#include "encoder.h"
#include "hardware/gpio.h"

#define PIN_A 10
#define PIN_B 11
#define REST  3   /* A = B = 1: both contacts open at a detent */
#define DIR   -1  /* as wired on the bench, the raw count runs down clockwise */

static volatile int32_t steps, clicks;
static volatile int8_t acc;   /* edges since the last rest */
static volatile uint8_t prev;

/* index = previous AB << 2 | current AB; invalid (bounce) transitions count 0 */
static const int8_t TABLE[16] = { 0,-1, 1, 0,   1, 0, 0,-1,   -1, 0, 0, 1,   0, 1,-1, 0 };

static uint8_t read_ab(void){ return (uint8_t)((gpio_get(PIN_A) << 1) | gpio_get(PIN_B)); }

static void on_edge(uint gpio, uint32_t events){
  uint8_t cur;
  int8_t d;
  (void)events;
  if(gpio != PIN_A && gpio != PIN_B) return;
  cur = read_ab();
  d = TABLE[(prev << 2) | cur];
  steps += d; acc = (int8_t)(acc + d);
  prev = cur;
  if(cur == REST){
    /* a full click is 4 edges; accept 2 or more in case bounce hid some, ignore wiggles of 1 */
    if(acc >= 2) clicks += DIR;
    else if(acc <= -2) clicks -= DIR;
    acc = 0;
  }
}

void encoder_init(void){
  gpio_init(PIN_A); gpio_set_dir(PIN_A, GPIO_IN); gpio_pull_up(PIN_A);
  gpio_init(PIN_B); gpio_set_dir(PIN_B, GPIO_IN); gpio_pull_up(PIN_B);
  prev = read_ab();
  gpio_set_irq_enabled_with_callback(PIN_A, GPIO_IRQ_EDGE_RISE | GPIO_IRQ_EDGE_FALL, true, on_edge);
  gpio_set_irq_enabled(PIN_B, GPIO_IRQ_EDGE_RISE | GPIO_IRQ_EDGE_FALL, true);
}

int32_t encoder_count(void){ return clicks; }
int32_t encoder_steps(void){ return DIR * steps; }
int     encoder_ab(void){ return read_ab(); }