#!/usr/bin/env python3
"""
Database migration: Add mic_unit_pref column to user_preferences.

Adds a single field controlling the mic channel's unit on the event-
report waveform chart in the SFM event detail modal.  "dBL" (default)
or "psi".  Peaks and KPI tiles elsewhere are always dBL regardless.

Idempotent — safe to re-run.
"""

import sqlite3
from pathlib import Path


def migrate():
    possible_paths = [
        Path("data/seismo_fleet.db"),
        Path("data/sfm.db"),
        Path("data/seismo.db"),
    ]
    db_path = next((p for p in possible_paths if p.exists()), None)
    if db_path is None:
        print(f"Database not found in any of: {[str(p) for p in possible_paths]}")
        print("Will be created with the new column when models.py initialises.")
        return

    print(f"Using database: {db_path}")
    conn = sqlite3.connect(db_path)
    cur = conn.cursor()

    cur.execute("PRAGMA table_info(user_preferences)")
    existing = {row[1] for row in cur.fetchall()}

    if "mic_unit_pref" in existing:
        print("mic_unit_pref already exists — nothing to do.")
        conn.close()
        return

    cur.execute(
        "ALTER TABLE user_preferences "
        "ADD COLUMN mic_unit_pref TEXT DEFAULT 'dBL'"
    )
    # Backfill the single row that should exist (id=1) to the default,
    # in case the column ends up NULL on existing rows.
    cur.execute(
        "UPDATE user_preferences SET mic_unit_pref = 'dBL' "
        "WHERE mic_unit_pref IS NULL"
    )
    conn.commit()
    conn.close()
    print("Added mic_unit_pref to user_preferences (default 'dBL').")


if __name__ == "__main__":
    migrate()