#include "l3g4200d.h"

#include <stddef.h>

#define L3G4200D_REG_WHO_AM_I 0x0F
#define L3G4200D_REG_CTRL1    0x20
#define L3G4200D_REG_CTRL2    0x21
#define L3G4200D_REG_CTRL3    0x22
#define L3G4200D_REG_CTRL4    0x23
#define L3G4200D_REG_CTRL5    0x24
#define L3G4200D_REG_STATUS   0x27
#define L3G4200D_REG_OUT_X_L  0x28

#define L3G4200D_WHO_AM_I_VALUE 0xD3
#define L3G4200D_CTRL1_100_HZ   0x1F
#define L3G4200D_CTRL4_500_DPS  0x90
#define L3G4200D_CTRL5_LPF2_OUT 0x02
#define L3G4200D_AUTO_INCREMENT 0x80
#define L3G4200D_TIMEOUT_MS     100

static esp_err_t read_registers(i2c_master_dev_handle_t device, uint8_t start_register,
                                uint8_t *data, size_t length)
{
    return i2c_master_transmit_receive(device, &start_register, 1, data, length,
                                       L3G4200D_TIMEOUT_MS);
}

static esp_err_t write_register(i2c_master_dev_handle_t device, uint8_t reg, uint8_t value)
{
    const uint8_t bytes[] = {reg, value};
    return i2c_master_transmit(device, bytes, sizeof(bytes), L3G4200D_TIMEOUT_MS);
}

static esp_err_t verify_register(i2c_master_dev_handle_t device, uint8_t reg, uint8_t expected)
{
    uint8_t actual = 0;
    esp_err_t err = read_registers(device, reg, &actual, 1);
    if (err != ESP_OK) {
        return err;
    }
    return actual == expected ? ESP_OK : ESP_ERR_INVALID_RESPONSE;
}

esp_err_t l3g4200d_init(l3g4200d_t *sensor, i2c_master_bus_handle_t bus, uint32_t bus_speed_hz)
{
    if (sensor == NULL || bus == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    *sensor = (l3g4200d_t){0};
    static const uint8_t candidate_addresses[] = {0x69, 0x68};

    for (size_t i = 0;
         i < sizeof(candidate_addresses) / sizeof(candidate_addresses[0]); ++i) {
        const i2c_device_config_t config = {
            .dev_addr_length = I2C_ADDR_BIT_LEN_7,
            .device_address = candidate_addresses[i],
            .scl_speed_hz = bus_speed_hz,
        };

        i2c_master_dev_handle_t device = NULL;
        esp_err_t err = i2c_master_bus_add_device(bus, &config, &device);
        if (err != ESP_OK) {
            return err;
        }

        uint8_t device_id = 0;
        err = read_registers(device, L3G4200D_REG_WHO_AM_I, &device_id, 1);
        if (err == ESP_OK && device_id == L3G4200D_WHO_AM_I_VALUE) {
            sensor->device = device;
            sensor->address = candidate_addresses[i];
            break;
        }

        i2c_master_bus_rm_device(device);
    }

    if (sensor->device == NULL) {
        return ESP_ERR_NOT_FOUND;
    }

    // Configure control registers before enabling normal mode in CTRL1.
    esp_err_t err = write_register(sensor->device, L3G4200D_REG_CTRL1, 0x00);
    if (err == ESP_OK) {
        err = write_register(sensor->device, L3G4200D_REG_CTRL2, 0x00);
    }
    if (err == ESP_OK) {
        err = write_register(sensor->device, L3G4200D_REG_CTRL3, 0x00);
    }
    if (err == ESP_OK) {
        // Block data updates while a six-byte sample is being read; select +/-500 dps.
        err = write_register(sensor->device, L3G4200D_REG_CTRL4, L3G4200D_CTRL4_500_DPS);
    }
    if (err == ESP_OK) {
        // Route LPF2 to the output. CTRL1 BW=01 selects its 25 Hz cutoff.
        err = write_register(sensor->device, L3G4200D_REG_CTRL5,
                             L3G4200D_CTRL5_LPF2_OUT);
    }
    if (err == ESP_OK) {
        // 100 Hz ODR, 25 Hz bandwidth, normal mode, all axes enabled.
        err = write_register(sensor->device, L3G4200D_REG_CTRL1, L3G4200D_CTRL1_100_HZ);
    }
    if (err == ESP_OK) {
        err = verify_register(sensor->device, L3G4200D_REG_CTRL1, L3G4200D_CTRL1_100_HZ);
    }
    if (err == ESP_OK) {
        err = verify_register(sensor->device, L3G4200D_REG_CTRL4, L3G4200D_CTRL4_500_DPS);
    }
    if (err == ESP_OK) {
        err = verify_register(sensor->device, L3G4200D_REG_CTRL5,
                              L3G4200D_CTRL5_LPF2_OUT);
    }

    if (err != ESP_OK) {
        l3g4200d_deinit(sensor);
    }
    return err;
}

esp_err_t l3g4200d_deinit(l3g4200d_t *sensor)
{
    if (sensor == NULL) {
        return ESP_ERR_INVALID_ARG;
    }
    if (sensor->device == NULL) {
        sensor->address = 0;
        return ESP_OK;
    }

    esp_err_t err = i2c_master_bus_rm_device(sensor->device);
    if (err == ESP_OK) {
        *sensor = (l3g4200d_t){0};
    }
    return err;
}

esp_err_t l3g4200d_read_raw(const l3g4200d_t *sensor, l3g4200d_sample_t *sample,
                            uint8_t *status)
{
    if (sensor == NULL || sensor->device == NULL || sample == NULL || status == NULL) {
        return ESP_ERR_INVALID_ARG;
    }

    esp_err_t err = read_registers(sensor->device, L3G4200D_REG_STATUS, status, 1);
    if (err != ESP_OK) {
        return err;
    }

    uint8_t data[6] = {0};
    uint8_t start_register = L3G4200D_REG_OUT_X_L | L3G4200D_AUTO_INCREMENT;
    err = read_registers(sensor->device, start_register, data, sizeof(data));
    if (err != ESP_OK) {
        return err;
    }

    sample->x = (int16_t)((uint16_t)data[0] | ((uint16_t)data[1] << 8));
    sample->y = (int16_t)((uint16_t)data[2] | ((uint16_t)data[3] << 8));
    sample->z = (int16_t)((uint16_t)data[4] | ((uint16_t)data[5] << 8));
    return ESP_OK;
}

uint8_t l3g4200d_address(const l3g4200d_t *sensor)
{
    return sensor != NULL ? sensor->address : 0;
}