import datetime
import json
import sqlite3
from contextlib import contextmanager
from pathlib import Path

from pyra.memory import _MEMORY_ROOT
from pyra.utils.paths import safe_chmod

_DB_PATH = _MEMORY_ROOT / "memory.db"
_EXCLUDED = {"MEMORY_INDEX.md", "memory_index.json"}


@contextmanager
def _connect():
    conn = sqlite3.connect(str(_DB_PATH))
    conn.row_factory = sqlite3.Row
    try:
        yield conn
        conn.commit()
    except Exception:
        conn.rollback()
        raise
    finally:
        conn.close()


def init_db() -> None:
    with _connect() as conn:
        conn.execute("""
            CREATE TABLE IF NOT EXISTS memory_meta (
                id         INTEGER PRIMARY KEY,
                path       TEXT UNIQUE NOT NULL,
                category   TEXT NOT NULL DEFAULT 'root',
                size_bytes INTEGER NOT NULL DEFAULT 0,
                modified   TEXT NOT NULL DEFAULT '',
                summary    TEXT NOT NULL DEFAULT '',
                keywords   TEXT NOT NULL DEFAULT '[]',
                embedding  BLOB DEFAULT NULL
            )
        """)
        conn.execute("""
            CREATE VIRTUAL TABLE IF NOT EXISTS memory_fts USING fts5(
                path     UNINDEXED,
                body,
                summary,
                keywords
            )
        """)
    safe_chmod(_DB_PATH, 0o600)


def upsert(
    path: str,
    *,
    content: str,
    category: str = "root",
    size_bytes: int = 0,
    modified: str = "",
    summary: str = "",
    keywords: list[str] | None = None,
) -> None:
    kw_json = json.dumps(keywords or [])
    kw_text = " ".join(keywords or [])
    with _connect() as conn:
        conn.execute(
            """INSERT INTO memory_meta (path, category, size_bytes, modified, summary, keywords)
               VALUES (?, ?, ?, ?, ?, ?)
               ON CONFLICT(path) DO UPDATE SET
                   category=excluded.category,
                   size_bytes=excluded.size_bytes,
                   modified=excluded.modified,
                   summary=excluded.summary,
                   keywords=excluded.keywords""",
            (path, category, size_bytes, modified, summary, kw_json),
        )
        conn.execute("DELETE FROM memory_fts WHERE path = ?", (path,))
        conn.execute(
            "INSERT INTO memory_fts (path, body, summary, keywords) VALUES (?, ?, ?, ?)",
            (path, content, summary, kw_text),
        )


def remove(path: str) -> None:
    with _connect() as conn:
        conn.execute("DELETE FROM memory_meta WHERE path = ?", (path,))
        conn.execute("DELETE FROM memory_fts WHERE path = ?", (path,))


def search(query: str, limit: int = 20) -> list[dict]:
    """FTS5 full-text search; returns [{file, summary, keywords, snippet}]."""
    if not _DB_PATH.exists():
        return []
    try:
        with _connect() as conn:
            fts_rows = conn.execute(
                """SELECT path, snippet(memory_fts, 1, '[', ']', '…', 32) AS snip
                   FROM memory_fts
                   WHERE memory_fts MATCH ?
                   ORDER BY rank
                   LIMIT ?""",
                (query, limit),
            ).fetchall()
            if not fts_rows:
                return []
            paths = [r["path"] for r in fts_rows]
            snippets = {r["path"]: r["snip"] for r in fts_rows}
            placeholders = ",".join("?" * len(paths))
            meta_rows = conn.execute(
                f"SELECT path, summary, keywords FROM memory_meta WHERE path IN ({placeholders})",
                paths,
            ).fetchall()
        meta = {
            r["path"]: {
                "summary": r["summary"],
                "keywords": json.loads(r["keywords"] or "[]"),
            }
            for r in meta_rows
        }
        return [
            {
                "file": p,
                "summary": meta.get(p, {}).get("summary", ""),
                "keywords": meta.get(p, {}).get("keywords", []),
                "snippet": snippets.get(p, ""),
            }
            for p in paths
            if p in meta
        ]
    except sqlite3.OperationalError:
        return []


def list_all() -> list[dict]:
    """Return all rows from memory_meta ordered by path."""
    if not _DB_PATH.exists():
        return []
    with _connect() as conn:
        rows = conn.execute(
            "SELECT path, category, size_bytes, modified, summary, keywords "
            "FROM memory_meta ORDER BY path"
        ).fetchall()
    return [
        {
            "path": r["path"],
            "category": r["category"],
            "size_bytes": r["size_bytes"],
            "modified": r["modified"],
            "summary": r["summary"],
            "keywords": json.loads(r["keywords"] or "[]"),
        }
        for r in rows
    ]


def migrate_from_files() -> None:
    """Populate DB from existing .md files on first run; no-op if DB already has entries."""
    if not _DB_PATH.exists():
        return
    with _connect() as conn:
        count = conn.execute("SELECT COUNT(*) FROM memory_meta").fetchone()[0]
    if count > 0:
        return

    json_index_path = _MEMORY_ROOT / "memory_index.json"
    existing: dict = {}
    if json_index_path.exists():
        try:
            existing = json.loads(json_index_path.read_text())
        except (json.JSONDecodeError, OSError):
            pass

    for f in sorted(_MEMORY_ROOT.rglob("*.md")):
        if f.name in _EXCLUDED:
            continue
        rel = f.relative_to(_MEMORY_ROOT)
        rel_key = rel.as_posix()
        category = rel.parts[0] if len(rel.parts) > 1 else "root"
        stat = f.stat()
        mtime = datetime.datetime.fromtimestamp(stat.st_mtime).isoformat(timespec="seconds")
        prev = existing.get(rel_key, {})
        try:
            content = f.read_text()
        except OSError:
            content = ""
        upsert(
            rel_key,
            content=content,
            category=category,
            size_bytes=stat.st_size,
            modified=mtime,
            summary=prev.get("summary", ""),
            keywords=prev.get("keywords", []),
        )