/**
 * @file usart0.cpp
 * @brief USART0 串口模块实现与 printf 重定向。
 */

#include "main.h"
#include "device/usart0.h"
#include "sys/config.h"

uint8_t           Usart0::s_txBuf[Usart0::kTxBufSize];
volatile uint16_t Usart0::s_txHead = 0U;
volatile uint16_t Usart0::s_txTail = 0U;

uint16_t Usart0::nextIndex(uint16_t idx)
{
    return (idx + 1U) % kTxBufSize;
}

bool Usart0::isBufferFull()
{
    return nextIndex(s_txHead) == s_txTail;
}

bool Usart0::isBufferEmpty()
{
    return s_txHead == s_txTail;
}

int Usart0::putChar(int ch, FILE *f)
{
    (void)f;
    uint16_t next = nextIndex(s_txHead);
    while(next == s_txTail) { /* 缓冲满，忙等重试 */ }

    s_txBuf[s_txHead] = static_cast<uint8_t>(ch);
    s_txHead = next;
    usart_interrupt_enable(USART0, USART_INT_TBE);
    return ch;
}

void Usart0::onInterrupt()
{
    if(usart_interrupt_flag_get(USART0, USART_INT_FLAG_TBE) != RESET) {
        if(!isBufferEmpty()) {
            usart_data_transmit(USART0, s_txBuf[s_txTail]);
            s_txTail = nextIndex(s_txTail);
        }
        if(isBufferEmpty()) {
            usart_interrupt_disable(USART0, USART_INT_TBE);
        }
    }
}

void Usart0::configurePins()
{
    rcu_periph_clock_enable(RCU_GPIOA);
    gpio_init(GPIOA, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ, GPIO_PIN_9);
    gpio_init(GPIOA, GPIO_MODE_IN_FLOATING, GPIO_OSPEED_50MHZ, GPIO_PIN_10);
}

void Usart0::init()
{
    rcu_periph_clock_enable(RCU_USART0);
    usart_deinit(USART0);
    usart_baudrate_set(USART0, CONFIG_USART0_BAUDRATE);
    usart_word_length_set(USART0, USART_WL_8BIT);
    usart_stop_bit_set(USART0, USART_STB_1BIT);
    usart_parity_config(USART0, USART_PM_NONE);
    usart_receive_config(USART0, USART_RECEIVE_ENABLE);
    usart_transmit_config(USART0, USART_TRANSMIT_ENABLE);
    usart_enable(USART0);
    nvic_irq_enable(USART0_IRQn, 2U, 0U);
}

/* ----- 中断入口 / printf 重定向的 C 包装 --------------------------- */
extern "C" int fputc(int ch, FILE *f)       { return Usart0::putChar(ch, f); }
extern "C" void USART0_IRQHandler(void)     { Usart0::onInterrupt(); }