#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Wire.h>
#include <Fonts/FreeSansBold9pt7b.h>
#include <Fonts/Picopixel.h>

#define ENCODE_CLK 2
#define ENCODE_DT 3
#define ENCODE_SW 4

uint8_t volume = 50;
uint8_t bass = 25;
uint8_t treble = 66;

enum Mode {
    SET_VOLUME,
    SET_BASS,
    SET_TREBLE,
};

Mode mode = SET_VOLUME;

Adafruit_SSD1306 display(128, 64, &Wire, -1);

void nextMode() {
    switch (mode) {
        case SET_VOLUME:
            mode = SET_BASS;
            break;
        case SET_BASS:
            mode = SET_TREBLE;
            break;
        case SET_TREBLE:
            mode = SET_VOLUME;
            break;
    }
}

void updateValue(int delta) {
    switch (mode) {
        case SET_VOLUME:
            volume = constrain(volume + delta, 0, 100);
            break;
        case SET_BASS:
            bass = constrain(bass + delta, 0, 100);
            break;
        case SET_TREBLE:
            treble = constrain(treble + delta, 0, 100);
            break;
    }
}

void updateDisplay() {
    display.clearDisplay();
    display.setTextColor(1);

    display.setCursor(42, 2);
    display.print("Volume");
    display.drawRoundRect(10, 12, 102, 9, 2, WHITE);
    display.fillRect(11, 13, volume, 7, WHITE);
    if (mode == SET_VOLUME) {
        display.setCursor(32, 2);
        display.print("]");
    }

    display.setCursor(48, 22);
    display.print("Bass");
    display.drawRoundRect(10, 32, 102, 9, 2, WHITE);
    display.fillRect(11, 33, bass, 7, WHITE);
    if (mode == SET_BASS) {
        display.setCursor(38, 22);
        display.print("]");
    }

    display.setCursor(42, 42);
    display.print("Treble");
    display.drawRoundRect(10, 52, 102, 9, 2, WHITE);
    display.fillRect(11, 53, treble, 7, WHITE);
    if (mode == SET_TREBLE) {
        display.setCursor(32, 42);
        display.print("]");
    }

    display.display();
}

void setup() {
    display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
    pinMode(ENCODE_CLK, INPUT);
    pinMode(ENCODE_DT, INPUT);
    pinMode(ENCODE_SW, INPUT_PULLUP);
    updateDisplay();
}

long int modeLastChanged = 0;
int prevClk = HIGH;

void loop() {
    if (digitalRead(ENCODE_SW) == LOW && millis() - modeLastChanged > 500) {
        modeLastChanged = millis();
        nextMode();
        updateDisplay();
    }

    int clk = digitalRead(ENCODE_CLK);
    if (clk != prevClk) {
        int delta = (digitalRead(ENCODE_DT) == HIGH) ? 5 : -5;
        updateValue(delta);
        updateDisplay();
    }
    prevClk = clk;
}