#include "renderer.h"

#include "fb.h"

#include <assert.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <xf86drm.h>

static int drm_fd;
static drmModeConnector *conn;
static drmModeCrtc *crtc;
static uint32_t conn_id;

static fb_info_t fbs[2];
static int front, back;

static uint32_t width, height;
static void page_flip_handler(int, unsigned, unsigned, unsigned, void *)
{
}

static void
set_pixel(uint32_t x, uint32_t y, uint8_t r, uint8_t g, uint8_t b)
{
	/* x %= width; */
	/* y %= height; */
	const uint32_t offset = y * (fbs[back].pitch / 4) + x;
	assert(offset < fbs[back].size);
	fbs[back].buf[offset] = (r << 16) | (g << 8) | b;
}

renderer_params_t renderer_init()
{
	drm_fd = open("/dev/dri/card1", O_RDWR | O_CLOEXEC);
	assert(drm_fd != -1);

	drmModeRes *res = drmModeGetResources(drm_fd);
	assert(res != nullptr);
	conn = drmModeGetConnector(drm_fd, res->connectors[0]);
	assert(conn != nullptr);
	drmModeModeInfo mode = conn->modes[0];
	conn_id = conn->connector_id;

	fbs[0] = fb_init(drm_fd, mode);
	fbs[1] = fb_init(drm_fd, mode);
	front = 0;
	back = 1;

	const int err = drmModeSetCrtc(
	    drm_fd, res->crtcs[0], fbs[front].id, 0, 0, &conn_id, 1, &mode);
	assert(err == 0);
	crtc = drmModeGetCrtc(drm_fd, res->crtcs[0]);
	assert(crtc != nullptr);

	drmModeFreeResources(res);

	width = mode.hdisplay;
	height = mode.vdisplay;

	return (renderer_params_t) {
		.drm_fd = drm_fd,
		.aspect = (float)mode.hdisplay / (float)mode.vdisplay,
	};
}

void renderer_cleanup()
{
	drmModeSetCrtc(
	    drm_fd, crtc->crtc_id, crtc->buffer_id, crtc->x, crtc->y, &conn_id,
	    1, &crtc->mode);

	fb_cleanup(drm_fd, fbs[0]);
	fb_cleanup(drm_fd, fbs[1]);
	drmModeFreeCrtc(crtc);
	drmModeFreeConnector(conn);
	close(drm_fd);
}

void renderer_handle()
{
	drmEventContext ev = {
		.version = DRM_EVENT_CONTEXT_VERSION,
		.page_flip_handler = page_flip_handler,
	};
	drmHandleEvent(drm_fd, &ev);
}

void renderer_clear()
{
	memset(fbs[back].buf, 0, fbs[back].size);
}

void renderer_swap()
{
	const int err = drmModePageFlip(
	    drm_fd, crtc->crtc_id, fbs[back].id, DRM_MODE_PAGE_FLIP_EVENT,
	    nullptr);
	assert(err == 0);

	front = (front + 1) & 1;
	back = (back + 1) & 1;
}

void renderer_draw()
{
	for (unsigned y = 0; y < height; ++y) {
		for (unsigned x = 0; x < width; ++x)
			set_pixel(x, y, (x * 255) / width, (y * 255) / height, 128);
	}
}