<?php
if (!defined('ABSPATH')) {
    exit;
}

/**
 * Chat API 类
 * 提供流式聊天接口，代理转发到 Antom Bot Chat API
 */
class Antom_Shomi_Chat_API
{
    /**
     * Antom Bot Chat API 地址
     */
    const BOT_CHAT_URL = 'https://dashboard-apiv2.antom.com/ai/online/portal/api/bot/chat';

    /**
     * 构造函数
     */
    public function __construct()
    {
        add_action('rest_api_init', [$this, 'register_routes']);
    }

    /**
     * 注册 REST 路由
     */
    public function register_routes()
    {
        $namespace = '/chat';

        register_rest_route($namespace, '/v1', [
            'methods'             => 'POST',
            'callback'            => [$this, 'handle_chat'],
            'permission_callback' => ['Antom_Shomi_Setup_Wizard', 'check_api_permission'],
            'args'                => [],
        ]);
    }

    /**
     * 处理聊天请求（流式 SSE 代理）
     *
     * 前端发送 POST 请求，本接口将请求转发到 Antom Bot Chat API，
     * 并以 Server-Sent Events (SSE) 流式方式将响应逐块返回给前端。
     *
     * @param WP_REST_Request $request
     * @return void|WP_REST_Response
     */
    public function handle_chat(WP_REST_Request $request)
    {
        $body = $request->get_json_params();
        if (!is_array($body)) {
            return new WP_REST_Response(
                ['success' => false, 'message' => 'Invalid JSON body'],
                400
            );
        }

        // 必填参数校验
        $question = isset($body['question']) ? sanitize_text_field($body['question']) : '';
        if (empty($question)) {
            return new WP_REST_Response(
                ['success' => false, 'message' => 'Missing required field: question'],
                400
            );
        }

        $session_id    = isset($body['sessionId']) ? sanitize_text_field($body['sessionId']) : '';
        $external_user = isset($body['externalUserId']) ? sanitize_text_field($body['externalUserId']) : '';

        // 从请求 Header 中获取 Cookie，放入 extraMap.platformSession
        $platform_session = $request->get_header('cookie');

        // 构造发送给 Antom Bot Chat API 的请求体
        $upstream_body = [
            'customScene'    => 'paymentAgent',
            'sessionId'      => $session_id,
            'externalUserId' => $external_user,
            'question'       => $question,
            'extraMap'       => [
                'greet'              => '',
                'responseType'       => 'json',
                'messageFrom'        => 'copilot',
                'submitType'         => 'normal',
                'questionContext'     => isset($body['extraMap']['questionContext'])
                    ? $body['extraMap']['questionContext']
                    : ['scene' => '', 'currentUrl' => '', 'fileList' => []],
                'from'               => 'paymentAgent',
                'platformSession'    => $platform_session,
            ],
        ];

        $upstream_json = wp_json_encode($upstream_body);
        if (false === $upstream_json) {
            return new WP_REST_Response(
                ['success' => false, 'message' => 'Failed to encode request body'],
                500
            );
        }

        // 使用 cURL 发起流式请求并逐块转发给客户端
        $this->stream_upstream_response($upstream_json);
    }

    /**
     * 通过 WordPress HTTP API 发起流式请求，按完整 SSE 消息边界实时输出到客户端
     *
     * 利用 WordPress 提供的 'http_api_curl' 钩子注入 CURLOPT_WRITEFUNCTION，
     * 实现边接收边输出的真正流式 SSE 代理，同时满足 WordPress 代码规范。
     *
     * @param string $upstream_json 发送给上游 API 的 JSON 字符串
     * @return void
     */
    private function stream_upstream_response($upstream_json)
    {
        // 设置 SSE 响应头
        header('Content-Type: text/event-stream; charset=UTF-8');
        header('Cache-Control: no-cache');
        header('Connection: keep-alive');
        header('X-Accel-Buffering: no');

        // 禁用 PHP 输出缓冲
        while (ob_get_level() > 0) {
            ob_end_flush();
        }

        if (function_exists('apache_setenv')) {
            apache_setenv('no-gzip', '1');
        }
        ini_set('zlib.output_compression', '0');

        // SSE 行缓冲，只在完整消息边界 flush
        $buffer = '';
        $stream_error = '';

        /**
         * 通过 http_api_curl 钩子注入流式写回调
         *
         * WordPress 在使用 cURL transport 时会触发此钩子，允许修改 cURL handle 选项。
         * 我们利用此机制注入 WRITEFUNCTION 实现实时 SSE 输出。
         */
        $streaming_callback = function (&$curl_handle) use (&$buffer, &$stream_error) {
            curl_setopt($curl_handle, CURLOPT_WRITEFUNCTION, function ($ch, $chunk) use (&$buffer) {
                $buffer .= $chunk;

                // SSE 消息以 "\n\n" 分隔，逐条输出完整消息
                while (($boundary = strpos($buffer, "\n\n")) !== false) {
                    $message = substr($buffer, 0, $boundary + 2);
                    $buffer = substr($buffer, $boundary + 2);

                    // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Raw SSE passthrough from trusted upstream API; content is JSON-encoded event data.
                    echo $message;

                    if (ob_get_level() > 0) {
                        ob_flush();
                    }
                    flush();
                }

                return strlen($chunk);
            });
        };

        // 注册钩子（一次性使用，优先级高以确保最后执行）
        add_action('http_api_curl', $streaming_callback, 99);

        // 使用 WordPress HTTP API 发起请求
        $response = wp_remote_post(self::BOT_CHAT_URL, [
            'body'    => $upstream_json,
            'headers' => [
                'Content-Type'  => 'application/json',
                'Accept'        => '*/*',
                'appname'       => 'paymentAgent',
                'Cache-Control' => 'no-cache',
                'Origin'        => 'http://paymentagent.alipay.net',
                'Referer'       => 'http://paymentagent.alipay.net/',
            ],
            'timeout' => 120,
        ]);

        // 移除钩子，防止影响后续请求
        remove_action('http_api_curl', $streaming_callback, 99);

        // 输出缓冲区中剩余的数据（如果有）
        if (!empty($buffer)) {
            // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Raw SSE passthrough from trusted upstream API.
            echo $buffer;

            if (ob_get_level() > 0) {
                ob_flush();
            }
            flush();
        }

        // 处理请求错误
        if (is_wp_error($response)) {
            $error_data = wp_json_encode([
                'success' => false,
                'message' => 'Upstream request failed: ' . $response->get_error_message(),
            ]);
            // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- JSON-encoded error message for SSE stream.
            echo 'data: ' . $error_data . "\n\n";

            if (ob_get_level() > 0) {
                ob_flush();
            }
            flush();
        }

        // 结束请求，阻止 WordPress 继续输出
        exit;
    }
}