<?php
declare(strict_types=1);

/**
 * Game Maker API.
 *
 * Routing uses the `r` query parameter (e.g. `index.php?r=projects/abc123`) because the
 * site's nginx configuration does not pass PATH_INFO to PHP.
 *
 *   GET    ?r=auth/session      → {user, role}                  (both null while nobody is signed in)
 *   POST   ?r=auth/login        {username,password}  → {user, role} | 401
 *   POST   ?r=auth/logout       → 204
 *   POST   ?r=auth/password     {currentPassword,newPassword} → 204 | 401 | 422
 *                               (the only auth route that needs a session; ends the account's
 *                                other logins, keeps the one asking)
 *
 * Everything below needs a signed-in user (401 otherwise), and projects belong to one: a project
 * of somebody else answers like one that is not there – unless the one asking is an administrator
 * (#179), who reads, saves and deletes it like their own; a save keeps its owner.
 *
 * Administrators only (403 for everybody else, #180):
 *
 *   GET    ?r=users             → [{username,role,createdAt,projects:[{id,name,revision,updatedAt}]}]
 *   POST   ?r=users             {username,password,role}           → 201 {username,role,createdAt} | 409 | 422
 *   PATCH  ?r=users/{name}      {username?,role?,password?}        → {username,role,createdAt} | 404 | 409 | 422
 *   DELETE ?r=users/{name}      → 204 | 404 | 409 (still owns projects) | 422
 *                               (renaming or deleting signs the account out everywhere; a new
 *                                password ends its other sessions)
 *
 *   GET    ?r=projects          → [{id,name,revision,updatedAt}]
 *   POST   ?r=projects          {name}               → {id,name,revision,updatedAt,project}
 *   GET    ?r=projects/{id}     → {id,name,revision,updatedAt,project}
 *   PUT    ?r=projects/{id}     {revision, project}  → {revision,updatedAt} | 409 {error,revision}
 *   DELETE ?r=projects/{id}     → 204
 *
 *   GET    ?r=textures            → [{file,name,width,height,bytes,updatedAt}]
 *   POST   ?r=textures&name=x.png raw image bytes    → {file,name,width,height,bytes}
 *   DELETE ?r=textures/{file}     → 204
 *
 *   GET    ?r=fonts               → [{file,name,bytes,updatedAt}]
 *   POST   ?r=fonts&name=x.ttf    raw font bytes     → {file,name,bytes}
 *   DELETE ?r=fonts/{file}        → 204
 *
 *   GET    ?r=sounds              → [{file,name,bytes,updatedAt}]
 *   POST   ?r=sounds&name=x.wav   raw sound bytes    → {file,name,bytes}
 *   DELETE ?r=sounds/{file}       → 204
 *
 *   POST   ?r=pixels              raw cel bytes      → {file,bytes}   (pixel art, #130)
 *
 *   GET    ?r=plugins             → [{file,bytes,updatedAt}], sorted by file name
 *   GET    ?r=plugins/{file}      → the module source as text/javascript
 *
 * `name` is the file's original name, kept beside it as `{file}.json` (see OriginalName) and
 * empty when none is known. It is a caption, never a path: the stored file is always `{hash}.{ext}`.
 *
 * Stored images, fonts, sounds and cels are served straight from `data/textures/`, `data/fonts/`,
 * `data/sounds/` and `data/pixels/` as static files; the API only writes them.
 */

require __DIR__ . '/lib/AccountRules.php';
require __DIR__ . '/lib/Auth.php';
require __DIR__ . '/lib/FontStore.php';
require __DIR__ . '/lib/OriginalName.php';
require __DIR__ . '/lib/PixelStore.php';
require __DIR__ . '/lib/PluginStore.php';
require __DIR__ . '/lib/Response.php';
require __DIR__ . '/lib/SessionStore.php';
require __DIR__ . '/lib/SoundStore.php';
require __DIR__ . '/lib/Store.php';
require __DIR__ . '/lib/TextureStore.php';
require __DIR__ . '/lib/UserStore.php';

/** Has to clear the largest single upload below, which is a sound; the web server has its own say. */
const MAX_BODY_BYTES = 20 * 1024 * 1024;

/** Upload ceiling for a single image. The editor downscales larger pictures before sending. */
const MAX_TEXTURE_BYTES = 4 * 1024 * 1024;

/** Upload ceiling for a single font. A font cannot be shrunk on the way, so this is a plain limit. */
const MAX_FONT_BYTES = 4 * 1024 * 1024;

/** The same for a sound, four times as high: one music track is worth more than four typefaces. */
const MAX_SOUND_BYTES = 16 * 1024 * 1024;

set_error_handler(static function (int $severity, string $message, string $file, int $line): bool {
    throw new ErrorException($message, 0, $severity, $file, $line);
});

/** @param list<string> $parts */
function routeAuth(array $parts, string $method, Auth $auth): never
{
    $what = $parts[1] ?? '';

    if ($what === 'session') {
        if ($method !== 'GET') {
            Response::error('Method not allowed', 405);
        }
        // Always 200, never 401: "nobody is signed in" is an answer, not a failure, and the
        // login screen asks this before it can know either way.
        $user = $auth->user();
        Response::json(['user' => $user, 'role' => $user === null ? null : $auth->role($user)]);
    }

    if ($what === 'login') {
        if ($method !== 'POST') {
            Response::error('Method not allowed', 405);
        }
        $body = Response::body();
        $user = $auth->logIn((string) ($body['username'] ?? ''), (string) ($body['password'] ?? ''));
        if ($user === null) {
            // One message for both halves: which of the two was wrong is the attacker's question.
            Response::error('Wrong user name or password', 401);
        }
        Response::json(['user' => $user, 'role' => $auth->role($user)]);
    }

    if ($what === 'password') {
        if ($method !== 'POST') {
            Response::error('Method not allowed', 405);
        }
        // The one route under `auth/` that needs a session: it changes the password of whoever is
        // signed in, so there has to be somebody.
        $user = $auth->require();
        $body = Response::body();
        $new = (string) ($body['newPassword'] ?? '');
        if (!UserStore::isValidPassword($new)) {
            Response::error('The new password needs at least ' . UserStore::MIN_PASSWORD_LENGTH . ' characters', 422);
        }
        if (!$auth->changePassword($user, (string) ($body['currentPassword'] ?? ''), $new)) {
            Response::error('Wrong password', 401);
        }
        Response::noContent();
    }

    if ($what === 'logout') {
        if ($method !== 'POST') {
            Response::error('Method not allowed', 405);
        }
        $auth->logOut();
        Response::noContent();
    }

    Response::error('Not found', 404);
}

/** @param list<string> $parts */
function routeProjects(array $parts, string $method, string $owner, bool $seesAll): never
{
    $store = new Store(dirname(__DIR__) . '/data/projects', $owner, $seesAll);

    if (count($parts) === 1) {
        if ($method === 'GET') {
            Response::json($store->list());
        }
        if ($method === 'POST') {
            $body = Response::body();
            $name = trim((string) ($body['name'] ?? ''));
            if ($name === '' || mb_strlen($name) > 120) {
                Response::error('Project name must be 1–120 characters', 422);
            }
            Response::json($store->create($name), 201);
        }
        Response::error('Method not allowed', 405);
    }

    $id = $parts[1];
    if (!Store::isValidId($id)) {
        Response::error('Invalid project id', 400);
    }

    if ($method === 'GET') {
        $doc = $store->load($id);
        if ($doc === null) {
            Response::error('Project not found', 404);
        }
        Response::json($doc);
    }

    if ($method === 'PUT') {
        $body = Response::body();
        if (!isset($body['revision']) || !is_int($body['revision']) || !is_array($body['project'] ?? null)) {
            Response::error('Body must contain integer "revision" and object "project"', 422);
        }
        try {
            $result = $store->save($id, $body['revision'], $body['project']);
        } catch (StaleRevisionException $e) {
            Response::error('Project was modified elsewhere', 409, ['revision' => $e->currentRevision]);
        }
        if ($result === null) {
            Response::error('Project not found', 404);
        }
        Response::json(['revision' => $result['revision'], 'updatedAt' => $result['updatedAt']]);
    }

    if ($method === 'DELETE') {
        if (!$store->delete($id)) {
            Response::error('Project not found', 404);
        }
        Response::noContent();
    }

    Response::error('Method not allowed', 405);
}

/** @param list<string> $parts */
function routeUsers(array $parts, string $method, Auth $auth, UserStore $users): never
{
    $actor = $auth->requireAdmin();
    $projects = new Store(dirname(__DIR__) . '/data/projects', $actor, true);
    $shown = static function (string $name) use ($users): array {
        foreach ($users->accounts() as $account) {
            if (strcasecmp($account['username'], $name) === 0) {
                return $account;
            }
        }
        throw new RuntimeException("Account {$name} vanished");
    };

    if (count($parts) === 1) {
        if ($method === 'GET') {
            Response::json(array_map(
                static fn(array $a): array => $a + ['projects' => $projects->listOf($a['username'])],
                $users->accounts(),
            ));
        }
        if ($method === 'POST') {
            $body = Response::body();
            $name = (string) ($body['username'] ?? '');
            $password = (string) ($body['password'] ?? '');
            $role = (string) ($body['role'] ?? 'user');
            if (!UserStore::isValidName($name)) {
                Response::error('A user name is 2–32 letters, digits, dots, dashes or underscores', 422);
            }
            if (!UserStore::isValidPassword($password)) {
                Response::error('The password needs at least ' . UserStore::MIN_PASSWORD_LENGTH . ' characters', 422);
            }
            if (!UserStore::isValidRole($role)) {
                Response::error('Unknown role', 422);
            }
            if ($users->exists($name)) {
                Response::error("The name {$name} is taken", 409);
            }
            $users->put($name, $password, $role);
            Response::json($shown($name), 201);
        }
        Response::error('Method not allowed', 405);
    }

    $target = $parts[1];
    if (!$users->exists($target)) {
        Response::error('User not found', 404);
    }
    $role = $users->role($target);

    if ($method === 'PATCH') {
        $body = Response::body();
        $newName = array_key_exists('username', $body) ? (string) $body['username'] : null;
        $newRole = array_key_exists('role', $body) ? (string) $body['role'] : null;
        $password = array_key_exists('password', $body) ? (string) $body['password'] : null;
        // Everything is checked before anything is written: half an edit is worse than none.
        if ($newName !== null && $newName !== $target) {
            $refusal = AccountRules::renameRefusal($actor, $target);
            if ($refusal !== null) {
                Response::error($refusal, 422);
            }
            if (!UserStore::isValidName($newName)) {
                Response::error('A user name is 2–32 letters, digits, dots, dashes or underscores', 422);
            }
            if (strcasecmp($newName, $target) !== 0 && $users->exists($newName)) {
                Response::error("The name {$newName} is taken", 409);
            }
        }
        if ($newRole !== null) {
            if (!UserStore::isValidRole($newRole)) {
                Response::error('Unknown role', 422);
            }
            $refusal = AccountRules::roleRefusal($actor, $target, $role, $newRole, $users->adminCount());
            if ($refusal !== null) {
                Response::error($refusal, 422);
            }
        }
        if ($password !== null && !UserStore::isValidPassword($password)) {
            Response::error('The password needs at least ' . UserStore::MIN_PASSWORD_LENGTH . ' characters', 422);
        }

        if ($password !== null) {
            $auth->resetPassword($target, $password);
        }
        if ($newRole !== null && $newRole !== $role) {
            $users->setRole($target, $newRole);
        }
        $name = $shown($target)['username'];
        if ($newName !== null && $newName !== $name) {
            $users->rename($name, $newName);
            $projects->transfer($name, $newName);
            $auth->endSessionsOf($name);
            $name = $newName;
        }
        Response::json($shown($name));
    }

    if ($method === 'DELETE') {
        $refusal = AccountRules::deleteRefusal($actor, $target, $role, $users->adminCount());
        if ($refusal !== null) {
            Response::error($refusal, 422);
        }
        $refusal = AccountRules::ownerRefusal($target, count($projects->listOf($shown($target)['username'])));
        if ($refusal !== null) {
            Response::error($refusal, 409);
        }
        $users->remove($target);
        $auth->endSessionsOf($target);
        Response::noContent();
    }

    Response::error('Method not allowed', 405);
}

/** @param list<string> $parts */
function routeTextures(array $parts, string $method): never
{
    $store = new TextureStore(dirname(__DIR__) . '/data/textures');

    if (count($parts) === 1) {
        if ($method === 'GET') {
            Response::json($store->list());
        }
        if ($method === 'POST') {
            $bytes = Response::rawBody();
            if (strlen($bytes) > MAX_TEXTURE_BYTES) {
                Response::error('Image must be at most ' . (MAX_TEXTURE_BYTES / 1024 / 1024) . ' MB', 413);
            }
            try {
                Response::json($store->store($bytes, (string) ($_GET['name'] ?? '')), 201);
            } catch (InvalidImageException $e) {
                Response::error($e->getMessage(), 422);
            }
        }
        Response::error('Method not allowed', 405);
    }

    if ($method === 'DELETE') {
        if (!$store->delete($parts[1])) {
            Response::error('Texture not found', 404);
        }
        Response::noContent();
    }

    Response::error('Method not allowed', 405);
}

/** @param list<string> $parts */
function routeFonts(array $parts, string $method): never
{
    $store = new FontStore(dirname(__DIR__) . '/data/fonts');

    if (count($parts) === 1) {
        if ($method === 'GET') {
            Response::json($store->list());
        }
        if ($method === 'POST') {
            $bytes = Response::rawBody();
            if (strlen($bytes) > MAX_FONT_BYTES) {
                Response::error('Font must be at most ' . (MAX_FONT_BYTES / 1024 / 1024) . ' MB', 413);
            }
            try {
                Response::json($store->store($bytes, (string) ($_GET['name'] ?? '')), 201);
            } catch (InvalidFontException $e) {
                Response::error($e->getMessage(), 422);
            }
        }
        Response::error('Method not allowed', 405);
    }

    if ($method === 'DELETE') {
        if (!$store->delete($parts[1])) {
            Response::error('Font not found', 404);
        }
        Response::noContent();
    }

    Response::error('Method not allowed', 405);
}

/** @param list<string> $parts */
function routeSounds(array $parts, string $method): never
{
    $store = new SoundStore(dirname(__DIR__) . '/data/sounds');

    if (count($parts) === 1) {
        if ($method === 'GET') {
            Response::json($store->list());
        }
        if ($method === 'POST') {
            $bytes = Response::rawBody();
            if (strlen($bytes) > MAX_SOUND_BYTES) {
                Response::error('Sound must be at most ' . (MAX_SOUND_BYTES / 1024 / 1024) . ' MB', 413);
            }
            try {
                Response::json($store->store($bytes, (string) ($_GET['name'] ?? '')), 201);
            } catch (InvalidSoundException $e) {
                Response::error($e->getMessage(), 422);
            }
        }
        Response::error('Method not allowed', 405);
    }

    if ($method === 'DELETE') {
        if (!$store->delete($parts[1])) {
            Response::error('Sound not found', 404);
        }
        Response::noContent();
    }

    Response::error('Method not allowed', 405);
}

/** @param list<string> $parts */
function routePixels(array $parts, string $method): never
{
    if (count($parts) !== 1 || $method !== 'POST') {
        Response::error('Method not allowed', 405);
    }
    $store = new PixelStore(dirname(__DIR__) . '/data/pixels');
    $bytes = Response::rawBody();
    if (strlen($bytes) > PixelStore::MAX_BYTES) {
        Response::error('A cel is at most ' . PixelStore::MAX_BYTES . ' bytes', 413);
    }
    try {
        Response::json($store->store($bytes), 201);
    } catch (InvalidPixelsException $e) {
        Response::error($e->getMessage(), 422);
    }
}

/** @param list<string> $parts */
function routePlugins(array $parts, string $method): never
{
    $store = new PluginStore(dirname(__DIR__) . '/data/plugins');

    if (count($parts) === 1) {
        if ($method !== 'GET') {
            Response::error('Method not allowed', 405);
        }
        Response::json($store->list());
    }

    if ($method !== 'GET') {
        Response::error('Method not allowed', 405);
    }

    $source = $store->read($parts[1]);
    if ($source === null) {
        Response::error('Plugin not found', 404);
    }
    // Every plugin file is handed out: the project says which of them the editor runs (#119),
    // and the server has no way of knowing which project the asking tab has open.
    header('Content-Type: text/javascript; charset=utf-8');
    header('X-Content-Type-Options: nosniff');
    // A replaced file has to be the one the next editor start runs.
    header('Cache-Control: no-cache');
    echo $source;
    exit;
}

try {
    if ((int) ($_SERVER['CONTENT_LENGTH'] ?? 0) > MAX_BODY_BYTES) {
        Response::error('Request body too large', 413);
    }

    $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
    $route = trim((string) ($_GET['r'] ?? ''), '/');
    $parts = $route === '' ? [] : explode('/', $route);

    if (count($parts) < 1 || count($parts) > 2) {
        Response::error('Not found', 404);
    }

    $users = new UserStore(dirname(__DIR__) . '/data/users.json');
    $auth = new Auth($users, new SessionStore(dirname(__DIR__) . '/data/sessions'));
    if ($parts[0] === 'auth') {
        routeAuth($parts, $method, $auth);
    }
    if ($parts[0] === 'users') {
        routeUsers($parts, $method, $auth, $users);
    }
    // Images, fonts, sounds, cels and plugins are shared between accounts; being signed in is still the
    // price of admission, so an uploaded file cannot be dropped in by a stranger.
    $user = $auth->require();

    match ($parts[0]) {
        'projects' => routeProjects($parts, $method, $user, $auth->role($user) === 'admin'),
        'textures' => routeTextures($parts, $method),
        'fonts' => routeFonts($parts, $method),
        'sounds' => routeSounds($parts, $method),
        'pixels' => routePixels($parts, $method),
        'plugins' => routePlugins($parts, $method),
        default => Response::error('Not found', 404),
    };
} catch (Throwable $e) {
    error_log('[game-maker api] ' . $e->getMessage());
    Response::error('Internal server error', 500);
}