/**
 * 원(CIRCLE) — 337 설계 1-1 · 오토캐드 차례.
 * 「원에 대한 중심점 지정 또는 [3점(3P)/2점(2P)]:」 → 「원의 반지름 지정 또는 [지름(D)] <r>:」 ·
 * D → 「원의 지름 지정 <2r>:」 · 3P → 원 위 세 점 · 2P → 지름 두 끝점.
 * 반지름 기억(CIRCLERAD · 처음 없음 → <> 안 그림 · 빈 Enter 아무 일 없음) · 누른 점 · 3P · 2P 반지름도 기억. 하나 그리면 끝.
 */
import { Point } from '@flatten-js/core';
import { assign, createMachine } from 'xstate';
import { type PromptSpec, recall, remember } from '../commands/prompt';
import { CircleEntity } from '../entities/CircleEntity';
import { getPointFromEvent } from '../helpers/get-point-from-event.ts';
import { arcThroughThreePoints } from '../helpers/geometry/shape-points';
import {
	addEntities,
	getActiveLayerId,
	setAngleGuideOriginPoint,
	setGhostHelperEntities,
	setSelectedEntityIds,
	setShouldDrawHelpers,
} from '../state';
import { Tool } from '../tools';
import { END, firstPointEvents, option, pointEvents } from './draw/draw-steps';
import { styled } from './factories/entity-factory';
import {
	type DrawEvent,
	END_STATE,
	type NumberInputEvent,
	type PointInputEvent,
	type StateEvent,
	type ToolContext,
} from './tool.types';

export interface CircleContext extends ToolContext {
	centerPoint: Point | null;
	/** 3P · 2P 에서 이미 찍은 점 */
	points: Point[];
	threePoints: boolean;
}

export enum CircleState {
	INIT = 'INIT',
	WAITING_FOR_CENTER_POINT = 'WAITING_FOR_CENTER_POINT',
	WAITING_FOR_RADIUS = 'WAITING_FOR_RADIUS',
	WAITING_FOR_DIAMETER = 'WAITING_FOR_DIAMETER',
	THREE_POINTS = 'THREE_POINTS',
	TWO_POINTS = 'TWO_POINTS',
}

const RADIUS_KEY = 'CIRCLERAD';
/** 지름 기본 = 2 × 기억 반지름 — 이 열쇠엔 쓰지 않음 */
const DIAMETER_KEY = 'CIRCLERAD.D';

const CENTER_PROMPT: PromptSpec = {
	text: '원에 대한 중심점 지정',
	options: [option('3P', '3P', '3점'), option('2P', '2P', '2점')],
	absent: [option('TTR', 'T', 'Ttr - 접선 접선 반지름')],
};
const RADIUS_PROMPT: PromptSpec = {
	text: '원의 반지름 지정',
	options: [option('DIAMETER', 'D', '지름')],
	default: { kind: 'value', remember: RADIUS_KEY, initial: null },
	number: { positive: true },
};
const diameterPrompt = (): PromptSpec => {
	const radius = recall<number>(RADIUS_KEY);
	return {
		text: '원의 지름 지정',
		default: { kind: 'value', remember: DIAMETER_KEY, initial: radius ? radius * 2 : null },
		number: { positive: true },
	};
};
const ORDINAL = ['첫 번째', '두 번째', '세 번째'];
const threePrompt = (context: Partial<CircleContext>): PromptSpec => ({
	text: `원 위의 ${ORDINAL[context.points?.length ?? 0]} 점 지정`,
});
const twoPrompt = (context: Partial<CircleContext>): PromptSpec => ({
	text: `원 지름의 ${ORDINAL[context.points?.length ?? 0]} 끝점 지정`,
});

function addCircle(center: Point, radius: number) {
	setGhostHelperEntities([]);
	if (!(radius > 0)) return;
	addEntities([styled(new CircleEntity(getActiveLayerId(), center, radius))], true);
	remember(RADIUS_KEY, radius);
}

/** 3P · 2P — 찍은 점들 + 마지막 점으로 원(점 모자람 · 한 줄 = null) */
function circleThrough(context: CircleContext, last: Point) {
	const [a, b] = context.points;
	if (!context.threePoints) {
		return a
			? {
					center: new Point((a.x + last.x) / 2, (a.y + last.y) / 2),
					radius: a.distanceTo(last)[0] / 2,
				}
			: null;
	}
	const arc = b ? arcThroughThreePoints(a, b, last) : null;
	return arc ? { center: arc.center, radius: arc.radius } : null;
}

/** 점 사건 → 점(앞 점 기준 · 첫 점이면 기준 없음) */
const pointAt = (base: Point | null, event: StateEvent) =>
	getPointFromEvent(base, event as PointInputEvent);
const lastOf = (points: Point[]) => points[points.length - 1] ?? null;

/** 3P 는 세 점 · 2P 는 두 점째에 원 */
const pointsEvents = (count: number, self: CircleState) => {
	const enough = ({ context }: { context: CircleContext }) => context.points.length === count - 1;
	const done = { guard: enough, actions: 'drawThrough', target: END_STATE };
	const more = { actions: 'recordPoint', target: self };
	return {
		DRAW: { actions: 'previewThrough' },
		MOUSE_CLICK: [done, more],
		ABSOLUTE_POINT_INPUT: [done, more],
		RELATIVE_POINT_INPUT: [done, more],
		NUMBER_INPUT: [done, more],
		ESC: { target: END_STATE },
	};
};

export const circleToolStateMachine = createMachine(
	{
		types: {} as { context: CircleContext; events: StateEvent },
		context: { centerPoint: null, points: [], threePoints: false, type: Tool.CIRCLE },
		initial: CircleState.INIT,
		states: {
			[CircleState.INIT]: {
				always: { actions: 'init', target: CircleState.WAITING_FOR_CENTER_POINT },
			},
			[CircleState.WAITING_FOR_CENTER_POINT]: {
				meta: { kind: 'point', prompt: CENTER_PROMPT },
				on: {
					...firstPointEvents('recordCenter', CircleState.WAITING_FOR_RADIUS),
					'OPTION.3P': { actions: 'pickThree', target: CircleState.THREE_POINTS },
					'OPTION.2P': { actions: 'pickTwo', target: CircleState.TWO_POINTS },
					ESC: { target: END_STATE },
				},
			},
			[CircleState.WAITING_FOR_RADIUS]: {
				meta: { kind: 'point', prompt: RADIUS_PROMPT },
				on: {
					DRAW: { actions: 'previewRadius' },
					...pointEvents('drawByRadius', END_STATE),
					'OPTION.DIAMETER': { target: CircleState.WAITING_FOR_DIAMETER },
					ESC: { target: END_STATE },
				},
			},
			[CircleState.WAITING_FOR_DIAMETER]: {
				meta: { kind: 'point', prompt: diameterPrompt },
				on: {
					DRAW: { actions: 'previewDiameter' },
					...pointEvents('drawByDiameter', END_STATE),
					ESC: { target: END_STATE },
				},
			},
			[CircleState.THREE_POINTS]: {
				meta: { kind: 'point', prompt: threePrompt },
				on: pointsEvents(3, CircleState.THREE_POINTS),
			},
			[CircleState.TWO_POINTS]: {
				meta: { kind: 'point', prompt: twoPrompt },
				on: pointsEvents(2, CircleState.TWO_POINTS),
			},
			...END,
		},
	},
	{
		actions: {
			init: assign(() => {
				setShouldDrawHelpers(true);
				setGhostHelperEntities([]);
				setSelectedEntityIds([]);
				setAngleGuideOriginPoint(null);
				return { centerPoint: null, points: [], threePoints: false };
			}),
			pickThree: assign({ threePoints: true }),
			pickTwo: assign({ threePoints: false }),
			recordCenter: assign(({ event }) => {
				const centerPoint = pointAt(null, event);
				setAngleGuideOriginPoint(centerPoint);
				return { centerPoint };
			}),
			previewRadius: ({ context, event }) => {
				const center = context.centerPoint as Point;
				const radius = center.distanceTo(getPointFromEvent(center, event as DrawEvent))[0];
				setGhostHelperEntities([styled(new CircleEntity(getActiveLayerId(), center, radius))]);
			},
			previewDiameter: ({ context, event }) => {
				const center = context.centerPoint as Point;
				const radius = center.distanceTo(getPointFromEvent(center, event as DrawEvent))[0] / 2;
				setGhostHelperEntities([styled(new CircleEntity(getActiveLayerId(), center, radius))]);
			},
			drawByRadius: ({ context, event }) => {
				const center = context.centerPoint as Point;
				const radius =
					event.type === 'NUMBER_INPUT'
						? (event as NumberInputEvent).value
						: center.distanceTo(pointAt(center, event))[0];
				addCircle(center, radius);
			},
			drawByDiameter: ({ context, event }) => {
				const center = context.centerPoint as Point;
				const diameter =
					event.type === 'NUMBER_INPUT'
						? (event as NumberInputEvent).value
						: center.distanceTo(pointAt(center, event))[0];
				addCircle(center, diameter / 2);
			},
			recordPoint: assign(({ context, event }) => {
				const point = pointAt(lastOf(context.points), event);
				setAngleGuideOriginPoint(point);
				return { points: [...context.points, point] };
			}),
			previewThrough: ({ context, event }) => {
				const last = lastOf(context.points);
				if (!last) return;
				const circle = circleThrough(context, getPointFromEvent(last, event as DrawEvent));
				setGhostHelperEntities(
					circle ? [styled(new CircleEntity(getActiveLayerId(), circle.center, circle.radius))] : []
				);
			},
			drawThrough: ({ context, event }) => {
				const circle = circleThrough(context, pointAt(lastOf(context.points), event));
				if (circle) addCircle(circle.center, circle.radius);
				else setGhostHelperEntities([]);
			},
		},
	}
);