package main

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"sync/atomic"
	"testing"
	"text/template"
	"time"

	"github.com/fluxcd/flux2/internal/utils"
	"github.com/google/go-cmp/cmp"
	"github.com/mattn/go-shellwords"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	k8syaml "k8s.io/apimachinery/pkg/util/yaml"
	"k8s.io/client-go/tools/clientcmd"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/envtest"
)

var nextNamespaceId int64

// Return a unique namespace with the specified prefix, for tests to create
// objects that won't collide with each other.
func allocateNamespace(prefix string) string {
	id := atomic.AddInt64(&nextNamespaceId, 1)
	return fmt.Sprintf("%s-%d", prefix, id)
}

func readYamlObjects(rdr io.Reader) ([]unstructured.Unstructured, error) {
	objects := []unstructured.Unstructured{}
	reader := k8syaml.NewYAMLReader(bufio.NewReader(rdr))
	for {
		doc, err := reader.Read()
		if err != nil {
			if err == io.EOF {
				break
			}
		}
		unstructuredObj := &unstructured.Unstructured{}
		decoder := k8syaml.NewYAMLOrJSONDecoder(bytes.NewBuffer(doc), len(doc))
		err = decoder.Decode(unstructuredObj)
		if err != nil {
			return nil, err
		}
		objects = append(objects, *unstructuredObj)
	}
	return objects, nil
}

// A KubeManager that can create objects that are subject to a test.
type testEnvKubeManager struct {
	client         client.WithWatch
	testEnv        *envtest.Environment
	kubeConfigPath string
}

func (m *testEnvKubeManager) CreateObjectFile(objectFile string, templateValues map[string]string, t *testing.T) {
	buf, err := os.ReadFile(objectFile)
	if err != nil {
		t.Fatalf("Error reading file '%s': %v", objectFile, err)
	}
	content, err := executeTemplate(string(buf), templateValues)
	if err != nil {
		t.Fatalf("Error evaluating template file '%s': '%v'", objectFile, err)
	}
	clientObjects, err := readYamlObjects(strings.NewReader(content))
	if err != nil {
		t.Fatalf("Error decoding yaml file '%s': %v", objectFile, err)
	}
	err = m.CreateObjects(clientObjects, t)
	if err != nil {
		t.Logf("Error creating test objects: '%v'", err)
	}
}

func (m *testEnvKubeManager) CreateObjects(clientObjects []unstructured.Unstructured, t *testing.T) error {
	for _, obj := range clientObjects {
		// First create the object then set its status if present in the
		// yaml file. Make a copy first since creating an object may overwrite
		// the status.
		createObj := obj.DeepCopy()
		err := m.client.Create(context.Background(), createObj)
		if err != nil {
			return err
		}
		obj.SetResourceVersion(createObj.GetResourceVersion())
		err = m.client.Status().Update(context.Background(), &obj)
		if err != nil {
			return err
		}
	}
	return nil
}

func (m *testEnvKubeManager) Stop() error {
	if m.testEnv == nil {
		return fmt.Errorf("do nothing because testEnv is nil")
	}
	return m.testEnv.Stop()
}

func NewTestEnvKubeManager(testClusterMode TestClusterMode) (*testEnvKubeManager, error) {
	switch testClusterMode {
	case TestEnvClusterMode:
		useExistingCluster := false
		testEnv := &envtest.Environment{
			UseExistingCluster: &useExistingCluster,
			CRDDirectoryPaths:  []string{"manifests"},
		}
		cfg, err := testEnv.Start()
		if err != nil {
			return nil, err
		}
		user, err := testEnv.ControlPlane.AddUser(envtest.User{
			Name:   "envtest-admin",
			Groups: []string{"system:masters"},
		}, nil)
		if err != nil {
			return nil, err
		}

		kubeConfig, err := user.KubeConfig()
		if err != nil {
			return nil, err
		}

		tmpFilename := filepath.Join("/tmp", "kubeconfig-"+time.Nanosecond.String())
		os.WriteFile(tmpFilename, kubeConfig, 0644)
		k8sClient, err := client.NewWithWatch(cfg, client.Options{
			Scheme: utils.NewScheme(),
		})
		if err != nil {
			return nil, err
		}
		return &testEnvKubeManager{
			testEnv:        testEnv,
			client:         k8sClient,
			kubeConfigPath: tmpFilename,
		}, nil
	case ExistingClusterMode:
		// TEST_KUBECONFIG is mandatory to prevent destroying a current cluster accidentally.
		testKubeConfig := os.Getenv("TEST_KUBECONFIG")
		if testKubeConfig == "" {
			return nil, fmt.Errorf("environment variable TEST_KUBECONFIG is required to run tests against an existing cluster")
		}

		useExistingCluster := true
		config, err := clientcmd.BuildConfigFromFlags("", testKubeConfig)
		testEnv := &envtest.Environment{
			UseExistingCluster: &useExistingCluster,
			Config:             config,
		}
		cfg, err := testEnv.Start()
		if err != nil {
			return nil, err
		}
		k8sClient, err := client.NewWithWatch(cfg, client.Options{
			Scheme: utils.NewScheme(),
		})
		if err != nil {
			return nil, err
		}
		return &testEnvKubeManager{
			testEnv:        testEnv,
			client:         k8sClient,
			kubeConfigPath: testKubeConfig,
		}, nil
	}

	return nil, nil
}

// Function that sets an expectation on the output of a command. Tests can
// either implement this directly or use a helper below.
type assertFunc func(output string, err error) error

// Assemble multiple assertFuncs into a single assertFunc
func assert(fns ...assertFunc) assertFunc {
	return func(output string, err error) error {
		for _, fn := range fns {
			if assertErr := fn(output, err); assertErr != nil {
				return assertErr
			}
		}
		return nil
	}
}

// Expect the command to run without error
func assertSuccess() assertFunc {
	return func(output string, err error) error {
		if err != nil {
			return fmt.Errorf("Expected success but was error: %v", err)
		}
		return nil
	}
}

// Expect the command to fail with the specified error
func assertError(expected string) assertFunc {
	return func(output string, err error) error {
		if err == nil {
			return fmt.Errorf("Expected error but was success")
		}
		if expected != err.Error() {
			return fmt.Errorf("Expected error '%v' but got '%v'", expected, err.Error())
		}
		return nil
	}
}

// Expect the command to succeed with the expected test output.
func assertGoldenValue(expected string) assertFunc {
	return assert(
		assertSuccess(),
		func(output string, err error) error {
			diff := cmp.Diff(expected, output)
			if diff != "" {
				return fmt.Errorf("Mismatch from expected value (-want +got):\n%s", diff)
			}
			return nil
		})
}

// Filename that contains the expected test output.
func assertGoldenFile(goldenFile string) assertFunc {
	return assertGoldenTemplateFile(goldenFile, map[string]string{})
}

// Filename that contains the expected test output. The golden file is a template that
// is pre-processed with the specified templateValues.
func assertGoldenTemplateFile(goldenFile string, templateValues map[string]string) assertFunc {
	goldenFileContents, fileErr := os.ReadFile(goldenFile)
	return func(output string, err error) error {
		if fileErr != nil {
			return fmt.Errorf("Error reading golden file '%s': %s", goldenFile, fileErr)
		}
		var expectedOutput string
		if len(templateValues) > 0 {
			expectedOutput, err = executeTemplate(string(goldenFileContents), templateValues)
			if err != nil {
				return fmt.Errorf("Error executing golden template file '%s': %s", goldenFile, err)
			}
		} else {
			expectedOutput = string(goldenFileContents)
		}
		if assertErr := assertGoldenValue(expectedOutput)(output, err); assertErr != nil {
			return fmt.Errorf("Mismatch from golden file '%s': %v", goldenFile, assertErr)
		}
		return nil
	}
}

type TestClusterMode int

const (
	TestEnvClusterMode = TestClusterMode(iota + 1)
	ExistingClusterMode
)

// Structure used for each test to load objects into kubernetes, run
// commands and assert on the expected output.
type cmdTestCase struct {
	// The command line arguments to test.
	args string
	// Tests use assertFunc to assert on an output, success or failure. This
	// can be a function defined by the test or existing function above.
	assert assertFunc
	// Filename that contains yaml objects to load into Kubernetes
	objectFile string
}

func (cmd *cmdTestCase) runTestCmd(t *testing.T) {
	actual, testErr := executeCommand(cmd.args)
	if assertErr := cmd.assert(actual, testErr); assertErr != nil {
		t.Error(assertErr)
	}
}

func executeTemplate(content string, templateValues map[string]string) (string, error) {
	tmpl := template.Must(template.New("golden").Parse(content))
	var out bytes.Buffer
	if err := tmpl.Execute(&out, templateValues); err != nil {
		return "", err
	}
	return out.String(), nil
}

// Run the command and return the captured output.
func executeCommand(cmd string) (string, error) {
	args, err := shellwords.Parse(cmd)
	if err != nil {
		return "", err
	}

	buf := new(bytes.Buffer)

	rootCmd.SetOut(buf)
	rootCmd.SetErr(buf)
	rootCmd.SetArgs(args)

	logger.stderr = rootCmd.ErrOrStderr()

	_, err = rootCmd.ExecuteC()
	result := buf.String()

	return result, err
}