"""搜索服务封装"""

from app.database import get_connection, search_fts


def search(config, query: str, page: int = 1, page_size: int = 20) -> dict:
    """全文搜索，返回带高亮摘要的分页结果"""
    conn = get_connection(config.db_path)
    try:
        limit = page * page_size + page_size
        results = search_fts(conn, query, limit=limit)

        # 提取摘要（包含关键词的上下文）
        snippet_length = 100
        items = []
        for r in results:
            body = _get_body(conn, r["id"])
            snippet = _extract_snippet(body, query, snippet_length)
            items.append({
                "id": r["id"],
                "body_snippet": snippet,
                "difficulty": r.get("difficulty", 0.5),
                "question_type": r.get("question_type", ""),
                "import_type": r.get("import_type", ""),
                "chapters": r.get("chapters", []),
            })

        total = len(items)
        start = (page - 1) * page_size
        end = start + page_size

        return {
            "items": items[start:end],
            "total": total,
            "page": page,
            "page_size": page_size,
        }
    finally:
        conn.close()


def _get_body(conn, problem_id: str) -> str:
    """获取题目的 FTS body"""
    row = conn.execute(
        "SELECT body FROM problems_fts WHERE problem_id = ?",
        (problem_id,)
    ).fetchone()
    return row["body"] if row else ""


def _extract_snippet(text: str, query: str, length: int = 100) -> str:
    """从文本中提取包含查询关键词的摘要"""
    if not text:
        return ""

    # 查找关键词位置
    idx = text.lower().find(query.lower())
    if idx == -1:
        # 尝试部分匹配
        for word in query.split():
            idx = text.lower().find(word.lower())
            if idx != -1:
                break

    if idx == -1:
        # 无匹配，返回开头
        return text[:length] + ("..." if len(text) > length else "")

    # 提取上下文
    start = max(0, idx - length // 2)
    end = min(len(text), idx + length // 2)
    snippet = text[start:end]

    prefix = "..." if start > 0 else ""
    suffix = "..." if end < len(text) else ""

    return f"{prefix}{snippet}{suffix}"