#include <stdint.h>

#include "FreeRTOS.h"
#include "queue.h"

#include <xscugic.h>
#include <xuartps.h>

#undef XUARTPS_IXR_RXOVR
#define XUARTPS_IXR_RXOVR 0x00000020U /**< Rx Overrun error interrupt */
#define XUARTPS_IXR_RTRIG 0x00000001U /**< RX FIFO trigger interrupt. */

extern XScuGic xInterruptController; /* Interrupt controller instance */

uint8_t uart0_receive_buffer[1024 * 1];
StaticQueue_t uart0_static_queue;
QueueHandle_t uart0_receive_queue;

/** this is based on XUartPs_InterruptHandler() in xuartps_intr.c*/
void uart0_handle_interrupt(void *) {
  u32 IsrStatus;

  /*
   * Read the interrupt ID register to determine which
   * interrupt is active
   */
  IsrStatus = XUartPs_ReadReg(XPS_UART0_BASEADDR, XUARTPS_IMR_OFFSET);

  IsrStatus &= XUartPs_ReadReg(XPS_UART0_BASEADDR, XUARTPS_ISR_OFFSET);

  // Onlx RX intterupts are enabled
  // We do not care which interrupt actually triggered, just get all bytes
  // available into the stack
  uint8_t RecievedByte;
  BaseType_t xHigherPriorityTaskWoken;
  while (XUartPs_IsReceiveData(STDIN_BASEADDRESS)) {
    RecievedByte = XUartPs_ReadReg(STDIN_BASEADDRESS, XUARTPS_FIFO_OFFSET);
    xQueueSendToBackFromISR(uart0_receive_queue, &RecievedByte,
                            &xHigherPriorityTaskWoken);
  }

  /* Clear the interrupt status. */
  XUartPs_WriteReg(STDIN_BASEADDRESS, XUARTPS_ISR_OFFSET, IsrStatus);

  /* directly yield if sending to the queue woke something in ourselves */
  portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

void uart0_enable_receiver() {
  uart0_receive_queue =
      xQueueCreateStatic(sizeof(uart0_receive_buffer), 1, uart0_receive_buffer,
                         &uart0_static_queue);

  /* Install the UART Interrupt handler. */
  BaseType_t xStatus =
      XScuGic_Connect(&xInterruptController, XPAR_XUARTPS_0_INTR,
                      (Xil_ExceptionHandler)uart0_handle_interrupt, NULL);
  configASSERT(xStatus == XST_SUCCESS);
  (void)xStatus; /* Remove compiler warning if configASSERT() is not defined. */

  // Set trigger level to 62 of 64 bytes, giving interrupt some time to react
  XUartPs_WriteReg(XPS_UART0_BASEADDR, XUARTPS_RXWM_OFFSET, 62);

  // Setting the rx timeout to n*4 -1 bits
  XUartPs_WriteReg(XPS_UART0_BASEADDR, XUARTPS_RXTOUT_OFFSET, 50);

  // enable UART Interrupts
  u32 mask = XUARTPS_IXR_RTRIG | XUARTPS_IXR_RXOVR | XUARTPS_IXR_RXFULL |
             XUARTPS_IXR_TOUT;
  /* Write the mask to the IER Register */
  XUartPs_WriteReg(XPS_UART0_BASEADDR, XUARTPS_IER_OFFSET, mask);
  /* Write the inverse of the Mask to the IDR register */
  XUartPs_WriteReg(XPS_UART0_BASEADDR, XUARTPS_IDR_OFFSET, (~mask));

  /* Enable the interrupt for the UART0 in the interrupt controller. */
  XScuGic_Enable(&xInterruptController, XPAR_XUARTPS_0_INTR);
}

int uart0_read(char *ptr, int len) {
  int received = 0;
  while (len > 0) {
    BaseType_t result = xQueueReceive(uart0_receive_queue, ptr, 0);
    if (result == pdFAIL) {
      return received;
    }
    received++;
    ptr++;
    len--;
  }
  return received;
}