/* Shared SSE client for /api/analyze/stream.
 * 统一 analyze.html 内联逻辑与 ai-panel.js 的 SSE 逻辑.
 * 事件契约 (后端 services 层下发):
 *   step:    {step:'context'|'prompt'|'complete', content:string}
 *   token:   {text:string}  — 流式 LLM 输出, 分隔符已被后端剥离
 *   reasoning_start / conclusion_start: 无 payload, 切换当前 section
 *   error:   {error:string} — 业务错误帧
 *   onerror: 连接层错误 (非 JSON)
 *
 * callbacks 全部可选:
 *   {onStep, onToken, onSectionStart, onError, onComplete}
 *   onStep(step, content)        — step === 'complete' 时也会先调 onStep 再调 onComplete
 *   onToken(text, section)       — section: 'reasoning' | 'conclusion'
 *   onSectionStart(section)      — 'reasoning' | 'conclusion'
 *   onError(message, kind)       — kind: 'server' (业务帧) | 'connection'
 *   onComplete(content)          — step === 'complete'
 *
 * 返回句柄 {close(), getSection()}, close() 幂等.
 * complete / error 帧后 client 自动 close 并失效 (与原两个实现一致).
 */

export function createAnalysisStream(scope, question, preset, callbacks = {}) {
    const { onStep, onToken, onSectionStart, onError, onComplete } = callbacks;

    let currentSection = "reasoning"; // 'reasoning' | 'conclusion', 由 SSE section 事件驱动
    let closed = false;

    const params = new URLSearchParams({ scope });
    if (question) params.append("question", question);
    if (preset) params.append("preset", preset);

    const es = new EventSource(`/api/analyze/stream?${params.toString()}`);

    function close() {
        if (closed) return;
        closed = true;
        es.close();
    }

    es.addEventListener("step", (e) => {
        let data;
        try {
            data = JSON.parse(e.data);
        } catch (err) {
            return; // 非 JSON step 帧, 忽略
        }
        const { step, content } = data;
        if (onStep) onStep(step, content);
        if (step === "complete") {
            if (onComplete) onComplete(content);
            close();
        }
    });

    // Section 事件: 后端识别 ===REASONING=== / ===CONCLUSION=== 后显式下发
    es.addEventListener("reasoning_start", () => {
        currentSection = "reasoning";
        if (onSectionStart) onSectionStart("reasoning");
    });

    es.addEventListener("conclusion_start", () => {
        currentSection = "conclusion";
        if (onSectionStart) onSectionStart("conclusion");
    });

    es.addEventListener("token", (e) => {
        let data;
        try {
            data = JSON.parse(e.data);
        } catch (err) {
            return;
        }
        if (onToken) onToken(data.text || "", currentSection);
    });

    es.addEventListener("error", (e) => {
        let msg = "未知错误";
        try {
            const data = JSON.parse(e.data);
            msg = data.error || msg;
        } catch (ignore) {
            /* 非 JSON 错误帧 */
        }
        if (onError) onError(msg, "server");
        close();
    });

    es.onerror = () => {
        // 与旧实现一致: 仅当 stream 仍处于活跃状态时才上报连接错误,
        // 避免 complete 后浏览器触发 onerror 造成的误报.
        if (!closed) {
            if (onError) onError("连接错误, 请检查后端日志", "connection");
            close();
        }
    };

    return {
        close,
        getSection: () => currentSection,
    };
}