<?php

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

/*----------------------------------------------------------
  -  Create storage file if necessary
  ----------------------------------------------------------*/
if (!file_exists(CHAT_HISTORY_FILE)) {
    if (@file_put_contents(CHAT_HISTORY_FILE, '') === false) {
        http_response_code(500);
        echo json_encode([
            'error' => 'Cannot create history file.'
        ]);
        exit;
    }
}

/*----------------------------------------------------------
  - Helper
  ----------------------------------------------------------*/
function readChats() {
    $result = [];

    $fp = fopen(CHAT_HISTORY_FILE, 'c+');
    if (!$fp) {
        return [];
    }

    flock($fp, LOCK_SH);
    while (($line = fgets($fp)) !== false) {

        $line = trim($line);
        if ($line === '') {
            continue;
        }

        $obj = json_decode($line, true);
        if (is_array($obj)) {
            $result[] = $obj;
        }
    }

    flock($fp, LOCK_UN);
    fclose($fp);

    return $result;
}

function writeChats($chats) {
    $fp = fopen(CHAT_HISTORY_FILE, 'w');

    if (!$fp) {
        return false;
    }

    flock($fp, LOCK_EX);
    foreach ($chats as $chat) {
        fwrite($fp, json_encode($chat, JSON_UNESCAPED_UNICODE) . PHP_EOL);
    }

    fflush($fp);

    flock($fp, LOCK_UN);
    fclose($fp);

    return true;
}

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";
}

/*----------------------------------------------------------
  - Action
  ----------------------------------------------------------*/

$action = $_GET['action'] ?? '';
switch ($action) {
    /*------------------------------------------------------
      - LIST
      ------------------------------------------------------*/
    case 'list':
        $chats = readChats();
        $list = [];
        foreach ($chats as $chat) {
            $list[] = [
                'id' => $chat['id'],
                'title' => $chat['title'],
                'created' => $chat['created'],
                'model' => $chat['model'] ?? ''
            ];
        }

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

        echo json_encode($list);
        exit;

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

        $chats = readChats();
        foreach ($chats as $chat) {
            if ($chat['id'] === $id) {
                echo json_encode($chat);
                exit;
            }
        }
        echo json_encode([
            'error' => 'Chat not found.'
        ]);
        exit;
    /*------------------------------------------------------
      -  SAVE
      ------------------------------------------------------*/
    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 = $input['model'] ?? '';
        $chat = [
            'id' => $id,
            'title' => $title,
            'created' => date('Y-m-d H:i:s'),
            'model' => $model,
            'messages' => $messages
        ];

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

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

        if (!writeChats($chats)) {
            echo json_encode([
                'error' => 'Unable to save.'
            ]);
            exit;
        }

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

    /*------------------------------------------------------
      -  DELETE
      ------------------------------------------------------*/
    case 'delete':
        $id = $_GET['id'] ?? '';

        if ($id == '') {
            echo json_encode([
                'error' => 'Missing id.'
            ]);
            exit;
        }

        $chats = readChats();
        $newChats = [];

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

        writeChats($newChats);
        echo json_encode([
            'success' => true
        ]);
        exit;
    /*------------------------------------------------------
      -  DEFAULT
      ------------------------------------------------------*/

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