package db

import (
	"context"
	"database/sql"
	"testing"
)

// columnExists reports whether table has a column named column.
func columnExists(t *testing.T, ctx context.Context, conn *sql.DB, table, column string) bool {
	t.Helper()
	var n int
	if err := conn.QueryRowContext(ctx,
		"SELECT count(*) FROM pragma_table_info(?) WHERE name = ?", table, column).Scan(&n); err != nil {
		t.Fatalf("pragma_table_info(%s): %v", table, err)
	}
	return n == 1
}

// TestMigrate0009PinnedColumnIdempotent verifies the pinned migration (Android
// collaboration batch ③a / D5) is reversible and re-appliable: up adds the column,
// a second up is a no-op, down drops it, and a re-up restores it.
func TestMigrate0009PinnedColumnIdempotent(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	conn := openMemory(t)

	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("MigrateUp: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_sessions", "pinned") {
		t.Fatal("chat_sessions.pinned should exist after MigrateUp")
	}

	// Up twice: the recorded migration is skipped, so the column stays and no error.
	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("MigrateUp second call: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_sessions", "pinned") {
		t.Fatal("chat_sessions.pinned should still exist after idempotent re-run")
	}

	// Roll back every migration newer than 0008 (0009 itself plus any migration added
	// after it, currently 0010), so this test keeps validating the 0009 down no matter
	// how many later migrations the repo has grown.
	steps := len(upMigrationIDs(t)) - 8
	if err := MigrateDown(ctx, conn, steps, testLogger()); err != nil {
		t.Fatalf("MigrateDown(%d): %v", steps, err)
	}
	if columnExists(t, ctx, conn, "chat_sessions", "pinned") {
		t.Fatal("chat_sessions.pinned should be dropped by the 0009 down")
	}

	// Re-applying restores it end to end.
	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("re-MigrateUp: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_sessions", "pinned") {
		t.Fatal("chat_sessions.pinned should exist again after re-MigrateUp")
	}
}