package db

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

// openMemory opens an isolated in-memory DB for a test.
func openMemory(t *testing.T) *sql.DB {
	t.Helper()
	ctx := context.Background()
	db, err := Open(ctx, ":memory:", testLogger())
	if err != nil {
		t.Fatalf("Open(:memory:) failed: %v", err)
	}
	t.Cleanup(func() { db.Close() })
	return db
}

// registeredMigrations returns the ids currently recorded in schema_migrations.
func registeredMigrations(t *testing.T, ctx context.Context, db *sql.DB) []string {
	t.Helper()
	rows, err := db.QueryContext(ctx, "SELECT id FROM schema_migrations")
	if err != nil {
		t.Fatalf("query schema_migrations: %v", err)
	}
	defer rows.Close()
	var ids []string
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			t.Fatalf("scan migration id: %v", err)
		}
		ids = append(ids, id)
	}
	if err := rows.Err(); err != nil {
		t.Fatalf("iterate schema_migrations: %v", err)
	}
	return ids
}

// upMigrationIDs returns the ids of the embedded up-migrations in apply order.
func upMigrationIDs(t *testing.T) []string {
	t.Helper()
	migs, err := loadMigrations()
	if err != nil {
		t.Fatalf("loadMigrations: %v", err)
	}
	ids := make([]string, len(migs))
	for i, m := range migs {
		ids[i] = m.id
	}
	return ids
}

// appMetaExists reports whether the app_meta table is present.
func appMetaExists(t *testing.T, ctx context.Context, db *sql.DB) bool {
	t.Helper()
	var n int
	if err := db.QueryRowContext(ctx, "SELECT count(*) FROM sqlite_master WHERE type='table' AND name='app_meta'").Scan(&n); err != nil {
		t.Fatalf("check app_meta presence: %v", err)
	}
	return n == 1
}

func TestMigrateUp_FirstApply_正常(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	db := openMemory(t)

	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp first call: %v", err)
	}

	// Applies every embedded up-migration, in order.
	ids := registeredMigrations(t, ctx, db)
	if want := upMigrationIDs(t); !slices.Equal(ids, want) {
		t.Fatalf("schema_migrations = %v, want %v", ids, want)
	}
	if !appMetaExists(t, ctx, db) {
		t.Fatal("app_meta table should exist after MigrateUp")
	}

	// applied_at must be recorded on the first migration row.
	var appliedAt string
	if err := db.QueryRowContext(ctx, "SELECT applied_at FROM schema_migrations WHERE id = ?", "0001_init").Scan(&appliedAt); err != nil {
		t.Fatalf("read applied_at: %v", err)
	}
	if appliedAt == "" {
		t.Fatal("applied_at should not be empty")
	}
}

func TestMigrateUp_Idempotent_正常(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	db := openMemory(t)

	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp first call: %v", err)
	}

	// Second call must not re-execute or duplicate the records.
	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp second call: %v", err)
	}
	want := upMigrationIDs(t)
	ids := registeredMigrations(t, ctx, db)
	if !slices.Equal(ids, want) {
		t.Fatalf("idempotent: schema_migrations = %v, want %v", ids, want)
	}
	if !appMetaExists(t, ctx, db) {
		t.Fatal("app_meta should still exist after idempotent re-run")
	}
}

func TestMigrateDown_ThenReUp_正常(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	db := openMemory(t)

	want := upMigrationIDs(t)
	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp: %v", err)
	}

	// Roll back every applied migration.
	if err := MigrateDown(ctx, db, len(want), testLogger()); err != nil {
		t.Fatalf("MigrateDown(all): %v", err)
	}
	if appMetaExists(t, ctx, db) {
		t.Fatal("app_meta should be dropped after MigrateDown(all)")
	}
	if ids := registeredMigrations(t, ctx, db); len(ids) != 0 {
		t.Fatalf("schema_migrations should be empty after rollback, got %v", ids)
	}

	// Re-applying must work end to end again.
	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("re-MigrateUp: %v", err)
	}
	if !appMetaExists(t, ctx, db) {
		t.Fatal("app_meta should exist again after re-MigrateUp")
	}
	if ids := registeredMigrations(t, ctx, db); !slices.Equal(ids, want) {
		t.Fatalf("schema_migrations = %v, want %v", ids, want)
	}
}

func TestMigrateDown_ZeroSteps_异常(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	db := openMemory(t)

	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp: %v", err)
	}

	for _, steps := range []int{0, -1} {
		if err := MigrateDown(ctx, db, steps, testLogger()); !errors.Is(err, ErrInvalidSteps) {
			t.Fatalf("MigrateDown(%d) err = %v, want wrap of ErrInvalidSteps", steps, err)
		}
	}
}

func TestMigrateDown_StepsBeyondApplied_边界(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	db := openMemory(t)

	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp: %v", err)
	}

	// More steps than applied must roll everything back without error.
	if err := MigrateDown(ctx, db, 10, testLogger()); err != nil {
		t.Fatalf("MigrateDown(10): %v", err)
	}
	if appMetaExists(t, ctx, db) {
		t.Fatal("app_meta should be dropped when rolling back all")
	}
	if ids := registeredMigrations(t, ctx, db); len(ids) != 0 {
		t.Fatalf("schema_migrations should be empty, got %v", ids)
	}
}

func TestAppMeta_ReadWrite_正常(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	db := openMemory(t)

	if err := MigrateUp(ctx, db, testLogger()); err != nil {
		t.Fatalf("MigrateUp: %v", err)
	}

	// Parameterized insert.
	if _, err := db.ExecContext(ctx,
		"INSERT INTO app_meta (key, value) VALUES (?, ?)", "schema_version", "1"); err != nil {
		t.Fatalf("insert app_meta: %v", err)
	}

	// Parameterized read.
	var value string
	if err := db.QueryRowContext(ctx,
		"SELECT value FROM app_meta WHERE key = ?", "schema_version").Scan(&value); err != nil {
		t.Fatalf("read app_meta: %v", err)
	}
	if value != "1" {
		t.Fatalf("value = %q, want %q", value, "1")
	}

	// Parameterized update.
	if _, err := db.ExecContext(ctx,
		"UPDATE app_meta SET value = ? WHERE key = ?", "2", "schema_version"); err != nil {
		t.Fatalf("update app_meta: %v", err)
	}
	if err := db.QueryRowContext(ctx,
		"SELECT value FROM app_meta WHERE key = ?", "schema_version").Scan(&value); err != nil {
		t.Fatalf("read updated app_meta: %v", err)
	}
	if value != "2" {
		t.Fatalf("value after update = %q, want %q", value, "2")
	}

	// Parameterized delete.
	if _, err := db.ExecContext(ctx,
		"DELETE FROM app_meta WHERE key = ?", "schema_version"); err != nil {
		t.Fatalf("delete app_meta: %v", err)
	}
	var n int
	if err := db.QueryRowContext(ctx,
		"SELECT count(*) FROM app_meta WHERE key = ?", "schema_version").Scan(&n); err != nil {
		t.Fatalf("count app_meta after delete: %v", err)
	}
	if n != 0 {
		t.Fatalf("expected 0 rows after delete, got %d", n)
	}
}