#!/usr/bin/env python3
"""Update meta.json and topics/index.json after adding questions.

Usage:
    python3 update_meta.py <topics_dir> <group> <subtopic> <question_type>

- Reads the question file at topics/{group}/{subtopic}/{type}.json
- Updates/creates topics/{group}/{subtopic}/meta.json
- Updates/creates topics/index.json with subtopic stats

meta.json format:
    {
      "slug": "gc-jvm",
      "name": "...",
      "description": "...",
      "tags": [...],
      "difficulty_range": [1, 5],
      "schema_version": "1.0.0",
      "question_files": ["fill_blank", "single_choice"],
      "stats": { "total": 20, "by_type": { "fill_blank": 10, "single_choice": 10 } }
    }

index.json format:
    {
      "version": "1.0.0",
      "updated": "...",
      "topics": [
        {
          "slug": "qunar-ai-fullstack",
          "name": "...",
          "subtopics": [
            { "slug": "gc-jvm", "path": "topics/qunar-ai-fullstack/gc-jvm", "stats": {...} }
          ]
        }
      ]
    }

Exit codes: 0 = success, 1 = error, 2 = usage error.
"""
import json
import sys
from pathlib import Path
from datetime import date


def load_json(path: Path) -> dict:
    if path.exists() and path.stat().st_size > 0:
        with open(path, encoding="utf-8") as f:
            return json.load(f)
    return {}


def save_json(path: Path, data: dict):
    path.parent.mkdir(parents=True, exist_ok=True)
    with open(path, "w", encoding="utf-8") as f:
        json.dump(data, f, ensure_ascii=False, indent=2)
        f.write("\n")


def main():
    if len(sys.argv) != 5:
        print(f"Usage: {sys.argv[0]} <topics_dir> <group> <subtopic> <question_type>",
              file=sys.stderr)
        sys.exit(2)

    topics_dir = Path(sys.argv[1])
    group = sys.argv[2]
    subtopic = sys.argv[3]
    q_type = sys.argv[4]

    subtopic_dir = topics_dir / group / subtopic
    question_file = subtopic_dir / f"{q_type}.json"
    meta_file = subtopic_dir / "meta.json"
    index_file = topics_dir / "index.json"

    if not question_file.exists():
        print(f"❌ Question file not found: {question_file}", file=sys.stderr)
        sys.exit(1)

    # Load question file
    q_data = load_json(question_file)
    questions = q_data.get("questions", [])
    count = len(questions)

    # Compute difficulty stats
    difficulties = [q.get("difficulty", 3) for q in questions]
    diff_range = [min(difficulties), max(difficulties)] if difficulties else [1, 5]

    # Compute tag union
    all_tags = sorted(set(
        tag for q in questions for tag in q.get("tags", [])
    ))

    # --- Update meta.json ---
    meta = load_json(meta_file)
    meta["slug"] = meta.get("slug", subtopic)
    meta["name"] = meta.get("name", subtopic.replace("-", " ").title())
    meta.setdefault("description", "")
    meta["tags"] = all_tags
    meta["difficulty_range"] = diff_range
    meta["schema_version"] = "1.0.0"
    meta["updated"] = date.today().isoformat()

    # question_files is an array of type names
    if "question_files" not in meta:
        meta["question_files"] = []
    if q_type not in meta["question_files"]:
        meta["question_files"].append(q_type)

    # stats has total and by_type
    if "stats" not in meta:
        meta["stats"] = {"total": 0, "by_type": {}}
    meta["stats"]["by_type"][q_type] = count
    meta["stats"]["total"] = sum(meta["stats"]["by_type"].values())

    save_json(meta_file, meta)

    # --- Update index.json ---
    index = load_json(index_file)
    index.setdefault("version", "1.0.0")
    index["updated"] = date.today().isoformat()
    index.setdefault("topics", [])

    # Find or create the group topic entry
    group_entry = None
    for t in index["topics"]:
        if t.get("slug") == group:
            group_entry = t
            break

    if group_entry is None:
        group_entry = {
            "slug": group,
            "name": meta.get("name", group.replace("-", " ").title()),
            "description": meta.get("description", ""),
            "subtopics": [],
        }
        index["topics"].append(group_entry)

    group_entry.setdefault("subtopics", [])

    # Find or create the subtopic entry
    sub_entry = None
    for s in group_entry["subtopics"]:
        if s.get("slug") == subtopic:
            sub_entry = s
            break

    if sub_entry is None:
        sub_entry = {
            "slug": subtopic,
            "name": meta.get("name", subtopic.replace("-", " ").title()),
            "description": meta.get("description", ""),
            "path": f"topics/{group}/{subtopic}",
            "stats": {"total": 0, "by_type": {}},
        }
        group_entry["subtopics"].append(sub_entry)

    sub_entry["stats"]["by_type"][q_type] = count
    sub_entry["stats"]["total"] = sum(sub_entry["stats"]["by_type"].values())

    save_json(index_file, index)

    # Output summary
    result = {
        "subtopic": subtopic,
        "question_type": q_type,
        "count": count,
        "total": meta["stats"]["total"],
        "meta_file": str(meta_file),
        "index_file": str(index_file),
    }
    print(json.dumps(result, ensure_ascii=False))
    sys.exit(0)


if __name__ == "__main__":
    main()