#include "wokwi-api.h"
#include <stdio.h>
#include <stdlib.h>

/* -------------------------------------------------- */
/* States */

typedef enum { STATE_NORMAL, STATE_RISING, STATE_FALLING } hr_state_t;

typedef enum { STATE_SLOW = 0, STATE_FAST = 1 } hr_speed_t;

/* -------------------------------------------------- */
/* Chip state */

typedef struct {
  pin_t out_pin;
  pin_t btn_pin;

  float bpm;
  int last_target;

  hr_state_t state;
  hr_speed_t speed;

  int pulseValue;

  timer_t update_timer;
} chip_state_t;

/* -------------------------------------------------- */
/* Output mapping */

static void update_output_voltage(chip_state_t *chip) {
  float volts = (chip->bpm * 3.3f) / 675.0f;

  if (volts < 0.0f)
    volts = 0.0f;
  if (volts > 3.3f)
    volts = 3.3f;

  pin_dac_write(chip->out_pin, volts);

  printf("BPM: %.1f | Voltage: %.3fV\n", chip->bpm, volts);
}

/* -------------------------------------------------- */
/* Main update loop */

static void update_cb(void *user_data) {
  chip_state_t *chip = user_data;

  int target = attr_read(chip->pulseValue);

  /* Read pull-down switch: LOW=SLOW, HIGH=FAST */
  chip->speed = pin_read(chip->btn_pin) ? STATE_FAST : STATE_SLOW;

  /* Detect target change and re-evaluate direction */
  if (target != chip->last_target) {
    if (chip->bpm < target) {
      chip->state = STATE_RISING;
    } else if (chip->bpm > target) {
      chip->state = STATE_FALLING;
    } else {
      chip->state = STATE_NORMAL;
    }
    chip->last_target = target;
  }

  /* Step size */
  float step = (chip->speed == STATE_FAST) ? 2.0f : 0.5f;

  /* Rising */
  if (chip->state == STATE_RISING) {
    chip->bpm += step;
    if (chip->bpm >= target) {
      chip->bpm = target;
      chip->state = STATE_NORMAL;
    }
  }

  /* Falling */
  if (chip->state == STATE_FALLING) {
    chip->bpm -= step;
    if (chip->bpm <= target) {
      chip->bpm = target;
      chip->state = STATE_NORMAL;
    }
  }

  update_output_voltage(chip);
}

/* -------------------------------------------------- */
/* Init */

void chip_init(void) {
  printf("Heart Rate chip init\n");

  chip_state_t *chip = calloc(1, sizeof(chip_state_t));

  /* Attribute: target BPM */
  chip->pulseValue = attr_init("pulseValue", 100);

  chip->bpm = 100.0f;
  chip->last_target = 100;
  chip->state = STATE_NORMAL;
  chip->speed = STATE_SLOW;

  chip->out_pin = pin_init("OUT", ANALOG);
  chip->btn_pin = pin_init("BTN", INPUT); // pull-down switch

  timer_config_t update_cfg = {.callback = update_cb, .user_data = chip};

  chip->update_timer = timer_init(&update_cfg);

  /* 50 ms update rate */
  timer_start(chip->update_timer, 50000, true);
}