#include <stdint.h>
#include <stdio.h>
#include <unistd.h>

#include "platform.h"
#include "encoding.h"


extern int main(int argc, char** argv);
extern void trap_entry(void);
#define IRQ_M_SOFT   3
#define IRQ_M_TIMER  7
#define IRQ_M_EXT    11

#define NUM_INTERRUPTS 16
#define MTIMER_NEXT_TICK_INC 1000

void handle_m_ext_interrupt(void);
void handle_m_time_interrupt(void);
uint32_t handle_trap(uint32_t mcause, uint32_t mepc, uint32_t sp);
void default_handler(void);
void _init(void);

typedef void (*my_interrupt_function_ptr_t) (void);
my_interrupt_function_ptr_t localISR[NUM_INTERRUPTS] __attribute__((aligned(64)));

static unsigned long mtime_lo(void)
{
    unsigned long ret;
    __asm volatile("rdtime %0":"=r"(ret));
    return ret;
}


#if __riscv_xlen==32

static uint32_t mtime_hi(void)
{
    unsigned long ret;
    __asm volatile("rdtimeh %0":"=r"(ret));
    return ret;
}

uint64_t get_timer_value(void)
{
  while (1) {
    uint32_t hi = mtime_hi();
    uint32_t lo = mtime_lo();
    if (hi == mtime_hi())
      return ((uint64_t)hi << 32) | lo;
  }
}

#elif __riscv_xlen==64

uint64_t get_timer_value()
{
  return mtime_lo();
}

#endif

unsigned long get_timer_freq()
{
  return 32768;
}

unsigned long get_cpu_freq()
{
  return 100000000;
}

void init_pll(void){
    //TODO: implement initialization
}

static void uart_init(size_t baud_rate)
{
  //TODO: implement initialization
}

void __attribute__((weak)) handle_m_ext_interrupt(){
}

void __attribute__((weak)) handle_m_time_interrupt(){
  uint64_t time = get_aclint_mtime(aclint);
  time+=MTIMER_NEXT_TICK_INC;
  set_aclint_mtime(aclint, time);
}

void __attribute__((weak)) default_handler(void) {
  puts("default handler\n");
}

uint32_t handle_trap(uint32_t mcause, uint32_t mepc, uint32_t sp){
  if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
    handle_m_ext_interrupt();
    // External Machine-Level interrupt from PLIC
  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
    handle_m_time_interrupt();
  } else {
    write(1, "trap\n", 5);
    _exit(1 + mcause);
  }
  return mepc;
}

void _init()
{
  
#ifndef NO_INIT
  init_pll();
  uart_init(115200);
  printf("core freq at %lu Hz\n", get_cpu_freq());
  write_csr(mtvec, &trap_entry);
  if (read_csr(misa) & (1 << ('F' - 'A'))) { // if F extension is present
    write_csr(mstatus, MSTATUS_FS); // allow FPU instructions without trapping
    write_csr(fcsr, 0); // initialize rounding mode, undefined at reset
  }
  int i=0;
  while(i<NUM_INTERRUPTS)  {
    localISR[i++] = default_handler;
  }

#endif
  
}

void _fini(void)
{
}