package imagemgr

import (
	"crypto/sha256"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"testing"
)

// TestDebianBasePackagesReturnsCopy pins the contract that mutating the
// slice returned by DebianBasePackages() can't poison subsequent calls.
// hashPackages digests this list, so a caller that sorts or appends in
// place would silently change every image's package metadata.
func TestDebianBasePackagesReturnsCopy(t *testing.T) {
	t.Parallel()
	first := DebianBasePackages()
	original := append([]string(nil), first...)
	if len(first) == 0 {
		t.Fatal("DebianBasePackages returned empty slice")
	}
	first[0] = "tampered"
	second := DebianBasePackages()
	if second[0] == "tampered" {
		t.Fatalf("DebianBasePackages leaks internal state; second[0] = %q after first[0] mutation", second[0])
	}
	for i := range original {
		if second[i] != original[i] {
			t.Fatalf("DebianBasePackages drifted at %d: got %q, want %q", i, second[i], original[i])
		}
	}
}

// TestBuildMetadataPackagesMatchesDebianBase confirms the metadata
// packages used for image-drift detection are the same set we apply
// during build. If these diverge the hash recorded next to a rootfs
// stops matching the actual installed package set.
func TestBuildMetadataPackagesMatchesDebianBase(t *testing.T) {
	t.Parallel()
	build := BuildMetadataPackages()
	debian := DebianBasePackages()
	if len(build) != len(debian) {
		t.Fatalf("BuildMetadataPackages len = %d, DebianBasePackages len = %d", len(build), len(debian))
	}
	for i := range build {
		if build[i] != debian[i] {
			t.Fatalf("BuildMetadataPackages[%d] = %q, want %q", i, build[i], debian[i])
		}
	}
}

func TestHashPackagesStableForSameInput(t *testing.T) {
	t.Parallel()
	pkgs := []string{"git", "make", "vim"}
	first := hashPackages(pkgs)
	second := hashPackages(append([]string(nil), pkgs...))
	if first != second {
		t.Fatalf("hashPackages drifted between identical calls: %q vs %q", first, second)
	}
	// Sanity: hash differs when input differs.
	if first == hashPackages([]string{"git", "make"}) {
		t.Fatal("hashPackages collapsed two distinct inputs to the same hash")
	}
	// Verify the format is hex sha256 of "git\nmake\nvim\n" — pin the
	// concrete digest so a future refactor that changes joining (e.g.
	// drops the trailing newline) trips this test.
	want := fmt.Sprintf("%x", sha256.Sum256([]byte("git\nmake\nvim\n")))
	if first != want {
		t.Fatalf("hashPackages format drifted: got %q, want %q", first, want)
	}
}

func TestStageOptionalArtifactPathEmptyStaysEmpty(t *testing.T) {
	t.Parallel()
	if got := StageOptionalArtifactPath("/tmp/artifacts", "", "initrd.img"); got != "" {
		t.Fatalf("StageOptionalArtifactPath(empty staged) = %q, want empty", got)
	}
	if got := StageOptionalArtifactPath("/tmp/artifacts", "   ", "initrd.img"); got != "" {
		t.Fatalf("StageOptionalArtifactPath(whitespace staged) = %q, want empty", got)
	}
}

func TestStageOptionalArtifactPathJoinsName(t *testing.T) {
	t.Parallel()
	got := StageOptionalArtifactPath("/tmp/artifacts", "/host/path/initrd.img", "initrd.img")
	want := filepath.Join("/tmp/artifacts", "initrd.img")
	if got != want {
		t.Fatalf("StageOptionalArtifactPath = %q, want %q", got, want)
	}
}

func TestWritePackagesMetadataWritesHashFile(t *testing.T) {
	t.Parallel()
	dir := t.TempDir()
	rootfs := filepath.Join(dir, "rootfs.ext4")
	if err := os.WriteFile(rootfs, []byte("rootfs"), 0o644); err != nil {
		t.Fatalf("write rootfs: %v", err)
	}
	pkgs := []string{"git", "vim"}
	if err := WritePackagesMetadata(rootfs, pkgs); err != nil {
		t.Fatalf("WritePackagesMetadata: %v", err)
	}
	got, err := os.ReadFile(rootfs + ".packages.sha256")
	if err != nil {
		t.Fatalf("read metadata: %v", err)
	}
	want := hashPackages(pkgs) + "\n"
	if string(got) != want {
		t.Fatalf("metadata content = %q, want %q", got, want)
	}
}

func TestWritePackagesMetadataNoOpOnEmptyInputs(t *testing.T) {
	t.Parallel()
	dir := t.TempDir()
	rootfs := filepath.Join(dir, "rootfs.ext4")
	if err := os.WriteFile(rootfs, []byte("rootfs"), 0o644); err != nil {
		t.Fatalf("write rootfs: %v", err)
	}

	// Empty package list is the "managed-image build skipped apt" case.
	if err := WritePackagesMetadata(rootfs, nil); err != nil {
		t.Fatalf("WritePackagesMetadata(nil packages): %v", err)
	}
	if _, err := os.Stat(rootfs + ".packages.sha256"); !os.IsNotExist(err) {
		t.Fatalf("metadata file was created for empty packages; err = %v", err)
	}

	// Empty rootfs path is a no-op too — callers pass "" when they
	// haven't decided where to write yet.
	if err := WritePackagesMetadata("", []string{"git"}); err != nil {
		t.Fatalf("WritePackagesMetadata(empty rootfs): %v", err)
	}
}

// TestHashPackagesIgnoresOrder confirms the canonical join is
// strict-order-sensitive: callers must keep the ordering they want the
// hash to digest. Pin this so a future "convenience" sort doesn't
// silently invalidate every recorded image hash on disk.
func TestHashPackagesOrderSensitive(t *testing.T) {
	t.Parallel()
	a := hashPackages([]string{"git", "make"})
	b := hashPackages([]string{"make", "git"})
	if a == b {
		t.Fatal("hashPackages collapsed two orderings to the same hash; metadata-on-disk would be ambiguous")
	}
	// Trailing newlines must be normalised by the joiner, not the
	// caller. If callers had to remember to add their own, every
	// historical hash on disk would be a footgun.
	withTrailing := hashPackages([]string{"git", "make", ""})
	if withTrailing == a {
		t.Fatalf("hashPackages tolerated an empty trailing element silently; got %q == %q", withTrailing, a)
	}
}

// TestDebianBasePackagesContainsCriticalEntries pins the small core of
// packages every managed image must have. Stops a future refactor
// from dropping (say) ca-certificates without the owner noticing — a
// rebuilt image without it can't talk to TLS endpoints.
func TestDebianBasePackagesContainsCriticalEntries(t *testing.T) {
	t.Parallel()
	pkgs := strings.Join(DebianBasePackages(), " ")
	for _, must := range []string{"ca-certificates", "curl", "git"} {
		if !strings.Contains(pkgs, must) {
			t.Errorf("DebianBasePackages missing critical entry %q; got %q", must, pkgs)
		}
	}
}