#include "fire_sensor.h"

#include "MQ-2.h"

#include "esp_adc/adc_oneshot.h"
#include "esp_check.h"

#define FIRE_ADC_UNIT ADC_UNIT_1
#define FIRE_ADC_CHANNEL ADC_CHANNEL_2
#define FIRE_SAMPLE_COUNT 8

static const char *TAG = "fire_sensor";
static adc_oneshot_unit_handle_t s_adc_handle = NULL;
static bool s_inited = false;

esp_err_t fire_sensor_init(void)
{
    if (s_inited) {
        return ESP_OK;
    }

    // Reuse ADC1 oneshot unit created by MQ-2 to avoid "adc1 is already in use".
    ESP_RETURN_ON_ERROR(mq2_init(), TAG, "mq2 init failed");
    s_adc_handle = mq2_get_adc_handle();
    ESP_RETURN_ON_FALSE(s_adc_handle != NULL, ESP_ERR_INVALID_STATE, TAG, "shared adc handle is null");

    adc_oneshot_chan_cfg_t chan_cfg = {
        .atten = ADC_ATTEN_DB_12,
        .bitwidth = ADC_BITWIDTH_DEFAULT,
    };
    ESP_RETURN_ON_ERROR(adc_oneshot_config_channel(s_adc_handle, FIRE_ADC_CHANNEL, &chan_cfg),
                        TAG, "adc channel config failed");

    s_inited = true;
    return ESP_OK;
}

esp_err_t fire_sensor_read_raw(int *raw_out)
{
    ESP_RETURN_ON_FALSE(raw_out != NULL, ESP_ERR_INVALID_ARG, TAG, "raw_out is null");
    ESP_RETURN_ON_FALSE(s_inited, ESP_ERR_INVALID_STATE, TAG, "fire sensor not initialized");

    int sum = 0;
    for (int i = 0; i < FIRE_SAMPLE_COUNT; ++i) {
        int sample = 0;
        ESP_RETURN_ON_ERROR(adc_oneshot_read(s_adc_handle, FIRE_ADC_CHANNEL, &sample),
                            TAG, "adc read failed");
        sum += sample;
    }

    *raw_out = sum / FIRE_SAMPLE_COUNT;
    return ESP_OK;
}

esp_err_t fire_sensor_read_percent(float *percent_out)
{
    ESP_RETURN_ON_FALSE(percent_out != NULL, ESP_ERR_INVALID_ARG, TAG, "percent_out is null");

    int raw = 0;
    ESP_RETURN_ON_ERROR(fire_sensor_read_raw(&raw), TAG, "read raw failed");

    // Most flame modules output lower voltage when flame is stronger.
    // Map raw inversely to "danger percent":
    // raw=4095 -> 0%, raw=0 -> 100%
    *percent_out = ((4095.0f - (float)raw) * 100.0f) / 4095.0f;
    if (*percent_out < 0.0f) {
        *percent_out = 0.0f;
    } else if (*percent_out > 100.0f) {
        *percent_out = 100.0f;
    }
    return ESP_OK;
}

bool fire_sensor_is_danger(float percent, float threshold_percent)
{
    return percent >= threshold_percent;
}