// SPDX-License-Identifier: GPL-3.0-only
/*
 * Wayland buffer management.
 *
 * Copyright (c) 2024, Richard Acayan. All rights reserved.
 */

#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <sys/mman.h>
#include <unistd.h>
#include <wayland-client-protocol.h>

#include "wayland.h"

static void on_buffer_release(void *data, struct wl_buffer *buf)
{
	struct ufkbd_wl_buffer *ctx = data;

	ufkbd_wl_buffer_release(ctx);
}

static const struct wl_buffer_listener buf_listener = {
	.release = on_buffer_release,
};

static int commit_buffer_resize(struct ufkbd_wl_buffer *ctx)
{
	int ret;

	wl_buffer_destroy(ctx->buf);

	ret = ftruncate(ctx->fd, ctx->size);
	if (ret == -1) {
		perror("wl: failed to resize shared memory");
		return -errno;
	}

	ctx->ptr = mmap(NULL, ctx->size, PROT_READ | PROT_WRITE, MAP_SHARED, ctx->fd, 0);
	if (ctx->ptr == MAP_FAILED) {
		perror("wl: failed to map buffer");
		return -errno;
	}

	wl_shm_pool_resize(ctx->pool, ctx->size);

	ctx->buf = wl_shm_pool_create_buffer(ctx->pool, 0,
					     ctx->width, ctx->height,
					     ctx->width * 4,
					     WL_SHM_FORMAT_XRGB8888);
	if (ctx->buf == NULL) {
		fprintf(stderr, "wl: lost a buffer to failed resize\n");
		ctx->avail = false;
	}

	wl_buffer_add_listener(ctx->buf, &buf_listener, ctx);

	ctx->resize = false;

	return 0;
}

static void on_wl_shm(void *data,
		      struct wl_registry *reg,
		      uint32_t name, uint32_t ver)
{
	struct ufkbd_wl_buffer *ctx = data;

	ctx->wl = wl_registry_bind(reg, name, &wl_shm_interface, ver);
	if (ctx->wl == NULL) {
		fprintf(stderr, "wl: failed to bind to shared memory\n");
		return;
	}

	ctx->pool = wl_shm_create_pool(ctx->wl, ctx->fd, 4);
	if (ctx->pool == NULL) {
		fprintf(stderr, "wl: failed to create memory pool\n");
		return;
	}

	ctx->buf = wl_shm_pool_create_buffer(ctx->pool, 0,
					     1, 1, 4,
					     WL_SHM_FORMAT_XRGB8888);
	if (ctx->buf == NULL) {
		fprintf(stderr, "wl: failed to create buffer\n");
		return;
	}

	wl_buffer_add_listener(ctx->buf, &buf_listener, ctx);
}

int ufkbd_wl_buffer_consume(struct ufkbd_wl_buffer *ctx,
				    struct wl_buffer **buf, void **ptr)
{
	if (buf == NULL || ptr == NULL)
		return -EINVAL;

	if (!ctx->avail)
		return -EBUSY;

	ctx->avail = false;

	*buf = ctx->buf;
	*ptr = ctx->ptr;

	return 0;
}

int ufkbd_wl_buffer_resize(struct ufkbd_wl_buffer *ctx,
				   uint32_t width, uint32_t height)
{
	int ret;

	if (width == 0 && height == 0)
		return -EINVAL;

	ctx->width = width;
	ctx->height = height;

	if (ctx->size < ctx->width * ctx->height * 4) {
		munmap(ctx->ptr, ctx->size);

		ctx->size = ctx->width * ctx->height * 4;
	}

	if (ctx->avail) {
		ret = commit_buffer_resize(ctx);
		if (ret)
			return ret;
	} else {
		ctx->resize = true;
	}

	return 0;
}

void ufkbd_wl_buffer_release(struct ufkbd_wl_buffer *ctx)
{
	if (ctx->resize)
		commit_buffer_resize(ctx);

	ctx->avail = true;
}

int ufkbd_wl_buffer_init(struct ufkbd_wl_buffer *ctx,
				 struct ufkbd_input_wayland *ufkbd_wl,
				 unsigned int id)
{
	intmax_t pid;
	int ret;

	ctx->ufkbd = ufkbd_wl->ufkbd;
	ctx->id = id;

	ctx->avail = true;
	ctx->dirty = false;
	ctx->resize = false;

	ctx->listener.iface = &wl_shm_interface;
	ctx->listener.cb = on_wl_shm;
	ctx->listener.data = ctx;

	pid = getpid();

	snprintf(ctx->path, SHM_PATH_SIZE, "/wl_shm_ufkbd_pid%jd_%u", pid, id);
	ctx->path[SHM_PATH_SIZE - 1] = '\0';

	ctx->fd = shm_open(ctx->path, O_RDWR | O_CREAT | O_EXCL, 0600);
	if (ctx->fd == -1) {
		perror("wl: failed to create shared memory");
		return -errno;
	}

	ret = ftruncate(ctx->fd, 4);
	if (ret) {
		perror("wl: failed to allocate 4 bytes on shm");
		ret = -errno;
		goto err;
	}

	ctx->ptr = mmap(NULL, 4, PROT_READ | PROT_WRITE, MAP_SHARED, ctx->fd, 0);
	if (ctx->ptr == MAP_FAILED) {
		perror("wl: failed to map buffer");
		ret = -errno;
		goto err;
	}

	ret = ufkbd_wl_global_listener_add(ufkbd_wl, &ctx->listener);
	if (ret)
		goto err;

	ctx->width = 1; 
	ctx->height = 1; 
	ctx->size = 4;

	return 0;

err:
	close(ctx->fd);
	shm_unlink(ctx->path);
	return ret;
}

void ufkbd_wl_buffer_uninit(struct ufkbd_wl_buffer *ctx)
{
	if (ctx->buf != NULL)
		wl_buffer_destroy(ctx->buf);

	if (ctx->pool != NULL)
		wl_shm_pool_destroy(ctx->pool);

	if (ctx->wl != NULL)
		wl_shm_destroy(ctx->wl);

	close(ctx->fd);
	shm_unlink(ctx->path);
}