"""
firebase_progress.py
--------------------
學生學習進度的讀寫邏輯。
放在專案根目錄，由 dt_callbacks.py 和頁面呼叫。

Firestore 資料結構：
  students/{student_id}/
    profile:  { name, student_id, last_seen }
    progress: { quiz_correct, solutions_viewed, ai_hints_used, ... }
    events:   [ { type, unit, qid, ts, ... }, ... ]  ← 子集合
"""
from __future__ import annotations
import datetime
from firebase_init import get_db

# ─── 時間戳 ────────────────────────────────────────────────────────────────
def _now() -> str:
    return datetime.datetime.now(datetime.timezone.utc).isoformat()


# ─── 學生個人資料 ──────────────────────────────────────────────────────────

def upsert_student(student_id: str, name: str = "") -> None:
    """建立或更新學生個人資料。"""
    db = get_db()
    ref = db.collection("students").document(student_id)
    ref.set({
        "student_id": student_id,
        "name": name or student_id,
        "last_seen": _now(),
    }, merge=True)


# ─── 記錄事件 ─────────────────────────────────────────────────────────────

def log_event(student_id: str, event_type: str, **kwargs) -> None:
    """
    記錄一筆學習事件到 students/{student_id}/events 子集合。

    event_type 範例：
        "quiz_correct"    - 填空/選擇題答對
        "quiz_wrong"      - 答錯
        "solution_viewed" - 展開詳細解法
        "hint_used"       - 按下 AI 提示
        "quiz_ai_done"    - AI 批改完成
    """
    db = get_db()
    payload = {
        "type": event_type,
        "ts": _now(),
        **kwargs,  # unit, qid, answer, ...
    }
    db.collection("students").document(student_id)\
      .collection("events").add(payload)


def log_quiz_result(
    student_id: str,
    unit: str,
    qid: str,
    correct: bool,
    answer: str = "",
) -> None:
    """記錄一題答題結果，同時更新 progress 計數。"""
    event_type = "quiz_correct" if correct else "quiz_wrong"
    log_event(student_id, event_type, unit=unit, qid=qid, answer=answer)

    # 更新統計計數
    db = get_db()
    ref = db.collection("students").document(student_id)
    field = "quiz_correct_count" if correct else "quiz_wrong_count"
    ref.set({field: _increment(1), "last_seen": _now()}, merge=True)


def log_solution_viewed(student_id: str, unit: str, solution_id: str) -> None:
    """記錄學生展開了某個解法區塊。"""
    log_event(student_id, "solution_viewed", unit=unit, solution_id=solution_id)
    db = get_db()
    db.collection("students").document(student_id)\
      .set({"solutions_viewed_count": _increment(1), "last_seen": _now()}, merge=True)


def log_choice_option(unit: str, qid: str, option_key: str) -> None:
    """記錄某題某選項被選擇的次數（全班統計，存在 question_stats 集合）。"""
    db = get_db()
    ref = (
        db.collection("question_stats")
          .document(f"{unit}__{qid}")
    )
    ref.set({
        "unit": unit,
        "qid":  qid,
        f"option_{option_key}": _increment(1),
    }, merge=True)


def log_quiz_question_stat(unit: str, qid: str, correct: bool) -> None:
    """記錄某題全班答對/答錯次數（存在 question_stats 集合）。"""
    db = get_db()
    ref = db.collection("question_stats").document(f"{unit}__{qid}")
    field = "correct_count" if correct else "wrong_count"
    ref.set({"unit": unit, "qid": qid, field: _increment(1)}, merge=True)


def get_all_question_stats() -> list[dict]:
    """讀取所有題目的答題統計（老師後台用）。"""
    db = get_db()
    docs = db.collection("question_stats").stream()
    return [d.to_dict() for d in docs]


def register_question(
    unit: str,
    qid: str,
    qtype: str,
    prompt_runs: list | None = None,
    prompt_md: str = "",
    options: list | None = None,
    correct_answer: str | list | None = None,
) -> None:
    """
    在學生作答時，記錄題目原始內容到 question_stats。
    每次都更新（允許覆蓋），確保每道題目各自正確記錄。
    prompt_runs:    題目的 run 清單（含文字與 LaTeX）
    prompt_md:      題目的 markdown 純文字（備援）
    options:        選項清單 [{"key": "a", "text": "..."}, ...]
    correct_answer: 正確答案 key（單選為 str，多選為 list）
    """
    db = get_db()
    ref = db.collection("question_stats").document(f"{unit}__{qid}")
    update: dict = {"unit": unit, "qid": qid, "qtype": qtype}
    if prompt_runs is not None:
        # 只存 text/latex 欄位，避免多餘 key 佔空間
        update["prompt_runs"] = [
            {k: v for k, v in r.items() if k in ("text", "latex", "kind", "style", "newline")}
            for r in (prompt_runs or [])
        ]
    if prompt_md:
        update["prompt_md"] = prompt_md[:300]
    if options:
        update["options"] = [{"key": o.get("key", ""), "text": o.get("text", "")} for o in options]
    if correct_answer is not None:
        if isinstance(correct_answer, list):
            update["correct_answers"] = [str(k).lower() for k in correct_answer]
        else:
            update["correct_answers"] = [str(correct_answer).lower()]
    ref.set(update, merge=True)


def log_hint_used(student_id: str, unit: str, qid: str) -> None:
    """記錄學生使用了 AI 提示。"""
    log_event(student_id, "hint_used", unit=unit, qid=qid)
    db = get_db()
    db.collection("students").document(student_id)\
      .set({"ai_hints_used_count": _increment(1), "last_seen": _now()}, merge=True)


# ─── 讀取 ────────────────────────────────────────────────────────────────

def get_student_progress(student_id: str) -> dict:
    """讀取單一學生的 progress 計數（老師後台用）。"""
    db = get_db()
    doc = db.collection("students").document(student_id).get()
    if doc.exists:
        return doc.to_dict()
    return {}


def get_all_students() -> list[dict]:
    """讀取所有學生的 profile（老師後台列表用）。"""
    db = get_db()
    docs = db.collection("students").stream()
    return [d.to_dict() for d in docs]


def get_student_events(student_id: str, limit: int = 100) -> list[dict]:
    """讀取某學生最近的事件記錄。"""
    db = get_db()
    docs = (
        db.collection("students").document(student_id)
          .collection("events")
          .order_by("ts", direction="DESCENDING")
          .limit(limit)
          .stream()
    )
    return [d.to_dict() for d in docs]


# ─── Firestore 遞增輔助 ───────────────────────────────────────────────────

def _increment(n: int):
    from google.cloud.firestore import Increment
    return Increment(n)