package build

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

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

// requireSandbox skips where bwrap or unprivileged user namespaces are
// not usable, exactly as the engine's integration tests do.
func requireSandbox(t *testing.T) {
	t.Helper()
	if _, err := exec.LookPath("bwrap"); err != nil {
		t.Skip("bwrap not installed")
	}
	if err := exec.Command("bwrap", "--unshare-user", "--uid", "0", "--ro-bind", "/", "/", "true").Run(); err != nil {
		t.Skipf("unprivileged user namespaces not usable here: %v", err)
	}
}

// TestBuildAndRunInARealSandbox builds a small image from a Dockerfile
// in a real bwrap sandbox and then runs the result, the way `werkdock
// run` would. The base image is assembled from the host's own shell
// and its shared libraries, so the test needs no network and no
// registry. The apt path — the one the uid levers exist for — is in
// TestBuildInstallsWithApt below.
func TestBuildAndRunInARealSandbox(t *testing.T) {
	requireSandbox(t)
	base := hostToolsImage(t, "/bin/sh", "/bin/cat")

	dir := t.TempDir()
	st := store.Store{Root: filepath.Join(dir, "store")}
	context := filepath.Join(dir, "context")
	if err := os.MkdirAll(context, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(context, "greeting"), []byte("from the context\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	dockerfile := filepath.Join(dir, "Dockerfile")
	if err := os.WriteFile(dockerfile, []byte(`
FROM base:probe
WORKDIR /srv
COPY greeting /srv/greeting
RUN echo "from a RUN step" > /srv/built \
 && cat /srv/greeting >> /srv/built
CMD ["/bin/cat", "/srv/built"]
`), 0o644); err != nil {
		t.Fatal(err)
	}

	log := &bytes.Buffer{}
	result, err := Run(st, Options{
		Dockerfile: dockerfile,
		Context:    context,
		Tag:        "probe-built:1",
		Backend:    CopyBackend{},
		Resolve:    staticBase(base),
		Stdout:     log,
		Stderr:     log,
	})
	if err != nil {
		t.Fatalf("build failed: %v\n%s", err, log.String())
	}
	if !strings.Contains(log.String(), "Successfully tagged probe-built:1") {
		t.Errorf("build log:\n%s", log.String())
	}

	// Now run the built image the way `werkdock run` does: its CMD,
	// the rootfs bound read-only.
	rootfs, err := st.RootFS(result.Reference)
	if err != nil {
		t.Fatal(err)
	}
	meta, err := st.Meta(result.Reference)
	if err != nil {
		t.Fatal(err)
	}
	var stdout, stderr bytes.Buffer
	code, err := (&engine.Bwrap{Stdout: &stdout, Stderr: &stderr}).Run(engine.RunSpec{
		RootFS:  rootfs,
		Workdir: meta.Config.WorkingDir,
		Command: meta.Config.Cmd,
	})
	if err != nil || code != 0 {
		t.Fatalf("running the built image: code %d, err %v, stderr %q", code, err, stderr.String())
	}
	if want := "from a RUN step\nfrom the context\n"; stdout.String() != want {
		t.Errorf("the built image printed %q, want %q", stdout.String(), want)
	}
	if meta.Config.WorkingDir != "/srv" {
		t.Errorf("workdir %q", meta.Config.WorkingDir)
	}
}

// TestBuildInstallsWithApt is the test the two uid levers exist for:
// without `APT::Sandbox::User root` apt's methods die on seteuid, and
// without fakeroot plus FAKEROOTDONTTRYCHOWN a package whose postinst
// chowns (nginx-common) fails in dpkg — both measured (RFC 0006).
//
// It needs a Debian-shaped base image with apt and fakeroot, and
// network access to a mirror, so it is pointed at one explicitly:
//
//	WERKDOCK_TEST_BASE_ROOTFS=/path/to/unpacked/rootfs go test ./internal/build/
//
// The rootfs is only read; the build works in a copy of it.
func TestBuildInstallsWithApt(t *testing.T) {
	requireSandbox(t)
	base := os.Getenv("WERKDOCK_TEST_BASE_ROOTFS")
	if base == "" {
		t.Skip("set WERKDOCK_TEST_BASE_ROOTFS to an unpacked Debian rootfs with apt and fakeroot")
	}
	if fi, err := os.Stat(filepath.Join(base, "usr/bin/fakeroot")); err != nil || fi.IsDir() {
		t.Skipf("%s has no fakeroot; the apt path needs one in the base image", base)
	}

	dir := t.TempDir()
	st := store.Store{Root: filepath.Join(dir, "store")}
	context := filepath.Join(dir, "context")
	if err := os.MkdirAll(context, 0o755); err != nil {
		t.Fatal(err)
	}
	dockerfile := filepath.Join(dir, "Dockerfile")
	if err := os.WriteFile(dockerfile, []byte(`
FROM base:trixie
ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update \
 && apt-get install -y --no-install-recommends nginx jq \
 && rm -rf /var/lib/apt/lists/*
CMD ["/usr/sbin/nginx", "-v"]
`), 0o644); err != nil {
		t.Fatal(err)
	}

	log := &bytes.Buffer{}
	result, err := Run(st, Options{
		Dockerfile: dockerfile,
		Context:    context,
		Tag:        "apt-built:1",
		Backend:    CopyBackend{},
		Resolve:    staticBase(base),
		Stdout:     log,
		Stderr:     log,
	})
	if err != nil {
		t.Fatalf("build failed: %v\n%s", err, log.String())
	}

	rootfs, err := st.RootFS(result.Reference)
	if err != nil {
		t.Fatal(err)
	}
	// nginx-common's postinst is where a build without the levers
	// stops; dpkg records the package as installed only if it ran.
	var stdout, stderr bytes.Buffer
	code, err := (&engine.Bwrap{Stdout: &stdout, Stderr: &stderr}).Run(engine.RunSpec{
		RootFS:  rootfs,
		Command: []string{"/usr/bin/dpkg-query", "-W", "-f", "${Status}", "nginx"},
	})
	if err != nil || code != 0 {
		t.Fatalf("dpkg-query in the built image: code %d, err %v, stderr %q", code, err, stderr.String())
	}
	if !strings.Contains(stdout.String(), "install ok installed") {
		t.Errorf("nginx is %q in the built image, want it configured", stdout.String())
	}
	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 built image: %v", err)
	}
}

func staticBase(rootfs string) func(string) (string, store.ImageMeta, error) {
	return func(string) (string, store.ImageMeta, error) {
		return rootfs, store.ImageMeta{}, nil
	}
}

// hostToolsImage assembles a base rootfs from host binaries and the
// shared libraries ldd reports for them — a real, runnable image
// without a registry. The test skips when a tool or ldd is missing.
func hostToolsImage(t *testing.T, binaries ...string) string {
	t.Helper()
	if _, err := exec.LookPath("ldd"); err != nil {
		t.Skip("ldd not available to assemble a base rootfs")
	}
	rootfs := filepath.Join(t.TempDir(), "base")
	for _, binary := range binaries {
		for _, file := range append([]string{binary}, sharedLibraries(t, binary)...) {
			copyHostFile(t, rootfs, file)
		}
	}
	// A base image needs the mountpoints a sandbox brings in.
	for _, dir := range []string{"proc", "dev", "tmp", "root", "run", "etc"} {
		if err := os.MkdirAll(filepath.Join(rootfs, dir), 0o755); err != nil {
			t.Fatal(err)
		}
	}
	if err := os.WriteFile(filepath.Join(rootfs, "etc/resolv.conf"), nil, 0o644); err != nil {
		t.Fatal(err)
	}
	return rootfs
}

func sharedLibraries(t *testing.T, binary string) []string {
	t.Helper()
	out, err := exec.Command("ldd", binary).Output()
	if err != nil {
		t.Skipf("ldd %s: %v", binary, err)
	}
	var libraries []string
	for _, line := range strings.Split(string(out), "\n") {
		for _, field := range strings.Fields(line) {
			if strings.HasPrefix(field, "/") && strings.Contains(field, ".so") {
				libraries = append(libraries, field)
			}
		}
	}
	return libraries
}

// copyHostFile places one host file in the rootfs at its own path,
// following a symlink to its target and keeping the link as well, so
// that /bin/sh -> dash works inside the sandbox.
func copyHostFile(t *testing.T, rootfs, file string) {
	t.Helper()
	target := filepath.Join(rootfs, file)
	if _, err := os.Lstat(target); err == nil {
		return
	}
	if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
		t.Fatal(err)
	}
	fi, err := os.Lstat(file)
	if err != nil {
		t.Skipf("%s is not on this host: %v", file, err)
	}
	if fi.Mode()&os.ModeSymlink != 0 {
		link, err := os.Readlink(file)
		if err != nil {
			t.Fatal(err)
		}
		resolved := link
		if !filepath.IsAbs(resolved) {
			resolved = filepath.Join(filepath.Dir(file), link)
		}
		copyHostFile(t, rootfs, resolved)
		if err := os.Symlink(link, target); err != nil {
			t.Fatal(err)
		}
		return
	}
	if err := copyFile(file, target, 0o755); err != nil {
		t.Fatal(err)
	}
}