/*
 * bmp280.c — BMP280/BME280 barometer driver (I2C1, shared bus)
 *
 * Probes 0x76 first, then 0x77. Requires i2c1_init() before bmp280_init().
 * Returns chip_id on success (0x58=BMP280, 0x60=BME280), negative if absent.
 */
#include "bmp280.h"
#include "i2c1.h"
#include <math.h>

/* Shift I2C address for HAL (7-bit left-shifted) */
static uint16_t s_addr;

/* Calibration data */
static uint16_t dig_T1;
static int16_t  dig_T2, dig_T3;
static uint16_t dig_P1;
static int16_t  dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9;
static int32_t  t_fine;

static uint8_t i2c_read(uint8_t reg) {
    uint8_t val = 0;
    HAL_I2C_Mem_Read(&hi2c1, s_addr, reg, 1, &val, 1, 100);
    return val;
}

static void i2c_read_burst(uint8_t reg, uint8_t *buf, uint8_t len) {
    HAL_I2C_Mem_Read(&hi2c1, s_addr, reg, 1, buf, len, 100);
}

static void i2c_write(uint8_t reg, uint8_t val) {
    HAL_I2C_Mem_Write(&hi2c1, s_addr, reg, 1, &val, 1, 100);
}

static int try_init(uint16_t addr) {
    s_addr = addr;
    uint8_t id = i2c_read(0xD0);
    if (id != 0x58 && id != 0x60) return -(int)id;

    /* Read calibration */
    uint8_t cal[26];
    i2c_read_burst(0x88, cal, 26);
    dig_T1 = (uint16_t)(cal[1] << 8 | cal[0]);
    dig_T2 = (int16_t) (cal[3] << 8 | cal[2]);
    dig_T3 = (int16_t) (cal[5] << 8 | cal[4]);
    dig_P1 = (uint16_t)(cal[7] << 8 | cal[6]);
    dig_P2 = (int16_t) (cal[9] << 8 | cal[8]);
    dig_P3 = (int16_t) (cal[11] << 8 | cal[10]);
    dig_P4 = (int16_t) (cal[13] << 8 | cal[12]);
    dig_P5 = (int16_t) (cal[15] << 8 | cal[14]);
    dig_P6 = (int16_t) (cal[17] << 8 | cal[16]);
    dig_P7 = (int16_t) (cal[19] << 8 | cal[18]);
    dig_P8 = (int16_t) (cal[21] << 8 | cal[20]);
    dig_P9 = (int16_t) (cal[23] << 8 | cal[22]);

    /* Normal mode, ×16 oversampling temp+press, 0.5 ms standby */
    i2c_write(0xF5, 0x00);  /* config: standby=0.5ms, filter=off */
    i2c_write(0xF4, 0xB7);  /* ctrl_meas: osrs_t=×16, osrs_p=×16, normal mode */

    return (int)id;
}

int bmp280_init(void) {
    int ret = try_init(0x76 << 1);
    if (ret > 0) return ret;
    return try_init(0x77 << 1);
}

void bmp280_read(int32_t *pressure_pa, int16_t *temp_x10) {
    uint8_t buf[6];
    i2c_read_burst(0xF7, buf, 6);

    int32_t adc_P = (int32_t)((buf[0] << 12) | (buf[1] << 4) | (buf[2] >> 4));
    int32_t adc_T = (int32_t)((buf[3] << 12) | (buf[4] << 4) | (buf[5] >> 4));

    /* Temperature compensation (BMP280 datasheet Section 4.2.3) */
    int32_t v1 = ((((adc_T >> 3) - ((int32_t)dig_T1 << 1))) * ((int32_t)dig_T2)) >> 11;
    int32_t v2 = (((((adc_T >> 4) - (int32_t)dig_T1) *
                    ((adc_T >> 4) - (int32_t)dig_T1)) >> 12) * (int32_t)dig_T3) >> 14;
    t_fine = v1 + v2;
    *temp_x10 = (int16_t)((t_fine * 5 + 128) >> 8);  /* 0.1 °C */

    /* Pressure compensation */
    int64_t p1 = ((int64_t)t_fine) - 128000;
    int64_t p2 = p1 * p1 * (int64_t)dig_P6;
    p2 += (p1 * (int64_t)dig_P5) << 17;
    p2 += ((int64_t)dig_P4) << 35;
    p1 = ((p1 * p1 * (int64_t)dig_P3) >> 8) + ((p1 * (int64_t)dig_P2) << 12);
    p1 = ((((int64_t)1 << 47) + p1)) * ((int64_t)dig_P1) >> 33;
    if (p1 == 0) { *pressure_pa = 0; return; }
    int64_t p = 1048576 - adc_P;
    p = (((p << 31) - p2) * 3125) / p1;
    p1 = ((int64_t)dig_P9 * (p >> 13) * (p >> 13)) >> 25;
    p2 = ((int64_t)dig_P8 * p) >> 19;
    *pressure_pa = (int32_t)(((p + p1 + p2) >> 8) + ((int64_t)dig_P7 << 4)) / 256;
}

int32_t bmp280_pressure_to_alt_cm(int32_t pressure_pa) {
    /* Barometric formula: h = 44330 * (1 - (p/p0)^(1/5.255)) metres */
    float ratio = (float)pressure_pa / 101325.0f;
    float alt_m = 44330.0f * (1.0f - powf(ratio, 0.1902949f));
    return (int32_t)(alt_m * 100.0f);  /* cm */
}