/**
 * 한 번 스냅 — 점 단계에서 END · MID · CEN · QUA · INT · PER · NEA · NOD · NON 을 치면 다음 한 점만 그 스냅(오토캐드).
 * 이름 = 앞 세 글자 ~ 영문 전체(END · ENDP · ENDPOINT) · 우리에 없는 스냅(TAN · EXT …)은 안내.
 * F3(객체 스냅) 꺼져 있어도 먹음. 커서 둘레에 맞는 점이 없으면 클릭을 버리고 기다림 · Esc 로 풂.
 */
import type { Point } from '@flatten-js/core';
import { SNAP_POINT_DISTANCE } from '../App.consts.ts';
import { SnapPointType } from '../App.types.ts';
import { findClosestEntity } from '../helpers/find-closest-entity.ts';
import { getIntersectionPoints } from '../helpers/get-intersection-points.ts';
import { queryEntitiesNearPoint } from '../helpers/spatial-index.ts';
import { getLayerById, getScreenCanvasDrawController } from '../state.ts';

const SNAP_LABELS = {
	END: '끝점',
	MID: '중간점',
	CEN: '중심',
	QUA: '사분점',
	INT: '교차점',
	PER: '수직',
	NEA: '근처점',
	NOD: '노드',
	NON: '스냅 없음',
} as const;
type SnapName = keyof typeof SNAP_LABELS;

const SNAP_TYPES: Partial<Record<SnapName, SnapPointType>> = {
	END: SnapPointType.LineEndPoint,
	MID: SnapPointType.LineMidPoint,
	CEN: SnapPointType.CircleCenter,
	QUA: SnapPointType.CircleCardinal,
	NOD: SnapPointType.Point,
};

/** 오토캐드 영문 전체 이름 — 세 글자 줄임부터 받음 */
const FULL_NAMES: Record<SnapName, string> = {
	END: 'ENDPOINT',
	MID: 'MIDPOINT',
	CEN: 'CENTER',
	QUA: 'QUADRANT',
	INT: 'INTERSECTION',
	PER: 'PERPENDICULAR',
	NEA: 'NEAREST',
	NOD: 'NODE',
	NON: 'NONE',
};
/** 오토캐드엔 있고 우리엔 없는 스냅 */
const ABSENT_NAMES: Record<string, string> = {
	TAN: 'TANGENT',
	EXT: 'EXTENSION',
	INS: 'INSERTION',
	APP: 'APPINT',
	PAR: 'PARALLEL',
	GCE: 'GCEN',
};

const byName = <K extends string>(table: Record<K, string>, text: string): K | null => {
	const typed = text.trim().toUpperCase().replace(/^_/, '');
	if (typed.length < 3) return null;
	const hit = (Object.keys(table) as K[]).find(
		(short) => typed.startsWith(short) && table[short].startsWith(typed)
	);
	return hit ?? null;
};
/** 친 글 → 스냅 이름(END · ENDP · ENDPOINT → END) · 아니면 null */
export const snapName = (text: string): SnapName | null => byName(FULL_NAMES, text);
/** 우리에 없는 오토캐드 스냅 이름(세 글자 꼴) · 아니면 null */
export const absentSnapName = (text: string): string | null => byName(ABSENT_NAMES, text);

let override: SnapName | null = null;

export const getSnapOverride = (): SnapName | null => override;
export const setSnapOverride = (name: SnapName | null) => {
	override = name;
};
export const isSnapName = (text: string): text is SnapName => snapName(text) === text;

/** 커서 옆 안내 줄 */
export const snapOverrideHint = (): string | null =>
	override ? `${SNAP_LABELS[override]}(${override}) 한 번 — 점 지정` : null;

const closest = (points: Point[], mouse: Point, radius: number): Point | null => {
	let best: Point | null = null;
	let bestDistance = radius;
	for (const point of points) {
		const distance = Math.hypot(point.x - mouse.x, point.y - mouse.y);
		if (distance <= bestDistance) {
			best = point;
			bestDistance = distance;
		}
	}
	return best;
};

/** 한 번 스냅이 고른 점 · 맞는 점 없으면 null. base = 앞 점(PER 기준) */
export function snapOverridePoint(mouse: Point, base: Point | null): Point | null {
	if (override === 'NON') return mouse;
	// ponytail: 일반 스냅(15px)의 두 배 둘레 — 오토캐드 조준 상자 크기 설정이 필요하면 설정 모달로
	const radius = (SNAP_POINT_DISTANCE * 2) / getScreenCanvasDrawController().getScreenScale();
	const entities = queryEntitiesNearPoint(mouse.x, mouse.y, radius).filter(
		(entity) => !getLayerById(entity.layerId)?.isLocked
	);
	const type = override ? SNAP_TYPES[override] : undefined;
	if (type) {
		const points = entities.flatMap((entity) =>
			entity
				.getSnapPoints()
				.filter((snap) => snap.type === type)
				.map((snap) => snap.point)
		);
		return closest(points, mouse, radius);
	}
	if (override === 'INT') return closest(getIntersectionPoints(entities), mouse, radius);
	const near = findClosestEntity(mouse, entities);
	if (!near.entity || near.distance > radius) return null;
	if (override === 'NEA') return near.segment.start;
	// PER — 앞 점에서 커서 아래 객체로 내린 발(선분이면 수선의 발)
	if (!base) return null;
	return near.entity.distanceTo(base)?.[1].start ?? null;
}