feat: add ICY metadata parser with artist/title extraction

Made-with: Cursor

app/src/main/java/xyz/cottongin/radio247/audio/IcyMetadata.kt

@@ -0,0 +1,7 @@
+package xyz.cottongin.radio247.audio
+
+data class IcyMetadata(
+    val raw: String,
+    val title: String?,
+    val artist: String?
+)

app/src/main/java/xyz/cottongin/radio247/audio/IcyParser.kt

@@ -0,0 +1,91 @@
+package xyz.cottongin.radio247.audio
+
+import java.io.InputStream
+
+class IcyParser(
+    private val input: InputStream,
+    private val metaint: Int?,
+    private val onAudioData: (ByteArray, Int, Int) -> Unit,
+    private val onMetadata: (IcyMetadata) -> Unit
+) {
+    private val buffer = ByteArray(8192)
+
+    fun readAll() {
+        if (metaint == null) {
+            passthrough()
+        } else {
+            parseWithMetadata(metaint)
+        }
+    }
+
+    private fun passthrough() {
+        while (true) {
+            val n = input.read(buffer)
+            if (n <= 0) break
+            onAudioData(buffer, 0, n)
+        }
+    }
+
+    private fun parseWithMetadata(metaint: Int) {
+        val audioBuf = ByteArray(metaint)
+        while (true) {
+            val audioRead = readFully(audioBuf, 0, metaint)
+            if (audioRead <= 0) break
+            if (audioRead < metaint) {
+                onAudioData(audioBuf, 0, audioRead)
+                break
+            }
+            onAudioData(audioBuf, 0, metaint)
+
+            val lengthByte = input.read()
+            if (lengthByte < 0) break
+
+            val metadataSize = (lengthByte and 0xFF) * 16
+            if (metadataSize == 0) continue
+
+            val metaBytes = ByteArray(metadataSize)
+            val metaRead = readFully(metaBytes, 0, metadataSize)
+            if (metaRead < metadataSize) break
+
+            val raw = String(metaBytes, Charsets.UTF_8).trimEnd { it == '\u0000' }
+            val parsed = parseMetaString(raw)
+            onMetadata(parsed)
+        }
+    }
+
+    private fun readFully(buf: ByteArray, off: Int, len: Int): Int {
+        var total = 0
+        while (total < len) {
+            val n = input.read(buf, off + total, len - total)
+            if (n <= 0) return total
+            total += n
+        }
+        return total
+    }
+
+    private fun parseMetaString(raw: String): IcyMetadata {
+        val streamTitle = extractStreamTitle(raw)
+        if (streamTitle != null) {
+            val separatorIndex = streamTitle.indexOf(" - ")
+            if (separatorIndex >= 0) {
+                return IcyMetadata(
+                    raw = raw,
+                    artist = streamTitle.substring(0, separatorIndex).trim(),
+                    title = streamTitle.substring(separatorIndex + 3).trim()
+                )
+            }
+            return IcyMetadata(raw = raw, title = streamTitle.trim(), artist = null)
+        }
+        return IcyMetadata(raw = raw, title = null, artist = null)
+    }
+
+    private fun extractStreamTitle(meta: String): String? {
+        val key = "StreamTitle='"
+        val start = meta.indexOf(key)
+        if (start < 0) return null
+        val valueStart = start + key.length
+        val end = meta.indexOf("';", valueStart)
+        if (end < 0) return null
+        return meta.substring(valueStart, end)
+    }
+}