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

#include <errno.h>
#include <math.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <xkbcommon/xkbcommon.h>

#include "graphics.h"
#include "input.h"
#include "layout.h"
#include "modifier.h"
#include "ufkbd.h"

// Simple function to add nanoseconds to a time struct.
static inline void time_add(struct timespec *time, long ns)
{
	time->tv_nsec += ns;

	if (time->tv_nsec >= 1000000000) {
		time->tv_sec += time->tv_nsec / 1000000000;
		time->tv_nsec = time->tv_nsec % 1000000000;
	}
}

static enum ufkbd_part part_calc(struct ufkbd_ctx *ctx,
				 struct ufkbd_key *key,
				 int x1, int y1, int x2, int y2)
{
	double angle;
	int dx, dy;
	int r_square;
	int idx;

	dx = x2 - x1;
	dy = y2 - y1;

	r_square = dx * dx + dy * dy;

	if (r_square < ctx->dist_squared)
		return UFKBD_PART_CENTER;

	angle = atan2(dy, dx);
	if (angle < 0)
		angle += M_PI * 2;

	idx = floor(angle * 8 / M_PI);

	return key->lut[idx];
}

int ufkbd_input_press(struct ufkbd_ctx *ctx, int id)
{
	struct ufkbd_press *press;
	int x1, y1, x2, y2;
	int ret;

	if (id >= UFKBD_PRESS_MAX)
		return -EINVAL;

	press = &ctx->presses[id];

	// Only reset the press if it is new.
	if (press->key == NULL) {
		press->x1 = press->x2;
		press->y1 = press->y2;
	}

	// Failure to find a key results in ignoring the press.
	press->key = ufkbd_layout_search(ctx->layout, press->x1, press->y1,
					 &x1, &y1, &x2, &y2);

	press->part = UFKBD_PART_CENTER;

	if (press->key != NULL) {
		ufkbd_modifier_press(ctx, press);

		press->key->presses[press->part]++;
		ctx->n_presses++;

		press->xl = x1;
		press->yt = y1;
		press->xr = x2;
		press->yb = y2;

		ufkbd_graphics_draw_key(ctx, press->key, x1, y1, x2, y2);
	}

	// The keypress may function partially if this fails.
	ret = clock_gettime(CLOCK_REALTIME, &press->repeat);
	if (ret == -1)
		return 0;
	time_add(&press->repeat, ctx->repeat_delay_ns);

	return 0;
}

int ufkbd_input_position(struct ufkbd_ctx *ctx, int id, int x, int y)
{
	struct ufkbd_press *press;
	enum ufkbd_part part;

	if (id >= UFKBD_PRESS_MAX)
		return -EINVAL;

	press = &ctx->presses[id];

	press->x2 = x;
	press->y2 = y;

	// We only want to do this if a valid key is being pressed.
	if (press->key != NULL) {
		part = part_calc(ctx, press->key,
				 press->x1, press->y1,
				 press->x2, press->y2);

		if (press->part != part) {
			press->key->presses[press->part]--;
			press->key->presses[part]++;

			ufkbd_graphics_draw_key(ctx, press->key,
						press->xl, press->yt,
						press->xr, press->yb);

			ufkbd_modifier_cancel(ctx, press);
			press->part = part;
			ufkbd_modifier_press(ctx, press);
		}
	}

	return 0;
}

int ufkbd_input_release(struct ufkbd_ctx *ctx, int id)
{
	struct ufkbd_press *press;
	int part, code;
	int ret = 0;

	if (ctx->drv->send_key == NULL)
		return -ENOTSUP;

	if (ctx->presses[id].part >= UFKBD_PART_MAX)
		return -EINVAL;

	press = &ctx->presses[id];

	if (press->key == NULL)
		return 0;

	part = press->part;
	code = press->key->keyids[part];

	/*
	 * If the key is a modifier, a state change is needed, and the key
	 * should only be sent to the driver when the modifier is released.
	 * Otherwise, the key should be sent to the driver and any latched
	 * modifiers should be released.
	 */
	if (ufkbd_is_modifier(press)) {
		ufkbd_modifier_release(ctx, press);
	} else if (code != -1) {
		ret = ctx->drv->send_key(ctx->drv_data, code, false);
		ufkbd_modifier_unlatch_all(ctx);
	}

	press->key->presses[part]--;
	ctx->n_presses--;

	ufkbd_graphics_draw_key(ctx, press->key,
				press->xl, press->yt,
				press->xr, press->yb);

	press->key = NULL;

	return ret;
}

int ufkbd_input_repeat(struct ufkbd_ctx *ctx, int id)
{
	struct ufkbd_press *press;
	enum ufkbd_part part;
	int code;

	press = &ctx->presses[id];

	// Modifier keys are not repeated.
	if (ufkbd_is_modifier(press))
		return 0;

	time_add(&press->repeat, ctx->repeat_interval_ns);

	part = press->part;
	code = press->key->keyids[part];

	return ctx->drv->send_key(ctx->drv_data, code, true);
}

int ufkbd_input_repeat_held(struct ufkbd_ctx *ctx)
{
	struct ufkbd_press *press;
	struct timespec time;
	size_t i;
	int ret;

	ret = clock_gettime(CLOCK_REALTIME, &time);
	if (ret == -1)
		return 0;

	for (i = 0; i < UFKBD_PRESS_MAX; i++) {
		press = &ctx->presses[i];
		if (press->key == NULL)
			continue;

		if (time.tv_sec > press->repeat.tv_sec
		 || (time.tv_sec == press->repeat.tv_sec
		  && time.tv_nsec > press->repeat.tv_nsec)) {
			ufkbd_input_repeat(ctx, i);
		}
	}

	return 0;
}