from __future__ import annotations

import re
import uuid

import aiosqlite

from backend.config import settings
from backend.database import get_user_id

TAG_RE = re.compile(r"#[A-Za-z0-9_-]+")


def extract_tags(text: str) -> list[str]:
    seen: list[str] = []
    for match in TAG_RE.finditer(text):
        tag = match.group(0)[1:].lower()
        if tag not in seen:
            seen.append(tag)
    return seen


def extract_title(text: str) -> str:
    for line in text.splitlines():
        stripped = line.strip()
        if not stripped:
            continue
        if stripped.startswith("# "):
            title = stripped[2:].strip()
        else:
            title = stripped
        if title:
            return title[:200]
    return "Untitled"


def note_path(username: str, note_id: str) -> str:
    return f"{username}/{note_id}.md"


async def ensure_user_dir(username: str) -> None:
    import os

    os.makedirs(os.path.join(settings.data_dir, username), exist_ok=True)


async def write_note_file(username: str, note_id: str, body: str) -> str:
    from pathlib import Path

    await ensure_user_dir(username)
    rel = note_path(username, note_id)
    full = Path(settings.data_dir) / rel
    full.write_text(body, encoding="utf-8")
    return rel


async def read_note_file(rel_path: str) -> str:
    from pathlib import Path

    full = Path(settings.data_dir) / rel_path
    if not full.is_file():
        raise FileNotFoundError(rel_path)
    return full.read_text(encoding="utf-8")


async def delete_note_file(rel_path: str) -> None:
    from pathlib import Path

    full = Path(settings.data_dir) / rel_path
    if full.is_file():
        full.unlink()


def new_note_id() -> str:
    return uuid.uuid4().hex


# ---------------------------------------------------------------------------
# Note CRUD (metadata + tags + FTS)
# ---------------------------------------------------------------------------


async def create_note(
    username: str,
    body: str,
    ip: str | None = None,
    ua: str | None = None,
) -> dict:
    title = extract_title(body)
    tags = extract_tags(body)
    note_id = new_note_id()
    rel = await write_note_file(username, note_id, body)

    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        user_id = await get_user_id(db, username)
        if user_id is None:
            raise ValueError(f"unknown user: {username}")

        await db.execute(
            "INSERT INTO notes (id, user_id, title, path) VALUES (?, ?, ?, ?)",
            (note_id, user_id, title, rel),
        )
        await _set_tags(db, note_id, tags)
        await _index_note(db, note_id, user_id, title, body)
        await _record_history(db, note_id, user_id, "create", ip, ua)
        await db.commit()

        row = await db.execute(
            "SELECT n.id, n.title, n.path, n.created_at, n.updated_at,"
            " u.name AS username"
            " FROM notes n JOIN users u ON u.id = n.user_id WHERE n.id = ?",
            (note_id,),
        )
        note = dict(await row.fetchone())
        note["tags"] = tags
        note["body"] = body
        return note


async def update_note(
    note_id: str,
    body: str,
    ip: str | None = None,
    ua: str | None = None,
) -> dict | None:
    title = extract_title(body)
    tags = extract_tags(body)

    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        row = await db.execute(
            "SELECT n.id, n.user_id, n.path, u.name AS username"
            " FROM notes n JOIN users u ON u.id = n.user_id WHERE n.id = ?",
            (note_id,),
        )
        row = await row.fetchone()
        if row is None:
            return None

        await write_note_file(row["username"], note_id, body)
        await db.execute(
            "UPDATE notes SET title = ?, updated_at = datetime('now') WHERE id = ?",
            (title, note_id),
        )
        await _set_tags(db, note_id, tags)
        await _index_note(db, note_id, row["user_id"], title, body)
        await _record_history(db, note_id, row["user_id"], "update", ip, ua)
        await db.commit()

        return await get_note(note_id)


async def get_note(note_id: str) -> dict | None:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        row = await db.execute(
            "SELECT n.id, n.title, n.path, n.created_at, n.updated_at,"
            " u.name AS username"
            " FROM notes n JOIN users u ON u.id = n.user_id"
            " WHERE n.id = ? AND n.deleted_at IS NULL",
            (note_id,),
        )
        row = await row.fetchone()
        if row is None:
            return None
        note = dict(row)
        note["tags"] = await get_note_tags(note_id)
        note["body"] = await read_note_file(note["path"])
        return note


async def delete_note(
    note_id: str,
    ip: str | None = None,
    ua: str | None = None,
) -> bool:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        row = await db.execute(
            "SELECT user_id, path FROM notes WHERE id = ? AND deleted_at IS NULL",
            (note_id,),
        )
        row = await row.fetchone()
        if row is None:
            return False

        await delete_note_file(row["path"])
        await db.execute(
            "UPDATE notes SET deleted_at = datetime('now') WHERE id = ?",
            (note_id,),
        )
        await _record_history(db, note_id, row["user_id"], "delete", ip, ua)
        await db.commit()
        return True


async def list_notes(username: str, limit: int = 100) -> list[dict]:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        rows = await db.execute(
            "SELECT n.id, n.title, n.updated_at, n.created_at, u.name AS username"
            " FROM notes n JOIN users u ON u.id = n.user_id"
            " WHERE n.deleted_at IS NULL AND u.name = ?"
            " ORDER BY n.updated_at DESC LIMIT ?",
            (username, limit),
        )
        notes = [dict(r) for r in await rows.fetchall()]
        for note in notes:
            note["tags"] = await get_note_tags(note["id"])
        return notes


async def list_recent(limit: int = 30) -> list[dict]:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        rows = await db.execute(
            "SELECT n.id, n.title, n.updated_at, n.created_at, u.name AS username"
            " FROM notes n JOIN users u ON u.id = n.user_id"
            " WHERE n.deleted_at IS NULL"
            " ORDER BY n.updated_at DESC LIMIT ?",
            (limit,),
        )
        notes = [dict(r) for r in await rows.fetchall()]
        for note in notes:
            note["tags"] = await get_note_tags(note["id"])
        return notes


async def get_note_tags(note_id: str) -> list[str]:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        rows = await db.execute(
            "SELECT t.name FROM tags t JOIN note_tags nt ON nt.tag_id = t.id"
            " WHERE nt.note_id = ? ORDER BY t.name",
            (note_id,),
        )
        return [r["name"] for r in await rows.fetchall()]


async def tag_counts() -> list[dict]:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        rows = await db.execute(
            "SELECT t.name, COUNT(nt.note_id) AS count"
            " FROM tags t JOIN note_tags nt ON nt.tag_id = t.id"
            " JOIN notes n ON n.id = nt.note_id AND n.deleted_at IS NULL"
            " GROUP BY t.id ORDER BY count DESC, t.name LIMIT 50"
        )
        return [dict(r) for r in await rows.fetchall()]


async def search_notes(query: str, limit: int = 50) -> list[dict]:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        rows = await db.execute(
            "SELECT f.note_id AS id, f.title, f.body, n.updated_at,"
            " n.created_at, u.name AS username, bm25(notes_fts) AS rank"
            " FROM notes_fts f"
            " JOIN notes n ON n.id = f.note_id AND n.deleted_at IS NULL"
            " JOIN users u ON u.id = n.user_id"
            " WHERE notes_fts MATCH ? ORDER BY rank LIMIT ?",
            (query, limit),
        )
        notes = [dict(r) for r in await rows.fetchall()]
        for note in notes:
            note["tags"] = await get_note_tags(note["id"])
            note.pop("body", None)
        return notes


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------


async def _set_tags(db: aiosqlite.Connection, note_id: str, tags: list[str]) -> None:
    await db.execute("DELETE FROM note_tags WHERE note_id = ?", (note_id,))
    for tag in tags:
        await db.execute("INSERT OR IGNORE INTO tags (name) VALUES (?)", (tag,))
        row = await db.execute("SELECT id FROM tags WHERE name = ?", (tag,))
        row = await row.fetchone()
        await db.execute(
            "INSERT OR IGNORE INTO note_tags (note_id, tag_id) VALUES (?, ?)",
            (note_id, row["id"]),
        )


async def _index_note(
    db: aiosqlite.Connection,
    note_id: str,
    user_id: int,
    title: str,
    body: str,
) -> None:
    await db.execute("DELETE FROM notes_fts WHERE note_id = ?", (note_id,))
    await db.execute(
        "INSERT INTO notes_fts (note_id, user_id, title, body) VALUES (?, ?, ?, ?)",
        (note_id, user_id, title, body),
    )


async def _record_history(
    db: aiosqlite.Connection,
    note_id: str,
    user_id: int,
    action: str,
    ip: str | None,
    ua: str | None,
) -> None:
    await db.execute(
        "INSERT INTO history (note_id, user_id, action, ip, ua) VALUES (?, ?, ?, ?, ?)",
        (note_id, user_id, action, ip, ua),
    )


async def get_history(note_id: str) -> list[dict]:
    async with aiosqlite.connect(settings.database_path) as db:
        db.row_factory = aiosqlite.Row
        rows = await db.execute(
            "SELECT h.id, h.action, h.at, h.ip, h.ua, u.name AS username"
            " FROM history h JOIN users u ON u.id = h.user_id"
            " WHERE h.note_id = ? ORDER BY h.at DESC",
            (note_id,),
        )
        return [dict(r) for r in await rows.fetchall()]