import type { Box, Point, Polygon } from '@flatten-js/core';
import { compact } from 'es-toolkit';
import { toast } from 'react-toastify';
import {
	EPSILON,
	SELECTION_RECTANGLE_COLOR_CONTAINS,
	SELECTION_RECTANGLE_COLOR_INTERSECTION,
	SELECTION_RECTANGLE_STYLE,
	SELECTION_RECTANGLE_WIDTH,
} from '../App.consts';
import type { Entity } from '../entities/Entity';
import { RectangleEntity } from '../entities/RectangleEntity';
import { pointDistance } from '../helpers/distance-between-points';
import { expandSelectionWithGroups } from '../helpers/entity-groups';
import { findEntitiesWithinDistance } from '../helpers/find-closest-entity';
import { findGripAt, removePolylineVertex } from '../helpers/grips';
import { pickRadius } from '../helpers/pick-radius';
import {
	getActiveLayerId,
	getEntities,
	getPickableEntities,
	getLayers,
	getSelectedEntities,
	getSelectedEntityIds,
	isEntitySelected,
	setEntities,
	setGhostHelperEntities,
	setSelectedEntityIds,
} from '../state';
import { startGripEdit } from './grip-edit-tool';
import type { SelectContext } from './select-tool';
import type { MouseClickEvent } from './tool.types';

/** 선택 순환 — 같은 자리를 다시 클릭하면 겹친 후보를 차례로 돌린다 */
let lastPickPoint: Point | null = null;
let pickCycleIndex = 0;

function pickEntityAt(worldPoint: Point): Entity | null {
	const radius = pickRadius();
	const candidates = findEntitiesWithinDistance(worldPoint, getPickableEntities(), radius);
	if (!candidates.length) {
		lastPickPoint = null;
		return null;
	}
	const samePlace = !!lastPickPoint && pointDistance(lastPickPoint, worldPoint) < radius;
	pickCycleIndex = samePlace ? (pickCycleIndex + 1) % candidates.length : 0;
	lastPickPoint = worldPoint;
	return candidates[pickCycleIndex];
}

export function handleFirstSelectionPoint(
	context: SelectContext,
	event: MouseClickEvent
): SelectContext {
	// 선택된 객체의 그립이 먼저다 — 집으면 그립 편집으로 넘어간다
	const gripHit = findGripAt(getSelectedEntities(), event.worldMouseLocation, pickRadius());
	if (gripHit) {
		if (event.holdingCtrl) {
			// Ctrl+클릭 => 폴리선 정점 제거 (다기능 그립)
			const trimmed = removePolylineVertex(gripHit.entity, gripHit.grip);
			if (trimmed) {
				setEntities(
					getEntities().map((entity) => (entity.id === trimmed.id ? trimmed : entity)),
					true
				);
				return { ...context, startPoint: null };
			}
		} else {
			startGripEdit(gripHit.entity, gripHit.grip);
			return { ...context, startPoint: null };
		}
	}

	const pickedEntity = pickEntityAt(event.worldMouseLocation);

	// Mouse is close to entity and is not dragging a rectangle
	if (pickedEntity) {
		// Select the entity close to the mouse
		const closestEntity = pickedEntity;
		if (!event.holdingCtrl && !event.holdingShift) {
			// 그룹으로 묶인 객체는 하나만 집어도 함께 선택된다 (GROUP)
			setSelectedEntityIds(expandSelectionWithGroups([closestEntity.id]));
		} else if (event.holdingCtrl) {
			// ctrl => toggle selection
			if (isEntitySelected(closestEntity)) {
				// Remove the entity from the selection
				setSelectedEntityIds(getSelectedEntityIds().filter((id) => id !== closestEntity.id));
			} else {
				// Add the entity to the selection
				setSelectedEntityIds(
					expandSelectionWithGroups([...getSelectedEntityIds(), closestEntity.id])
				);
			}
		} else {
			// shift => add to selection
			setSelectedEntityIds(
				expandSelectionWithGroups([...getSelectedEntityIds(), closestEntity.id])
			);
		}
		return {
			...context,
			startPoint: null,
		};
	}

	// No elements are close to the mouse and no selection dragging is in progress
	// Start a new selection rectangle drag
	return {
		...context,
		startPoint: event.worldMouseLocation,
	};
}

export function selectEntitiesInsideRectangle(
	startPoint: Point,
	endPoint: Point,
	holdingCtrl: boolean
	// holdingShift: boolean, // TODO implement add to selection using shift
): void {
	// Finish the selection
	const activeSelectionRectangle = new RectangleEntity(getActiveLayerId(), startPoint, endPoint);
	const intersectionSelection = getIsIntersectionSelection(activeSelectionRectangle, startPoint);
	const newSelectedEntityIds: string[] = compact(
		getEntities().map((entity): string | null => {
			const layer = getLayers().find((layer) => layer.id === entity.layerId);
			if (!layer) {
				toast.error(`Failed to find layer for entity: ${entity?.id}`);
				console.error('Failed to find layer for entity', entity);
				return null;
			}
			if (intersectionSelection) {
				// Select all entities that are inside the selection rectangle or intersect with the selection rectangle
				if (
					entity.intersectsWithBox(activeSelectionRectangle.getBoundingBox() as Box) ||
					entity.isContainedInBox(activeSelectionRectangle.getBoundingBox() as Box)
				) {
					if (holdingCtrl) {
						if (isEntitySelected(entity)) {
							return null;
						}
						if (!layer.isLocked) {
							return entity.id;
						}
					}
					if (!layer.isLocked) {
						return entity.id;
					}
				}
			} else {
				// Select only entities that are completely inside the selection rectangle
				if (entity.isContainedInBox(activeSelectionRectangle.getBoundingBox() as Box)) {
					if (holdingCtrl) {
						if (isEntitySelected(entity)) {
							return null;
						}
						if (!layer.isLocked) {
							return entity.id;
						}
					}
					if (!layer.isLocked) {
						return entity.id;
					}
				}
			}
			return null;
		})
	);
	setSelectedEntityIds(expandSelectionWithGroups(newSelectedEntityIds));
}

export function drawTempSelectionRectangle(startPoint: Point, endPoint: Point) {
	const activeSelectionRectangle = new RectangleEntity(getActiveLayerId(), startPoint, endPoint);
	const isIntersectionSelection: boolean = getIsIntersectionSelection(
		activeSelectionRectangle,
		startPoint
	);
	activeSelectionRectangle.lineColor = isIntersectionSelection
		? SELECTION_RECTANGLE_COLOR_INTERSECTION
		: SELECTION_RECTANGLE_COLOR_CONTAINS;
	activeSelectionRectangle.lineWidth = SELECTION_RECTANGLE_WIDTH;
	activeSelectionRectangle.lineDash = SELECTION_RECTANGLE_STYLE;
	setGhostHelperEntities([activeSelectionRectangle]);
}

/**
 * Selections to the left of the start point are intersection selections (green), and everything intersecting with the selection rectangle will be selected
 * Selections to the right of the start point are normal selections (blue), and only the entities fully inside the selection rectangle will be selected
 */
export function getIsIntersectionSelection(
	rectangleEntity: RectangleEntity,
	startPoint: Point
): boolean {
	if (!rectangleEntity.getShape() || !startPoint) {
		return false;
	}
	const selectionRectangleMinX = Math.min(
		...(rectangleEntity.getShape() as Polygon).vertices.map((v) => v.x)
	);
	return Math.abs(startPoint.x - selectionRectangleMinX) > EPSILON;
}