#include "klibc.h"
#include "serial.h"
#include "vga.h"

int memcmp(const void *aptr, const void *bptr, size_t size)
{
    const unsigned char *a = (const unsigned char *)aptr;
    const unsigned char *b = (const unsigned char *)bptr;
    for (size_t i = 0; i < size; i++) {
        if (a[i] < b[i])
            return -1;
        else if (b[i] < a[i])
            return 1;
    }
    return 0;
}

void *memcpy(void *dst, const void *src, size_t n)
{
    char *dstChar       = dst;
    const char *srcChar = src;
    for (size_t i = 0; i < n; i++) {
        *(dstChar++) = *(srcChar++);
    }
    return dst;
}

void *memset(void *src, int c, size_t n)
{
    for (char *ptr = (char *)src; n > 0; n--, ptr++) {
        *ptr = (char)c;
    }
    return src;
}

char *itoa(int value, char *str, int base)
{
    char *rc;
    char *ptr;
    char *low;
    // Check for supported base.
    if (base < 2 || base > 36) {
        *str = '\0';
        return str;
    }
    rc = ptr = str;
    // Set '-' for negative decimals.
    if (value < 0 && base == 10) {
        *ptr++ = '-';
    }
    // Remember where the numbers start.
    low = ptr;
    // The actual conversion.
    do {
        // Modulo is negative for negative value. This trick makes abs() unnecessary.
        *ptr++ = "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"
            [35 + value % base];
        value /= base;
    } while (value);
    // Terminating the string.
    *ptr-- = '\0';
    // Invert the numbers.
    while (low < ptr) {
        char tmp = *low;
        *low++   = *ptr;
        *ptr--   = tmp;
    }
    return rc;
}

/* K&R */
void reverse(char s[])
{
    int c, i, j;
    for (i = 0, j = strlen(s) - 1; i < j; i++, j--) {
        c    = s[i];
        s[i] = s[j];
        s[j] = c;
    }
}

/* K&R */
int strlen(char s[])
{
    int i = 0;
    while (s[i] != '\0')
        ++i;
    return i;
}

/* K&R
 * Returns <0 if s1<s2, 0 if s1==s2, >0 if s1>s2 */
int strcmp(char s1[], char s2[])
{
    int i;
    for (i = 0; s1[i] == s2[i]; i++) {
        if (s1[i] == '\0')
            return 0;
    }
    return s1[i] - s2[i];
}

void printf(const char *format, ...)
{
    va_list ap;
    va_start(ap, format);
    vprintf(format, ap);
    va_end(ap);
}

void puts(const char *str)
{
    while (*str) {
        putc(*(str++));
    }
}

void putc(const char str){
    VGAputc(str);
    serialPutc(str);
}

void printInt(int integer)
{
    char num[sizeof(int) * 3]; // int max is 2^(sizeof(int)*8) which is (2^3)^(sizeof(int)*8/3)
                               // = 8^(sizeof(int)*8/3) ~ 10^(sizeof(int)*8/3)
    int i = 0, k = 0;
    if (integer < 0) {
        putc('-');
    }
    if (integer == 0) {
        num[i++] = 0;
    }
    while (integer != 0) {
        int digit = integer % 10;
        num[i++]  = (digit > 0) ? digit : -digit;
        integer   = integer / 10;
    }
    for (k = i - 1; k >= 0; k--) {
        putc(num[k] + '0');
    }
}

void vprintf(const char *format, va_list ap)
{
    int i = 0;
    while (format[i] != '\0') {
        switch (format[i]) {
            case '%':
                switch (format[i + 1]) {
                    case 'i':
                    case 'd': {
                        int d = va_arg(ap, int);
                        printInt(d);
                        break;
                    }
                    case 'x': {
                        char val[sizeof(int) * 2];
                        int d = va_arg(ap, int);
                        itoa(d, val, 16);
                        puts(val);
                        break;
                    }
                    case 'c': {
                        int c = va_arg(ap, int);
                        putc((char)c);
                        break;
                    }
                    case 's': {
                        char *str = va_arg(ap, char *);
                        if (!str)
                            str = "[NULL STR]";
                        puts(str);
                        break;
                    }
                    case '%':
                        putc('%');
                        break;
                }
                i++;
                break;

            default:
                putc(format[i]);
        }
        i++;
    }
}