#include "dht22.h"
#include "esp_log.h"
#include "hal/gpio_types.h"
#include "sdkconfig.h"
#include "driver/gpio.h"
#include <rom/ets_sys.h>
#include "esp_timer.h"
#include "freertos/portmacro.h"

#define DATA_GPIO CONFIG_DHT22_DATA_GPIO

#if DATA_GPIO == -1
#error "Please define your DHT22 GPIO Data Pin"
#endif /* CONFIG_DHT22_DATA_GPIO == -1 */

static const char *TAG = "DHT22";
deci_percent _dht22_relative_humidity = UINT16_MAX;
deci_degrees_c _dht22_temperature = INT16_MIN;

void dht22_handle_error(dht22_error e) {
  if (e == DHT22_OK) {
    ESP_LOGI(TAG, "No errors reading DHT22 value");
  } else if (e == DHT22_CHECKSUM_ERROR) {
    ESP_LOGE(TAG, "Error calculating checksum");
  } else if (e == DHT22_TIMING_ERROR) {
    ESP_LOGE(TAG, "Timing error while obtaining data");
  } else if (e == DHT22_TIMEOUT_ERROR) {
    ESP_LOGE(TAG, "Timeout error - waited >2ms for signal to change");
  } else {
    ESP_LOGE(TAG, "Unknown error: %i", e);
  }
}

uint32_t wait_for_signal_to_change_from(int signal_level) {
  uint64_t start_time = esp_timer_get_time();
  uint64_t next_time = start_time;
  while (gpio_get_level(DATA_GPIO) == signal_level) {
    next_time = esp_timer_get_time();
    ets_delay_us(2); // just incase of lagging/debouncing/jitter/whatever

    // TODO think about a way to pass in a max time - although 10ms isn't bad
    if ((next_time - start_time) >= 1000 * 10) {
      return DHT22_TIMEOUT_ERROR;
    }
  }

  uint32_t elapsed_time = next_time - start_time;
  if (elapsed_time == 0) {
    return 1000;
  }
  return elapsed_time;
}

dht22_error dht22_read() {
  portDISABLE_INTERRUPTS();

  /*
   * From datasheet:
   *  - Host pulls low "beyond at least 1ms"
   *  - Host pulls up 20us to 40us
   */
  gpio_set_direction(DATA_GPIO, GPIO_MODE_OUTPUT);

  gpio_set_level(DATA_GPIO, 0);
  ets_delay_us(5000);

  gpio_set_level(DATA_GPIO, 1);
  ets_delay_us(25);

  gpio_set_direction(DATA_GPIO, GPIO_MODE_INPUT);

  // Wait here until it goes high DHT "responds" after being pulled high
  // The 40 is pretty arbitrary - but there's probably a problem if it goes higher
  uint32_t elapsed_time;
  elapsed_time = wait_for_signal_to_change_from(1);
  if (elapsed_time == DHT22_TIMEOUT_ERROR) {
    portENABLE_INTERRUPTS();
    return DHT22_TIMEOUT_ERROR;
  } else if (elapsed_time > 40) {
    portENABLE_INTERRUPTS();
    return DHT22_TIMING_ERROR;
  }

  /*
   * From datasheet:
   *  - DHT pulls low 80us
   *  - DHT pulls high 80us
   */

  elapsed_time = wait_for_signal_to_change_from(0);
  if (elapsed_time == DHT22_TIMEOUT_ERROR) {
    portENABLE_INTERRUPTS();
    return DHT22_TIMEOUT_ERROR;
  } else if (elapsed_time < 70 || elapsed_time > 90) {
    portENABLE_INTERRUPTS();
    return DHT22_TIMING_ERROR;
  }

  elapsed_time = wait_for_signal_to_change_from(1);
  if (elapsed_time == DHT22_TIMEOUT_ERROR) {
    portENABLE_INTERRUPTS();
    return DHT22_TIMEOUT_ERROR;
  } else if (elapsed_time < 70 || elapsed_time > 90) {
    portENABLE_INTERRUPTS();
    return DHT22_TIMING_ERROR;
  }

  /*
   * From datasheet:
   *  - DHT pulls low 50us -> into to next bit
   *  - DHT pulls high:
   *     - if 26-28us -> 0 bit
   *     - if 70us -> 1 bit
   */
  uint8_t data[5] = {0, 0, 0, 0, 0};
  for (uint8_t i = 0; i < 40; i++) {
      elapsed_time = wait_for_signal_to_change_from(0);
      if (elapsed_time == DHT22_TIMEOUT_ERROR || elapsed_time < 30 ||
          elapsed_time > 70) {
        portENABLE_INTERRUPTS();
        return DHT22_TIMEOUT_ERROR;
      }

      elapsed_time = wait_for_signal_to_change_from(1);
      if (elapsed_time > 50) {
        data[i / 8] |= (1 << (7 - (i % 8)));
      }
  }
  portENABLE_INTERRUPTS();

  _dht22_relative_humidity = (data[0] << 8) | data[1];
  _dht22_temperature = ((data[2] & 0x7f) << 8) | data[3];
  if (data[2] & 0x80) {
    _dht22_temperature = -1 * _dht22_temperature;
  }

  uint8_t checksum_val = (data[0] + data[1] + data[2] + data[3]) & 0xff;
  if (checksum_val != data[4]) {
    _dht22_relative_humidity = UINT16_MAX;
    _dht22_temperature = INT16_MIN;
    return DHT22_CHECKSUM_ERROR;
  }

  return DHT22_OK;
}

deci_percent dht22_relative_humidity() { return _dht22_relative_humidity; }
deci_degrees_c dht22_temperature() { return _dht22_temperature; }