#include "file.h"

#include <errno.h>
#include <mango/log.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define DEFAULT_BUFFER_SIZE 4096

static int ringbuf_init(struct ringbuf *buf)
{
	if (buf->buf_ptr) {
		return SUCCESS;
	}

	if (!buf->buf_max) {
		buf->buf_max = DEFAULT_BUFFER_SIZE;
	}

	buf->buf_ptr = malloc(buf->buf_max);
	if (!buf->buf_ptr) {
		return ENOMEM;
	}

	memset(buf->buf_ptr, 0x0, buf->buf_max);
	return SUCCESS;
}

int __libc_ringbuf_get_read_buffer(
	struct ringbuf *buf,
	const char **out_bufp,
	size_t *out_len)
{
	int r = ringbuf_init(buf);
	if (r != SUCCESS) {
		return r;
	}

	size_t contiguous_capacity = 0;
	if (buf->buf_readp > buf->buf_writep) {
		contiguous_capacity = buf->buf_max - buf->buf_readp;
	} else {
		contiguous_capacity = buf->buf_writep - buf->buf_readp;
	}

	kern_tracef(
		"OPEN READ: readp=%zu, writep=%zu, max=%zu -> %p cap=%zu",
		buf->buf_readp,
		buf->buf_writep,
		buf->buf_max,
		buf->buf_ptr + buf->buf_readp,
		contiguous_capacity);
	*out_len = contiguous_capacity;

	if (contiguous_capacity == 0) {
		*out_bufp = NULL;
	} else {
		*out_bufp = buf->buf_ptr + buf->buf_readp;
	}

	return SUCCESS;
}

void __libc_ringbuf_put_read_buffer(
	struct ringbuf *buf,
	const char **bufp,
	size_t *len)
{
	buf->buf_readp += *len;

	if (buf->buf_readp == buf->buf_writep) {
		buf->buf_readp = buf->buf_writep = 0;
	}

	kern_tracef("CLOSE READ: %p r=%zu", *bufp, *len);

	*bufp = NULL;
	*len = 0;
}

int __libc_ringbuf_get_write_buffer(
	struct ringbuf *buf,
	char **out_bufp,
	size_t *out_len)
{
	int r = ringbuf_init(buf);
	if (r != SUCCESS) {
		return r;
	}

	size_t contiguous_capacity = 0;
	if (buf->buf_writep >= buf->buf_readp) {
		contiguous_capacity = buf->buf_max - buf->buf_writep - 1;

		if (buf->buf_readp > 0) {
			contiguous_capacity++;
		}
	} else {
		contiguous_capacity = buf->buf_readp - buf->buf_writep - 1;
	}

	kern_tracef(
		"OPEN WRITE: readp=%zu, writep=%zu, max=%zu -> %p cap=%zu",
		buf->buf_readp,
		buf->buf_writep,
		buf->buf_max,
		buf->buf_ptr + buf->buf_readp,
		contiguous_capacity);

	*out_len = contiguous_capacity;

	if (contiguous_capacity == 0) {
		*out_bufp = NULL;
	} else {
		*out_bufp = buf->buf_ptr + buf->buf_writep;
	}

	return SUCCESS;
}

void __libc_ringbuf_put_write_buffer(
	struct ringbuf *buf,
	char **bufp,
	size_t *len)
{
	buf->buf_writep += *len;

	if (buf->buf_readp == buf->buf_writep) {
		buf->buf_readp = buf->buf_writep = 0;
	}

	kern_tracef(
		"CLOSE WRITE: %p r=%zu (%c)",
		*bufp,
		*len,
		*(char *)(*bufp));

	*bufp = NULL;
	*len = 0;
}

long __libc_ringbuf_read(struct ringbuf *buf, void *p, size_t count)
{
	size_t nr_read = 0;
	long r = 0;

	while (nr_read < count) {
		const char *src = NULL;
		size_t available = 0;
		r = __libc_ringbuf_get_read_buffer(buf, &src, &available);
		if (r < 0) {
			break;
		}

		char *dest = p + nr_read;
		size_t to_copy = count - nr_read;

		if (available == 0) {
			__libc_ringbuf_put_read_buffer(buf, &src, &available);
			break;
		}

		if (to_copy > available) {
			to_copy = available;
		}

		memcpy(dest, src, to_copy);

		nr_read += available;
		__libc_ringbuf_put_read_buffer(buf, &src, &to_copy);
	}

	if (r < 0) {
		return r;
	}

	return nr_read;
}

long __libc_ringbuf_write(struct ringbuf *buf, const void *p, size_t count)
{
	size_t nr_written = 0;
	long r = 0;

	while (nr_written < count) {
		char *dest = NULL;
		size_t available = 0;
		r = __libc_ringbuf_get_write_buffer(buf, &dest, &available);
		if (r < 0) {
			break;
		}

		const char *src = p + nr_written;
		size_t to_copy = count - nr_written;

		if (available == 0) {
			__libc_ringbuf_put_write_buffer(buf, &dest, &available);
			break;
		}

		if (to_copy > available) {
			to_copy = available;
		}

		memcpy(dest, src, to_copy);

		nr_written += available;
		__libc_ringbuf_put_write_buffer(buf, &dest, &to_copy);
	}

	if (r < 0) {
		return r;
	}

	return nr_written;
}

int __libc_ringbuf_clear(struct ringbuf *buf)
{
	buf->buf_readp = buf->buf_writep = 0;
	return 0;
}

int __libc_ringbuf_resize(struct ringbuf *buf, size_t max)
{
	if (!(buf->buf_flags & RINGBUF_STATIC)) {
		free(buf->buf_ptr);
		buf->buf_ptr = NULL;
	}

	buf->buf_readp = buf->buf_writep = 0;
	buf->buf_flags &= ~RINGBUF_STATIC;
	buf->buf_max = max;
	return 0;
}

int __libc_ringbuf_resize_static(struct ringbuf *buf, void *p, size_t max)
{
	if (!(buf->buf_flags & RINGBUF_STATIC)) {
		free(buf->buf_ptr);
		buf->buf_ptr = NULL;
	}

	buf->buf_readp = buf->buf_writep = 0;
	buf->buf_flags |= RINGBUF_STATIC;
	buf->buf_ptr = p;
	buf->buf_max = max;
	return 0;
}

size_t __libc_ringbuf_available(const struct ringbuf *buf)
{
	if (buf->buf_readp < buf->buf_writep) {
		return buf->buf_writep - buf->buf_readp;
	} else if (buf->buf_readp > buf->buf_writep) {
		return buf->buf_max - buf->buf_readp + buf->buf_writep;
	} else {
		return 0;
	}
}

size_t __libc_ringbuf_capacity(const struct ringbuf *buf)
{
	if (buf->buf_readp > buf->buf_writep) {
		return buf->buf_readp - buf->buf_writep - 1;
	} else {
		return buf->buf_max - buf->buf_writep + buf->buf_readp - 1;
	}
}