get_json_error()) !== false)
{
    fprintf($fp, "webHookReceiver: Invalid Json received: {$error}\n"); // DEBUG
    http_response_code(400);  // Return a "bad request" http error.
    exit;
}

fprintf($fp, "webHookReceiver: %s\n", $event->type); // DEBUG
if ($event->secret != 'topsecret!!')
{
    // The post did not contain the secret code configured for my webhook.  Fail the request
    http_response_code(401);
    fprintf($fp, "Invalid secret code (%s) received\n", $event->secret); // DEBUG
    exit;
}

if ($event->type == 'alert')
{
    // Got an alert webhook
    $alert = $event->data;

    date_default_timezone_set('America/Toronto');
    fprintf($fp, "Got Alert Event: %s\n%s\n", date('r'), print_r($alert, true));  // DEBUG
    date_default_timezone_set('UTC');
}

http_response_code(200);
exit;
// End of Mainline

// Helper Functions

// Function to provide informative error message if the json decode fails.
function get_json_error()
{
    switch (json_last_error())
    {
        case JSON_ERROR_NONE:
            return false;
            break;
        case JSON_ERROR_DEPTH:
            return 'Maximum stack depth exceeded';
            break;
        case JSON_ERROR_STATE_MISMATCH:
            return 'Underflow or the modes mismatch';
            break;
        case JSON_ERROR_CTRL_CHAR:
            return 'Unexpected control character found';
            break;
        case JSON_ERROR_SYNTAX:
            return 'Syntax error, malformed JSON';
            break;
        case JSON_ERROR_UTF8:
            return 'Malformed UTF-8 characters, possibly incorrectly encoded';
            break;
    }
    return 'Unknown error';
}