#include <luna/CType.h>
#include <luna/NumberParsing.h>

// This function assumes you have called is_valid_digit_for_base() to validate the digit first.
static isize parse_digit_unchecked(char c)
{
    if (_isdigit(c)) return c - '0';
    if (_islower(c)) return (c - 'a') + 10;
    return (c - 'A') + 10;
}

static bool is_valid_digit_for_base(int base, char c)
{
    if (!_isalnum(c)) return false;
    if (parse_digit_unchecked(c) >= (isize)base) return false;
    return true;
}

usize _strtou(const char* str, const char** endptr, int base)
{
    usize val = 0;

    while (_isspace(*str)) str++;

    if ((base == 0 || base == 16) && *str == '0')
    {
        str++;
        if (_tolower(*str) == 'x')
        {
            base = 16;
            str++;
        }
        else if (base == 0)
            base = 8;
    }
    else if (base == 0)
        base = 10;

    while (is_valid_digit_for_base(base, *str))
    {
        val = ((usize)base * val) + (usize)parse_digit_unchecked(*str);
        str++;
    }

    if (endptr) *endptr = str;

    return val;
}

isize _strtoi(const char* str, const char** endptr, int base)
{
    bool negative = false;

    while (_isspace(*str)) str++;

    if (*str == '-' || *str == '+')
    {
        if (*str == '-') negative = true;
        str++;
    }

    usize rc = _strtou(str, endptr,
                       base); // FIXME: Check for overflow (the unsigned usize value might not fit into a signed isize)

    return negative ? -(isize)rc : (isize)rc;
}

usize _atou(const char** str)
{
    return _strtou(*str, str, 10);
}

isize _atos(const char** str)
{
    return _strtoi(*str, str, 10);
}