#include "kernel.h"

extern uint8_t __bss[], __bss_end[], __stack_top[];

sbiret sbi_call(long arg0, long arg1, long arg2, long arg3, long arg4,
                long arg5, long fid, long eid)
{
    register long a0 __asm__("a0") = arg0;
    register long a1 __asm__("a1") = arg1;
    register long a2 __asm__("a2") = arg2;
    register long a3 __asm__("a3") = arg3;
    register long a4 __asm__("a4") = arg4;
    register long a5 __asm__("a5") = arg5;
    register long a6 __asm__("a6") = fid;
    register long a7 __asm__("a7") = eid;

    __asm__ __volatile__(
        "ecall"
        : "=r"(a0), "=r"(a1)
        : "r"(a0), "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(a5), "r"(a6), "r"(a7)
        : "memory"
    );

    return (sbiret) { .error = a0, .value = a1 };
}

void putchar(char c)
{
    // 1 => sbi_console_putchar()
    sbi_call(c, 0, 0, 0, 0, 0, 0, 1);
}

void kernel_main(void)
{
    const char *s = "\n\nHello World!\n";
    for (int i = 0; s[i] != '\0'; i++) {
        putchar(s[i]);
    }

    while(1) {
        // wfi -> wait for interrupt
        __asm__ __volatile__("wfi");
    }
}

__attribute__((section(".text.boot")))
__attribute__((naked))
void boot(void)
{
    __asm__ __volatile__ (
        "mv sp, %[stack_top]\n"         // Initialize the kernel stack pointer
        "j kernel_main\n"               // Unconditional jump to kernel_main
        :                               // No output
        : [stack_top] "r" (__stack_top) // Pass the stack top address
    );
}