"""Beaver session 子系统的检索能力。"""

from __future__ import annotations

import re
import sqlite3
from typing import Any

from .store import SessionStore


class SessionSearchService:
    """围绕 `SessionStore` 提供 browsing / FTS / lineage 辅助能力。"""

    def __init__(self, store: SessionStore) -> None:
        self.store = store

    @staticmethod
    def _sanitize_fts5_query(query: str) -> str:
        quoted_parts: list[str] = []

        def preserve(match: re.Match[str]) -> str:
            quoted_parts.append(match.group(0))
            return f"\x00Q{len(quoted_parts) - 1}\x00"

        sanitized = re.sub(r'"[^"]*"', preserve, query)
        sanitized = re.sub(r'[+{}()\"^]', " ", sanitized)
        sanitized = re.sub(r"\*+", "*", sanitized)
        sanitized = re.sub(r"(^|\s)\*", r"\1", sanitized)
        sanitized = re.sub(r"(?i)^(AND|OR|NOT)\b\s*", "", sanitized.strip())
        sanitized = re.sub(r"(?i)\s+(AND|OR|NOT)\s*$", "", sanitized.strip())
        sanitized = re.sub(r"\b(\w+(?:[.-]\w+)+)\b", r'"\1"', sanitized)

        for index, quoted in enumerate(quoted_parts):
            sanitized = sanitized.replace(f"\x00Q{index}\x00", quoted)
        return sanitized.strip()

    def resolve_session_id(self, session_id_or_prefix: str) -> str | None:
        """用完整 ID 或唯一前缀解析出目标 session_id。"""

        exact = self.store.get_session_record(session_id_or_prefix)
        if exact is not None:
            return exact.session_id

        escaped = (
            session_id_or_prefix
            .replace("\\", "\\\\")
            .replace("%", "\\%")
            .replace("_", "\\_")
        )
        rows = self.store._fetchall(
            """
            SELECT id
            FROM sessions
            WHERE id LIKE ? ESCAPE '\\'
            ORDER BY started_at DESC
            LIMIT 2
            """,
            (f"{escaped}%",),
        )
        if len(rows) == 1:
            return rows[0]["id"]
        return None

    def list_sessions_rich(
        self,
        *,
        limit: int = 20,
        offset: int = 0,
        include_children: bool = False,
        source: str | None = None,
        exclude_sources: list[str] | None = None,
        exclude_end_reasons: list[str] | None = None,
    ) -> list[dict[str, Any]]:
        """列出最近活跃的 session 及其摘要元数据。"""

        clauses: list[str] = []
        params: list[Any] = []

        if not include_children:
            clauses.append("parent_session_id IS NULL")
        if source:
            clauses.append("source = ?")
            params.append(source)
        if exclude_sources:
            placeholders = ",".join("?" for _ in exclude_sources)
            clauses.append(f"source NOT IN ({placeholders})")
            params.extend(exclude_sources)
        if exclude_end_reasons:
            placeholders = ",".join("?" for _ in exclude_end_reasons)
            clauses.append(f"(end_reason IS NULL OR end_reason NOT IN ({placeholders}))")
            params.extend(exclude_end_reasons)

        where = f"WHERE {' AND '.join(clauses)}" if clauses else ""
        params.extend([limit, offset])
        rows = self.store._fetchall(
            f"""
            SELECT *
            FROM sessions
            {where}
            ORDER BY last_active DESC
            LIMIT ? OFFSET ?
            """,
            tuple(params),
        )
        return rows

    def search_messages(
        self,
        *,
        query: str,
        role_filter: list[str] | None = None,
        exclude_sources: list[str] | None = None,
        limit: int = 20,
        offset: int = 0,
    ) -> list[dict[str, Any]]:
        """使用 FTS5 搜索 session transcript。"""

        query = self._sanitize_fts5_query(query)
        if not query:
            return []

        clauses = ["messages_fts MATCH ?", "m.context_visible = 1"]
        params: list[Any] = [query]

        if exclude_sources:
            placeholders = ",".join("?" for _ in exclude_sources)
            clauses.append(f"s.source NOT IN ({placeholders})")
            params.extend(exclude_sources)
        if role_filter:
            placeholders = ",".join("?" for _ in role_filter)
            clauses.append(f"m.role IN ({placeholders})")
            params.extend(role_filter)

        params.extend([limit, offset])
        sql = f"""
            SELECT
                m.id,
                m.session_id,
                m.role,
                s.source,
                s.model,
                s.started_at AS session_started,
                snippet(messages_fts, 0, '>>>', '<<<', '...', 40) AS snippet
            FROM messages_fts
            JOIN messages m ON m.id = messages_fts.rowid
            JOIN sessions s ON s.id = m.session_id
            WHERE {' AND '.join(clauses)}
            ORDER BY rank
            LIMIT ? OFFSET ?
        """

        try:
            return self.store._fetchall(sql, tuple(params))
        except sqlite3.Error as exc:
            raise RuntimeError(f"Session transcript search failed for query={query!r}") from exc