<?php
declare(strict_types=1);

/**
 * Who is asking. The browser sends the session cookie; the check tools log in the same way and
 * send the same cookie, so there is exactly one way into the API.
 */
final class Auth
{
    public function __construct(
        private readonly UserStore $users,
        private readonly SessionStore $sessions,
    ) {}

    /** The signed-in user, or null when nobody is. */
    public function user(): ?string
    {
        $token = (string) ($_COOKIE[SessionStore::COOKIE] ?? '');
        return $token === '' ? null : $this->sessions->user($token);
    }

    /** The signed-in user, or a 401 answer – every route but `auth/*` goes through here. */
    public function require(): string
    {
        $user = $this->user();
        if ($user === null) {
            Response::error('Sign in first', 401);
        }
        return $user;
    }

    /**
     * The signed-in user if they are an administrator (#180), else 401 or 403. Every route that
     * may do more than a user goes through here: the editor only hides what it may not offer, the
     * decision is made on this side.
     */
    public function requireAdmin(): string
    {
        $user = $this->require();
        if ($this->users->role($user) !== 'admin') {
            Response::error('Administrators only', 403);
        }
        return $user;
    }

    /** `admin` or `user`; the session answer carries it so the editor knows what to offer. */
    public function role(string $user): string
    {
        return $this->users->role($user);
    }

    /** Checks the pair, starts a session and sets the cookie. Null when the pair is wrong. */
    public function logIn(string $username, string $password): ?string
    {
        $name = $this->users->verify($username, $password);
        if ($name === null) {
            return null;
        }
        $this->setCookie($this->sessions->create($name), time() + SessionStore::LIFETIME_SECONDS);
        return $name;
    }

    public function logOut(): void
    {
        $token = $this->token();
        if ($token !== '') {
            $this->sessions->destroy($token);
        }
        $this->setCookie('', time() - 3600);
    }

    /**
     * Sets a new password for `$user`, who has to type the old one again: a session alone is not
     * enough, or somebody else's open tab would be all it takes to take an account over.
     *
     * Every other login of the account ends with it – a session that was started with the old
     * password has no business outliving it. The one asking keeps theirs.
     *
     * @return bool False when the current password does not match; the caller answers 401 then.
     */
    public function changePassword(string $user, string $current, string $new): bool
    {
        if ($this->users->verify($user, $current) === null) {
            return false;
        }
        $this->users->put($user, $new);
        $this->sessions->destroyAllFor($user, $this->token());
        return true;
    }

    /**
     * An administrator sets somebody's password without knowing the old one (#179). That account's
     * sessions end with it, except the one asking when it is their own.
     */
    public function resetPassword(string $user, string $new): void
    {
        $this->users->put($user, $new);
        $this->sessions->destroyAllFor($user, $this->token());
    }

    /** Signs an account out everywhere – it was renamed or deleted, and its sessions carry the old name. */
    public function endSessionsOf(string $user): void
    {
        $this->sessions->destroyAllFor($user);
    }

    private function token(): string
    {
        return (string) ($_COOKIE[SessionStore::COOKIE] ?? '');
    }

    private function setCookie(string $value, int $expires): void
    {
        setcookie(SessionStore::COOKIE, $value, [
            'expires' => $expires,
            'path' => self::basePath(),
            'httponly' => true,
            'samesite' => 'Lax',
            'secure' => ($_SERVER['HTTPS'] ?? '') !== '',
        ]);
    }

    /**
     * The path the editor is served under (`/feuerwerk/`), read off the script rather than
     * written down: the same checkout answers under a different prefix in CI.
     */
    private static function basePath(): string
    {
        $script = (string) ($_SERVER['SCRIPT_NAME'] ?? '/feuerwerk/api/index.php');
        $base = dirname(dirname($script));
        return $base === '/' || $base === '\\' || $base === '.' ? '/' : $base . '/';
    }
}