#include <kernel.h>

void memset(void* ptr, int value, size_t num) {
    unsigned char* p = (unsigned char*)ptr;
    for (size_t i = 0; i < num; i++) {
        p[i] = (unsigned char)value;
    }
}

void memcpy(void* dest, const void* src, size_t num) {
    unsigned char* d = (unsigned char*)dest;
    const unsigned char* s = (const unsigned char*)src;
    for (size_t i = 0; i < num; i++) {
        d[i] = s[i];
    }
}

void memmove(void* dest, const void* src, size_t num) {
    unsigned char* d = (unsigned char*)dest;
    const unsigned char* s = (const unsigned char*)src;

    if (d <= s) {
        for (size_t i = 0; i < num; i++) d[i] = s[i];
    } else {
        for (size_t i = num; i > 0; i--) d[i - 1] = s[i - 1];
    }
}

int memcmp(const void* ptr1, const void* ptr2, size_t num) {
    const unsigned char* p1 = (const unsigned char*)ptr1;
    const unsigned char* p2 = (const unsigned char*)ptr2;

    for (size_t i = 0; i < num; i++) {
        if (p1[i] != p2[i]) return p1[i] - p2[i];
    }
    return 0;
}

size_t strlen(const char* str) {
    size_t len = 0;
    while (str[len]) len++;
    return len;
}

int strcmp(const char* s1, const char* s2) {
    while (*s1 && (*s1 == *s2)) {
        s1++;
        s2++;
    }
    return *(unsigned char*)s1 - *(unsigned char*)s2;
}

int strncmp(const char* s1, const char* s2, size_t n) {
    while (n-- && *s1 && (*s1 == *s2)) {
        s1++;
        s2++;
    }
    if (n == 0) return 0;
    return *(unsigned char*)s1 - *(unsigned char*)s2;
}

char* strcpy(char* dest, const char* src) {
    char* d = dest;
    while ((*d++ = *src++));
    return dest;
}

char* strncpy(char* dest, const char* src, size_t n) {
    size_t i;
    for (i = 0; i < n && src[i]; i++) {
        dest[i] = src[i];
    }
    for (; i < n; i++) {
        dest[i] = '\0';
    }
    return dest;
}

char* strcat(char* dest, const char* src) {
    char* d = dest;
    while (*d) d++;
    while ((*d++ = *src++));
    return dest;
}

int atoi(const char* str) {
    int result = 0;
    int sign = 1;

    if (*str == '-') {
        sign = -1;
        str++;
    } else if (*str == '+') {
        str++;
    }

    while (*str >= '0' && *str <= '9') {
        result = result * 10 + (*str - '0');
        str++;
    }

    return sign * result;
}

char* itoa(int value, char* str, int base) {
    char* ptr = str;
    char* low;
    int is_negative = 0;

    if (base < 2 || base > 36) {
        *str = '\0';
        return str;
    }

    if (value < 0 && base == 10) {
        is_negative = 1;
        value = -value;
    }

    do {
        int digit = value % base;
        *ptr++ = (digit < 10) ? '0' + digit : 'a' + digit - 10;
        value /= base;
    } while (value > 0);

    if (is_negative) *ptr++ = '-';
    *ptr-- = '\0';

    /* Reverse the string */
    low = str;
    while (low < ptr) {
        char tmp = *low;
        *low++ = *ptr;
        *ptr-- = tmp;
    }

    return str;
}