<?php

header('Content-Type: application/json');
require_once __DIR__ . '/default.php';
require_once __DIR__ . '/auth.php';

requireAuthentication();

$username = getAuthenticatedUsername();
$action = $_GET['action'] ?? '';
$defaultModel = getConfiguredDefaultModel();

if (isGuestSession()) {
    switch ($action) {
        case 'load-config':
            echo json_encode(['defaultModel' => $defaultModel]);
            exit;
        case 'save-config':
            echo json_encode(['success' => true, 'defaultModel' => $defaultModel]);
            exit;
        case 'list':
            echo json_encode([]);
            exit;
        case 'load':
            echo json_encode(['error' => 'Guest users do not have saved chats.']);
            exit;
        case 'save':
            echo json_encode(['success' => true, 'id' => '', 'title' => '']);
            exit;
        case 'delete':
            echo json_encode(['success' => true]);
            exit;
        default:
            echo json_encode(['error' => 'Unknown action.']);
            exit;
    }
}

function createTitle($messages) {
    foreach ($messages as $msg) {
        if (($msg['role'] ?? '') === 'user') {
            $title = trim($msg['content']);
            if (mb_strlen($title) > 60) {
                $title = mb_substr($title, 0, 60) . '...';
            }
            return $title;
        }
    }
    return 'Untitled Chat';
}

switch ($action) {
    case 'load-config':
        echo json_encode([
            'defaultModel' => getDefaultModelForUser($username)
        ]);
        exit;

    case 'save-config':
        if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
            echo json_encode(['error' => 'POST required.']);
            exit;
        }

        $input = json_decode(file_get_contents('php://input'), true);
        if (!is_array($input)) {
            echo json_encode(['error' => 'Invalid JSON.']);
            exit;
        }

        $config = getUserConfig($username);
        $config['defaultModel'] = isset($input['defaultModel']) && trim((string) $input['defaultModel']) !== ''
            ? (string) $input['defaultModel']
            : getConfiguredDefaultModel();

        if (!saveUserConfigData($username, $config)) {
            echo json_encode(['error' => 'Unable to save config.']);
            exit;
        }

        echo json_encode(['success' => true, 'defaultModel' => $config['defaultModel']]);
        exit;

    case 'list':
        $chats = readUserChat($username);
        $list = [];
        foreach ($chats as $chat) {
            $list[] = [
                'id' => $chat['id'] ?? '',
                'title' => $chat['title'] ?? 'Untitled Chat',
                'created' => $chat['created'] ?? '',
                'model' => $chat['model'] ?? ''
            ];
        }

        usort($list, function ($a, $b) {
            return strcmp($b['created'], $a['created']);
        });

        echo json_encode($list);
        exit;

    case 'load':
        $id = $_GET['id'] ?? '';
        if ($id === '') {
            echo json_encode(['error' => 'Missing id.']);
            exit;
        }

        $chats = readUserChat($username);
        foreach ($chats as $chat) {
            if (($chat['id'] ?? '') === $id) {
                echo json_encode($chat);
                exit;
            }
        }
        echo json_encode(['error' => 'Chat not found.']);
        exit;

    case 'save':
        if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
            echo json_encode(['error' => 'POST required.']);
            exit;
        }

        $input = json_decode(file_get_contents('php://input'), true);
        if (!is_array($input)) {
            echo json_encode(['error' => 'Invalid JSON.']);
            exit;
        }

        $messages = $input['messages'] ?? [];
        if (!is_array($messages) || count($messages) === 0) {
            echo json_encode(['error' => 'No messages.']);
            exit;
        }

        $id = $input['id'] ?? '';
        if ($id === '') {
            $id = uniqid('', true);
        }

        $title = createTitle($messages);
        $model = isset($input['model']) && trim((string) $input['model']) !== ''
            ? (string) $input['model']
            : getDefaultModelForUser($username);
        $chat = [
            'id' => $id,
            'title' => $title,
            'created' => date('Y-m-d H:i:s'),
            'model' => $model,
            'messages' => $messages
        ];

        $chats = readUserChat($username);
        $found = false;
        foreach ($chats as &$existing) {
            if (($existing['id'] ?? '') === $id) {
                $existing = $chat;
                $found = true;
                break;
            }
        }

        if (!$found) {
            $chats[] = $chat;
        }

        $config = getUserConfig($username);
        $config['defaultModel'] = $model;
        if (!saveUserConfigData($username, $config) || !writeUserChat($username, $chats)) {
            echo json_encode(['error' => 'Unable to save.']);
            exit;
        }

        echo json_encode([
            'success' => true,
            'id' => $id,
            'title' => $title
        ]);
        exit;

    case 'delete':
        $id = $_GET['id'] ?? '';
        if ($id === '') {
            echo json_encode(['error' => 'Missing id.']);
            exit;
        }

        $chats = readUserChat($username);
        $newChats = [];
        foreach ($chats as $chat) {
            if (($chat['id'] ?? '') !== $id) {
                $newChats[] = $chat;
            }
        }

        writeUserChat($username, $newChats);
        echo json_encode(['success' => true]);
        exit;

    default:
        echo json_encode(['error' => 'Unknown action.']);
        exit;
}