package migration_test

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/stretchr/testify/require"

	"github.com/grafana/grafana/apps/dashboard/pkg/migration"
	"github.com/grafana/grafana/apps/dashboard/pkg/migration/schemaversion"
	"github.com/grafana/grafana/apps/dashboard/pkg/migration/testutil"
)

const INPUT_DIR = "testdata/input"
const OUTPUT_DIR = "testdata/output"

func TestMigrate(t *testing.T) {
	files, err := os.ReadDir(INPUT_DIR)
	require.NoError(t, err)

	// Use the same datasource provider as the frontend test to ensure consistency
	migration.Initialize(testutil.GetTestProvider())

	t.Run("minimum version check", func(t *testing.T) {
		err := migration.Migrate(map[string]interface{}{
			"schemaVersion": schemaversion.MIN_VERSION - 1,
		}, schemaversion.MIN_VERSION)

		var minVersionErr = schemaversion.NewMinimumVersionError(schemaversion.MIN_VERSION - 1)
		require.ErrorAs(t, err, &minVersionErr)
	})

	for _, f := range files {
		if f.IsDir() {
			continue
		}

		// Validate filename format
		if !strings.HasPrefix(f.Name(), "v") || !strings.HasSuffix(f.Name(), ".json") {
			t.Fatalf("input filename must use v{N}.{name}.json format, got: %s", f.Name())
		}

		inputDash := loadDashboard(t, filepath.Join(INPUT_DIR, f.Name()))
		inputVersion := getSchemaVersion(t, inputDash)

		t.Run("input check "+f.Name(), func(t *testing.T) {
			// use input version as the target version to ensure there are no changes
			require.NoError(t, migration.Migrate(inputDash, inputVersion), "input check migration failed")
			outBytes, err := json.MarshalIndent(inputDash, "", "  ")
			require.NoError(t, err, "failed to marshal migrated dashboard")
			// We can ignore gosec G304 here since it's a test
			// nolint:gosec
			expectedDash, err := os.ReadFile(filepath.Join(INPUT_DIR, f.Name()))
			require.NoError(t, err, "failed to read expected output file")
			require.JSONEq(t, string(expectedDash), string(outBytes), "%s input check did not match", f.Name())
		})

		testName := fmt.Sprintf("%s v%d to v%d", f.Name(), inputVersion, schemaversion.LATEST_VERSION)
		t.Run(testName, func(t *testing.T) {
			testMigration(t, inputDash, f.Name(), inputVersion, schemaversion.LATEST_VERSION)
		})
	}
}

func testMigration(t *testing.T, dash map[string]interface{}, inputFileName string, inputVersion, targetVersion int) {
	t.Helper()
	require.NoError(t, migration.Migrate(dash, targetVersion), "%d migration failed", targetVersion)

	outPath := filepath.Join(OUTPUT_DIR, inputFileName)
	outBytes, err := json.MarshalIndent(dash, "", "  ")
	require.NoError(t, err, "failed to marshal migrated dashboard")

	if _, err := os.Stat(outPath); os.IsNotExist(err) {
		err = os.WriteFile(outPath, outBytes, 0644)
		require.NoError(t, err, "failed to write new output file", outPath)
		return
	}

	// We can ignore gosec G304 here since it's a test
	// nolint:gosec
	existingBytes, err := os.ReadFile(outPath)
	require.NoError(t, err, "failed to read existing output file")
	require.JSONEq(t, string(existingBytes), string(outBytes), "%s did not match", outPath)
}

func getSchemaVersion(t *testing.T, dash map[string]interface{}) int {
	t.Helper()
	version, ok := dash["schemaVersion"]
	require.True(t, ok, "dashboard missing schemaVersion")

	switch v := version.(type) {
	case int:
		return v
	case float64:
		return int(v)
	default:
		t.Fatalf("invalid schemaVersion type: %T", version)
		return 0
	}
}

func loadDashboard(t *testing.T, path string) map[string]interface{} {
	t.Helper()
	// We can ignore gosec G304 here since it's a test
	// nolint:gosec
	inputBytes, err := os.ReadFile(path)
	require.NoError(t, err, "failed to read input file")

	var dash map[string]interface{}
	require.NoError(t, json.Unmarshal(inputBytes, &dash), "failed to unmarshal dashboard JSON")
	return dash
}