#include <luna/Alloc.h>
#include <luna/CString.h>

extern "C"
{
    void* memcpy(void* dest, const void* src, usize n)
    {
        for (usize i = 0; i < n; ++i) { *((u8*)dest + i) = *((const u8*)src + i); }
        return dest;
    }

    void* memset(void* buf, int c, usize n)
    {
        for (usize i = 0; i < n; ++i) { *((u8*)buf + i) = (u8)c; }
        return buf;
    }

    int memcmp(const void* a, const void* b, usize n)
    {
        if (!n) return 0;
        const u8* ap = (const u8*)a;
        const u8* bp = (const u8*)b;
        while (--n && *ap == *bp)
        {
            ap++;
            bp++;
        }
        return *ap - *bp;
    }

    void* memmove(void* dest, const void* src, usize n)
    {
        if (dest == src) return dest;
        if (dest > src)
            for (long i = (long)n - 1; i >= 0; i++) { *((u8*)dest + i) = *((const u8*)src + i); }
        else
            for (long i = 0; i < (long)n; i++) { *((u8*)dest + i) = *((const u8*)src + i); }
        return dest;
    }

    usize strlen(const char* str)
    {
        const char* i = str;
        for (; *i; ++i)
            ;
        return (usize)(i - str);
    }

    usize strnlen(const char* str, usize max)
    {
        const char* i = str;
        for (; *i && max; ++i, --max)
            ;
        return (usize)(i - str);
    }

    int strcmp(const char* a, const char* b)
    {
        while (*a && (*a == *b))
        {
            a++;
            b++;
        }
        return *(const u8*)a - *(const u8*)b;
    }

    int wcscmp(const wchar_t* a, const wchar_t* b)
    {
        while (*a && (*a == *b))
        {
            a++;
            b++;
        }
        return *(const u8*)a - *(const u8*)b;
    }

    int strncmp(const char* a, const char* b, usize max)
    {
        const char* s = a;
        while (*a && (*a == *b) && (usize)(a - s) < (max - 1))
        {
            a++;
            b++;
        }
        return *(const u8*)a - *(const u8*)b;
    }

    usize wcslen(const wchar_t* str)
    {
        const wchar_t* i = str;
        for (; *i; ++i)
            ;
        return (usize)(i - str);
    }

    char* strdup(const char* str)
    {
        const usize len = strlen(str);

        char* dest = (char*)calloc_impl(len + 1, 1, false).value_or(nullptr);
        if (!dest) return nullptr;

        memcpy(dest, str, len);

        return dest;
    }

    char* strndup(const char* str, usize max)
    {
        const usize len = strnlen(str, max);

        char* dest = (char*)calloc_impl(len + 1, 1, false).value_or(nullptr);
        if (!dest) return nullptr;

        memcpy(dest, str, len);

        return dest;
    }

    char* strcpy(char* dest, const char* src)
    {
        char* s = dest;
        for (; *src; dest++, src++) *dest = *src;
        *dest = 0;
        return s;
    }

    char* strcat(char* dest, const char* src)
    {
        char* s = dest;
        while (*dest) dest++;
        for (; *src; dest++, src++) *dest = *src;
        *dest = 0;
        return s;
    }

    char* strncpy(char* dest, const char* src, usize max)
    {
        usize i;
        for (i = 0; i < max && src[i] != 0; i++) dest[i] = src[i];
        for (; i < max; i++) dest[i] = 0;
        return dest;
    }

    char* strncat(char* dest, const char* src, usize max)
    {
        usize len = strlen(dest);
        usize i;

        for (i = 0; i < max && *(src + i); i++) *(dest + len + i) = *(src + i);

        *(dest + len + i) = '\0';

        return dest;
    }

    char* strchr(const char* str, int c)
    {
        while (*str && *str != c) str++;
        if (*str) return const_cast<char*>(str);
        return NULL;
    }

    char* strrchr(const char* str, int c)
    {
        const char* s = str + strlen(str);
        while (s != str && *s != (char)c) s--;
        if (s != str) return const_cast<char*>(s);
        if (*s == (char)c) return const_cast<char*>(s);
        return NULL;
    }

    usize strlcpy(char* dest, const char* src, usize len)
    {
        usize src_len = strlen(src);
        usize copy_len = src_len;
        if (len == 0) return src_len;
        if (src_len >= (len - 1)) copy_len = len - 1;
        memcpy(dest, src, copy_len);
        dest[copy_len] = 0;
        return src_len;
    }

    usize strcspn(const char* str, const char* reject)
    {
        const char* s = str;
        while (*s)
        {
            const char* rp = reject;
            while (*rp)
            {
                if (*s == *rp) return (usize)(s - str);
                rp++;
            }
            s++;
        }
        return (usize)(s - str);
    }

    usize strspn(const char* str, const char* accept)
    {
        const char* s = str;
        while (*s)
        {
            const char* ap = accept;
            bool match = false;
            while (*ap)
            {
                if (*s == *ap)
                {
                    match = true;
                    break;
                }
                ap++;
            }
            if (!match) return (usize)(s - str);
            s++;
        }
        return (usize)(s - str);
    }

    char* strtok(char* str, const char* delim)
    {
        static char* s = nullptr;
        if (str) s = str;
        if (!s) return nullptr;

        if (*s)
        {
            usize skip = strspn(s, delim);
            s += skip;

            if (*s == 0) return nullptr;

            usize use = strcspn(s, delim);
            char* result = s;

            if (s[use] != 0)
            {
                s[use] = 0;
                s += (use + 1);
            }
            else { s = nullptr; }

            return result;
        }

        return nullptr;
    }

    char* strpbrk(const char* s, const char* accept)
    {
        usize index = strcspn(s, accept);

        const char* ptr = s + index;

        if (*ptr) return const_cast<char*>(ptr);

        return nullptr;
    }
}