from __future__ import annotations

import json
import logging
import secrets
from pathlib import Path

from sqlalchemy import inspect, text

from app.auth.tokens import hash_token
from app.character.card import DEFAULT_CARD, normalize_card
from app.config import get_settings
from app.db.base import engine

logger = logging.getLogger(__name__)

TENANT_TABLES = (
    "chat_sessions",
    "user_profile",
    "memory_facts",
    "fitness_profiles",
    "body_metrics",
    "food_logs",
    "water_logs",
    "workout_logs",
    "step_logs",
    "fitness_reminders",
    "shopping_lists",
    "reminders",
    "documents",
    "pomodoro_cycles",
    "pomodoro_sessions",
    "project_bindings",
    "work_items",
)

LEGACY_CARD_PATH = Path("./data/character.json")


def _table_exists(name: str) -> bool:
    return name in inspect(engine).get_table_names()


def _columns(table: str) -> set[str]:
    if not _table_exists(table):
        return set()
    return {col["name"] for col in inspect(engine).get_columns(table)}


def _add_column_if_missing(table: str, column: str, ddl: str) -> None:
    if column in _columns(table):
        return
    with engine.begin() as conn:
        conn.execute(text(ddl))


def _ensure_users_table() -> None:
    if _table_exists("users"):
        return
    with engine.begin() as conn:
        conn.execute(
            text(
                "CREATE TABLE users ("
                "id INTEGER PRIMARY KEY AUTOINCREMENT, "
                "username VARCHAR(64) NOT NULL UNIQUE, "
                "display_name VARCHAR(255) DEFAULT '', "
                "api_token_hash VARCHAR(64) NOT NULL, "
                "is_active BOOLEAN DEFAULT 1, "
                "created_at DATETIME DEFAULT CURRENT_TIMESTAMP"
                ")"
            )
        )
        conn.execute(text("CREATE INDEX IF NOT EXISTS ix_users_api_token_hash ON users (api_token_hash)"))


def _ensure_character_cards_table() -> None:
    if _table_exists("character_cards"):
        return
    with engine.begin() as conn:
        conn.execute(
            text(
                "CREATE TABLE character_cards ("
                "id INTEGER PRIMARY KEY AUTOINCREMENT, "
                "user_id INTEGER NOT NULL UNIQUE REFERENCES users(id) ON DELETE CASCADE, "
                "card_json TEXT DEFAULT '{}', "
                "updated_at DATETIME DEFAULT CURRENT_TIMESTAMP"
                ")"
            )
        )
        conn.execute(text("CREATE INDEX IF NOT EXISTS ix_character_cards_user_id ON character_cards (user_id)"))


def _add_user_id_columns() -> None:
    for table in TENANT_TABLES:
        if not _table_exists(table):
            continue
        _add_column_if_missing(
            table,
            "user_id",
            f"ALTER TABLE {table} ADD COLUMN user_id INTEGER REFERENCES users(id) ON DELETE CASCADE",
        )
        with engine.begin() as conn:
            conn.execute(text(f"CREATE INDEX IF NOT EXISTS ix_{table}_user_id ON {table} (user_id)"))


def _ensure_default_user() -> tuple[int, str | None]:
    settings = get_settings()
    with engine.begin() as conn:
        row = conn.execute(text("SELECT id FROM users ORDER BY id LIMIT 1")).fetchone()
        if row:
            return int(row[0]), None

        username = settings.default_user_username or "owner"
        display_name = settings.default_user_display_name or username
        plain_token = (settings.default_api_token or "").strip()
        generated = False
        if not plain_token:
            plain_token = secrets.token_urlsafe(32)
            generated = True

        token_hash = hash_token(plain_token)
        conn.execute(
            text(
                "INSERT INTO users (id, username, display_name, api_token_hash, is_active) "
                "VALUES (1, :username, :display_name, :token_hash, 1)"
            ),
            {"username": username, "display_name": display_name, "token_hash": token_hash},
        )
    if generated:
        logger.warning(
            "DEFAULT_API_TOKEN not set — generated token for user '%s': %s",
            username,
            plain_token,
        )
        return 1, plain_token
    return 1, None


def _backfill_user_id(default_user_id: int = 1) -> None:
    with engine.begin() as conn:
        for table in TENANT_TABLES:
            if not _table_exists(table):
                continue
            conn.execute(
                text(f"UPDATE {table} SET user_id = :uid WHERE user_id IS NULL"),
                {"uid": default_user_id},
            )


def _rebuild_shopping_unique() -> None:
    if not _table_exists("shopping_lists"):
        return
    with engine.begin() as conn:
        conn.execute(text("CREATE UNIQUE INDEX IF NOT EXISTS uq_shopping_lists_user_name ON shopping_lists (user_id, name)"))


def _rebuild_project_bindings_unique() -> None:
    if not _table_exists("project_bindings"):
        return
    with engine.begin() as conn:
        conn.execute(
            text(
                "CREATE UNIQUE INDEX IF NOT EXISTS uq_project_bindings_user_slug "
                "ON project_bindings (user_id, taiga_slug)"
            )
        )


def _import_character_card(user_id: int) -> None:
    with engine.begin() as conn:
        existing = conn.execute(
            text("SELECT id FROM character_cards WHERE user_id = :uid"),
            {"uid": user_id},
        ).fetchone()
        if existing:
            return

        card = normalize_card(DEFAULT_CARD)
        if LEGACY_CARD_PATH.is_file():
            try:
                raw = json.loads(LEGACY_CARD_PATH.read_text(encoding="utf-8"))
                card = normalize_card(raw)
            except (json.JSONDecodeError, OSError):
                pass

        conn.execute(
            text("INSERT INTO character_cards (user_id, card_json) VALUES (:uid, :json)"),
            {"uid": user_id, "json": json.dumps(card, ensure_ascii=False)},
        )


def _backfill_qdrant_user_id(default_user_id: int = 1) -> None:
    settings = get_settings()
    if not settings.rag_enabled:
        return
    try:
        from app.rag.store import COLLECTION_DOC_CHUNKS, COLLECTION_FACTS, COLLECTION_SUMMARIES, _client
    except Exception:
        logger.exception("Qdrant backfill skipped")
        return

    try:
        client = _client()
    except Exception:
        logger.warning('Qdrant unavailable, skipping user_id backfill')
        return

    for collection in (COLLECTION_FACTS, COLLECTION_SUMMARIES, COLLECTION_DOC_CHUNKS):
        try:
            if not client.collection_exists(collection):
                continue
        except Exception:
            logger.warning('Qdrant unavailable for collection %s', collection)
            continue
        offset = None
        while True:
            points, offset = client.scroll(
                collection_name=collection,
                limit=100,
                offset=offset,
                with_payload=True,
                with_vectors=False,
            )
            if not points:
                break
            missing = [point.id for point in points if (point.payload or {}).get("user_id") is None]
            if missing:
                client.set_payload(
                    collection_name=collection,
                    payload={"user_id": default_user_id},
                    points=missing,
                )
            if offset is None:
                break
    logger.info("Qdrant user_id backfill completed for user_id=%s", default_user_id)


def run_multi_user_migrations() -> str | None:
    """Returns newly generated API token if any."""
    _ensure_users_table()
    _ensure_character_cards_table()
    _add_user_id_columns()
    user_id, new_token = _ensure_default_user()
    _backfill_user_id(user_id)
    _rebuild_shopping_unique()
    _rebuild_project_bindings_unique()
    _import_character_card(user_id)
    _backfill_qdrant_user_id(user_id)
    return new_token