// xuchao: 解答题 AI 判分引擎——阿里云百炼 Qwen-VL,按评分点(rubric)部分给分
// 无 DASHSCOPE_API_KEY 时进入演示判分(mock),供本地开发;生产必须配真 key

export type SolveStatus = "ok" | "blank" | "blurry" | "printed" | "unrelated" | "error";
export type RubricItem = { point: string; score: number };
export type RubricHit = { point: string; score: number; hit: boolean; reason: string };
export type GradeVerdict = {
  status: SolveStatus;
  hits: RubricHit[];
  earned: number; // 由 hits 重算,不信任模型自报
  comment: string;
  mock: boolean;
  model: string;
  ms: number;
};

const ENDPOINT = "https://dashscope.aliyuncs.com/compatible-mode/v1/chat/completions";
const MODEL = process.env.AI_GRADE_MODEL || "qwen-vl-max";
const TIMEOUT_MS = 60_000;

// xuchao: 判分提示词——题干+参考解答+评分点+学生手写照片,只允许离散给分
function buildPrompt(stem: string, points: number, reference: string, rubric: RubricItem[], hasFigure: boolean) {
  const rubricText = rubric.map((r, i) => `${i + 1}. ${r.point}(${r.score} 分)`).join("\n");
  return `你是一位经验丰富的数学阅卷老师,正在批改学生手写的解答题照片。

【题目】${stem}${hasFigure ? "\n(题目配有示意图,以题意为准)" : ""}
【本题满分】${points} 分
【参考解答】
${reference}
【评分点】
${rubricText}

请按以下步骤评判:
1. 判断照片状态,status 只能是以下之一:
   - ok:正常的手写解答
   - blank:空白或没有作答内容
   - blurry:字迹模糊无法辨认
   - printed:印刷体内容(非手写,拒绝批改)
   - unrelated:照片内容与本题无关
2. 仅当 status=ok 时逐条评判评分点。学生方法可以与参考解答不同,只要该评分点的要求确实达成就 hit=true 并给该评分点满分,否则 hit=false 给 0 分。不允许给某个评分点部分分数。
3. earned = 所有 hit=true 评分点分数之和,不得超过满分 ${points}。
4. comment 给一句面向小学生的总体点评(指出亮点或主要问题)。

只输出一个 JSON 对象,不要输出任何其他文字:
{"status":"ok","hits":[{"hit":true,"reason":"简短理由"}],"earned":数字,"comment":"点评"}
hits 数组元素个数必须等于评分点个数(${rubric.length}),顺序与评分点一致。status 非 ok 时 hits 为空数组、earned 为 0。`;
}

// xuchao: 演示判分(无 key):确定性模拟——最后一个评分点不得分,便于本地验证部分给分与错题链路
function mockVerdict(stem: string, points: number, rubric: RubricItem[]): GradeVerdict {
  const hits: RubricHit[] = rubric.map((r, i) => ({
    point: r.point,
    score: r.score,
    hit: i < rubric.length - 1 || rubric.length === 1,
    reason: i < rubric.length - 1 || rubric.length === 1 ? "演示判分:达成" : "演示判分:未达成(模拟扣分)",
  }));
  const earned = hits.reduce((s, h) => s + (h.hit ? h.score : 0), 0);
  return {
    status: "ok",
    hits,
    earned: rubric.length === 1 ? points : Math.min(earned, points),
    comment: "这是演示判分(未配置百炼 API Key),结果仅用于流程测试。",
    mock: true,
    model: "mock",
    ms: 0,
  };
}

// xuchao: 从模型回复里稳健提取 JSON(容忍代码块包裹与多余文字)
function extractJson(text: string): Record<string, unknown> | null {
  const fenced = text.match(/```(?:json)?\s*([\s\S]*?)```/);
  const body = fenced ? fenced[1] : text;
  const start = body.indexOf("{");
  const end = body.lastIndexOf("}");
  if (start < 0 || end <= start) return null;
  try {
    return JSON.parse(body.slice(start, end + 1));
  } catch {
    return null;
  }
}

const VALID_STATUS = new Set(["ok", "blank", "blurry", "printed", "unrelated"]);

// xuchao: 校验并归一化模型判定;earned 一律按 hits 重算
function normalizeVerdict(raw: Record<string, unknown>, rubric: RubricItem[], model: string, ms: number): GradeVerdict | null {
  const status = typeof raw.status === "string" && VALID_STATUS.has(raw.status) ? (raw.status as SolveStatus) : null;
  if (!status) return null;
  let hits: RubricHit[] = [];
  if (status === "ok") {
    const arr = Array.isArray(raw.hits) ? raw.hits : null;
    if (!arr || arr.length !== rubric.length) return null;
    hits = rubric.map((r, i) => {
      const h = (arr[i] ?? {}) as Record<string, unknown>;
      return { point: r.point, score: r.score, hit: h.hit === true, reason: typeof h.reason === "string" ? h.reason : "" };
    });
  }
  const earned = Math.min(
    points_cap(rubric),
    hits.reduce((s, h) => s + (h.hit ? h.score : 0), 0),
  );
  return {
    status,
    hits,
    earned,
    comment: typeof raw.comment === "string" ? raw.comment : "",
    mock: false,
    model,
    ms,
  };
}

const points_cap = (rubric: RubricItem[]) => rubric.reduce((s, r) => s + r.score, 0);

// xuchao: 判分主入口;photoUrl 必须是公网可达地址(OSS 签名 URL)
export async function gradeSolvePhoto(opts: {
  stem: string;
  points: number;
  rubric: RubricItem[];
  reference: string;
  photoUrl: string;
  figureUrl?: string;
}): Promise<GradeVerdict> {
  const { stem, points, rubric, reference, photoUrl, figureUrl } = opts;
  const apiKey = process.env.DASHSCOPE_API_KEY;
  if (!apiKey) return mockVerdict(stem, points, rubric);

  const content: Record<string, unknown>[] = [
    { type: "text", text: buildPrompt(stem, points, reference, rubric, !!figureUrl) },
    { type: "image_url", image_url: { url: photoUrl } },
  ];
  if (figureUrl) content.push({ type: "image_url", image_url: { url: figureUrl } });

  let lastErr = "";
  for (let attempt = 0; attempt < 2; attempt++) {
    const t0 = Date.now();
    try {
      const ctrl = new AbortController();
      const timer = setTimeout(() => ctrl.abort(), TIMEOUT_MS);
      const resp = await fetch(ENDPOINT, {
        method: "POST",
        headers: { "Content-Type": "application/json", Authorization: `Bearer ${apiKey}` },
        body: JSON.stringify({
          model: MODEL,
          messages: [{ role: "user", content }],
          temperature: 0.1,
        }),
        signal: ctrl.signal,
      });
      clearTimeout(timer);
      if (!resp.ok) {
        lastErr = `HTTP ${resp.status}`;
        continue;
      }
      const data = (await resp.json()) as { choices?: { message?: { content?: string } }[] };
      const text = data.choices?.[0]?.message?.content ?? "";
      const raw = extractJson(text);
      if (!raw) {
        lastErr = "JSON 解析失败";
        continue;
      }
      const v = normalizeVerdict(raw, rubric, MODEL, Date.now() - t0);
      if (!v) {
        lastErr = "判定结构不符";
        continue;
      }
      return v;
    } catch (e) {
      lastErr = e instanceof Error ? e.message : String(e);
    }
  }
  // xuchao: 两次均失败——返回 error 状态,前端提示重拍,不写入得分
  return { status: "error", hits: [], earned: 0, comment: `判分失败(${lastErr}),请重试`, mock: false, model: MODEL, ms: 0 };
}