PicoWaveTracker/LSystemStrategy.h

#ifndef LSYSTEM_STRATEGY_H
#define LSYSTEM_STRATEGY_H

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

struct Rule {
    char from;
    const char* to;
};

struct RuleSet {
    const char* axiom;
    const Rule* rules;
    uint8_t numRules;
};

// --- L-System Rule Definitions ---
const Rule rules1[] = { {'A', "B-A-B"}, {'B', "A+B+A"} };
const Rule rules2[] = { {'F', "F+F-F-F+F"} };
const Rule rules3[] = { {'X', "F+[[X]-X]-F[-FX]+X"}, {'F', "FF"} };

const RuleSet ruleSets[] = {
    {"A", rules1, 2},      // Sierpinski triangle
    {"F", rules2, 1},      // Koch curve
    {"X", rules3, 2}       // Fractal plant
};
const uint8_t numRuleSets = sizeof(ruleSets) / sizeof(RuleSet);

class LSystemStrategy : public MelodyStrategy {
public:
    void generate(Step (*sequence)[NUM_STEPS], int track, int numSteps, int* scaleNotes, int numScaleNotes, int seed) override {
        randomSeed(seed);
        if (numScaleNotes == 0) {
            // Fill with silence if no scale
            for (int i = 0; i < numSteps; i++) {
                sequence[track][i].note = -1;
                sequence[track][i].accent = false;
                sequence[track][i].tie = false;
            }
            return;
        }

        // 1. Select a rule set and expand the axiom
        const RuleSet& selectedRuleSet = ruleSets[random(numRuleSets)];
        String currentString = selectedRuleSet.axiom;
        int iterations = random(2, 5); // 2-4 iterations

        for (int i = 0; i < iterations; i++) {
            String nextString = "";
            for (char c : currentString) {
                bool replaced = false;
                for (int j = 0; j < selectedRuleSet.numRules; j++) {
                    if (c == selectedRuleSet.rules[j].from) {
                        nextString += selectedRuleSet.rules[j].to;
                        replaced = true;
                        break;
                    }
                }
                if (!replaced) {
                    nextString += c;
                }
                if (nextString.length() > 256) break; // Memory safety
            }
            currentString = nextString;
            if (currentString.length() > 256) break;
        }

        // 2. Interpret the string to create the sequence
        int stepIndex = 0;
        int noteIndex = random(numScaleNotes);
        int octave = 4;

        // Stack for branching rules
        int note_stack[8];
        int octave_stack[8];
        int stack_ptr = 0;

        for (char c : currentString) {
            if (stepIndex >= numSteps) break;

            switch(c) {
                case 'F': case 'G': case 'A': case 'B': // Characters that draw notes
                    sequence[track][stepIndex].note = 12 * octave + scaleNotes[noteIndex];
                    sequence[track][stepIndex].accent = (random(100) < 25);
                    sequence[track][stepIndex].tie = (random(100) < 10);
                    stepIndex++;
                    break;
                case '+': // Go up in scale
                    noteIndex = (noteIndex + 1) % numScaleNotes;
                    break;
                case '-': // Go down in scale
                    noteIndex = (noteIndex - 1 + numScaleNotes) % numScaleNotes;
                    break;
                case '[': // Push current state
                    if(stack_ptr < 8) {
                        note_stack[stack_ptr] = noteIndex;
                        octave_stack[stack_ptr] = octave;
                        stack_ptr++;
                    }
                    break;
                case ']': // Pop state
                    if(stack_ptr > 0) {
                        stack_ptr--;
                        noteIndex = note_stack[stack_ptr];
                        octave = octave_stack[stack_ptr];
                    }
                    break;
                // Any other characters (like 'X' in rule 3) are ignored for drawing
            }
        }

        // 3. Fill any remaining steps with rests
        for (int i = 0; i < numSteps; i++) {
            if (i >= stepIndex) {
                sequence[track][i].note = -1;
                sequence[track][i].accent = false;
                sequence[track][i].tie = false;
            }
        }
        randomSeed(micros());
    }

    void generateScale(int* scaleNotes, int& numScaleNotes) override {
        numScaleNotes = random(5, 8);
        for (int i = 0; i < 12; i++) {
            scaleNotes[i] = i;
        }
        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)[NUM_STEPS], int track, int numSteps, int* scaleNotes, int numScaleNotes) override {
        // Swap two non-rest steps to create a variation
        int s1 = random(numSteps);
        int s2 = random(numSteps);
        int attempts = 0;

        // Try to find two different, non-rest steps
        while((sequence[track][s1].note == -1 || sequence[track][s2].note == -1 || s1 == s2) && attempts < 20) {
            s1 = random(numSteps);
            s2 = random(numSteps);
            attempts++;
        }

        if (sequence[track][s1].note != -1 && sequence[track][s2].note != -1) {
            Step temp = sequence[track][s1];
            sequence[track][s1] = sequence[track][s2];
            sequence[track][s2] = temp;
        }
    }

    const char* getName() override {
        return "L-System";
    }
};

#endif