#include "exception.h"
#include "vriscv.h"

#include <stdio.h>

__attribute__((noreturn)) void exception_trigger(rv32_cpu_t* cpu, uint32_t scause, uint32_t tval)
{
	// An exception can only be triggered by the CPU itself,
	// so we know we already own the mutex
	// We are in the CPU thread itself, but we need
	// the return of this function to be the beginning of
	// the cpu loop
	// To achieve that, we can just call cpu_loop (noreturn)
	// at the end of this function

	// Exceptions cannot be disabled

	// TODO : Check medeleg to see if we should handle exception in S mode or M mode

	// Unset SIE (interrupt enable) bit
	csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) & (~STATUS_SIE));

	// Set xCAUSE : exception cause, with interrupt bit set to null
	csr_write(cpu, CSR_SCAUSE, scause);
	if(gdbstub && scause == SCAUSE_BREAKPOINT)
	{
		cpu->sim_ticks_left = 0;
		// No simulation ticks left : wakeup people waiting on sim end
		pthread_cond_signal(&cpu->sim_condition);
		// Then, wait for simulation state to change until we get more ticks to simulate
		while(!cpu->sim_ticks_left)
			pthread_cond_wait(&cpu->sim_condition, &cpu->mutex);
	}

	// Save previous interrupt enable in xSTATUS.xPIE
	if(csr_read(cpu, CSR_SSTATUS) & STATUS_SIE)
		csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | STATUS_SPIE);
	else
		csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) & (~STATUS_SPIE));

	// Set previous privilege mode in xSTATUS.xPP
	if(cpu->privilege_mode == SUPERVISOR)
		csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) | STATUS_SPP);
	else if(cpu->privilege_mode == USER)
		csr_write(cpu, CSR_SSTATUS, csr_read(cpu, CSR_SSTATUS) & (~STATUS_SPP));

	// Set privilege mode for exception handling, checking for delegation
	// TODO

	// Set xTVAL, exception-specific information related to xCAUSE
	csr_write(cpu, CSR_STVAL, tval);

	// Set SEPC to instruction that caused exception
	csr_write(cpu, CSR_SEPC, cpu->pc);

	// Set PC to xTVEC : exception handling code
	// xTVEC: [Base(30bits) Mode(2 bits)], address 4-byte aligned in base
	// Exceptions are not vectored (we can safely ignore mode)
	cpu->pc = csr_read(cpu, CSR_STVEC) & 0xFFFFFFFC;

	// Unlock cpu mutex, cpu_loop will lock it just after
	pthread_mutex_unlock(&cpu->mutex);

	// TODO : Hard reset the stack pointer
	// cpu loop
	cpu_loop(cpu);

	__builtin_unreachable();
}