Replace hardcoded magic values with named constants and improve type safety

Adds new constants for file format identifiers (FormatFILP), fork types
(ForkTypeINFO), and platform identifiers (PlatformAMAC, PlatformMWIN) to
improve code maintainability and readability. Changes FlatFileForkHeader.ForkType
field from [4]byte to ForkType type alias for better compile-time type checking,
matching the pattern used in ForkInfoList.Fork.

4 files changed, 13 insertions, 8 deletions

diff --git a/hotline/file_resume_data.go b/hotline/file_resume_data.go
index 80f5fe5..c9f27f6 100644
--- a/hotline/file_resume_data.go
+++ b/hotline/file_resume_data.go
@@ -32,6 +32,7 @@ type ForkInfoList struct {
 
 var (
 	ForkTypeDATA = ForkType{0x44, 0x41, 0x54, 0x41} // DATA: Data fork
+	ForkTypeINFO = ForkType{0x49, 0x4E, 0x46, 0x4F} // INFO: Information fork
 	ForkTypeMACR = ForkType{0x4d, 0x41, 0x43, 0x52} // MACR: Mac resource fork
 )
 
@@ -45,7 +46,11 @@ func NewForkInfoList(b []byte) *ForkInfoList {
 }
 
 var (
+	FormatFILP = [4]byte{0x46, 0x49, 0x4c, 0x50} // Flattened file format: "FILP"
 	FormatRFLT = [4]byte{0x52, 0x46, 0x4C, 0x54} // File resume format: "RFLT" (?)
+
+	PlatformAMAC = [4]byte{0x41, 0x4D, 0x41, 0x43} // Mac platform: "AMAC"
+	PlatformMWIN = [4]byte{0x4D, 0x57, 0x49, 0x4E} // Windows platform: "MWIN"
 )
 
 func NewFileResumeData(list []ForkInfoList) *FileResumeData {
diff --git a/hotline/file_wrapper.go b/hotline/file_wrapper.go
index b6aff94..5ec99c3 100644
--- a/hotline/file_wrapper.go
+++ b/hotline/file_wrapper.go
@@ -227,7 +227,7 @@ func (f *fileWrapper) flattenedFileObject() (*flattenedFileObject, error) {
 	}
 
 	f.Ffo.FlatFileHeader = FlatFileHeader{
-		Format:    [4]byte{0x46, 0x49, 0x4c, 0x50}, // "FILP"
+		Format:    FormatFILP,
 		Version:   [2]byte{0, 1},
 		ForkCount: [2]byte{0, 2},
 	}
@@ -247,7 +247,7 @@ func (f *fileWrapper) flattenedFileObject() (*flattenedFileObject, error) {
 		}
 	} else {
 		f.Ffo.FlatFileInformationFork = FlatFileInformationFork{
-			Platform:         [4]byte{0x41, 0x4D, 0x41, 0x43}, // "AMAC" TODO: Remove hardcode to support "AWIN" Platform (maybe?)
+			Platform:         PlatformAMAC, // TODO: Remove hardcode to support "MWIN" Platform (maybe?)
 			TypeSignature:    [4]byte([]byte(ft.TypeCode)),
 			CreatorSignature: [4]byte([]byte(ft.CreatorCode)),
 			PlatformFlags:    [4]byte{0, 0, 1, 0}, // TODO: What is this?
@@ -263,12 +263,12 @@ func (f *fileWrapper) flattenedFileObject() (*flattenedFileObject, error) {
 	}
 
 	f.Ffo.FlatFileInformationForkHeader = FlatFileForkHeader{
-		ForkType: [4]byte{0x49, 0x4E, 0x46, 0x4F}, // "INFO"
+		ForkType: ForkTypeINFO,
 		DataSize: f.Ffo.FlatFileInformationFork.Size(),
 	}
 
 	f.Ffo.FlatFileDataForkHeader = FlatFileForkHeader{
-		ForkType: [4]byte{0x44, 0x41, 0x54, 0x41}, // "DATA"
+		ForkType: ForkTypeDATA,
 		DataSize: [4]byte{dataSize[0], dataSize[1], dataSize[2], dataSize[3]},
 	}
 	f.Ffo.FlatFileResForkHeader = f.rsrcForkHeader()
diff --git a/hotline/flattened_file_object.go b/hotline/flattened_file_object.go
index 99ce204..7c0cd7d 100644
--- a/hotline/flattened_file_object.go
+++ b/hotline/flattened_file_object.go
@@ -45,7 +45,7 @@ type FlatFileInformationFork struct {
 
 func NewFlatFileInformationFork(fileName string, modifyTime [8]byte, typeSignature string, creatorSignature string) FlatFileInformationFork {
 	return FlatFileInformationFork{
-		Platform:         [4]byte{0x41, 0x4D, 0x41, 0x43},   // "AMAC" TODO: Remove hardcode to support "AWIN" Platform (maybe?)
+		Platform:         PlatformAMAC,                       // TODO: Remove hardcode to support "MWIN" Platform (maybe?)
 		TypeSignature:    [4]byte([]byte(typeSignature)),    // TODO: Don't infer types from filename
 		CreatorSignature: [4]byte([]byte(creatorSignature)), // TODO: Don't infer types from filename
 		PlatformFlags:    [4]byte{0, 0, 1, 0},               // TODO: What is this?
@@ -128,7 +128,7 @@ func (ffif *FlatFileInformationFork) ReadNameSize() []byte {
 }
 
 type FlatFileForkHeader struct {
-	ForkType        [4]byte // Either INFO, DATA or MACR
+	ForkType        ForkType // Either INFO, DATA or MACR
 	CompressionType [4]byte
 	RSVD            [4]byte
 	DataSize        [4]byte
diff --git a/hotline/transfer_test.go b/hotline/transfer_test.go
index 4aa142b..c915498 100644
--- a/hotline/transfer_test.go
+++ b/hotline/transfer_test.go
@@ -120,14 +120,14 @@ func Test_receiveFile(t *testing.T) {
 				conn: func() io.Reader {
 					testFile := flattenedFileObject{
 						FlatFileHeader: FlatFileHeader{
-							Format:    [4]byte{0x46, 0x49, 0x4c, 0x50}, // "FILP"
+							Format:    FormatFILP,
 							Version:   [2]byte{0, 1},
 							ForkCount: [2]byte{0, 2},
 						},
 						FlatFileInformationForkHeader: FlatFileForkHeader{},
 						FlatFileInformationFork:       NewFlatFileInformationFork("testfile.txt", [8]byte{}, "TEXT", "TEXT"),
 						FlatFileDataForkHeader: FlatFileForkHeader{
-							ForkType: [4]byte{0x4d, 0x41, 0x43, 0x52}, // DATA
+							ForkType: ForkTypeMACR,
 							DataSize: [4]byte{0x00, 0x00, 0x00, 0x03},
 						},
 					}