/**
 * I2C BSP — STM32 Standard Peripheral Library implementation
 *
 * I2C1: PB6(SCL), PB7(SDA)
 * Speed: 400kHz standard mode
 */

#include "i2c_bsp.h"

/*===========================================================================
 * Pin definitions
 *===========================================================================*/

#define I2Cx                I2C1
#define I2C_GPIO_PORT       GPIOB
#define I2C_SCL_PIN         GPIO_Pin_6
#define I2C_SDA_PIN         GPIO_Pin_7
#define I2C_GPIO_CLK        RCC_APB2Periph_GPIOB
#define I2C_CLK             RCC_APB1Periph_I2C1
#define I2C_SPEED           400000

/*===========================================================================
 * Private: wait for flag with timeout
 *===========================================================================*/

static int wait_flag(FlagStatus flag, uint32_t timeout_us)
{
    while (timeout_us--) {
        if (I2C_GetFlagStatus(I2Cx, flag) == SET) {
            return 0;
        }
        /* ~1us at 72MHz */
        uint32_t dly = 12;
        while (dly--) { __NOP(); }
    }
    return -1;
}

/*===========================================================================
 * Init
 *===========================================================================*/

void I2C_BSP_Init(void)
{
    GPIO_InitTypeDef gpio;
    I2C_InitTypeDef   i2c;

    RCC_APB2PeriphClockCmd(I2C_GPIO_CLK | RCC_APB2Periph_AFIO, ENABLE);
    RCC_APB1PeriphClockCmd(I2C_CLK, ENABLE);

    GPIO_StructInit(&gpio);
    gpio.GPIO_Pin   = I2C_SCL_PIN | I2C_SDA_PIN;
    gpio.GPIO_Speed = GPIO_Speed_10MHz;
    gpio.GPIO_Mode  = GPIO_Mode_AF_OD;
    GPIO_Init(I2C_GPIO_PORT, &gpio);

    I2C_StructInit(&i2c);
    i2c.I2C_Mode                = I2C_Mode_I2C;
    i2c.I2C_DutyCycle           = I2C_DutyCycle_2;
    i2c.I2C_OwnAddress1         = 0x00;
    i2c.I2C_Ack                = I2C_Ack_Enable;
    i2c.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
    i2c.I2C_ClockSpeed         = I2C_SPEED;

    I2C_Init(I2Cx, &i2c);
    I2C_Cmd(I2Cx, ENABLE);
}

/*===========================================================================
 * Write
 *===========================================================================*/

int I2C_BSP_Write(uint8_t slave_addr, const uint8_t *pdata, uint16_t len)
{
    /* START */
    I2C_GenerateSTART(I2Cx, ENABLE);
    if (wait_flag(I2C_FLAG_SB, 10000) != 0) return -1;

    /* Address + write direction */
    I2C_Send7bitAddress(I2Cx, slave_addr, I2C_Direction_Transmitter);
    if (wait_flag(I2C_FLAG_ADDR, 10000) != 0) return -1;

    /* Clear ADDR */
    (void)I2Cx->SR1;
    (void)I2Cx->SR2;

    /* Send data bytes */
    for (uint16_t i = 0; i < len; i++) {
        if (wait_flag(I2C_FLAG_TXE, 10000) != 0) return -1;
        I2C_SendData(I2Cx, pdata[i]);
    }

    /* Wait for last byte to be sent */
    if (wait_flag(I2C_FLAG_BTF, 10000) != 0) return -1;

    /* STOP */
    I2C_GenerateSTOP(I2Cx, ENABLE);

    return 0;
}

/*===========================================================================
 * Read (register address first, then repeated-start + read)
 *===========================================================================*/

int I2C_BSP_Read(uint8_t slave_addr, uint8_t reg_addr,
                  uint8_t *pbuf, uint16_t len)
{
    if (len == 0) return 0;

    /* Phase 1: Write register address */
    I2C_GenerateSTART(I2Cx, ENABLE);
    if (wait_flag(I2C_FLAG_SB, 10000) != 0) return -1;

    I2C_Send7bitAddress(I2Cx, slave_addr, I2C_Direction_Transmitter);
    if (wait_flag(I2C_FLAG_ADDR, 10000) != 0) return -1;
    (void)I2Cx->SR1;
    (void)I2Cx->SR2;

    if (wait_flag(I2C_FLAG_TXE, 10000) != 0) return -1;
    I2C_SendData(I2Cx, reg_addr);
    if (wait_flag(I2C_FLAG_BTF, 10000) != 0) return -1;

    /* Phase 2: Repeated start + read */
    I2C_GenerateSTART(I2Cx, ENABLE);
    if (wait_flag(I2C_FLAG_SB, 10000) != 0) return -1;

    I2C_Send7bitAddress(I2Cx, slave_addr, I2C_Direction_Receiver);
    if (wait_flag(I2C_FLAG_ADDR, 10000) != 0) return -1;
    (void)I2Cx->SR1;
    (void)I2Cx->SR2;

    /* Read bytes: ACK for all except last */
    for (uint16_t i = 0; i < len; i++) {
        if (i == (len - 1)) {
            /* Last byte: NACK before reading */
            I2C_AcknowledgeConfig(I2Cx, DISABLE);
        }
        if (wait_flag(I2C_FLAG_RXNE, 10000) != 0) return -1;
        pbuf[i] = I2C_ReceiveData(I2Cx);
    }

    /* STOP */
    I2C_GenerateSTOP(I2Cx, ENABLE);
    I2C_AcknowledgeConfig(I2Cx, ENABLE);  /* restore */

    return 0;
}