#include <fx/core/ringbuffer.h>
#include <stdlib.h>
#include <string.h>

#define BUF_LOCKED(buf)                                                        \
	(((buf)->r_flags & (RINGBUFFER_READ_LOCKED | RINGBUFFER_WRITE_LOCKED)) \
	 != 0)

/*** PRIVATE DATA *************************************************************/

enum ringbuffer_flags {
	RINGBUFFER_BUFFER_MALLOC = 0x02u,
	RINGBUFFER_READ_LOCKED = 0x04u,
	RINGBUFFER_WRITE_LOCKED = 0x08u,
};

struct fx_ringbuffer_p {
	enum ringbuffer_flags r_flags;
	void *r_buf, *r_opened_buf;
	unsigned long r_capacity, r_opened_capacity;
	unsigned long r_write_ptr, r_read_ptr;
};

/*** PRIVATE FUNCTIONS ********************************************************/

static enum fx_status ringbuffer_clear(struct fx_ringbuffer_p *buf)
{
	if (BUF_LOCKED(buf)) {
		return FX_ERR_BUSY;
	}

	buf->r_read_ptr = buf->r_write_ptr = 0;

	return FX_SUCCESS;
}

static size_t ringbuffer_write_capacity_remaining(const struct fx_ringbuffer_p *buf)
{
	if (buf->r_read_ptr > buf->r_write_ptr) {
		return buf->r_read_ptr - buf->r_write_ptr - 1;
	} else {
		return buf->r_capacity - buf->r_write_ptr + buf->r_read_ptr - 1;
	}
}

static size_t ringbuffer_available_data_remaining(const struct fx_ringbuffer_p *buf)
{
	if (buf->r_read_ptr < buf->r_write_ptr) {
		return buf->r_write_ptr - buf->r_read_ptr;
	} else if (buf->r_read_ptr > buf->r_write_ptr) {
		return buf->r_capacity - buf->r_read_ptr + buf->r_write_ptr;
	} else {
		return 0;
	}
}

static enum fx_status ringbuffer_open_read_buffer(
	struct fx_ringbuffer_p *buf, const void **ptr, size_t *length)
{
	if (BUF_LOCKED(buf)) {
		return FX_ERR_BUSY;
	}

	size_t contiguous_capacity = 0;
	if (buf->r_read_ptr > buf->r_write_ptr) {
		contiguous_capacity = buf->r_capacity - buf->r_read_ptr;
	} else {
		contiguous_capacity = buf->r_write_ptr - buf->r_read_ptr;
	}

	if (contiguous_capacity == 0) {
		return FX_ERR_NO_DATA;
	}

	buf->r_opened_buf = (char *)buf->r_buf + buf->r_read_ptr;
	buf->r_opened_capacity = contiguous_capacity;

	buf->r_flags |= RINGBUFFER_READ_LOCKED;
	*ptr = buf->r_opened_buf;
	*length = contiguous_capacity;

	return FX_SUCCESS;
}

static enum fx_status ringbuffer_close_read_buffer(
	struct fx_ringbuffer_p *buf, const void **ptr, size_t nr_read)
{
	if (!(buf->r_flags & RINGBUFFER_READ_LOCKED)) {
		return FX_ERR_BAD_STATE;
	}

	if (*ptr != buf->r_opened_buf) {
		return FX_ERR_INVALID_ARGUMENT;
	}

	if (nr_read > buf->r_opened_capacity) {
		return FX_ERR_INVALID_ARGUMENT;
	}

	buf->r_read_ptr += nr_read;
	if (buf->r_read_ptr >= buf->r_capacity) {
		buf->r_read_ptr = 0;
	}

	if (buf->r_read_ptr == buf->r_write_ptr) {
		/* the ringbuffer is now empty. set both pointers to 0.
		 * this ensures that the whole buffer will be available
		 * contiguously to the next call to open_write_buffer */
		buf->r_read_ptr = 0;
		buf->r_write_ptr = 0;
	}

	buf->r_opened_buf = NULL;
	buf->r_opened_capacity = 0;
	buf->r_flags &= ~RINGBUFFER_READ_LOCKED;

	return FX_SUCCESS;
}

static enum fx_status ringbuffer_open_write_buffer(
	struct fx_ringbuffer_p *buf, void **ptr, size_t *capacity)
{
	if (BUF_LOCKED(buf)) {
		return FX_ERR_BUSY;
	}

	size_t contiguous_capacity = 0;
	if (buf->r_write_ptr >= buf->r_read_ptr) {
		contiguous_capacity = buf->r_capacity - buf->r_write_ptr - 1;

		if (buf->r_read_ptr > 0) {
			contiguous_capacity++;
		}
	} else {
		contiguous_capacity = buf->r_read_ptr - buf->r_write_ptr - 1;
	}

	if (contiguous_capacity == 0) {
		return FX_ERR_NO_SPACE;
	}

	buf->r_opened_buf = (char *)buf->r_buf + buf->r_write_ptr;
	buf->r_opened_capacity = contiguous_capacity;

	buf->r_flags |= RINGBUFFER_WRITE_LOCKED;
	*ptr = buf->r_opened_buf;
	*capacity = contiguous_capacity;

	return FX_SUCCESS;
}

static enum fx_status ringbuffer_close_write_buffer(
	struct fx_ringbuffer_p *buf, void **ptr, size_t nr_written)
{
	if (!(buf->r_flags & RINGBUFFER_WRITE_LOCKED)) {
		return FX_ERR_BAD_STATE;
	}

	if (*ptr != buf->r_opened_buf) {
		return FX_ERR_INVALID_ARGUMENT;
	}

	if (nr_written > buf->r_opened_capacity) {
		return FX_ERR_INVALID_ARGUMENT;
	}

	buf->r_write_ptr += nr_written;
	if (buf->r_write_ptr >= buf->r_capacity) {
		buf->r_write_ptr = 0;
	}

	buf->r_opened_buf = NULL;
	buf->r_opened_capacity = 0;
	buf->r_flags &= ~RINGBUFFER_WRITE_LOCKED;

	return FX_SUCCESS;
}

static enum fx_status ringbuffer_read(
	struct fx_ringbuffer_p *buf, void *p, size_t count, size_t *nr_read)
{
	if (BUF_LOCKED(buf)) {
		return FX_ERR_BUSY;
	}

	size_t r = 0;
	unsigned char *dest = p;
	size_t remaining = count;

	while (remaining > 0) {
		const void *src;
		size_t available;
		enum fx_status status
			= ringbuffer_open_read_buffer(buf, &src, &available);

		if (status == FX_ERR_NO_DATA) {
			break;
		}

		if (!FX_OK(status)) {
			return status;
		}

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

		memcpy(dest, src, to_copy);

		remaining -= to_copy;
		dest += to_copy;
		r += to_copy;

		ringbuffer_close_read_buffer(buf, &src, to_copy);
	}

	*nr_read = r;
	return FX_SUCCESS;
}

static enum fx_status ringbuffer_write(
	struct fx_ringbuffer_p *buf, const void *p, size_t count, size_t *nr_written)
{
	if (BUF_LOCKED(buf)) {
		return FX_ERR_BUSY;
	}

	size_t w = 0;
	const unsigned char *src = p;
	size_t remaining = count;

	while (remaining > 0) {
		void *dest;
		size_t available;
		enum fx_status status
			= ringbuffer_open_write_buffer(buf, &dest, &available);

		if (status == FX_ERR_NO_SPACE) {
			break;
		}

		if (!FX_OK(status)) {
			return status;
		}

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

		memcpy(dest, src, to_copy);

		remaining -= to_copy;
		src += to_copy;
		w += to_copy;

		ringbuffer_close_write_buffer(buf, &dest, to_copy);
	}

	*nr_written = w;
	return FX_SUCCESS;
}

static int ringbuffer_getc(struct fx_ringbuffer_p *buf)
{
	size_t available = ringbuffer_available_data_remaining(buf);
	if (available == 0) {
		return -1;
	}

	char *p = buf->r_buf;
	char c = p[buf->r_read_ptr++];

	if (buf->r_read_ptr >= buf->r_capacity) {
		buf->r_read_ptr = 0;
	}

	return c;
}

static enum fx_status ringbuffer_putc(struct fx_ringbuffer_p *buf, int c)
{
	size_t available = ringbuffer_write_capacity_remaining(buf);
	if (available == 0) {
		return FX_ERR_NO_SPACE;
	}

	char *p = buf->r_buf;
	p[buf->r_write_ptr++] = c;

	if (buf->r_write_ptr >= buf->r_capacity) {
		buf->r_write_ptr = 0;
	}

	return c;
}

/*** PUBLIC FUNCTIONS *********************************************************/

fx_ringbuffer *fx_ringbuffer_create(size_t capacity)
{
	fx_ringbuffer *ringbuf = fx_object_create(FX_TYPE_RINGBUFFER);
	if (!ringbuf) {
		return NULL;
	}

	struct fx_ringbuffer_p *p
		= fx_object_get_private(ringbuf, FX_TYPE_RINGBUFFER);

	void *buffer = malloc(capacity);
	if (!buffer) {
		fx_ringbuffer_unref(ringbuf);
		return NULL;
	}

	p->r_flags = RINGBUFFER_BUFFER_MALLOC;
	p->r_buf = buffer;
	p->r_capacity = capacity;

	return ringbuf;
}

fx_ringbuffer *fx_ringbuffer_create_with_buffer(void *ptr, size_t capacity)
{
	fx_ringbuffer *ringbuf = fx_object_create(FX_TYPE_RINGBUFFER);
	if (!ringbuf) {
		return NULL;
	}

	struct fx_ringbuffer_p *p
		= fx_object_get_private(ringbuf, FX_TYPE_RINGBUFFER);

	p->r_flags = 0;
	p->r_buf = ptr;
	p->r_capacity = capacity;

	return ringbuf;
}

enum fx_status fx_ringbuffer_clear(fx_ringbuffer *buf)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_RINGBUFFER, ringbuffer_clear, buf);
}

enum fx_status fx_ringbuffer_read(
	fx_ringbuffer *buf, void *p, size_t count, size_t *nr_read)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_RINGBUFFER, ringbuffer_read, buf, p, count, nr_read);
}

enum fx_status fx_ringbuffer_write(
	fx_ringbuffer *buf, const void *p, size_t count, size_t *nr_written)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_RINGBUFFER, ringbuffer_write, buf, p, count, nr_written);
}

int fx_ringbuffer_getc(fx_ringbuffer *buf)
{
	FX_CLASS_DISPATCH_STATIC_0(FX_TYPE_RINGBUFFER, ringbuffer_getc, buf);
}

enum fx_status fx_ringbuffer_putc(fx_ringbuffer *buf, int c)
{
	FX_CLASS_DISPATCH_STATIC(FX_TYPE_RINGBUFFER, ringbuffer_putc, buf, c);
}

size_t fx_ringbuffer_write_capacity_remaining(const fx_ringbuffer *buf)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_TYPE_RINGBUFFER, ringbuffer_write_capacity_remaining, buf);
}

size_t fx_ringbuffer_available_data_remaining(const fx_ringbuffer *buf)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_TYPE_RINGBUFFER, ringbuffer_available_data_remaining, buf);
}

enum fx_status fx_ringbuffer_open_read_buffer(
	fx_ringbuffer *buf, const void **ptr, size_t *length)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_RINGBUFFER, ringbuffer_open_read_buffer, buf, ptr, length);
}

enum fx_status fx_ringbuffer_close_read_buffer(
	fx_ringbuffer *buf, const void **ptr, size_t nr_read)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_RINGBUFFER, ringbuffer_close_read_buffer, buf, ptr, nr_read);
}

enum fx_status fx_ringbuffer_open_write_buffer(
	fx_ringbuffer *buf, void **ptr, size_t *capacity)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_RINGBUFFER, ringbuffer_open_write_buffer, buf, ptr,
		capacity);
}

enum fx_status fx_ringbuffer_close_write_buffer(
	fx_ringbuffer *buf, void **ptr, size_t nr_written)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_TYPE_RINGBUFFER, ringbuffer_close_write_buffer, buf, ptr,
		nr_written);
}

/*** VIRTUAL FUNCTIONS ********************************************************/

static void ringbuffer_init(fx_object *obj, void *priv)
{
	struct fx_ringbuffer_p *buf = priv;
}

static void ringbuffer_fini(fx_object *obj, void *priv)
{
	struct fx_ringbuffer_p *buf = priv;

	if (buf->r_flags & RINGBUFFER_BUFFER_MALLOC) {
		free(buf->r_buf);
	}
}

/*** CLASS DEFINITION *********************************************************/

FX_TYPE_CLASS_DEFINITION_BEGIN(fx_ringbuffer)
	FX_TYPE_CLASS_INTERFACE_BEGIN(fx_object, FX_TYPE_OBJECT)
		FX_INTERFACE_ENTRY(to_string) = NULL;
	FX_TYPE_CLASS_INTERFACE_END(fx_object, FX_TYPE_OBJECT)
FX_TYPE_CLASS_DEFINITION_END(fx_ringbuffer)

FX_TYPE_DEFINITION_BEGIN(fx_ringbuffer)
	FX_TYPE_ID(0xb0493774, 0xef13, 0x4905, 0xa865, 0x1595607ccad9);
	FX_TYPE_CLASS(fx_ringbuffer_class);
	FX_TYPE_INSTANCE_PRIVATE(struct fx_ringbuffer_p);
	FX_TYPE_INSTANCE_INIT(ringbuffer_init);
	FX_TYPE_INSTANCE_FINI(ringbuffer_fini);
FX_TYPE_DEFINITION_END(fx_ringbuffer)