#!/usr/bin/env python3
"""Apply pending SQL migrations to the accounts database.

This project has no Alembic. SQLAlchemy ``create_all()`` only creates *missing
tables*, so column additions to the long-lived accounts DB are done with the
hand-written ``.sql`` files in ``deploy/migrations/``. This runner applies the
ones a given database hasn't seen yet and records them in a ``schema_migrations``
table, so it is safe (and cheap) to run on every deploy.

It resolves the database exactly as the app does (``db.py``):
``THERMOGRAPH_ACCOUNTS_DB`` if set, otherwise ``<repo>/data/accounts.sqlite``.

Fresh database: the app's ``create_all()`` builds the *current* schema on first
start, so there is nothing to ALTER. This runner detects that (no file yet, or no
``user`` table) and records the existing migrations as a baseline instead of
replaying them, so they never run against a schema that already has the columns.

Usage (wired into deploy.sh / deploy-dev.sh, but runnable by hand too):

    /opt/thermograph/.venv/bin/python deploy/migrate-db.py
"""
import glob
import os
import shutil
import sqlite3
import sys
import time

HERE = os.path.dirname(os.path.abspath(__file__))
REPO = os.path.dirname(HERE)
MIGRATIONS_DIR = os.path.join(HERE, "migrations")
DB_PATH = os.environ.get("THERMOGRAPH_ACCOUNTS_DB") or os.path.join(REPO, "data", "accounts.sqlite")


def _applied(conn: sqlite3.Connection) -> set[str]:
    conn.execute(
        "CREATE TABLE IF NOT EXISTS schema_migrations ("
        "name TEXT PRIMARY KEY, applied_at TEXT NOT NULL)"
    )
    return {row[0] for row in conn.execute("SELECT name FROM schema_migrations")}


def _record(conn: sqlite3.Connection, name: str) -> None:
    conn.execute(
        "INSERT OR IGNORE INTO schema_migrations(name, applied_at) "
        "VALUES (?, datetime('now'))",
        (name,),
    )


def _has_user_table(conn: sqlite3.Connection) -> bool:
    row = conn.execute(
        "SELECT 1 FROM sqlite_master WHERE type='table' AND name='user'"
    ).fetchone()
    return row is not None


def main() -> None:
    migrations = sorted(glob.glob(os.path.join(MIGRATIONS_DIR, "*.sql")))
    if not migrations:
        print("migrate-db: no migrations found")
        return

    os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)
    fresh = not os.path.exists(DB_PATH)
    conn = sqlite3.connect(DB_PATH)
    try:
        applied = _applied(conn)
        pending = [m for m in migrations if os.path.basename(m) not in applied]
        if not pending:
            print(f"migrate-db: up to date ({len(applied)} applied) -> {DB_PATH}")
            return

        # Fresh DB (or one whose accounts schema hasn't been built yet): the app's
        # create_all() will produce the current schema on next start, so record the
        # existing migrations as a baseline rather than ALTERing a table that isn't
        # there. Only genuinely older databases need the ALTERs replayed.
        if fresh or not _has_user_table(conn):
            for m in pending:
                _record(conn, os.path.basename(m))
            conn.commit()
            print(f"migrate-db: fresh database, baselined {len(pending)} migration(s) -> {DB_PATH}")
            return

        # These are the authoritative, non-regenerable accounts. Back the DB up
        # before touching it, next to the DB with a timestamp.
        backup = f"{DB_PATH}.bak-{time.strftime('%Y%m%d-%H%M%S')}"
        shutil.copy2(DB_PATH, backup)
        print(f"migrate-db: backed up -> {backup}")

        for m in pending:
            name = os.path.basename(m)
            with open(m, encoding="utf-8") as f:
                sql = f.read()
            try:
                conn.executescript(sql)
            except sqlite3.OperationalError as e:
                msg = str(e).lower()
                # Idempotent: a column/index this migration adds already exists
                # (applied by hand before, or created fresh from the model). Treat
                # as already-applied and record it; re-raise anything unexpected.
                if "duplicate column" in msg or "already exists" in msg:
                    print(f"migrate-db: {name} already present in schema, recording")
                else:
                    conn.rollback()
                    print(f"migrate-db: FAILED on {name}: {e}", file=sys.stderr)
                    raise
            _record(conn, name)
            conn.commit()
            print(f"migrate-db: applied {name}")

        print(f"migrate-db: done ({len(pending)} newly recorded) -> {DB_PATH}")
    finally:
        conn.close()


if __name__ == "__main__":
    main()