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

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

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_mtimecmp(aclint, time);
}

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

void __attribute__((weak)) interrupt_handler(unsigned) { puts("interrupt handler\n"); }

uint32_t handle_trap(uint32_t mcause, uint32_t mepc, uint32_t sp) {
    if((mcause & MCAUSE_INT)) {
        if((mcause & MCAUSE_CAUSE) == IRQ_M_EXT) {
            handle_m_ext_interrupt();
        } else if(((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)) {
            handle_m_time_interrupt();
        } else {
            interrupt_handler(mcause & ~MCAUSE_INT);
        }
    } else {
        write(1, "trap\n", 5);
        _exit(1 + mcause);
    }
    return mepc;
}

void __attribute__((weak)) _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) {}