#include "rs485.h"
#include "gd32f4xx_usart.h"
#include "gd32f4xx_rcu.h"
#include "gd32f4xx_gpio.h"
#include "board_config.h"

/* 独立接收环形缓冲区（与 debug 串口的 uart_ring_buffer 隔离），
   采用"预留一格"区分空/满，最大可用容量为 RS485_RX_BUFFER_SIZE-1 */
static __IO uint8_t rs485_rx_buffer[RS485_RX_BUFFER_SIZE];
static __IO uint8_t rs485_write_index = 0;
static __IO uint8_t rs485_read_index = 0;

static inline uint32_t rs485_irq_save(void) {
    uint32_t primask = __get_PRIMASK();
    __disable_irq();
    return primask;
}

static inline void rs485_irq_restore(uint32_t primask) {
    if ((primask & 0x1) == 0) {
        __enable_irq();
    }
}

/**
 * @brief 配置 RS485 收发引脚（PA9 TX / PA10 RX 复用，DE PA8 推挽输出）。
 */
static void rs485_gpio_config(void) {
    /* 使能 GPIOA 和 USART0 时钟 */
    rcu_periph_clock_enable(RS485_GPIO_RCU);
    rcu_periph_clock_enable(RS485_RCU);

    /* PA9 为 USART0_TX，PA10 为 USART0_RX（AF7） */
    gpio_af_set(RS485_GPIO_PORT, GPIO_AF_7, RS485_TX_PIN | RS485_RX_PIN);

    gpio_mode_set(RS485_GPIO_PORT, GPIO_MODE_AF, GPIO_PUPD_PULLUP, RS485_TX_PIN | RS485_RX_PIN);
    gpio_output_options_set(RS485_GPIO_PORT, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ, RS485_TX_PIN | RS485_RX_PIN);

    /* DE 引脚为普通推挽输出，默认接收态 */
    rcu_periph_clock_enable(RS485_DE_RCU);
    gpio_mode_set(RS485_DE_PORT, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, RS485_DE_PIN);
    gpio_output_options_set(RS485_DE_PORT, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ, RS485_DE_PIN);
    gpio_bit_reset(RS485_DE_PORT, RS485_DE_PIN);
}

void rs485_init(void) {
    rs485_gpio_config();

    /* 配置波特率、数据位、停止位等 */
    usart_deinit(RS485_PHY);
    usart_word_length_set(RS485_PHY, USART_WL_8BIT);
    usart_stop_bit_set(RS485_PHY, USART_STB_1BIT);
    usart_parity_config(RS485_PHY, USART_PM_NONE);
    usart_baudrate_set(RS485_PHY, RS485_BAUDRATE);
    usart_receive_config(RS485_PHY, USART_RECEIVE_ENABLE);
    usart_transmit_config(RS485_PHY, USART_TRANSMIT_ENABLE);

    usart_enable(RS485_PHY);

    /* 使能接收非空中断 */
    nvic_irq_enable(RS485_IRQ, 0, 0);
    usart_interrupt_enable(RS485_PHY, USART_INT_RBNE);
}

void rs485_send(const uint8_t *data, uint16_t len) {
    /* 进入发送态 */
    gpio_bit_set(RS485_DE_PORT, RS485_DE_PIN);

    for (uint16_t i = 0; i < len; i++) {
        /* 等待发送缓冲区空 */
        while (RESET == usart_flag_get(RS485_PHY, USART_FLAG_TBE)) {}
        usart_data_transmit(RS485_PHY, data[i]);
    }
    /* 等待最后一字节移位完成，再切回接收态（避免截断尾字节） */
    while (RESET == usart_flag_get(RS485_PHY, USART_FLAG_TC)) {}

    /* 回到接收态 */
    gpio_bit_reset(RS485_DE_PORT, RS485_DE_PIN);
}

uint8_t rs485_rx_available(void) {
    uint8_t w = rs485_write_index;
    uint8_t r = rs485_read_index;
    return (uint8_t)((w + RS485_RX_BUFFER_SIZE - r) % RS485_RX_BUFFER_SIZE);
}

int rs485_rx_get(void) {
    if (rs485_read_index == rs485_write_index) return -1; /* 空 */
    uint8_t data = rs485_rx_buffer[rs485_read_index];
    rs485_read_index = (rs485_read_index + 1) % RS485_RX_BUFFER_SIZE;
    return data;
}

void rs485_rx_clear(void) {
    uint32_t primask = rs485_irq_save();
    rs485_write_index = 0;
    rs485_read_index = 0;
    rs485_irq_restore(primask);
}

void rs485_irq_handler(void) {
    /* 处理USART0的接收中断 */
    if (usart_interrupt_flag_get(RS485_PHY, USART_INT_FLAG_RBNE)) {
        uint8_t data = usart_data_receive(RS485_PHY);
        uint32_t primask = rs485_irq_save();
        uint8_t next = (rs485_write_index + 1) % RS485_RX_BUFFER_SIZE;
        if (next != rs485_read_index) {
            /* 缓冲区未满 */
            rs485_rx_buffer[rs485_write_index] = data;
            rs485_write_index = next;
        }
        /* 缓冲满时丢弃 */
        rs485_irq_restore(primask);
    }

    /* 处理USART0的空闲中断（帧间隔提示，后续协议解析用） */
    if (usart_interrupt_flag_get(RS485_PHY, USART_INT_FLAG_IDLE)) {
        usart_interrupt_flag_clear(RS485_PHY, USART_INT_FLAG_IDLE);
    }
}