package updater

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// makeReleaseTarball writes a tarball whose root contains the three
// expected entries with the given bodies. Used by stage + download
// tests so they don't need a real banger build to exercise the
// extraction path.
func makeReleaseTarball(t *testing.T, bodies map[string][]byte) []byte {
	t.Helper()
	var buf bytes.Buffer
	gz := gzip.NewWriter(&buf)
	tw := tar.NewWriter(gz)
	for name, body := range bodies {
		hdr := &tar.Header{
			Name:     name,
			Mode:     0o755,
			Size:     int64(len(body)),
			Typeflag: tar.TypeReg,
		}
		if err := tw.WriteHeader(hdr); err != nil {
			t.Fatalf("write header: %v", err)
		}
		if _, err := tw.Write(body); err != nil {
			t.Fatalf("write body: %v", err)
		}
	}
	if err := tw.Close(); err != nil {
		t.Fatalf("close tar: %v", err)
	}
	if err := gz.Close(); err != nil {
		t.Fatalf("close gzip: %v", err)
	}
	return buf.Bytes()
}

func sha256Hex(b []byte) string {
	sum := sha256.Sum256(b)
	return hex.EncodeToString(sum[:])
}

func TestStageTarballHappyPath(t *testing.T) {
	body := makeReleaseTarball(t, map[string][]byte{
		"banger":             []byte("BANGER"),
		"bangerd":            []byte("BANGERD"),
		"banger-vsock-agent": []byte("AGENT"),
	})
	tarball := filepath.Join(t.TempDir(), "release.tar.gz")
	if err := os.WriteFile(tarball, body, 0o644); err != nil {
		t.Fatalf("write tarball: %v", err)
	}
	staging := filepath.Join(t.TempDir(), "staged")

	got, err := StageTarball(tarball, staging)
	if err != nil {
		t.Fatalf("StageTarball: %v", err)
	}
	for _, p := range []string{got.BangerPath, got.BangerdPath, got.VsockAgentPath} {
		info, err := os.Stat(p)
		if err != nil {
			t.Fatalf("stat %s: %v", p, err)
		}
		if info.Mode().Perm() != 0o755 {
			t.Errorf("%s mode = %o, want 0755", p, info.Mode().Perm())
		}
	}
	bs, _ := os.ReadFile(got.BangerPath)
	if string(bs) != "BANGER" {
		t.Fatalf("banger content = %q", bs)
	}
}

func TestStageTarballRejectsExtraEntry(t *testing.T) {
	body := makeReleaseTarball(t, map[string][]byte{
		"banger":             []byte("a"),
		"bangerd":            []byte("b"),
		"banger-vsock-agent": []byte("c"),
		"bonus.txt":          []byte("not allowed"),
	})
	tarball := filepath.Join(t.TempDir(), "rel.tar.gz")
	_ = os.WriteFile(tarball, body, 0o644)
	_, err := StageTarball(tarball, t.TempDir())
	if err == nil || !strings.Contains(err.Error(), "unexpected entry") {
		t.Fatalf("err = %v, want unexpected-entry rejection", err)
	}
}

func TestStageTarballRejectsMissingEntry(t *testing.T) {
	body := makeReleaseTarball(t, map[string][]byte{
		"banger":  []byte("a"),
		"bangerd": []byte("b"),
		// banger-vsock-agent intentionally missing
	})
	tarball := filepath.Join(t.TempDir(), "rel.tar.gz")
	_ = os.WriteFile(tarball, body, 0o644)
	_, err := StageTarball(tarball, t.TempDir())
	if err == nil || !strings.Contains(err.Error(), "missing required entry") {
		t.Fatalf("err = %v, want missing-required rejection", err)
	}
}

func TestStageTarballRejectsPathTraversal(t *testing.T) {
	// Build the tarball manually so we can inject a `../` entry —
	// makeReleaseTarball's expected-entry filter would otherwise
	// catch it earlier.
	var buf bytes.Buffer
	gz := gzip.NewWriter(&buf)
	tw := tar.NewWriter(gz)
	for _, e := range []struct{ name, body string }{
		{"banger", "a"},
		{"bangerd", "b"},
		{"../escape", "x"},
	} {
		_ = tw.WriteHeader(&tar.Header{Name: e.name, Size: int64(len(e.body)), Mode: 0o755, Typeflag: tar.TypeReg})
		_, _ = tw.Write([]byte(e.body))
	}
	_ = tw.Close()
	_ = gz.Close()
	tarball := filepath.Join(t.TempDir(), "rel.tar.gz")
	_ = os.WriteFile(tarball, buf.Bytes(), 0o644)
	_, err := StageTarball(tarball, t.TempDir())
	if err == nil || !strings.Contains(err.Error(), "unsafe path") {
		t.Fatalf("err = %v, want unsafe-path rejection", err)
	}
}

func TestSwapAndRollback(t *testing.T) {
	root := t.TempDir()
	binDir := filepath.Join(root, "bin")
	libDir := filepath.Join(root, "lib", "banger")
	if err := os.MkdirAll(binDir, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(libDir, 0o755); err != nil {
		t.Fatal(err)
	}
	for _, p := range []string{
		filepath.Join(binDir, "banger"),
		filepath.Join(binDir, "bangerd"),
		filepath.Join(libDir, "banger-vsock-agent"),
	} {
		if err := os.WriteFile(p, []byte("OLD-"+filepath.Base(p)), 0o755); err != nil {
			t.Fatal(err)
		}
	}

	staging := filepath.Join(root, "staging")
	_ = os.MkdirAll(staging, 0o700)
	staged := StagedRelease{
		BangerPath:     filepath.Join(staging, "banger"),
		BangerdPath:    filepath.Join(staging, "bangerd"),
		VsockAgentPath: filepath.Join(staging, "banger-vsock-agent"),
	}
	for _, pair := range []struct{ p, body string }{
		{staged.BangerPath, "NEW-banger"},
		{staged.BangerdPath, "NEW-bangerd"},
		{staged.VsockAgentPath, "NEW-banger-vsock-agent"},
	} {
		if err := os.WriteFile(pair.p, []byte(pair.body), 0o755); err != nil {
			t.Fatal(err)
		}
	}

	targets := InstallTargets{
		Banger:     filepath.Join(binDir, "banger"),
		Bangerd:    filepath.Join(binDir, "bangerd"),
		VsockAgent: filepath.Join(libDir, "banger-vsock-agent"),
	}

	res, err := Swap(staged, targets)
	if err != nil {
		t.Fatalf("Swap: %v", err)
	}
	if len(res.SwappedTargets) != 3 {
		t.Fatalf("SwappedTargets len = %d, want 3", len(res.SwappedTargets))
	}
	for _, p := range []string{targets.Banger, targets.Bangerd, targets.VsockAgent} {
		got, _ := os.ReadFile(p)
		want := "NEW-" + filepath.Base(p)
		if string(got) != want {
			t.Fatalf("%s content = %q, want %q", p, got, want)
		}
		prev, err := os.ReadFile(p + previousSuffix)
		if err != nil {
			t.Fatalf("missing backup at %s.previous: %v", p, err)
		}
		if string(prev) != "OLD-"+filepath.Base(p) {
			t.Fatalf(".previous content = %q", prev)
		}
	}

	if err := Rollback(res); err != nil {
		t.Fatalf("Rollback: %v", err)
	}
	for _, p := range []string{targets.Banger, targets.Bangerd, targets.VsockAgent} {
		got, _ := os.ReadFile(p)
		want := "OLD-" + filepath.Base(p)
		if string(got) != want {
			t.Fatalf("post-rollback %s = %q, want %q", p, got, want)
		}
		if _, err := os.Stat(p + previousSuffix); !os.IsNotExist(err) {
			t.Fatalf(".previous should be cleaned after rollback; stat err = %v", err)
		}
	}
}

func TestSwapPartialFailureRollsBackCleanly(t *testing.T) {
	root := t.TempDir()
	binDir := filepath.Join(root, "bin")
	libDir := filepath.Join(root, "lib", "banger")
	if err := os.MkdirAll(binDir, 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.MkdirAll(libDir, 0o755); err != nil {
		t.Fatal(err)
	}
	// Pre-create the two binaries that will swap successfully.
	for _, p := range []string{
		filepath.Join(binDir, "bangerd"),
		filepath.Join(libDir, "banger-vsock-agent"),
	} {
		_ = os.WriteFile(p, []byte("OLD-"+filepath.Base(p)), 0o755)
	}

	staging := filepath.Join(root, "staging")
	_ = os.MkdirAll(staging, 0o700)
	staged := StagedRelease{
		BangerPath:     filepath.Join(staging, "banger"),
		BangerdPath:    filepath.Join(staging, "bangerd"),
		VsockAgentPath: filepath.Join(staging, "banger-vsock-agent"),
	}
	for _, pair := range []struct{ p, body string }{
		{staged.BangerPath, "NEW-banger"},
		{staged.BangerdPath, "NEW-bangerd"},
		{staged.VsockAgentPath, "NEW-banger-vsock-agent"},
	} {
		_ = os.WriteFile(pair.p, []byte(pair.body), 0o755)
	}

	// Block the banger swap (which is LAST in the order) by putting
	// a regular file where its parent dir should be — MkdirAll fails
	// with "not a directory". Vsock + bangerd succeed first.
	blockedParent := filepath.Join(root, "blocked-bin")
	if err := os.WriteFile(blockedParent, []byte("blocking"), 0o644); err != nil {
		t.Fatal(err)
	}
	targets := InstallTargets{
		Banger:     filepath.Join(blockedParent, "banger"),
		Bangerd:    filepath.Join(binDir, "bangerd"),
		VsockAgent: filepath.Join(libDir, "banger-vsock-agent"),
	}

	res, err := Swap(staged, targets)
	if err == nil {
		t.Fatal("Swap unexpectedly succeeded; banger parent should be blocked by a regular file")
	}
	if len(res.SwappedTargets) != 2 {
		t.Fatalf("SwappedTargets = %v, want 2 (vsock + bangerd before banger failed)", res.SwappedTargets)
	}
	// Rolling back the partial swap should restore the filesystem.
	if err := Rollback(res); err != nil {
		t.Fatalf("Rollback after partial swap: %v", err)
	}
	for _, p := range res.SwappedTargets {
		got, _ := os.ReadFile(p)
		want := "OLD-" + filepath.Base(p)
		if string(got) != want {
			t.Fatalf("post-rollback %s = %q", p, got)
		}
	}
}

func TestDownloadReleaseHappyPath(t *testing.T) {
	tarballBody := []byte("fake tarball bytes")
	tarballSHA := sha256Hex(tarballBody)
	mux := http.NewServeMux()
	mux.HandleFunc("/banger.tar.gz", func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write(tarballBody)
	})
	mux.HandleFunc("/SHA256SUMS", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "%s  banger.tar.gz\n", tarballSHA)
	})
	srv := httptest.NewServer(mux)
	defer srv.Close()

	dst := filepath.Join(t.TempDir(), "out.tar.gz")
	sums, err := DownloadRelease(context.Background(), srv.Client(), Release{
		Version:       "v0.1.0",
		TarballURL:    srv.URL + "/banger.tar.gz",
		SHA256SumsURL: srv.URL + "/SHA256SUMS",
	}, dst)
	if err != nil {
		t.Fatalf("DownloadRelease: %v", err)
	}
	if !strings.Contains(string(sums), "banger.tar.gz") {
		t.Fatalf("returned sums body missing tarball name: %q", sums)
	}
	got, _ := os.ReadFile(dst)
	if !bytes.Equal(got, tarballBody) {
		t.Fatalf("downloaded body differs from served body")
	}
}

func TestDownloadReleaseRejectsTarballMissingFromSums(t *testing.T) {
	mux := http.NewServeMux()
	mux.HandleFunc("/banger.tar.gz", func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("body"))
	})
	mux.HandleFunc("/SHA256SUMS", func(w http.ResponseWriter, r *http.Request) {
		// Sums for a different file; tarball name not listed.
		fmt.Fprintf(w, "%s  unrelated\n", sha256Hex([]byte("body")))
	})
	srv := httptest.NewServer(mux)
	defer srv.Close()

	dst := filepath.Join(t.TempDir(), "out.tar.gz")
	_, err := DownloadRelease(context.Background(), srv.Client(), Release{
		TarballURL:    srv.URL + "/banger.tar.gz",
		SHA256SumsURL: srv.URL + "/SHA256SUMS",
	}, dst)
	if err == nil || !strings.Contains(err.Error(), "does not list") {
		t.Fatalf("err = %v, want SHA256SUMS-missing rejection", err)
	}
}

func TestDownloadReleasePropagatesShaMismatch(t *testing.T) {
	mux := http.NewServeMux()
	mux.HandleFunc("/banger.tar.gz", func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("served body"))
	})
	mux.HandleFunc("/SHA256SUMS", func(w http.ResponseWriter, r *http.Request) {
		// Wrong digest for the tarball.
		fmt.Fprintf(w, "%s  banger.tar.gz\n", sha256Hex([]byte("expected body")))
	})
	srv := httptest.NewServer(mux)
	defer srv.Close()

	dst := filepath.Join(t.TempDir(), "out.tar.gz")
	_, err := DownloadRelease(context.Background(), srv.Client(), Release{
		TarballURL:    srv.URL + "/banger.tar.gz",
		SHA256SumsURL: srv.URL + "/SHA256SUMS",
	}, dst)
	if err == nil || !strings.Contains(err.Error(), "sha256 mismatch") {
		t.Fatalf("err = %v, want sha256 mismatch", err)
	}
	if _, statErr := os.Stat(dst); !os.IsNotExist(statErr) {
		t.Fatalf("partial tarball should be removed; stat err = %v", statErr)
	}
}