/*
Copyright 2021 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package tester

import (
	"archive/tar"
	"compress/gzip"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"os"
	"path"
	"path/filepath"
	"runtime"
	"strings"

	"k8s.io/klog/v2"
	"sigs.k8s.io/kubetest2/pkg/exec"
)

// AcquireKubectl obtains kubectl and places it in a temporary directory
func (t *Tester) AcquireKubectl() (string, error) {
	// first, get the name of the latest release (e.g. v1.20.0-alpha.0)
	if t.TestPackageVersion == "" {
		cmd := exec.Command(
			"gsutil",
			"cat",
			fmt.Sprintf("gs://%s/%s/%v", t.TestPackageBucket, t.TestPackageDir, t.TestPackageMarker),
		)
		lines, err := exec.OutputLines(cmd)
		if err != nil {
			return "", fmt.Errorf("failed to get latest release name: %s", err)
		}
		if len(lines) == 0 {
			return "", fmt.Errorf("getting latest release name had no output")
		}
		t.TestPackageVersion = lines[0]

		klog.Infof("Kubectl package version was not specified. Defaulting to version from %s: %s", t.TestPackageMarker, t.TestPackageVersion)
	}

	clientTar := fmt.Sprintf("kubernetes-client-%s-%s.tar.gz", runtime.GOOS, runtime.GOARCH)

	downloadDir, err := os.UserCacheDir()
	if err != nil {
		return "", fmt.Errorf("failed to get user cache directory: %v", err)
	}

	downloadPath := filepath.Join(downloadDir, clientTar)

	if err := t.ensureClientTar(downloadPath, clientTar); err != nil {
		return "", err
	}

	return t.extractBinaries(downloadPath)
}

func (t *Tester) extractBinaries(downloadPath string) (string, error) {
	// finally, search for the client package and extract it
	f, err := os.Open(downloadPath)
	if err != nil {
		return "", fmt.Errorf("failed to open downloaded tar at %s: %s", downloadPath, err)
	}
	defer f.Close()
	gzf, err := gzip.NewReader(f)
	if err != nil {
		return "", fmt.Errorf("failed to create gzip reader: %s", err)
	}
	tarReader := tar.NewReader(gzf)

	kubectlDir, err := os.MkdirTemp("", "kubectl")
	if err != nil {
		return "", err
	}

	// this is the expected path of the package inside the tar
	// it will be extracted to kubectlDir in the loop
	kubectlPackagePath := "kubernetes/client/bin/kubectl"
	for {
		header, err := tarReader.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return "", fmt.Errorf("error during tar read: %s", err)
		}

		if header.Name == kubectlPackagePath {
			kubectlPath := path.Join(kubectlDir, "kubectl")
			outFile, err := os.Create(kubectlPath)
			if err != nil {
				return "", fmt.Errorf("error creating file at %s: %s", kubectlPath, err)
			}
			defer outFile.Close()

			if err := outFile.Chmod(0700); err != nil {
				return "", fmt.Errorf("failed to make %s executable: %s", kubectlPath, err)
			}

			if _, err := io.Copy(outFile, tarReader); err != nil {
				return "", fmt.Errorf("error reading data from tar with header name %s: %s", header.Name, err)
			}
			return kubectlPath, nil
		}
	}
	return "", fmt.Errorf("failed to find %s in %s", kubectlPackagePath, downloadPath)
}

// ensureClientTar checks if the kubernetes client tarball already exists
// and verifies the hashes
// else downloads it from GCS
func (t *Tester) ensureClientTar(downloadPath, clientTar string) error {
	if _, err := os.Stat(downloadPath); err == nil {
		klog.V(0).Infof("Found existing tar at %v", downloadPath)
		if err := t.compareSHA(downloadPath, clientTar); err == nil {
			klog.V(0).Infof("Validated hash for existing tar at %v", downloadPath)
			return nil
		}
		klog.Warning(err)
	}

	args := []string{
		"gsutil", "cp",
		fmt.Sprintf(
			"gs://%s/%s/%s/%s",
			t.TestPackageBucket,
			t.TestPackageDir,
			t.TestPackageVersion,
			clientTar,
		),
		downloadPath,
	}
	klog.Info(strings.Join(args, " "))

	cmd := exec.Command(args[0], args[1:]...)
	exec.InheritOutput(cmd)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("failed to download release tar %s for release %s: %s", clientTar, t.TestPackageVersion, err)
	}
	return nil
}

func (t *Tester) compareSHA(downloadPath string, clientTar string) error {
	cmd := exec.Command("gsutil", "cat",
		fmt.Sprintf(
			"gs://%s/%s/%s/%s",
			t.TestPackageBucket,
			t.TestPackageDir,
			t.TestPackageVersion,
			clientTar+".sha256",
		),
	)
	expectedSHABytes, err := exec.Output(cmd)
	if err != nil {
		return fmt.Errorf("failed to get sha256 for release tar %s for release %s: %s", clientTar, t.TestPackageVersion, err)
	}
	expectedSHA := strings.TrimSuffix(string(expectedSHABytes), "\n")
	actualSHA, err := sha256sum(downloadPath)
	if err != nil {
		return fmt.Errorf("failed to compute sha256 for %q: %v", downloadPath, err)
	}
	if actualSHA != expectedSHA {
		return fmt.Errorf("sha256 does not match")
	}
	return nil
}

func sha256sum(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()

	h := sha256.New()
	if _, err := io.Copy(h, f); err != nil {
		return "", err
	}
	return hex.EncodeToString(h.Sum(nil)), nil
}
