"""wiki BM25 全文檢索（第一版不用向量庫，AGENTS.md §0）。

用法：python tools/search.py "查詢詞" [-k 10] [--root DIR]
輸出：JSON 陣列（path、title、description、tags、score），供 agent 與 MCP 使用。
"""
import argparse
import json
import pathlib
import re
import sys

sys.path.insert(0, str(pathlib.Path(__file__).parent))
import kb
from rank_bm25 import BM25Okapi


def tokenize(text):
    """英數字詞 + CJK bigram。

    ponytail: bigram 斷詞無語意理解（同義詞不匹配），天花板是字面重疊；
    升級路徑：Phase 6 後評估 EmbeddingGemma / snowflake-arctic-embed 向量檢索。
    """
    text = text.lower()
    tokens = re.findall(r"[a-z0-9]+", text)
    for run in re.findall(r"[一-鿿]+", text):
        tokens += [run] if len(run) == 1 else [run[i:i + 2] for i in range(len(run) - 1)]
    return tokens


def build_corpus(root):
    docs = []
    for p in kb.iter_pages(root):
        try:
            meta, body = kb.parse_page(p.read_text(encoding="utf-8"))
        except ValueError:
            continue  # 壞頁由 lint 報，檢索直接略過
        text = (f"{meta['title']} " * 3 + f"{meta['description']} " * 2
                + " ".join(meta.get("tags") or []) + " " + body)
        docs.append({"path": p.relative_to(root).as_posix(), "title": str(meta["title"]),
                     "description": str(meta["description"]),
                     "tags": [str(t) for t in meta.get("tags") or []],
                     "tokens": tokenize(text)})
    return docs


def search(root, query, k=10):
    docs = build_corpus(pathlib.Path(root))
    if not docs:
        return []
    bm = BM25Okapi([d["tokens"] for d in docs])
    scores = bm.get_scores(tokenize(query))
    ranked = sorted(zip(docs, scores), key=lambda x: -x[1])[:k]
    return [{"path": d["path"], "title": d["title"], "description": d["description"],
             "tags": d["tags"], "score": round(float(s), 4)}
            for d, s in ranked if s > 0]


def main(argv=None):
    ap = argparse.ArgumentParser(description=__doc__)
    ap.add_argument("query")
    ap.add_argument("-k", type=int, default=10, help="回傳筆數上限（查詢工作流上限 10）")
    ap.add_argument("--root", default=str(kb.ROOT))
    a = ap.parse_args(argv)
    hits = search(a.root, a.query, max(1, min(a.k, 10)))
    print(json.dumps(hits, ensure_ascii=False, indent=2))


if __name__ == "__main__":
    main()