package build

import (
	"bytes"
	"os"
	"path/filepath"
	"strings"
	"syscall"
	"testing"

	"werkdock/internal/engine"
	"werkdock/internal/store"
)

// fakeEngine records the specs it is asked to run and lets a test act
// on the work tree the way a real RUN step would.
type fakeEngine struct {
	specs []engine.RunSpec
	code  int
	do    func(spec engine.RunSpec) error
}

func (f *fakeEngine) Run(spec engine.RunSpec) (int, error) {
	f.specs = append(f.specs, spec)
	if f.do != nil {
		if err := f.do(spec); err != nil {
			return 0, err
		}
	}
	return f.code, nil
}

func (f *fakeEngine) Start(engine.RunSpec) (engine.Process, error) {
	panic("a build does not start background processes")
}

// baseImage writes a minimal base rootfs: enough of a Debian shape for
// the apt fragment to have a home, plus whatever files the test wants.
func baseImage(t *testing.T, files map[string]string) string {
	t.Helper()
	rootfs := filepath.Join(t.TempDir(), "base")
	for _, dir := range []string{"etc/apt/apt.conf.d", "usr/bin", "bin"} {
		if err := os.MkdirAll(filepath.Join(rootfs, dir), 0o755); err != nil {
			t.Fatal(err)
		}
	}
	for name, content := range files {
		path := filepath.Join(rootfs, name)
		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(path, []byte(content), 0o755); err != nil {
			t.Fatal(err)
		}
	}
	return rootfs
}

func buildFixture(t *testing.T, dockerfile string, context map[string]string, base string) (store.Store, *fakeEngine, Options) {
	t.Helper()
	dir := t.TempDir()
	st := store.Store{Root: filepath.Join(dir, "store")}
	contextDir := filepath.Join(dir, "context")
	if err := os.MkdirAll(contextDir, 0o755); err != nil {
		t.Fatal(err)
	}
	for name, content := range context {
		path := filepath.Join(contextDir, name)
		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	path := filepath.Join(dir, "Dockerfile")
	if err := os.WriteFile(path, []byte(dockerfile), 0o644); err != nil {
		t.Fatal(err)
	}
	eng := &fakeEngine{}
	return st, eng, Options{
		Dockerfile: path,
		Context:    contextDir,
		Tag:        "built:1",
		Backend:    CopyBackend{},
		Engine:     eng,
		Resolve: func(string) (string, store.ImageMeta, error) {
			return base, store.ImageMeta{Config: store.ImageConfig{Env: []string{"PATH=/usr/bin:/bin"}}}, nil
		},
		Stdout: &bytes.Buffer{},
		Stderr: &bytes.Buffer{},
	}
}

func TestRunBuildsAnOrdinaryFlatImage(t *testing.T) {
	base := baseImage(t, map[string]string{"usr/bin/fakeroot": "#!/bin/sh\n", "etc/os-release": "ID=debian\n"})
	st, eng, opts := buildFixture(t, `
# a build environment
FROM base:trixie
ENV LANG=C.UTF-8
WORKDIR /srv
RUN apt-get update \
 && apt-get install -y jq
COPY app /srv/app
COPY tools/ /usr/local/tools/
ENTRYPOINT ["/srv/app"]
CMD ["--serve"]
LABEL org.opencontainers.image.title="built"
`, map[string]string{"app": "#!/bin/sh\necho hello\n", "tools/t1": "one\n", "tools/sub/t2": "two\n"}, base)
	eng.do = func(spec engine.RunSpec) error {
		// what a real RUN step would leave behind
		return os.WriteFile(filepath.Join(spec.RootFS, "usr/bin/jq"), []byte("jq\n"), 0o755)
	}
	result, err := Run(st, opts)
	if err != nil {
		t.Fatal(err)
	}
	if result.Reference != "built:1" {
		t.Errorf("reference %q", result.Reference)
	}

	rootfs, err := st.RootFS("built:1")
	if err != nil {
		t.Fatalf("the image is not in the store: %v", err)
	}
	for path, want := range map[string]string{
		"usr/bin/jq":             "jq\n", // the RUN step's result
		"srv/app":                "#!/bin/sh\necho hello\n",
		"usr/local/tools/t1":     "one\n", // a directory source copies its CONTENTS
		"usr/local/tools/sub/t2": "two\n",
		"etc/os-release":         "ID=debian\n", // the base came along
	} {
		got, err := os.ReadFile(filepath.Join(rootfs, path))
		if err != nil {
			t.Errorf("%s: %v", path, err)
			continue
		}
		if string(got) != want {
			t.Errorf("%s: got %q, want %q", path, got, want)
		}
	}

	meta, err := st.Meta("built:1")
	if err != nil {
		t.Fatal(err)
	}
	config := meta.Config
	if want := []string{"/srv/app"}; len(config.Entrypoint) != 1 || config.Entrypoint[0] != want[0] {
		t.Errorf("entrypoint %q", config.Entrypoint)
	}
	if len(config.Cmd) != 1 || config.Cmd[0] != "--serve" {
		t.Errorf("cmd %q", config.Cmd)
	}
	if config.WorkingDir != "/srv" {
		t.Errorf("workdir %q", config.WorkingDir)
	}
	if config.Labels["org.opencontainers.image.title"] != "built" {
		t.Errorf("labels %v", config.Labels)
	}
	if !contains(config.Env, "LANG=C.UTF-8") || !contains(config.Env, "PATH=/usr/bin:/bin") {
		t.Errorf("env %q: the base's env and the Dockerfile's ENV both belong in it", config.Env)
	}
	if meta.Source != opts.Dockerfile {
		t.Errorf("source %q, want the Dockerfile", meta.Source)
	}
}

func TestRunStepGetsTheWritableRootAndBothUidLevers(t *testing.T) {
	base := baseImage(t, map[string]string{"usr/bin/fakeroot": "#!/bin/sh\n"})
	st, eng, opts := buildFixture(t, "FROM base\nWORKDIR /work\nENV TZ=UTC\nRUN apt-get install -y nginx\n", nil, base)
	var fragment string
	eng.do = func(spec engine.RunSpec) error {
		raw, err := os.ReadFile(filepath.Join(spec.RootFS, "etc/apt/apt.conf.d/00werkdock-sandbox"))
		fragment = string(raw)
		return err
	}
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	if len(eng.specs) != 1 {
		t.Fatalf("%d specs, want one RUN step", len(eng.specs))
	}
	spec := eng.specs[0]
	if !spec.WritableRoot {
		t.Error("a build step binds the root read-write")
	}
	if want := []string{"/usr/bin/fakeroot", "--", "/bin/sh", "-c", "apt-get install -y nginx"}; !equal(spec.Command, want) {
		t.Errorf("command %q, want %q", spec.Command, want)
	}
	if !hasEnv(spec.Env, "FAKEROOTDONTTRYCHOWN", "1") {
		t.Errorf("env %v: fakeroot without FAKEROOTDONTTRYCHOWN does not help (measured)", spec.Env)
	}
	if !hasEnv(spec.Env, "TZ", "UTC") {
		t.Errorf("env %v: the image's ENV applies to the following steps", spec.Env)
	}
	if spec.Workdir != "/work" {
		t.Errorf("workdir %q, want the image's WORKDIR", spec.Workdir)
	}
	if !strings.Contains(fragment, `APT::Sandbox::User "root"`) {
		t.Errorf("the apt fragment was not in the tree during the step: %q", fragment)
	}
	// ... and it is not in the finished image.
	rootfs, err := st.RootFS("built:1")
	if err != nil {
		t.Fatal(err)
	}
	if _, err := os.Stat(filepath.Join(rootfs, "etc/apt/apt.conf.d/00werkdock-sandbox")); !os.IsNotExist(err) {
		t.Errorf("the apt fragment stayed in the image: %v", err)
	}
}

func TestRunToleratesAStepThatRemovedTheAptFragment(t *testing.T) {
	base := baseImage(t, nil)
	st, eng, opts := buildFixture(t, "FROM base\nRUN rm -rf /etc/apt/apt.conf.d\n", nil, base)
	eng.do = func(spec engine.RunSpec) error {
		return os.RemoveAll(filepath.Join(spec.RootFS, "etc/apt/apt.conf.d"))
	}
	if _, err := Run(st, opts); err != nil {
		t.Fatalf("a step that removed the fragment must not fail the build: %v", err)
	}
}

func TestRunStepBindsTheResolverOnlyWhereTheBaseHasOne(t *testing.T) {
	if fi, err := os.Stat("/etc/resolv.conf"); err != nil || !fi.Mode().IsRegular() {
		t.Skip("the host has no regular /etc/resolv.conf to bind")
	}
	for _, c := range []struct {
		name  string
		files map[string]string
		want  int
	}{
		{"with one", map[string]string{"etc/resolv.conf": "nameserver 127.0.0.1\n"}, 1},
		{"without one", nil, 0},
	} {
		base := baseImage(t, c.files)
		st, eng, opts := buildFixture(t, "FROM base\nRUN true\n", nil, base)
		if _, err := Run(st, opts); err != nil {
			t.Fatal(err)
		}
		if got := len(eng.specs[0].Mounts); got != c.want {
			t.Errorf("%s: %d mounts, want %d: %+v", c.name, got, c.want, eng.specs[0].Mounts)
		}
	}
}

func TestRunCommandNamesRunInAParseError(t *testing.T) {
	_, err := runCommand(`["/bin/true"`)
	if err == nil || !strings.HasPrefix(err.Error(), `RUN ["/bin/true": `) || strings.Contains(err.Error(), "CMD") {
		t.Errorf("the error must name RUN, not CMD: %v", err)
	}
}

func TestCopyRefusesASymlinkThatLeavesTheContext(t *testing.T) {
	outside := t.TempDir()
	secret := filepath.Join(outside, "id_rsa")
	if err := os.WriteFile(secret, []byte("host secret"), 0o600); err != nil {
		t.Fatal(err)
	}
	for _, c := range []struct{ name, link, target, dockerfile string }{
		{"a linked file", "leak", secret, "FROM base\nCOPY leak /leak\n"},
		{"a file below a linked directory", "sub", outside, "FROM base\nCOPY sub/id_rsa /leak\n"},
		{"a linked file matched by a glob", "leak", secret, "FROM base\nCOPY le* /leak\n"},
	} {
		t.Run(c.name, func(t *testing.T) {
			st, _, opts := buildFixture(t, c.dockerfile, nil, baseImage(t, nil))
			if err := os.Symlink(c.target, filepath.Join(opts.Context, c.link)); err != nil {
				t.Fatal(err)
			}
			_, err := Run(st, opts)
			if err == nil || !strings.Contains(err.Error(), "leaves the build context") {
				t.Fatalf("a symlink out of the context must be refused, got %v", err)
			}
			if _, err := st.RootFS("built:1"); err == nil {
				t.Error("no image may be built from a host file")
			}
		})
	}
}

func TestCopyFollowsASymlinkWithinTheContext(t *testing.T) {
	st, _, opts := buildFixture(t, "FROM base\nCOPY link /copied\nCOPY link /dir/\n", map[string]string{"real": "inside"}, baseImage(t, nil))
	if err := os.Symlink("real", filepath.Join(opts.Context, "link")); err != nil {
		t.Fatal(err)
	}
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	rootfs, err := st.RootFS("built:1")
	if err != nil {
		t.Fatal(err)
	}
	if raw, err := os.ReadFile(filepath.Join(rootfs, "copied")); err != nil || string(raw) != "inside" {
		t.Errorf("a link inside the context copies its target: %q, %v", raw, err)
	}
	if _, err := os.Stat(filepath.Join(rootfs, "dir", "link")); err != nil {
		t.Errorf("the copy into a directory keeps the link's name: %v", err)
	}
}

func TestRunCreatesTheWorkdirOfTheFinishedImage(t *testing.T) {
	st, _, opts := buildFixture(t, "FROM base\nWORKDIR /srv/app\nCMD [\"/bin/true\"]\n", nil, baseImage(t, nil))
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	rootfs, err := st.RootFS("built:1")
	if err != nil {
		t.Fatal(err)
	}
	if fi, err := os.Stat(filepath.Join(rootfs, "srv/app")); err != nil || !fi.IsDir() {
		t.Errorf("a run of the image needs its WORKDIR, as docker creates it: %v", err)
	}
}

func TestRunBuildsFromScratchWithoutAskingForIt(t *testing.T) {
	st, _, opts := buildFixture(t, "FROM scratch\nCOPY app /app\nENTRYPOINT [\"/app\"]\n", map[string]string{"app": "binary"}, "")
	opts.Resolve = func(reference string) (string, store.ImageMeta, error) {
		t.Errorf("scratch is no image to look up or pull, got a lookup of %s", reference)
		return "", store.ImageMeta{}, os.ErrNotExist
	}
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	rootfs, err := st.RootFS("built:1")
	if err != nil {
		t.Fatal(err)
	}
	entries, err := os.ReadDir(rootfs)
	if err != nil || len(entries) != 1 || entries[0].Name() != "app" {
		t.Errorf("an image from scratch holds only what the steps put there: %v, %v", entries, err)
	}
}

func TestRunStepRunsUnwrappedWithoutFakerootInTheBase(t *testing.T) {
	base := baseImage(t, nil)
	st, eng, opts := buildFixture(t, "FROM base\nRUN true\n", nil, base)
	log := &bytes.Buffer{}
	opts.Stdout = log
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	if want := []string{"/bin/sh", "-c", "true"}; !equal(eng.specs[0].Command, want) {
		t.Errorf("command %q, want %q", eng.specs[0].Command, want)
	}
	if !strings.Contains(log.String(), "no fakeroot") {
		t.Errorf("a base image without fakeroot must be reported: %q", log.String())
	}
}

// The warning that belongs with store.copyTree: a build tree must be a
// REAL copy. Through a hardlink into the base image a RUN step would
// write into the base.
func TestBuildTreeIsARealCopyOfTheBase(t *testing.T) {
	base := baseImage(t, map[string]string{"usr/bin/busybox": "binary\n"})
	// two names, one inode — what busybox images look like
	if err := os.Link(filepath.Join(base, "usr/bin/busybox"), filepath.Join(base, "bin/ls")); err != nil {
		t.Fatal(err)
	}
	st, eng, opts := buildFixture(t, "FROM base\nRUN overwrite\n", nil, base)
	eng.do = func(spec engine.RunSpec) error {
		return os.WriteFile(filepath.Join(spec.RootFS, "usr/bin/busybox"), []byte("rewritten\n"), 0o755)
	}
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	if got, err := os.ReadFile(filepath.Join(base, "usr/bin/busybox")); err != nil || string(got) != "binary\n" {
		t.Fatalf("the base image was modified by the build: %q (%v)", got, err)
	}
	rootfs, err := st.RootFS("built:1")
	if err != nil {
		t.Fatal(err)
	}
	// hardlinks inside the base stay hardlinks inside the copy
	if a, b := inode(t, filepath.Join(rootfs, "usr/bin/busybox")), inode(t, filepath.Join(rootfs, "bin/ls")); a != b {
		t.Errorf("the copy broke the base's internal hardlink: %d != %d", a, b)
	}
	if a, b := inode(t, filepath.Join(rootfs, "bin/ls")), inode(t, filepath.Join(base, "bin/ls")); a == b {
		t.Error("the copy is hardlinked to the base image, so a RUN step would write into the base")
	}
}

func TestRunLeavesNoHalfImageBehind(t *testing.T) {
	base := baseImage(t, nil)
	st, eng, opts := buildFixture(t, "FROM base\nRUN false\n", nil, base)
	eng.code = 1
	_, err := Run(st, opts)
	if err == nil || !strings.Contains(err.Error(), "non-zero code: 1") {
		t.Fatalf("got %v, want the step's exit code", err)
	}
	if _, err := st.Dir("built:1"); err == nil {
		t.Error("a failed build must leave no image")
	}
	images, err := st.List()
	if err != nil {
		t.Fatal(err)
	}
	if len(images) != 0 {
		t.Errorf("store holds %v after a failed build", images)
	}
	if entries, err := os.ReadDir(filepath.Join(st.Root, "images")); err == nil && len(entries) != 0 {
		t.Errorf("a failed build left %v below images/", entries)
	}
}

func TestRunRefusesAnExistingReference(t *testing.T) {
	base := baseImage(t, nil)
	st, _, opts := buildFixture(t, "FROM base\nRUN true\n", nil, base)
	if _, err := Run(st, opts); err != nil {
		t.Fatal(err)
	}
	_, err := Run(st, opts)
	if err == nil || !strings.Contains(err.Error(), "already exists") {
		t.Errorf("got %v, want a refusal naming rmi", err)
	}
}

func TestRunRefusesWhatStagesTwoAndThreeWillBring(t *testing.T) {
	base := baseImage(t, nil)
	tests := []struct {
		name       string
		dockerfile string
		wantErr    string
	}{
		{"multi-stage FROM", "FROM base AS builder\nRUN true\n", "stage 3 of RFC 0006"},
		{"a second FROM", "FROM base\nRUN true\nFROM other\n", "stage 3 of RFC 0006"},
		{"COPY --from", "FROM base\nCOPY --from=builder /a /b\n", "stage 3 of RFC 0006"},
		{"COPY --chown", "FROM base\nCOPY --chown=1000:1000 a /b\n", "maps one uid"},
		{"FROM --platform", "FROM --platform=linux/arm64 base\nRUN true\n", "host's platform"},
		{"COPY without a destination", "FROM base\nCOPY only-one\n", "at least one source"},
		{"COPY outside the context", "FROM base\nCOPY ../outside /a\n", "leaves the build context"},
		{"COPY of a missing file", "FROM base\nCOPY nothing-here /a\n", "no such file or directory"},
		{"an absolute COPY source", "FROM base\nCOPY /etc/passwd /a\n", "relative to the build context"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			st, _, opts := buildFixture(t, tt.dockerfile, nil, base)
			_, err := Run(st, opts)
			if err == nil || !strings.Contains(err.Error(), tt.wantErr) {
				t.Errorf("got %v, want it to contain %q", err, tt.wantErr)
			}
		})
	}
}

func TestRunNeedsATag(t *testing.T) {
	base := baseImage(t, nil)
	st, _, opts := buildFixture(t, "FROM base\nRUN true\n", nil, base)
	opts.Tag = ""
	if _, err := Run(st, opts); err == nil || !strings.Contains(err.Error(), "-t REPOSITORY") {
		t.Errorf("got %v, want a refusal naming -t", err)
	}
}

func TestCopyBackendSaysWhatItCannotDo(t *testing.T) {
	backend, how := Select()
	if backend.Name() != "copy" {
		t.Errorf("backend %q", backend.Name())
	}
	if backend.CachesSteps() {
		t.Error("the copy backend caches no steps: a cached step would cost a whole tree copy")
	}
	if !strings.Contains(how, "no per-step cache") {
		t.Errorf("Select must say what the backend does: %q", how)
	}
}

func contains(list []string, want string) bool {
	for _, e := range list {
		if e == want {
			return true
		}
	}
	return false
}

func equal(got, want []string) bool {
	if len(got) != len(want) {
		return false
	}
	for i := range got {
		if got[i] != want[i] {
			return false
		}
	}
	return true
}

func hasEnv(env []engine.EnvVar, key, value string) bool {
	for _, e := range env {
		if e.Key == key {
			return e.Value == value
		}
	}
	return false
}

func inode(t *testing.T, path string) uint64 {
	t.Helper()
	fi, err := os.Stat(path)
	if err != nil {
		t.Fatal(err)
	}
	st, ok := fi.Sys().(*syscall.Stat_t)
	if !ok {
		t.Fatalf("%s: no stat", path)
	}
	return st.Ino
}