api.php

<?php
/*
    api.php
    AUTHOR: Lukas Bischof
    CREATED ON: 24.10.2016

    BRIEF: This file is the central connection point between the client, which displays the slides, and the database.
    HOW TO USE:
        Use the api via a normal Ajax call. Every call must contain a GET parameter, called "call". These call params exist:

            PARAM	MEANING
            1		This call returns all the screens available
            2		Load the playlist data for a screen. Send an extra GET argument called "screen" with the ID of the screen.
            3		Ask for any changes and return the changes, if there are some. Receives all the timestamps, which have to have the following JSON structure:
                    {
                        <playlist ID>: {
                            <slide ID>: <slide timestamp>,
                            <...>
                        }
                    }

                    Response structure:
                    [
                        [<Any changes / additions>],
                        [<Any deletions>]
                    ]

                    If the deletion array contains a playlist with no slides then the client should remove the whole playlist and all its slides

        Every call will return a JSON object with the information requested.
        If a call fails, an error will be returned. The error has the following structure:
            {
                "error": < An error title >,
                "desc": < A human readable description of the error. Use it for logging >,
                "code": < An error code to identify the error in code. See the class ErrorCodes for more information. >
            }
*/

include_once 'db.php';
include_once 'httpCodes.php';

class HTTPStatusCode
{
    const Ok = 200;
    const BadRequest = 400;
    const MethodNotAllowed = 405;
    const InternalError = 500;
    const CustomNoDataAvailable = 528;

    public static function getStr($code)
    {
        return strtohttpcode($code);
    }
}

class ErrorCodes
{
    const NO_CALL_PARAM = 1;
    const CALL_PARAM_INVALID = 2;
    const CALL_DOESNT_EXIST = 3;
    const CANT_RETREIVE_SCREENS = 4;
    const LACK_OF_ARGUMENTS = 5;
    const INVALID_ARGUMENT_TYPE = 6;
    const UNEXPECTED_ERROR = 7;
    const NO_DATA = 8;
}

function errObj($title, $desc, $code)
{
    return array(
        'error' => $title,
        'desc' => $desc,
        'code' => $code
    );
}

function complete($status, $obj)
{
    $msg = "HTTP/1.1 $status " . HTTPStatusCode::getStr($status);
    header($msg);
    die(json_encode($obj));
}

if (!isset($_GET['call'])) {
    complete(HTTPStatusCode::BadRequest, errObj('Invalid call', 'The call parameter is missing', ErrorCodes::NO_CALL_PARAM));
}

$call = $_GET['call'];
if (!is_numeric($call)) {
    complete(HTTPStatusCode::BadRequest, errObj('Invalid call', 'The call parameter is invalid', ErrorCodes::CALL_PARAM_INVALID));
}

$db = new Database();
switch ($call) {
    case 1:
        $list = $db->getScreensList();
        if ($list !== NULL && $list !== FALSE) {
            complete(HTTPStatusCode::Ok, $list);
        } else {
            complete(HTTPStatusCode::InternalError, errObj('Can\'t retrieve screens', 'Due to a database error, the screens list can\' be retrieved', ErrorCodes::CANT_RETREIVE_SCREENS));
        }
        break;

    case 2:
        if (!isset($_GET['screen'])) {
            complete(HTTPStatusCode::BadRequest, errObj('Missing screen param', 'Missing GET param "screen" with the screen ID', ErrorCodes::LACK_OF_ARGUMENTS));
        }

        $screenID = $_GET['screen'];
        if (!is_numeric($screenID)) {
            complete(HTTPStatusCode::BadRequest, errObj('Screen param not an ID', 'Screen param must be an ID integer', ErrorCodes::INVALID_ARGUMENT_TYPE));
        } else if ($screenID < 0) {
            complete(HTTPStatusCode::BadRequest, errObj('Screen param not valid', 'The screen ID is malformed', ErrorCodes::INVALID_ARGUMENT_TYPE));
        }

        $globalPlaylist = $db->getGlobalPlaylistForScreen($screenID);
        if (!$globalPlaylist || empty($globalPlaylist)) {
            $globalPlaylist = null;
        } else {
            $globalPlaylist = $globalPlaylist[0];

            if ($globalPlaylist['active'] == '0') {
                $globalPlaylist = NULL;
            }
        }

        $playlist = $db->getPlaylistForScreen($screenID);
        if ($playlist != FALSE) {
            $localPlaylist = null;
            if (!empty($playlist)) {
                $localPlaylist = $playlist[0];

                if ($localPlaylist['active'] == '0') {
                    $localPlaylist = NULL;
                }
            }

            $ret = array();
            if ($localPlaylist) {
                $slides = $db->getSlidesFromPlaylist($localPlaylist['ID']);

                $localPlaylist['slides'] = $slides;
                array_push($ret, $localPlaylist);
            }

            if ($globalPlaylist) {
                $slides = $db->getSlidesFromPlaylist($globalPlaylist['ID']);

                $globalPlaylist['slides'] = $slides;
                array_push($ret, $globalPlaylist);
            }

            complete(HTTPStatusCode::Ok, $ret);
        } else {
            if ($playlist === FALSE) {
                complete(HTTPStatusCode::InternalError, errObj('Can\'t retrieve playlist', 'An internal DB error occurred', ErrorCodes::UNEXPECTED_ERROR));
            } else if (empty($playlist)) {
                if ($globalPlaylist) {
                    $slides = $db->getSlidesFromPlaylist($globalPlaylist['ID']);

                    $globalPlaylist['slides'] = $slides;
                    complete(HTTPStatusCode::Ok, array($globalPlaylist));
                } else {
                    complete(HTTPStatusCode::CustomNoDataAvailable, errObj('There\'s no playlist specified for this screen', 'Please assign an active playlist to this screen', ErrorCodes::NO_DATA));
                }
            }
        }

        break;

    case 3:
        if (!isset($_GET['screen'])) {
            complete(HTTPStatusCode::BadRequest, errObj('Missing screen param', 'Missing GET param "screen" with the screen ID', ErrorCodes::LACK_OF_ARGUMENTS));
        }

        $screenID = $_GET['screen'];
        if (!is_numeric($screenID)) {
            complete(HTTPStatusCode::BadRequest, errObj('Screen param not an ID', 'Screen param must be an ID integer', ErrorCodes::INVALID_ARGUMENT_TYPE));
        } else if ($screenID < 0) {
            complete(HTTPStatusCode::BadRequest, errObj('Screen param not valid', 'The screen ID is malformed', ErrorCodes::INVALID_ARGUMENT_TYPE));
        }

        if (!isset($_GET['timestamps'])) {
            complete(HTTPStatusCode::BadRequest, errObj('Missing timestamps param', 'Missing GET param "timestamps" with the current timestamps of the client', ErrorCodes::LACK_OF_ARGUMENTS));
        }

        $timestamps = $_GET['timestamps'];
        try {
            $timestamps = json_decode($timestamps, true);
            if ($timestamps === NULL) {
                complete(HTTPStatusCode::BadRequest, errObj('Invalid timestamps param', 'The timestamps param has an invalid JSON encoding', ErrorCodes::INVALID_ARGUMENT_TYPE));
            }
        } catch (Exception $e) {
            complete(HTTPStatusCode::BadRequest, errObj('Invalid timestamps param', 'The timestamps param has an invalid JSON encoding', ErrorCodes::INVALID_ARGUMENT_TYPE));
        }

        $globalPlaylist = $db->getGlobalPlaylistForScreen($screenID);
        $playlist = $db->getPlaylistForScreen($screenID);

        $localPlaylist = null;
        if (!empty($playlist)) {
            if ($playlist[0]['active'] == '1') {
                $localPlaylist = $playlist[0];
            }
        }

        if (!empty($globalPlaylist)) {
            if ($globalPlaylist[0]['active'] == '1') {
                $globalPlaylist = $globalPlaylist[0];
            } else {
                $globalPlaylist = NULL;
            }
        }

        $deletions = array();
        $changes = array();

        // ******* CHANGES / ADDITIONS *******

        /// **** LOCAL CHANGES ****
        if ($localPlaylist) {
            if (!array_key_exists($localPlaylist['ID'], $timestamps)) {
                // screen playlist changed

                $localChanges = $db->getSlidesFromPlaylist($localPlaylist['ID']);
                $localPlaylist['slides'] = $localChanges;

                array_push($changes, $localPlaylist);
            } else {
                $localChanges = $db->getChangedSlidesForPlaylist($localPlaylist['ID'], $timestamps[$localPlaylist['ID']]);

                if ($localChanges && !empty($localChanges)) {
                    $localPlaylist['slides'] = $localChanges;
                    array_push($changes, $localPlaylist);
                }
            }
        }


        /// **** GLOBAL CHANGES ****
        if ($globalPlaylist) {
            if (!array_key_exists($globalPlaylist['ID'], $timestamps)) {
                // screen playlist changed

                $globalChanges = $db->getSlidesFromPlaylist($globalPlaylist['ID']);
                $globalPlaylist['slides'] = $globalChanges;

                array_push($changes, $globalPlaylist);
            } else {
                $globalChanges = $db->getChangedSlidesForPlaylist($globalPlaylist['ID'], $timestamps[$globalPlaylist['ID']]);

                if ($globalChanges && !empty($globalChanges)) {
                    $globalPlaylist['slides'] = $globalChanges;
                    array_push($changes, $globalPlaylist);
                }
            }
        }


        /// ******* DELETIONS *******
        $localPlaylistHasChanged = $localPlaylist && !array_key_exists($localPlaylist['ID'], $timestamps);
        $globalPlaylistHasChanged = $globalPlaylist && !array_key_exists($globalPlaylist['ID'], $timestamps);

        if (sizeof($timestamps) == 2) {
            // *** REMOVE CHANGED PLAYLISTS ***
            if ($localPlaylistHasChanged && $globalPlaylistHasChanged) {
                // both playlist have changed => remove the old ones on the client side

                $keys = array_keys($timestamps);
                array_push($deletions, array('ID' => $keys[0]));
                array_push($deletions, array('ID' => $keys[1]));
            } else if ($localPlaylistHasChanged) {
                // The global playlist is still the same => remove the old local playlist

                array_push($deletions, array('ID' => array_keys($timestamps)[0])); // Index 0 = local playlist
            } else if ($globalPlaylistHasChanged) {
                // The local playlist hasn't changed => remove just the old global playlist

                array_push($deletions, array('ID' => array_keys($timestamps)[1])); // Index 1 = global playlist
            } // else: No changes have been made so there's nothing to delete

            // *** REMOVE REMOVED PLAYLISTS ***
            if ($localPlaylist && !$globalPlaylist) {
                // The client still has both playlists, but the global playlist has been removed

                array_push($deletions, array('ID' => array_keys($timestamps)[1]));
            } else if (!$localPlaylist && $globalPlaylist) {
                // The client still has both playlists, but the local playlist has been removed

                array_push($deletions, array('ID' => array_keys($timestamps)[0]));
            } else if (!$localPlaylist && !$globalPlaylist) {
                // The client still has both playlists, but both have been removed

                array_push($deletions, array('ID' => array_keys($timestamps)[0]));
                array_push($deletions, array('ID' => array_keys($timestamps)[1]));
            }
        } else if (sizeof($timestamps) == 1) {
            if ($localPlaylistHasChanged && !$globalPlaylistHasChanged) {
                // There's currently just a local playlist and it has changed => remove the old one

                if (!$globalPlaylist || array_keys($timestamps)[0] != $globalPlaylist['ID']) {
                    array_push($deletions, array('ID' => array_keys($timestamps)[0]));
                }
            } else if ($globalPlaylistHasChanged && !$localPlaylistHasChanged) {
                // There's currently just a global playlist and it has changed => remove the old one

                if (!$localPlaylist || array_keys($timestamps)[0] != $localPlaylist['ID']) {
                    array_push($deletions, array('ID' => array_keys($timestamps)[0]));
                }
            } else if ($globalPlaylistHasChanged && $localPlaylistHasChanged) {
                // Two new playlists have been added => remove the single one the client has

                array_push($deletions, array('ID' => array_keys($timestamps)[0]));
            }
        }

        if ($localPlaylist && !$localPlaylistHasChanged) {
            // There's still the same local playlist on the server and client => check for deleted slides

            $slideDeletions = $db->getRemovedSlidesForPlaylist($localPlaylist['ID'], $timestamps[$localPlaylist['ID']]);
            if (!empty($slideDeletions)) {
                $playlist = array('ID' => $localPlaylist['ID'], 'slides' => $slideDeletions);
                array_push($deletions, $playlist);
            }
        }
        if ($globalPlaylist && !$globalPlaylistHasChanged) {
            $slideDeletions = $db->getRemovedSlidesForPlaylist($globalPlaylist['ID'], $timestamps[$globalPlaylist['ID']]);
            if (!empty($slideDeletions)) {
                $playlist = array('ID' => $globalPlaylist['ID'], 'slides' => $slideDeletions);
                array_push($deletions, $playlist);
            }
        }


        /*if ($localPlaylist) {
            if (!array_key_exists($localPlaylist['ID'], $timestamps)) {
                // Current local playlist has changed => remove old one

                $globalPlaylistHasChanged = $globalPlaylist && !array_key_exists($globalPlaylist['ID'], $timestamps);

                if (sizeof($timestamps) == 2) {
                    if ($globalPlaylistHasChanged) {
                        // remove both playlists, because the new ones will be added

                        $keys = array_keys($timestamps);
                        array_push($deletions, array('ID' => $keys[0]));
                        array_push($deletions, array('ID' => $keys[1]));
                    } else {
                        // Just the local playlist has changed

                        array_push($deletions, array('ID' => array_keys($timestamps)[0])); // Index 0 = local playlist
                    }
                }
            }
        }

        if ($globalPlaylist) {

        }*/

        complete(HTTPStatusCode::Ok, array($changes, $deletions));
        break;

    default:
        complete(HTTPStatusCode::BadRequest, errObj('Unknown call', 'The call param given doesn\'t exist', ErrorCodes::CALL_DOESNT_EXIST));
        break;
}