/*
 * battery.c — Vbat ADC reading for CRSF telemetry uplink (Issue #103)
 *
 * Hardware: ADC3 channel IN11 on PC1 (ADC_BATT 1, Mamba F722S FC).
 * Voltage divider: 10 kΩ (upper) / 1 kΩ (lower) → VBAT_SCALE_NUM = 11.
 *
 *   Vbat_mV = (raw × VBAT_AREF_MV × VBAT_SCALE_NUM) >> VBAT_ADC_BITS
 *           = (raw × 3300 × 11) / 4096
 */

#include "battery.h"
#include "config.h"
#include "stm32f7xx_hal.h"

static ADC_HandleTypeDef s_hadc;
static bool              s_ready = false;

void battery_init(void) {
    __HAL_RCC_ADC3_CLK_ENABLE();
    __HAL_RCC_GPIOC_CLK_ENABLE();

    /* PC1 → analog input (no pull, no speed) */
    GPIO_InitTypeDef gpio = {0};
    gpio.Pin  = GPIO_PIN_1;
    gpio.Mode = GPIO_MODE_ANALOG;
    gpio.Pull = GPIO_NOPULL;
    HAL_GPIO_Init(GPIOC, &gpio);

    /* ADC3 — single-conversion, software trigger, 12-bit right-aligned */
    s_hadc.Instance                   = ADC3;
    s_hadc.Init.ClockPrescaler        = ADC_CLOCK_SYNC_PCLK_DIV8;  /* APB2/8 */
    s_hadc.Init.Resolution            = ADC_RESOLUTION_12B;
    s_hadc.Init.ScanConvMode          = DISABLE;
    s_hadc.Init.ContinuousConvMode    = DISABLE;
    s_hadc.Init.DiscontinuousConvMode = DISABLE;
    s_hadc.Init.ExternalTrigConvEdge  = ADC_EXTERNALTRIGCONVEDGE_NONE;
    s_hadc.Init.ExternalTrigConv      = ADC_SOFTWARE_START;
    s_hadc.Init.DataAlign             = ADC_DATAALIGN_RIGHT;
    s_hadc.Init.NbrOfConversion       = 1;
    s_hadc.Init.DMAContinuousRequests = DISABLE;
    s_hadc.Init.EOCSelection          = ADC_EOC_SINGLE_CONV;
    if (HAL_ADC_Init(&s_hadc) != HAL_OK) return;

    /* Channel IN11 (PC1) with 480-cycle sampling for stability */
    ADC_ChannelConfTypeDef ch = {0};
    ch.Channel      = ADC_CHANNEL_11;
    ch.Rank         = 1;
    ch.SamplingTime = ADC_SAMPLETIME_480CYCLES;
    if (HAL_ADC_ConfigChannel(&s_hadc, &ch) != HAL_OK) return;

    s_ready = true;
}

uint32_t battery_read_mv(void) {
    if (!s_ready) return 0u;

    HAL_ADC_Start(&s_hadc);
    if (HAL_ADC_PollForConversion(&s_hadc, 2u) != HAL_OK) return 0u;
    uint32_t raw = HAL_ADC_GetValue(&s_hadc);
    HAL_ADC_Stop(&s_hadc);

    /* Vbat_mV = raw × (VREF_mV × scale) / ADC_counts */
    return (raw * (uint32_t)VBAT_AREF_MV * VBAT_SCALE_NUM) /
           ((1u << VBAT_ADC_BITS));
}

/*
 * Coarse SoC estimate.
 * 3S LiPo: 9.9 V (0%) – 12.6 V (100%) — detect by Vbat < 13 V
 * 4S LiPo: 13.2 V (0%) – 16.8 V (100%) — detect by Vbat ≥ 13 V
 */
uint8_t battery_estimate_pct(uint32_t voltage_mv) {
    uint32_t v_min_mv, v_max_mv;

    if (voltage_mv >= 13000u) {
        /* 4S LiPo */
        v_min_mv = 13200u;
        v_max_mv = 16800u;
    } else {
        /* 3S LiPo */
        v_min_mv = 9900u;
        v_max_mv = 12600u;
    }

    if (voltage_mv <= v_min_mv) return 0u;
    if (voltage_mv >= v_max_mv) return 100u;

    return (uint8_t)(((voltage_mv - v_min_mv) * 100u) / (v_max_mv - v_min_mv));
}