package db

import (
	"database/sql"
	"fmt"
)

// migrations is an ordered list of SQL DDL statements. Each index is the
// migration version (1-based).
var migrations = []string{
	// Version 1: initial schema
	`CREATE TABLE IF NOT EXISTS seal_config (
		id INTEGER PRIMARY KEY CHECK (id = 1),
		encrypted_mek BLOB NOT NULL,
		kdf_salt BLOB NOT NULL,
		argon2_time INTEGER NOT NULL,
		argon2_memory INTEGER NOT NULL,
		argon2_threads INTEGER NOT NULL,
		initialized_at DATETIME NOT NULL DEFAULT (datetime('now'))
	);

	CREATE TABLE IF NOT EXISTS barrier_entries (
		path TEXT PRIMARY KEY,
		value BLOB NOT NULL,
		created_at DATETIME NOT NULL DEFAULT (datetime('now')),
		updated_at DATETIME NOT NULL DEFAULT (datetime('now'))
	);

	CREATE TABLE IF NOT EXISTS schema_migrations (
		version INTEGER PRIMARY KEY,
		applied_at DATETIME NOT NULL DEFAULT (datetime('now'))
	);`,

	// Version 2: barrier key registry for per-engine DEKs
	`CREATE TABLE IF NOT EXISTS barrier_keys (
		key_id       TEXT PRIMARY KEY,
		version      INTEGER NOT NULL DEFAULT 1,
		encrypted_dek BLOB NOT NULL,
		created_at   DATETIME NOT NULL DEFAULT (datetime('now')),
		rotated_at   DATETIME NOT NULL DEFAULT (datetime('now'))
	);`,
}

// Migrate applies all pending migrations.
func Migrate(db *sql.DB) error {
	// Ensure the migrations table exists (bootstrap).
	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		version INTEGER PRIMARY KEY,
		applied_at DATETIME NOT NULL DEFAULT (datetime('now'))
	)`); err != nil {
		return fmt.Errorf("db: create migrations table: %w", err)
	}

	var current int
	row := db.QueryRow("SELECT COALESCE(MAX(version), 0) FROM schema_migrations")
	if err := row.Scan(&current); err != nil {
		return fmt.Errorf("db: get migration version: %w", err)
	}

	for i := current; i < len(migrations); i++ {
		version := i + 1
		tx, err := db.Begin()
		if err != nil {
			return fmt.Errorf("db: begin migration %d: %w", version, err)
		}
		if _, err := tx.Exec(migrations[i]); err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("db: migration %d: %w", version, err)
		}
		if _, err := tx.Exec("INSERT INTO schema_migrations (version) VALUES (?)", version); err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("db: record migration %d: %w", version, err)
		}
		if err := tx.Commit(); err != nil {
			return fmt.Errorf("db: commit migration %d: %w", version, err)
		}
	}
	return nil
}