package db

import "context"

// addColumn describes one ALTER TABLE ADD COLUMN migration step.
type addColumn struct {
	table  string
	column string
	ddl    string
}

// schema.sql is the source of truth and runs first, so every table already
// exists here. Column-level changes cannot be expressed with IF NOT EXISTS,
// so they are applied explicitly and guarded by a pragma check.
var columnMigrations = []addColumn{
	{"users", "is_pending", "ALTER TABLE users ADD COLUMN is_pending INTEGER NOT NULL DEFAULT 0"},
	{"users", "register_application", "ALTER TABLE users ADD COLUMN register_application TEXT"},
	{"users", "passkey_setup_started_at", "ALTER TABLE users ADD COLUMN passkey_setup_started_at TEXT"},
	{"patches", "version", "ALTER TABLE patches ADD COLUMN version TEXT NOT NULL DEFAULT ''"},
	{"repositories", "allow_user_labels", "ALTER TABLE repositories ADD COLUMN allow_user_labels INTEGER NOT NULL DEFAULT 0"},
	{"ci_runs", "repo_run_id", "ALTER TABLE ci_runs ADD COLUMN repo_run_id INTEGER"},
}

// migrate brings an existing database file up to date.
func (d *DB) migrate(ctx context.Context) error {
	for _, m := range columnMigrations {
		has, err := d.hasColumn(ctx, m.table, m.column)
		if err != nil {
			return err
		}
		if has {
			continue
		}
		if _, err := d.ExecContext(ctx, m.ddl); err != nil {
			return err
		}
	}
	// Backfill patch versions left empty by the column migration above.
	if _, err := d.ExecContext(ctx,
		"UPDATE patches SET version = lower(hex(randomblob(16))) WHERE version = ''"); err != nil {
		return err
	}
	// Expired sessions serve no purpose after a restart.
	return d.DeleteExpiredSessions(ctx)
}

func (d *DB) hasColumn(ctx context.Context, table, column string) (bool, error) {
	var n int
	err := d.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM pragma_table_info(?) WHERE name = ?`, table, column).Scan(&n)
	return n > 0, err
}