archive: add ExtractFormatLevel function (MR 25)

Extracts the format and level from a string in the form "format:level"

internal/archive/archive.go

@@ -68,6 +68,43 @@ type archiveItems struct {
 	sync.RWMutex
 }
 
+// ExtractFormatLevel parses the given string in the format format[:level],
+// where :level is one of CompressLevel consts. If level is omitted from the
+// string, or if it can't be parsed, the level is set to the default level for
+// the given format. If format is unknown, gzip is selected. This function is
+// designed to always return something usable within this package.
+func ExtractFormatLevel(s string) (format CompressFormat, level CompressLevel) {
+
+	f, l, found := strings.Cut(s, ":")
+	if !found {
+		l = "default"
+	}
+
+	level = CompressLevel(strings.ToLower(l))
+	format = CompressFormat(strings.ToLower(f))
+	switch level {
+
+	}
+	switch level {
+	case LevelBest:
+	case LevelDefault:
+	case LevelFast:
+	default:
+		log.Print("Unknown or no compression level set, using default")
+		level = LevelDefault
+	}
+
+	switch format {
+	case FormatGzip:
+	case FormatZstd:
+	default:
+		log.Print("Unknown or no compression format set, using gzip")
+		format = FormatGzip
+	}
+
+	return
+}
+
 // Adds the given item to the archiveItems, only if it doesn't already exist in
 // the list. The items are kept sorted in ascending order.
 func (a *archiveItems) add(item archiveItem) {

internal/archive/archive_test.go

@@ -187,3 +187,74 @@ func TestArchiveItemsAdd(t *testing.T) {
 		})
 	}
 }
+
+func TestExtractFormatLevel(t *testing.T) {
+	tests := []struct {
+		name           string
+		in             string
+		expectedFormat CompressFormat
+		expectedLevel  CompressLevel
+	}{
+		{
+			name:           "gzip, default level",
+			in:             "gzip:default",
+			expectedFormat: FormatGzip,
+			expectedLevel:  LevelDefault,
+		},
+		{
+			name:           "unknown format, level 12",
+			in:             "pear:12",
+			expectedFormat: FormatGzip,
+			expectedLevel:  LevelDefault,
+		},
+		{
+			name:           "zstd, level not given",
+			in:             "zstd",
+			expectedFormat: FormatZstd,
+			expectedLevel:  LevelDefault,
+		},
+		{
+			name:           "zstd, invalid level 'fast:'",
+			in:             "zstd:fast:",
+			expectedFormat: FormatZstd,
+			expectedLevel:  LevelDefault,
+		},
+		{
+			name:           "zstd, best",
+			in:             "zstd:best",
+			expectedFormat: FormatZstd,
+			expectedLevel:  LevelBest,
+		},
+		{
+			name:           "zstd, level empty :",
+			in:             "zstd:",
+			expectedFormat: FormatZstd,
+			expectedLevel:  LevelDefault,
+		},
+		{
+			name:           "gzip, best",
+			in:             "gzip:best",
+			expectedFormat: FormatGzip,
+			expectedLevel:  LevelBest,
+		},
+		{
+			name:           "none, none",
+			in:             "",
+			expectedFormat: FormatGzip,
+			expectedLevel:  LevelDefault,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			format, level := ExtractFormatLevel(test.in)
+			if format != test.expectedFormat {
+				t.Fatal("format expected: ", test.expectedFormat, " got: ", format)
+			}
+			if level != test.expectedLevel {
+				t.Fatal("level expected: ", test.expectedLevel, " got: ", level)
+			}
+
+		})
+	}
+}