PicoWaveTracker/ArpStrategy.h

#ifndef ARP_STRATEGY_H
#define ARP_STRATEGY_H

#include "MelodyStrategy.h"
#include <Arduino.h>

class ArpStrategy : public MelodyStrategy {
public:
    void generate(Step* sequence, int numSteps, int* scaleNotes, int numScaleNotes, int seed) override {
        randomSeed(seed);
        if (numScaleNotes == 0) return;

        // 1. Select Subset
        int subsetSize = random(2, numScaleNotes + 1);
        if (subsetSize > 12) subsetSize = 12;
        int subset[12];
        
        // Create indices to shuffle
        int indices[12];
        for(int i=0; i<numScaleNotes; i++) indices[i] = i;
        
        // Shuffle indices
        for(int i=0; i<numScaleNotes; i++) {
            int r = random(numScaleNotes);
            int temp = indices[i];
            indices[i] = indices[r];
            indices[r] = temp;
        }
        
        // Pick subset
        for(int i=0; i<subsetSize; i++) {
            subset[i] = scaleNotes[indices[i]];
        }
        sortArray(subset, subsetSize);

        // 2. Pick Arp Length & Pattern
        int arpLength = random(2, 17); // 2 to 16
        Step arpPattern[16];

        int mode = random(3); // 0: Up, 1: Down, 2: Up/Down
        int numOctaves = 3;
        int baseOctave = 3;
        int totalNotes = subsetSize * numOctaves;
        
        int currentIndex = 0;
        int direction = 1;

        if (mode == 1) { // Down
            currentIndex = totalNotes - 1;
            direction = -1;
        }

        for (int i = 0; i < arpLength; i++) {
            // Chance of rest (15%)
            if (random(100) < 15) {
                arpPattern[i].note = -1;
                arpPattern[i].accent = false;
                arpPattern[i].tie = false;
            } else {
                int octaveOffset = currentIndex / subsetSize;
                int noteIndex = currentIndex % subsetSize;
                int octave = baseOctave + octaveOffset;
                
                arpPattern[i].note = 12 * octave + subset[noteIndex];
                arpPattern[i].accent = (i % 4 == 0); // Accent on beat
                arpPattern[i].tie = false;
            }

            if (mode == 0) { // Up
                currentIndex++;
                if (currentIndex >= totalNotes) currentIndex = 0;
            } else if (mode == 1) { // Down
                currentIndex--;
                if (currentIndex < 0) currentIndex = totalNotes - 1;
            } else { // Up/Down
                currentIndex += direction;
                if (currentIndex >= totalNotes) {
                    currentIndex = max(0, totalNotes - 2);
                    direction = -1;
                } else if (currentIndex < 0) {
                    currentIndex = min(totalNotes - 1, 1);
                    direction = 1;
                }
            }
        }

        // 3. Fill Sequence
        for (int i = 0; i < numSteps; i++) {
            sequence[i] = arpPattern[i % arpLength];
        }
        randomSeed(micros());
    }

    void generateScale(int* scaleNotes, int& numScaleNotes) override {
        numScaleNotes = random(3, 13); // 3 to 12 notes
        for (int i = 0; i < 12; i++) {
            scaleNotes[i] = i; // Fill with all notes
        }
        // Shuffle
        for (int i = 0; i < 12; i++) {
            int j = random(12);
            int temp = scaleNotes[i];
            scaleNotes[i] = scaleNotes[j];
            scaleNotes[j] = temp;
        }
        sortArray(scaleNotes, numScaleNotes);
    }

    void mutate(Step* sequence, int numSteps, int* scaleNotes, int numScaleNotes) override {
        // Swap two notes
        int s1 = random(numSteps);
        int s2 = random(numSteps);
        if (sequence[s1].note != -1 && sequence[s2].note != -1) {
             int8_t temp = sequence[s1].note;
             sequence[s1].note = sequence[s2].note;
             sequence[s2].note = temp;
        }
    }

    const char* getName() override {
        return "Arp";
    }
};

#endif