#include "ringbuffer.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h> // for ptrdiff_t

int init_ringbuffer(struct ringbuffer* r, size_t size)
{
	r->buf = (char*)malloc(size);

	if (!r->buf)
	{
		return ERINGBUFFER_ALLOC_FAIL;
	}

	r->size = size;
	clear_ringbuffer(r);

	return 0;
}

void free_ringbuffer(struct ringbuffer* r)
{
	free(r->buf);
}

void clear_ringbuffer(struct ringbuffer* r)
{
	r->begin = 0;
	r->end = 0;
}

size_t ringbuffer_free_space(struct ringbuffer* r)
{
	if (r->begin == 0 && r->end == 0)
	{
		return r->size;
	}

	if (r->begin < r->end)
	{
		return r->size - (r->end - r->begin) - 1;
	}
	else
	{
		return r->begin - r->end - 1;
	}
}

size_t ringbuffer_data_size(struct ringbuffer* r)
{
	if (r->begin == 0 && r->end == 0)
	{
		return 0;
	}

	if (r->begin <= r->end)
	{
		return r->end - r->begin + 1;
	}
	else
	{
		return r->size - (r->begin - r->end) + 1;
	}
}


void ringbuffer_push(struct ringbuffer* r, const void* data, size_t size)
{
	if (ringbuffer_free_space(r) < size)
	{
		return;
	}

	if (r->begin == 0 && r->end == 0)
	{
		memcpy(r->buf, data, size);
		r->begin = r->buf;
		r->end = r->buf + size - 1;
		return;
	}

	r->end++;

	if (r->begin < r->end)
	{
		if ((size_t)(r->buf + (ptrdiff_t)r->size - r->begin) >= size)
		{
			// we can fit without cut
			memcpy(r->end, data, size);
			r->end += size - 1;
		}
		else
		{
			// make a cut
			size_t s = r->buf + r->size - r->end;
			memcpy(r->end, data, s);
			size -= s;
			memcpy(r->buf, (char*)data + s, size);
			r->end = r->buf + size - 1;
		}
	}
	else
	{
		memcpy(r->end, data, size);
		r->end += size - 1;
	}
}

void ringbuffer_pop(struct ringbuffer* r, void* data, size_t size)
{
	if (ringbuffer_data_size(r) < size)
	{
		return;
	}

	int need_clear = 0;

	if (ringbuffer_data_size(r) == size)
	{
		need_clear = 1;
	}

	if (r->begin < r->end)
	{
		if (data)
		{
			memcpy(data, r->begin, size);
		}

		r->begin += size;
	}
	else
	{
		if ((size_t)(r->buf + (ptrdiff_t)r->size - r->begin) >= size)
		{
			if (data)
			{
				memcpy(data, r->begin, size);
			}

			r->begin += size;
		}
		else
		{
			size_t s = r->buf + r->size - r->begin;

			if (data)
			{
				memcpy(data, r->begin, s);
			}

			size -= s;

			if (data)
			{
				memcpy((char*)data + s, r->buf, size);
			}

			r->begin = r->buf + size;
		}
	}

	if (need_clear)
	{
		clear_ringbuffer(r);
	}
}

void ringbuffer_read(struct ringbuffer* r, void* data, size_t size)
{
	if (ringbuffer_data_size(r) < size)
	{
		return;
	}

	if (r->begin < r->end)
	{
		memcpy(data, r->begin, size);
	}
	else
	{
		if ((size_t)(r->buf + (ptrdiff_t)r->size - r->begin) >= size)
		{
			memcpy(data, r->begin, size);
		}
		else
		{
			size_t s = r->buf + r->size - r->begin;
			memcpy(data, r->begin, s);
			size -= s;
			memcpy((char*)data + s, r->buf, size);
		}
	}
}