function playNextNote()

in libs/core/music.ts [490:539]
46 lines of code
30 McCabe index (conditional complexity)

    function playNextNote(melody: Melody): void {
        // cache elements
        let currNote = melody.nextNote();
        let currentPos = melody.currentPos;
        let currentDuration = melody.currentDuration;
        let currentOctave = melody.currentOctave;

        let note: number;
        let isrest: boolean = false;
        let beatPos: number;
        let parsingOctave: boolean = true;
        let prevNote: boolean = false;

        for (let pos = 0; pos < currNote.length; pos++) {
            let noteChar = currNote.charAt(pos);
            switch (noteChar) {
                case 'c': case 'C': note = 1; prevNote = true; break;
                case 'd': case 'D': note = 3; prevNote = true; break;
                case 'e': case 'E': note = 5; prevNote = true; break;
                case 'f': case 'F': note = 6; prevNote = true; break;
                case 'g': case 'G': note = 8; prevNote = true; break;
                case 'a': case 'A': note = 10; prevNote = true; break;
                case 'B': note = 12; prevNote = true; break;
                case 'r': case 'R': isrest = true; prevNote = false; break;
                case '#': note++; prevNote = false; break;
                case 'b': if (prevNote) note--; else { note = 12; prevNote = true; } break;
                case ':': parsingOctave = false; beatPos = pos; prevNote = false; break;
                default: prevNote = false; if (parsingOctave) currentOctave = parseInt(noteChar);
            }
        }
        if (!parsingOctave) {
            currentDuration = parseInt(currNote.substr(beatPos + 1, currNote.length - beatPos));
        }
        let beat = Math.idiv(60000, beatsPerMinute) >> 2;
        if (isrest) {
            music.rest(currentDuration * beat)
        } else {
            let keyNumber = note + (12 * (currentOctave - 1));
            let frequency = freqs.getNumber(NumberFormat.UInt16LE, keyNumber * 2) || 0;
            music.playTone(frequency, currentDuration * beat);
        }
        melody.currentDuration = currentDuration;
        melody.currentOctave = currentOctave;
        const repeating = melody.repeating && currentPos == melody.melodyArray.length - 1;
        melody.currentPos = repeating ? 0 : currentPos + 1;

        control.raiseEvent(MICROBIT_MELODY_ID, melody.background ? MusicEvent.BackgroundMelodyNotePlayed : MusicEvent.MelodyNotePlayed);
        if (repeating)
            control.raiseEvent(MICROBIT_MELODY_ID, melody.background ? MusicEvent.BackgroundMelodyRepeated : MusicEvent.MelodyRepeated);
    }