"""Exam-bank corpus coverage (/api/exam/corpus) — the state of the collected exam bank.

Read-only view over the seeded exam-board catalogue (eb_specifications + eb_exams): board → subject →
specification → papers, with per-session QP/MS/ER coverage and rollup counts. Shows what the app has
COLLECTED (question papers, mark schemes, examiner reports) so a teacher/admin can see the bank's state
and where science coverage is complete vs thin. Catalogue data is public reference — read as-the-user.
"""
from __future__ import annotations

import os
import re
from typing import Any, Dict, List, Optional

from fastapi import APIRouter, Depends

from modules.logger_tool import initialise_logger
from routers.exam.dependencies import ExamContext, get_exam_context

logger = initialise_logger(__name__, os.getenv("LOG_LEVEL"), os.getenv("LOG_PATH"), "default", True)

router = APIRouter()

DOC_TYPES = ("QP", "MS", "ER")


def _rows(result: Any) -> List[Dict[str, Any]]:
    data = getattr(result, "data", None)
    if not data:
        return []
    return data if isinstance(data, list) else [data]


def _award_level(spec: Dict[str, Any]) -> str:
    """Best-effort GCSE / AS / A-level from the spec code (AQA GCSE = 8xxx, A-level/AS = 7xxx)."""
    code = re.sub(r"\D", "", spec.get("award_code") or spec.get("spec_code") or "")
    if code.startswith("8"):
        return "GCSE"
    if code.startswith("7"):
        return "A-level"
    return spec.get("award_level") or "Other"


@router.get("/corpus")
async def corpus_coverage(ctx: ExamContext = Depends(get_exam_context)) -> Dict[str, Any]:
    specs = _rows(
        ctx.supabase.table("eb_specifications")
        .select("spec_code, exam_board_code, subject_code, award_code, first_teach").execute()
    )
    exams = _rows(
        ctx.supabase.table("eb_exams")
        .select("exam_code, spec_code, paper_code, tier, session, type_code, storage_loc").execute()
    )

    # group exam docs → per spec → per paper (paper_code + session) → which doc types are present
    by_spec: Dict[str, Dict[str, Dict[str, Any]]] = {}
    for e in exams:
        sc = e.get("spec_code")
        if not sc:
            continue
        key = f"{e.get('paper_code') or '?'}|{e.get('session') or '?'}"
        paper = by_spec.setdefault(sc, {}).setdefault(key, {
            "paper_code": e.get("paper_code"), "session": e.get("session"),
            "tier": e.get("tier"), "docs": {}, "exam_codes": {},
        })
        dt = (e.get("type_code") or "").upper()
        if dt in DOC_TYPES:
            paper["docs"][dt] = bool(e.get("storage_loc"))
            paper["exam_codes"][dt] = e.get("exam_code")

    totals = {"specs": 0, "papers": 0, "sessions": 0, **{d: 0 for d in DOC_TYPES}}
    boards: Dict[str, Dict[str, Any]] = {}
    for s in specs:
        sc = s["spec_code"]
        papers_map = by_spec.get(sc, {})
        if not papers_map:
            continue
        totals["specs"] += 1
        board = s.get("exam_board_code") or "?"
        level = _award_level(s)
        papers = sorted(papers_map.values(), key=lambda p: (str(p["session"]), str(p["paper_code"])))
        counts = {d: sum(1 for p in papers if p["docs"].get(d)) for d in DOC_TYPES}
        for d in DOC_TYPES:
            totals[d] += counts[d]
        totals["papers"] += len(papers)
        totals["sessions"] += len({p["session"] for p in papers})
        spec_entry = {
            "spec_code": sc, "subject": (s.get("subject_code") or "").title(), "level": level,
            "board": board, "first_teach": s.get("first_teach"),
            "n_papers": len(papers), "counts": counts, "papers": papers,
        }
        boards.setdefault(board, {"board": board, "specs": []})["specs"].append(spec_entry)

    board_list = []
    for board in sorted(boards):
        specs_sorted = sorted(boards[board]["specs"], key=lambda x: (x["level"], x["subject"], x["spec_code"]))
        board_list.append({"board": board, "n_specs": len(specs_sorted), "specs": specs_sorted})

    return {"totals": totals, "boards": board_list}