Add mp3 support + command line option to limit tracks + general redesign for more modularity

model/extractor.go

@@ -0,0 +1,17 @@
+package model
+
+import (
+	"io"
+)
+
+type Extractor interface {
+	// Reads a single "block" from a radio stream. A block can be any chunk of
+	// data, depending on the file format, for example in Ogg/Vorbis it would
+	// be equivalent to a chunk. Writes the part containing the actual music
+	// data into `w`.
+	// `isFirst` is true, if the block read was the first block of a file.
+	ReadBlock(r io.Reader, w io.Writer) (isFirst bool, err error)
+	// Potentially returns a filename using format-specific metadata. Usually
+	// available after the first few blocks of a file were read.
+	TryGetFilename() (filename string, hasFilename bool)
+}