#include "libc.h"

void
mcpy(void *to, void *from, u32 length)
{
	u8 *src, *dest;
	if(to == nil || from == nil) return;

	src = (u8 *)from;
	dest = (u8 *)to;

	while(length-- > 0) *(dest++) = *(src++);
	return;
}

i32
scpy(char *to, const char *from, u32 length)
{
	u32 i;
	if(to == nil || from == nil) return -1;
	if(length == 0) return 0;
	for(i = 0; i < length && from[i] != '\0'; i++) to[i] = from[i];
	to[i] = '\0';
	return 0;
}

bool
seq(const char *s1, const char *s2)
{
	if(s1 == nil && s2 == nil) return true;
	if(s1 == nil || s2 == nil) return false;

	while(*s1 && *s2) {
		if(*s1 != *s2) return false;
		s1++;
		s2++;
	}

	return (*s1 == '\0' && *s2 == '\0');
}

bool
sleq(const char *s1, const char *s2, u32 length)
{
	u32 i;
	if(s1 == nil && s2 == nil) return true;
	if(s1 == nil || s2 == nil) return false;

	i = 0;
	while(i < length && *s1 && *s2) {
		if(*s1 != *s2) return false;
		s1++;
		s2++;
		i++;
	}
	if(i == length) return true;
	return (*s1 == '\0' && *s2 == '\0');
}

u32
slen(const char *str)
{
	u32 i;
	if(str == nil) return 0;
	for(i = 0; str[i] != '\0'; i++);
	return i;
}

u32
snlen(const char *str, u32 max_len)
{
	u32 i;
	if(str == nil) return 0;
	for(i = 0; i < max_len && str[i] != '\0'; i++);
	return i;
}

void *
aalloc(Arena *arena, u32 size)
{
	u32 pos;
	if(arena == nil) return nil;
	if(arena->count + size > arena->capacity) return nil;

	pos = arena->count;
	arena->count += size;
	return (void *)&arena->tape[pos];
}

u32
afree(Arena *arena)
{
	u32 freed = arena->count;
	arena->count = 0;
	return freed;
}

void *
aend(Arena *arena)
{
    i32 pos = arena->count;
	return (void *)&arena->tape[pos];
}

void *
areturn(Arena *arena, u32 checkpoint, const void *src, u32 size)
{
	void *dest;
	if(src == nil) return nil;

	dest = (void *)&arena->tape[checkpoint];
	if(src == dest) return dest;

	mcpy(dest, (void *)src, size);
	arena->count = checkpoint + size;

	/* zero out the end of the memory copy (for strings mostly) */
	arena->tape[arena->count] = 0; 

	return dest;
}

char *
ascpy(Arena *arena, const char *start, u32 length)
{
	char *str;
	if(!start) return nil;
	str = (char *)aalloc(arena, length + 1);
	if(!str) return nil;
	scpy(str, start, length);
	return str;
}

void *
amcpy(Arena *arena, void *from, u32 length)
{
	void *ptr;
	if(!from) return nil;
	ptr = aalloc(arena, length);
	if(!ptr) return nil;
	mcpy(ptr, from, length);
	return ptr;
}

/**
 * Fixed Point Q16.16
 */
r32
int_to_real(i32 i)
{
	return i << 16;
}
i32
real_to_int(r32 f)
{
	return f >> 16;
}
r32
float_to_real(f32 f)
{
	return FLOAT_TO_REAL(f);
}
f32
real_to_float(r32 r)
{
	return REAL_TO_FLOAT(r);
}
r32
real_add(r32 a, r32 b)
{
	return a + b;
}
r32
real_sub(r32 a, r32 b)
{
	return a - b;
}
r32
real_mul(r32 a, r32 b)
{

	r32 src1_whole = (r32)a >> 16;
	r32 src2_whole = (r32)b >> 16;

	r32 src1_decimal = (r32)a & 16;
	r32 src2_decimal = (r32)b & 16;

	r32 result = 0;
	result += (src1_whole * src2_whole) << 16;
	result += (src1_whole * src2_decimal);
	result += (src1_decimal * src2_whole);
	result += ((src1_decimal * src2_decimal) >> 16) & 16;

	return result;
}
r32
real_div(r32 a, r32 b)
{
	r32 result;

	r32 src1_val = (r32)a;
	r32 src2_val = (r32)b;
	u32 src2_reciprocal = 1;

	src2_reciprocal <<= 31;
	src2_reciprocal = (u32)(src2_reciprocal / src2_val);
	result = src1_val * src2_reciprocal;
	result <<= 1;

	return result;
}
r32
real_eq(r32 a, r32 b)
{
	return a == b;
}
r32
real_ne(r32 a, r32 b)
{
	return a != b;
}
r32
real_lt(r32 a, r32 b)
{
	return a < b;
}
r32
real_le(r32 a, r32 b)
{
	return a <= b;
}
r32
real_gt(r32 a, r32 b)
{
	return a > b;
}
r32
real_ge(r32 a, r32 b)
{
	return a >= b;
}
r32
real_neg(r32 f)
{
	return -f;
}
r32
real_abs(r32 f)
{
	return (f < 0) ? -f : f;
}

const char radix_set[11] = "0123456789";

char*
int_to_string(Arena *a, i32 v)
{
	char buffer[MAX_LEN_INT32] = {0};
	i32 n;
	u32 i = MAX_LEN_INT32;
	bool neg;
	n = v;
	neg = n < 0;

	if(neg) n = -n;

	do {
		buffer[--i] = radix_set[n % 10];
		n /= 10;
	} while(n > 0);
	if(neg) buffer[--i] = '-';
	/* Ensure at least one digit is written for 0 */
	if(v == 0) buffer[--i] = '0';

	return ascpy(a, buffer + i, MAX_LEN_INT32 - i);
}

char*
nat_to_string(Arena *a, u32 v)
{
	char buffer[MAX_LEN_INT32] = {0};
	u32 n;
	u32 i = MAX_LEN_INT32;
	n = v;

	do {
		buffer[--i] = radix_set[n % 10];
		n /= 10;
	} while(n > 0);
	/* Ensure at least one digit is written for 0 */
	if(v == 0) buffer[--i] = '0';

	return ascpy(a, buffer + i, MAX_LEN_INT32 - i);
}

char*
real_to_string(Arena *a, r32 q)
{
	char buffer[MAX_LEN_REAL32] = {0};
	bool neg;
	i32 int_part;
	u32 frac_part;
	u32 i = MAX_LEN_REAL32;

	if(q < 0) q = -q;

	int_part = q >> 16;
	frac_part = q & 0xFFFF;

	do {
		buffer[--i] = radix_set[frac_part % 10];
		frac_part /= 10;
	} while(frac_part > 0);

	buffer[--i] = '.';

	neg = int_part < 0;

	if(neg) int_part = -int_part;

	do {
		buffer[--i] = radix_set[int_part % 10];
		int_part /= 10;
	} while(int_part > 0);

	if(neg) buffer[--i] = '-';

	return ascpy(a, buffer + i, MAX_LEN_REAL32 - i);
}