package versionscript_test

import (
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"

	"github.com/stretchr/testify/require"
)

const (
	scriptPath     = "../../script/version"
	makefilePath   = "../../Makefile"
	dockerfilePath = "../../Dockerfile"

	// unknown is what a tree with no git metadata and no $VERSION must
	// report: a source tarball has no way to know its version, and the
	// one thing it must not do is name a tag it may not be at.
	unknown = "unknown"

	// scriptMode keeps the copied script runnable; dirMode and fileMode
	// are the ordinary permissions for the throwaway tree around it.
	scriptMode = 0o755
	dirMode    = 0o750
	fileMode   = 0o600
)

// checkout is a throwaway working tree carrying a copy of the script
// under test at the same path it lives at in this repository, since the
// script resolves the checkout root from its own location.
type checkout struct {
	dir  string
	head string
}

func TestVersion_CleanTagReportsExactlyTheTag(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	c.git(t, "tag", "v1.2.3")

	require.Equal(t, "v1.2.3", c.version(t))
}

func TestVersion_CommitAfterTagCarriesDistanceAndSHA(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	c.git(t, "tag", "v1.2.3")
	head := c.commit(t, "after the tag")

	got := c.version(t)

	require.NotEqual(t, "v1.2.3", got,
		"a commit past the tag must not claim to be the tag")
	require.True(t, strings.HasPrefix(got, "v1.2.3-1-g"),
		"want describe form v1.2.3-1-g<sha>, got %q", got)
	require.True(t, strings.HasPrefix(head, strings.TrimPrefix(
		got, "v1.2.3-1-g")),
		"%q must carry the abbreviated head SHA of %q", got, head)
}

func TestVersion_UntaggedHistoryReportsShortSHA(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)

	got := c.version(t)

	require.NotEmpty(t, got)
	require.NotEqual(t, unknown, got)
	require.True(t, strings.HasPrefix(c.head, got),
		"%q must be an abbreviation of head %q", got, c.head)
}

func TestVersion_UncommittedChangesAreMarkedDirty(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	c.git(t, "tag", "v1.2.3")

	require.NoError(t, os.WriteFile(
		filepath.Join(c.dir, "tracked.txt"), []byte("edited\n"), fileMode,
	))

	require.Equal(t, "v1.2.3-dirty", c.version(t))
}

// A source tarball, or any build context without .git, still has to
// build. It reports "unknown" rather than failing or naming a tag.
func TestVersion_NoGitMetadataReportsUnknown(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	require.NoError(t, os.RemoveAll(filepath.Join(c.dir, ".git")))

	require.Equal(t, unknown, c.version(t))
}

// An unpacked tarball can sit inside an unrelated working copy. The
// enclosing repository's version is not this tree's version.
func TestVersion_EnclosingRepositoryIsNotUsed(t *testing.T) {
	t.Parallel()

	outer := newCheckout(t)
	outer.git(t, "tag", "v9.9.9")

	inner := filepath.Join(outer.dir, "unpacked")
	require.NoError(t, os.MkdirAll(filepath.Join(inner, "script"), dirMode))
	copyScript(t, inner)

	require.Equal(t, unknown, runScript(t, inner, nil))
}

// The Docker build has no git metadata, so the version arrives as an
// environment override. It wins over anything derivable.
func TestVersion_EnvironmentOverrideWins(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	c.git(t, "tag", "v1.2.3")

	require.Equal(t, "v4.5.6",
		runScript(t, c.dir, []string{"VERSION=v4.5.6"}))
}

// An empty VERSION is treated as unset rather than stamping an empty
// string: the Dockerfile's build arg has a non-empty default, but a
// caller exporting VERSION= must not produce a binary reporting "".
func TestVersion_EmptyOverrideFallsBackToGit(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	c.git(t, "tag", "v1.2.3")

	require.Equal(t, "v1.2.3", runScript(t, c.dir, []string{"VERSION="}))
}

// Two builds of the same commit must produce a byte-identical binary,
// which they cannot if the stamped value moves between invocations.
func TestVersion_IsStableAcrossInvocations(t *testing.T) {
	t.Parallel()

	c := newCheckout(t)
	c.git(t, "tag", "v1.2.3")

	first := c.version(t)
	second := c.version(t)

	require.Equal(t, first, second)
}

// The build target is the only place composing linker flags. If a
// future edit drops either half, the binary silently reports "dev"
// again (the defect this package exists for) or fails to link on
// Alpine.
func TestMakefile_BuildComposesVersionAndExtraFlags(t *testing.T) {
	t.Parallel()

	makefile := read(t, makefilePath)

	require.Contains(t, makefile, "-X main.version=$(VERSION)")
	require.Contains(t, makefile, "$(GO_LDFLAGS)")
	require.Contains(t, makefile, "VERSION ?= $(shell script/version)")
}

// Every compile in the image goes through the build target, so the
// static relink cannot replace the flags that carry the stamp.
func TestDockerfile_BuildsThroughTheMakeTarget(t *testing.T) {
	t.Parallel()

	dockerfile := read(t, dockerfilePath)

	require.NotContains(t, dockerfile, "go build",
		"a raw go build bypasses the Makefile's -X flag")
	require.Contains(t, dockerfile, "ARG VERSION=")
	require.Contains(t, dockerfile,
		`make build VERSION="$VERSION" GO_LDFLAGS='-extldflags "-static"'`)
}

func read(t *testing.T, path string) string {
	t.Helper()

	//nolint:gosec // repo-local build file under test, fixed path
	b, err := os.ReadFile(path)
	require.NoError(t, err)

	return string(b)
}

// version runs the script in this checkout with no overrides.
func (c checkout) version(t *testing.T) string {
	t.Helper()

	return runScript(t, c.dir, nil)
}

func runScript(t *testing.T, dir string, env []string) string {
	t.Helper()

	//nolint:gosec // fixed argv, repo-local script under test
	cmd := exec.CommandContext(t.Context(), "sh",
		filepath.Join(dir, "script", "version"))
	cmd.Dir = dir

	cmd.Env = append(os.Environ(), env...)

	out, err := cmd.CombinedOutput()
	require.NoError(t, err, string(out))

	return strings.TrimSpace(string(out))
}

func (c checkout) git(t *testing.T, args ...string) string {
	t.Helper()

	//nolint:gosec // fixed argv, arguments are test constants
	cmd := exec.CommandContext(t.Context(), "git", args...)
	cmd.Dir = c.dir

	out, err := cmd.CombinedOutput()
	require.NoError(t, err, string(out))

	return strings.TrimSpace(string(out))
}

func (c checkout) commit(t *testing.T, message string) string {
	t.Helper()

	c.git(t,
		"-c", "user.email=ci@example.invalid",
		"-c", "user.name=ci",
		"-c", "commit.gpgsign=false",
		"commit", "-q", "--allow-empty", "-m", message,
	)

	return c.git(t, "rev-parse", "HEAD")
}

// newCheckout builds a one-commit repository with a tracked file, so a
// later edit to that file makes the tree dirty, and with a copy of the
// script at the path it occupies in this repository.
func newCheckout(t *testing.T) checkout {
	t.Helper()

	requireGit(t)

	dir := t.TempDir()
	c := checkout{dir: dir}

	require.NoError(t, os.MkdirAll(filepath.Join(dir, "script"), dirMode))
	copyScript(t, dir)

	require.NoError(t, os.WriteFile(
		filepath.Join(dir, "tracked.txt"), []byte("original\n"), fileMode,
	))

	c.git(t, "init", "-q", "-b", "main")
	c.git(t, "add", "tracked.txt")
	c.head = c.commit(t, "initial")

	return c
}

func copyScript(t *testing.T, dir string) {
	t.Helper()

	body, err := os.ReadFile(scriptPath)
	require.NoError(t, err)

	//nolint:gosec // the copy has to stay executable to be run
	err = os.WriteFile(
		filepath.Join(dir, "script", "version"), body, scriptMode,
	)
	require.NoError(t, err)
}

func requireGit(t *testing.T) {
	t.Helper()

	for _, tool := range []string{"sh", "git"} {
		_, err := exec.LookPath(tool)
		if err != nil {
			t.Skipf("%s is not installed: %v", tool, err)
		}
	}
}