add content-addressed hak source mode (#7)

Reviewed-on: #7
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

internal/erf/erf_test.go

@@ -2,9 +2,72 @@ package erf
 
 import (
 	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 )
 
+func writeTempPayload(t *testing.T, payload []byte) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "payload.bin")
+	if err := os.WriteFile(path, payload, 0o644); err != nil {
+		t.Fatalf("write payload: %v", err)
+	}
+	return path
+}
+
+func TestWriteRejectsSourcePathSHA256Mismatch(t *testing.T) {
+	payload := []byte("hello world")
+	path := writeTempPayload(t, payload)
+
+	archive := New("HAK ", []Resource{{
+		Name:           "asset",
+		Type:           0x0003,
+		SourcePath:     path,
+		Size:           int64(len(payload)),
+		ExpectedSHA256: strings.Repeat("a", 64),
+	}})
+
+	var buf bytes.Buffer
+	err := Write(&buf, archive)
+	if err == nil {
+		t.Fatal("expected sha256 mismatch error")
+	}
+	if !strings.Contains(err.Error(), "sha256 mismatch") {
+		t.Fatalf("error = %v, want sha256 mismatch", err)
+	}
+}
+
+func TestWriteAcceptsMatchingSourcePathSHA256(t *testing.T) {
+	payload := []byte("hello world")
+	path := writeTempPayload(t, payload)
+	sum := sha256.Sum256(payload)
+
+	archive := New("HAK ", []Resource{{
+		Name:           "asset",
+		Type:           0x0003,
+		SourcePath:     path,
+		Size:           int64(len(payload)),
+		ExpectedSHA256: hex.EncodeToString(sum[:]),
+	}})
+
+	var buf bytes.Buffer
+	if err := Write(&buf, archive); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+
+	decoded, err := Read(bytes.NewReader(buf.Bytes()))
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	if len(decoded.Resources) != 1 || string(decoded.Resources[0].Data) != string(payload) {
+		t.Fatalf("unexpected payload: %#v", decoded.Resources)
+	}
+}
+
 func TestArchiveRoundTrip(t *testing.T) {
 	archive := New("MOD ", []Resource{
 		{Name: "module", Type: 0x07DE, Data: []byte("ifo")},