// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"context"
	"flag"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"testing"

	"golang.org/x/mod/module"
	"golang.org/x/tools/txtar"
)

var (
	testwork     = flag.Bool("testwork", false, "preserve work directory")
	updateGolden = flag.Bool("u", false, "update expected text in test files instead of failing")
)

var hasGitCache struct {
	once  sync.Once
	found bool
}

// hasGit reports whether the git executable exists on the PATH.
func hasGit() bool {
	hasGitCache.once.Do(func() {
		if _, err := exec.LookPath("git"); err != nil {
			return
		}
		hasGitCache.found = true
	})
	return hasGitCache.found
}

// prepareProxy creates a proxy dir and returns an associated ctx.
//
// proxyVersions must be a map of module version to true. If proxyVersions is
// empty, all modules in mod/ will be included in the proxy list. If proxy
// versions is non-empty, only those modules in mod/ that match an entry in
// proxyVersions will be included.
//
// ctx must be used in runRelease.
// cleanup must be called when the relevant tests are finished.
func prepareProxy(proxyVersions map[module.Version]bool, tests []*test) (ctx context.Context, cleanup func(), _ error) {
	env := append(os.Environ(), "GO111MODULE=on", "GOSUMDB=off")

	proxyDir, proxyURL, err := buildProxyDir(proxyVersions, tests)
	if err != nil {
		return nil, nil, fmt.Errorf("error building proxy dir: %v", err)
	}
	env = append(env, fmt.Sprintf("GOPROXY=%s", proxyURL))

	cacheDir, err := os.MkdirTemp("", "gorelease_test-gocache")
	if err != nil {
		return nil, nil, err
	}
	env = append(env, fmt.Sprintf("GOPATH=%s", cacheDir))

	return context.WithValue(context.Background(), "env", env), func() {
		if *testwork {
			fmt.Fprintf(os.Stderr, "test cache dir: %s\n", cacheDir)
			fmt.Fprintf(os.Stderr, "test proxy dir: %s\ntest proxy URL: %s\n", proxyDir, proxyURL)
		} else {
			cmd := exec.Command("go", "clean", "-modcache")
			cmd.Env = env
			if err := cmd.Run(); err != nil {
				fmt.Fprintln(os.Stderr, fmt.Errorf("error running go clean: %v", err))
			}

			if err := os.RemoveAll(cacheDir); err != nil {
				fmt.Fprintln(os.Stderr, fmt.Errorf("error removing cache dir %s: %v", cacheDir, err))
			}
			if err := os.RemoveAll(proxyDir); err != nil {
				fmt.Fprintln(os.Stderr, fmt.Errorf("error removing proxy dir %s: %v", proxyDir, err))
			}
		}
	}, nil
}

// test describes an individual test case, written as a .test file in the
// testdata directory.
//
// Each test is a txtar archive (see golang.org/x/tools/txtar). The comment
// section (before the first file) contains a sequence of key=value pairs
// (one per line) that configure the test.
//
// Most tests include a file named "want". The output of gorelease is compared
// against this file. If the -u flag is set, this file is replaced with the
// actual output of gorelease, and the test is written back to disk. This is
// useful for updating tests after cosmetic changes.
type test struct {
	txtar.Archive

	// testPath is the name of the .test file describing the test.
	testPath string

	// modPath (set with mod=...) is the path of the module being tested. Used
	// to retrieve files from the test proxy.
	modPath string

	// version (set with version=...) is the name of a version to check out
	// from the test proxy into the working directory. Some tests use this
	// instead of specifying files they need in the txtar archive.
	version string

	// baseVersion (set with base=...) is the value of the -base flag to pass
	// to gorelease.
	baseVersion string

	// releaseVersion (set with release=...) is the value of the -version flag
	// to pass to gorelease.
	releaseVersion string

	// dir (set with dir=...) is the directory where gorelease should be invoked.
	// If unset, gorelease is invoked in the directory where the txtar archive
	// is unpacked. This is useful for invoking gorelease in a subdirectory.
	dir string

	// wantError (set with error=...) is true if the test expects a hard error
	// (returned by runRelease).
	wantError bool

	// wantSuccess (set with success=...) is true if the test expects a report
	// to be returned without errors or diagnostics. True by default.
	wantSuccess bool

	// skip (set with skip=...) is non-empty if the test should be skipped.
	skip string

	// want is set to the contents of the file named "want" in the txtar archive.
	want []byte

	// proxyVersions is used to set the exact contents of the GOPROXY.
	//
	// If empty, all of testadata/mod/ will be included in the proxy.
	// If it is not empty, each entry must be of the form <modpath>@v<version>
	// and exist in testdata/mod/.
	proxyVersions map[module.Version]bool

	// vcs is used to set the VCS that the root of the test should
	// emulate. Allowed values are git, and hg.
	vcs string
}

// readTest reads and parses a .test file with the given name.
func readTest(testPath string) (*test, error) {
	arc, err := txtar.ParseFile(testPath)
	if err != nil {
		return nil, err
	}
	t := &test{
		Archive:     *arc,
		testPath:    testPath,
		wantSuccess: true,
	}

	for n, line := range bytes.Split(t.Comment, []byte("\n")) {
		lineNum := n + 1
		if i := bytes.IndexByte(line, '#'); i >= 0 {
			line = line[:i]
		}
		line = bytes.TrimSpace(line)
		if len(line) == 0 {
			continue
		}

		var key, value string
		if i := bytes.IndexByte(line, '='); i < 0 {
			return nil, fmt.Errorf("%s:%d: no '=' found", testPath, lineNum)
		} else {
			key = strings.TrimSpace(string(line[:i]))
			value = strings.TrimSpace(string(line[i+1:]))
		}
		switch key {
		case "mod":
			t.modPath = value
		case "version":
			t.version = value
		case "base":
			t.baseVersion = value
		case "release":
			t.releaseVersion = value
		case "dir":
			t.dir = value
		case "skip":
			t.skip = value
		case "success":
			t.wantSuccess, err = strconv.ParseBool(value)
			if err != nil {
				return nil, fmt.Errorf("%s:%d: %v", testPath, lineNum, err)
			}
		case "error":
			t.wantError, err = strconv.ParseBool(value)
			if err != nil {
				return nil, fmt.Errorf("%s:%d: %v", testPath, lineNum, err)
			}
		case "proxyVersions":
			if len(value) == 0 {
				break
			}
			proxyVersions := make(map[module.Version]bool)
			parts := strings.Split(value, ",")
			for _, modpathWithVersion := range parts {
				vParts := strings.Split(modpathWithVersion, "@")
				if len(vParts) != 2 {
					return nil, fmt.Errorf("proxyVersions entry %s is invalid: it should be of the format <modpath>@v<semver> (ex: github.com/foo/bar@v1.2.3)", modpathWithVersion)
				}
				modPath, version := vParts[0], vParts[1]
				mv := module.Version{
					Path:    modPath,
					Version: version,
				}
				proxyVersions[mv] = true
			}
			t.proxyVersions = proxyVersions
		case "vcs":
			t.vcs = value
		default:
			return nil, fmt.Errorf("%s:%d: unknown key: %q", testPath, lineNum, key)
		}
	}
	if t.modPath == "" && (t.version != "" || (t.baseVersion != "" && t.baseVersion != "none")) {
		return nil, fmt.Errorf("%s: version or base was set but mod was not set", testPath)
	}

	haveFiles := false
	for _, f := range t.Files {
		if f.Name == "want" {
			t.want = bytes.TrimSpace(f.Data)
			continue
		}
		haveFiles = true
	}

	if haveFiles && t.version != "" {
		return nil, fmt.Errorf("%s: version is set but files are present", testPath)
	}

	return t, nil
}

// updateTest replaces the contents of the file named "want" within a test's
// txtar archive, then formats and writes the test file.
func updateTest(t *test, want []byte) error {
	var wantFile *txtar.File
	for i := range t.Files {
		if t.Files[i].Name == "want" {
			wantFile = &t.Files[i]
			break
		}
	}
	if wantFile == nil {
		t.Files = append(t.Files, txtar.File{Name: "want"})
		wantFile = &t.Files[len(t.Files)-1]
	}

	wantFile.Data = want
	data := txtar.Format(&t.Archive)
	return os.WriteFile(t.testPath, data, 0666)
}

func TestRelease(t *testing.T) {
	testPaths, err := filepath.Glob(filepath.FromSlash("testdata/*/*.test"))
	if err != nil {
		t.Fatal(err)
	}
	if len(testPaths) == 0 {
		t.Fatal("no .test files found in testdata directory")
	}

	var tests []*test
	for _, testPath := range testPaths {
		test, err := readTest(testPath)
		if err != nil {
			t.Fatal(err)
		}
		tests = append(tests, test)
	}

	defaultContext, cleanup, err := prepareProxy(nil, tests)
	if err != nil {
		t.Fatalf("preparing test proxy: %v", err)
	}
	t.Cleanup(cleanup)

	for _, test := range tests {
		testName := strings.TrimSuffix(strings.TrimPrefix(filepath.ToSlash(test.testPath), "testdata/"), ".test")
		t.Run(testName, testRelease(defaultContext, tests, test))
	}
}

func TestRelease_gitRepo_uncommittedChanges(t *testing.T) {
	ctx := context.Background()
	buf := &bytes.Buffer{}
	releaseDir, err := os.MkdirTemp("", "")
	if err != nil {
		t.Fatal(err)
	}

	goModInit(t, releaseDir)
	gitInit(t, releaseDir)

	// Create an uncommitted change.
	bContents := `package b
const B = "b"`
	if err := os.WriteFile(filepath.Join(releaseDir, "b.go"), []byte(bContents), 0644); err != nil {
		t.Fatal(err)
	}

	success, err := runRelease(ctx, buf, releaseDir, nil)
	if got, want := err.Error(), fmt.Sprintf("repo %s has uncommitted changes", releaseDir); got != want {
		t.Errorf("runRelease:\ngot error:\n%q\nwant error\n%q", got, want)
	}
	if success {
		t.Errorf("runRelease: expected failure, got success")
	}
}

func testRelease(ctx context.Context, tests []*test, test *test) func(t *testing.T) {
	return func(t *testing.T) {
		if test.skip != "" {
			t.Skip(test.skip)
		}

		t.Parallel()

		if len(test.proxyVersions) > 0 {
			var cleanup func()
			var err error
			ctx, cleanup, err = prepareProxy(test.proxyVersions, tests)
			if err != nil {
				t.Fatalf("preparing test proxy: %v", err)
			}
			t.Cleanup(cleanup)
		}

		// Extract the files in the release version. They may be part of the
		// test archive or in testdata/mod.
		testDir, err := os.MkdirTemp("", "")
		if err != nil {
			t.Fatal(err)
		}
		if *testwork {
			fmt.Fprintf(os.Stderr, "test dir: %s\n", testDir)
		} else {
			t.Cleanup(func() {
				os.RemoveAll(testDir)
			})
		}

		var arc *txtar.Archive
		if test.version != "" {
			arcBase := fmt.Sprintf("%s_%s.txt", strings.ReplaceAll(test.modPath, "/", "_"), test.version)
			arcPath := filepath.Join("testdata/mod", arcBase)
			var err error
			arc, err = txtar.ParseFile(arcPath)
			if err != nil {
				t.Fatal(err)
			}
		} else {
			arc = &test.Archive
		}
		if err := extractTxtar(testDir, arc); err != nil {
			t.Fatal(err)
		}

		switch test.vcs {
		case "git":
			// Convert testDir to a git repository with a single commit, to
			// simulate a real user's module-in-a-git-repo.
			gitInit(t, testDir)
		case "hg":
			// Convert testDir to a mercurial repository to simulate a real
			// user's module-in-a-hg-repo.
			hgInit(t, testDir)
		case "":
			// No VCS.
		default:
			t.Fatalf("unknown vcs %q", test.vcs)
		}

		// Generate the report and compare it against the expected text.
		var args []string
		if test.baseVersion != "" {
			args = append(args, "-base="+test.baseVersion)
		}
		if test.releaseVersion != "" {
			args = append(args, "-version="+test.releaseVersion)
		}
		buf := &bytes.Buffer{}
		releaseDir := filepath.Join(testDir, test.dir)
		success, err := runRelease(ctx, buf, releaseDir, args)
		if err != nil {
			if !test.wantError {
				t.Fatalf("unexpected error: %v", err)
			}
			if errMsg := []byte(err.Error()); !bytes.Equal(errMsg, bytes.TrimSpace(test.want)) {
				if *updateGolden {
					if err := updateTest(test, errMsg); err != nil {
						t.Fatal(err)
					}
				} else {
					t.Fatalf("got error: %s; want error: %s", errMsg, test.want)
				}
			}
			return
		}
		if test.wantError {
			t.Fatalf("got success; want error %s", test.want)
		}

		got := bytes.TrimSpace(buf.Bytes())
		if filepath.Separator != '/' {
			got = bytes.ReplaceAll(got, []byte{filepath.Separator}, []byte{'/'})
		}
		if !bytes.Equal(got, test.want) {
			if *updateGolden {
				if err := updateTest(test, got); err != nil {
					t.Fatal(err)
				}
			} else {
				t.Fatalf("got:\n%s\n\nwant:\n%s", got, test.want)
			}
		}
		if success != test.wantSuccess {
			t.Fatalf("got success: %v; want success %v", success, test.wantSuccess)
		}
	}
}

// hgInit initialises a directory as a mercurial repo.
func hgInit(t *testing.T, dir string) {
	t.Helper()

	if err := os.Mkdir(filepath.Join(dir, ".hg"), 0777); err != nil {
		t.Fatal(err)
	}

	if err := os.WriteFile(filepath.Join(dir, ".hg", "branch"), []byte("default"), 0777); err != nil {
		t.Fatal(err)
	}
}

// gitInit initialises a directory as a git repo, and adds a simple commit.
func gitInit(t *testing.T, dir string) {
	t.Helper()

	if !hasGit() {
		t.Skip("PATH does not contain git")
	}

	stdout := &bytes.Buffer{}
	stderr := &bytes.Buffer{}

	for _, args := range [][]string{
		{"git", "init"},
		{"git", "config", "user.name", "Gopher"},
		{"git", "config", "user.email", "gopher@golang.org"},
		{"git", "checkout", "-b", "test"},
		{"git", "add", "-A"},
		{"git", "commit", "-m", "test"},
	} {
		cmd := exec.Command(args[0], args[1:]...)
		cmd.Dir = dir
		cmd.Stdout = stdout
		cmd.Stderr = stderr
		if err := cmd.Run(); err != nil {
			cmdArgs := strings.Join(args, " ")
			t.Fatalf("%s\n%s\nerror running %q on dir %s: %v", stdout.String(), stderr.String(), cmdArgs, dir, err)
		}
	}
}

// goModInit runs `go mod init` in the given directory.
func goModInit(t *testing.T, dir string) {
	t.Helper()

	aContents := `package a
const A = "a"`
	if err := os.WriteFile(filepath.Join(dir, "a.go"), []byte(aContents), 0644); err != nil {
		t.Fatal(err)
	}

	stdout := &bytes.Buffer{}
	stderr := &bytes.Buffer{}
	cmd := exec.Command("go", "mod", "init", "example.com/uncommitted")
	cmd.Stdout = stdout
	cmd.Stderr = stderr
	cmd.Dir = dir
	if err := cmd.Run(); err != nil {
		t.Fatalf("error running `go mod init`: %s, %v", stderr.String(), err)
	}
}