#include "axl_string.h"

u32 axl_strlen(const i8* s)
{
    if(s == NULL)
    {
        return 0;
    }

    u32 len = 0;

    while(s[len] != '\0')
    {
        len++;
    }        

    return len;
}

i8* axl_strcpy(i8* dst, const i8* src)
{
    if(dst == NULL || src == NULL)
    {
        return dst;
    }

    i8* start = dst; 

    while((*(dst++) = *(src++)) != '\0');

    return start;
}

i8* axl_strncpy(i8* dst, const i8* src, u32 n)
{
    if(dst == NULL || src == NULL)
    {
        return dst;
    }

    u32 i = 0;

    for(; i < n && src[i] != '\0'; i++)
    {
        dst[i] = src[i];
    }

    for(; i < n; i++)
    {
        dst[i] = '\0';
    }

    return dst;
}

i8* axl_strcat(i8* dst, const i8* src)
{
    if(dst == NULL || src == NULL)
    {
        return dst;
    }

    axl_strcpy(dst + axl_strlen(dst), src);

    return dst;
}

i8* axl_strncat(i8* dst, const i8* src, u32 n) //n actually means "not more than"
{
    if(!dst || !src) 
    {
        return dst;
    }

    i8* p = dst + axl_strlen(dst);
    while (n-- && (*p++ = *src++)); //quick note: '\0' == 0

    *p = '\0';  //in case we copied exactly n without '\0'

    return dst;
}

i32 axl_strcmp(const i8* s1, const i8* s2)
{
    if(!s1 || !s2) 
    {
        return (s1 == s2) ? 0 : (!s1 ? -1 : 1);
    }

    for(;; s1++, s2++) 
    {
        u8 c1 = *(const u8*)s1;
        u8 c2 = *(const u8*)s2;

        if (c1 != c2 || c1 == '\0' || c2 == '\0') 
        {
            return c1 - c2;
        }
    }
    
    return 0;
}

i32 axl_strncmp(const i8* s1, const i8* s2, u32 n)
{
    if(!s1 || !s2) 
    {
        return (s1 == s2) ? 0 : (!s1 ? -1 : 1);
    }

    for(u32 i = 0; i < n; s1++, s2++, i++) 
    {
        u8 c1 = *(const u8*)s1;
        u8 c2 = *(const u8*)s2;

        if(c1 != c2 || c1 == '\0' || c2 == '\0') 
        {
            return c1 - c2;
        }
    }
    
    return 0;
}

const i8* axl_strchr(const i8* str, i8 c)
{
    if(!str) 
    {
        return NULL;
    }
    
    for(; *str != '\0'; ++str) 
    {
        if(*str == c) 
        {
            return str;
        }
    }
    
    return (c == '\0') ? str : NULL;
}

i8* axl_strstr(const i8* str, const i8* substr)
{
    if(!str || !substr)
    {
        return NULL;
    }

    if(*substr == '\0')
    {
        return (i8*)str;
    }

    u32 n = axl_strlen(substr);

    while(*str)
    {
        if(!axl_strncmp(str++, substr, n))
        {
            return (i8*)(str - 1);
        }
    }

    return NULL;
}

i8* axl_strrev(i8* str)
{
    if(!str)
    {
        return NULL;
    }

    i8* start = str;
    i8* end = str + axl_strlen(str) - 1;

    while(start < end)
    {
        i8 tmp = *start;
        *start = *end;
        *end = tmp;
        start++;
        end--;
    }
    
    return str;
}

/*static const char digits_lower[] = "0123456789abcdefghijklmnopqrstuvwxyz";*/
static const char digits_upper[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

i8* axl_utoa(u64 val, i8* str, u8 base)
{
    if(!str)
    {
        return NULL;
    }

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

    i8* head = str;
    const i8* digits = digits_upper;


    if (val == 0) 
    {
        *head++ = '0';
        *head++ = '\0';
        return str;
    }

    while (val != 0) 
    {
        *head++ = digits[val % base];
        val /= base;
    }

    *head = '\0';

    return axl_strrev(str);
}

i8* axl_itoa(i64 val, i8* str, u8 base)
{
    if(!str)
    {
        return NULL;
    }

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

    i8* head = str;
    u64 uval = val < 0 ? (u64)(-(val)) : (u64)val;

    if (uval == 0) 
    {
        *head++ = '0';
        *head++ = '\0';
        return str;
    }

    while (uval != 0) 
    {
        *head++ = digits_upper[uval % base];
        uval   /= base;
    }

    if (val < 0) 
    {
        *head++ = '-';
    } 

    *head = '\0';

    return axl_strrev(str);
}

#if !__STDC_HOSTED__
int _fltused;
#endif // !__STDC_HOSTED__

/*
 * @brief Converts float to string with specified precision
 * 
 * @param val: Float value to convert
 * @param str: Destination buffer (must be large enough)
 * @param precision: Digits after decimal point (0-AXL_F32_MAX_PRECISION)
 * @return Pointer to start of string
 * 
 * @note Handles nan, inf, -inf, zero
 * @note Uses scientific notation for very large/small numbers
 * @note Removes trailing zeros from fractional part
 */
i8* axl_ftoa(f32 val, i8* str, u32 precision)
{
    if (!str) return NULL;
    
    // Clamp precision to meaningful range
    if (precision > AXL_F32_MAX_PRECISION) 
    {
        precision = AXL_F32_MAX_PRECISION;
    }
    
    // Extract float components
    union { f32 f; u32 u; } bits = { .f = val };
    u32 sign = bits.u >> 31;
    u32 exponent = (bits.u >> 23) & 0xFF;
    u32 mantissa = bits.u & 0x7FFFFF;
    
    // Handle NaN
    if (exponent == 0xFF && mantissa != 0)
	{
        axl_strcpy(str, "nan");
        return str;
    }
    
    // Handle Infinity
    if (exponent == 0xFF && mantissa == 0)
	{
        if (sign) axl_strcpy(str, "-inf");
        else axl_strcpy(str, "inf");
        return str;
    }
    
    // Handle zero and denormalized numbers (treat as zero)
    if (exponent == 0)
	{
        i8* p = str;
        if (sign) *p++ = '-';
        *p++ = '0';
        if (precision > 0)
        {
            *p++ = '.';
            for (u32 i = 0; i < precision; i++)
            {
                *p++ = '0';
            }
        }
        *p = '\0';
        return str;
    }
    
    i8* start = str;
    f32 abs_val = val;
    
    // Apply sign
    if (sign)
	{
        *str++ = '-';
        abs_val = -abs_val;
    }
    
    // Calculate magnitude for format selection
    i32 magnitude = 0;
    f32 temp = abs_val;
    while (temp >= 10.0f)
	{ temp /= 10.0f; magnitude++; }
    while (temp > 0.0f && temp < 1.0f)
	{ temp *= 10.0f; magnitude--; }
    
    // Use scientific notation for extreme ranges
    if (magnitude > 15 || magnitude < -15)
	{
        // Normalize mantissa to [1, 10)
        f32 mant = abs_val;
        while (mant >= 10.0f) mant /= 10.0f;
        while (mant > 0.0f && mant < 1.0f) mant *= 10.0f;
        
        // Integer part (single digit)
        u64 int_part = (u64)mant;
        axl_utoa(int_part, str, 10);
        str += axl_strlen(str);
        
        // Fractional part
        if (precision > 0)
        {
            *str++ = '.';
            f32 frac = mant - (f32)int_part;
            for (u32 i = 0; i < precision; i++)
            {
                frac *= 10.0f;
                u32 digit = (u32)frac;
                *str++ = '0' + digit;
                frac -= (f32)digit;
            }
            // Trim trailing zeros
            while (*(str-1) == '0' && *(str-2) != '.') str--;
        }
        
        // Add exponent
        *str++ = 'e';
        if (magnitude >= 0) *str++ = '+';
        axl_itoa(magnitude, str, 10);
        return start;
    }
    
    // Fixed-point representation for normal range
    
    // Split into integer and fractional parts
    u64 int_part = (u64)abs_val;
    f32 frac_part = abs_val - (f32)int_part;
    
    // Write integer part
    if (int_part == 0)
	{
        *str++ = '0';
    } 
    else 
    {
        i8 buf[32];
        axl_utoa(int_part, buf, 10);
        axl_strcpy(str, buf);
        str += axl_strlen(buf);
    }
    
    // Write fractional part
    if (precision > 0)
	{
        *str++ = '.';
        f32 f = frac_part;
        u32 i;
        for (i = 0; i < precision; i++)
	    {
            f *= 10.0f;
            u32 digit = (u32)f;
            *str++ = '0' + digit;
            f -= (f32)digit;
        }
        
        // Remove trailing zeros
        while (str > start + 2 && *(str-1) == '0')
	    {
            str--;
        }
        // Remove decimal point if no fractional digits remain
        if (*(str-1) == '.')
	    {
            str--;
        }
    }
    
    *str = '\0';
    return start;
}