import type { ElementBounds } from "@/preview/element-bounds";

export interface FreeformPathPoint {
	id: string;
	x: number;
	y: number;
	inX: number;
	inY: number;
	outX: number;
	outY: number;
}

function isFreeformPathPoint(value: unknown): value is FreeformPathPoint {
	if (!value || typeof value !== "object") {
		return false;
	}

	return (
		"id" in value &&
		typeof value.id === "string" &&
		"x" in value &&
		typeof value.x === "number" &&
		"y" in value &&
		typeof value.y === "number" &&
		"inX" in value &&
		typeof value.inX === "number" &&
		"inY" in value &&
		typeof value.inY === "number" &&
		"outX" in value &&
		typeof value.outX === "number" &&
		"outY" in value &&
		typeof value.outY === "number"
	);
}

export function parseFreeformPath({
	path,
}: {
	path: string;
}): FreeformPathPoint[] {
	if (!path) {
		return [];
	}

	try {
		const parsed = JSON.parse(path);
		return Array.isArray(parsed) ? parsed.filter(isFreeformPathPoint) : [];
	} catch {
		return [];
	}
}

export function serializeFreeformPath({
	points,
}: {
	points: FreeformPathPoint[];
}): string {
	return JSON.stringify(points);
}

export function removeFreeformPathPoints({
	points,
	pointIds,
}: {
	points: FreeformPathPoint[];
	pointIds: string[];
}): FreeformPathPoint[] {
	if (pointIds.length === 0) {
		return points;
	}
	const pointIdsToRemove = new Set(pointIds);
	return points.filter((point) => !pointIdsToRemove.has(point.id));
}

export function getFreeformPathClosedStateAfterPointRemoval({
	wasClosed,
	remainingPointCount,
}: {
	wasClosed: boolean;
	remainingPointCount: number;
}): boolean {
	return wasClosed && remainingPointCount >= 3;
}

function rotatePoint({
	x,
	y,
	rotationDegrees,
}: {
	x: number;
	y: number;
	rotationDegrees: number;
}): { x: number; y: number } {
	const angleRad = (rotationDegrees * Math.PI) / 180;
	const cos = Math.cos(angleRad);
	const sin = Math.sin(angleRad);
	return {
		x: x * cos - y * sin,
		y: x * sin + y * cos,
	};
}

export function getFreeformCenterCanvasPoint({
	centerX,
	centerY,
	bounds,
}: {
	centerX: number;
	centerY: number;
	bounds: ElementBounds;
}): { x: number; y: number } {
	return {
		x: bounds.cx + centerX * bounds.width,
		y: bounds.cy + centerY * bounds.height,
	};
}

export function freeformLocalPointToCanvas({
	point,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
}: {
	point: { x: number; y: number };
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
}): { x: number; y: number } {
	const center = getFreeformCenterCanvasPoint({ centerX, centerY, bounds });
	const scaledLocal = {
		x: point.x * bounds.width * scale,
		y: point.y * bounds.height * scale,
	};
	const rotated = rotatePoint({
		x: scaledLocal.x,
		y: scaledLocal.y,
		rotationDegrees: rotation,
	});

	return {
		x: center.x + rotated.x,
		y: center.y + rotated.y,
	};
}

export function freeformCanvasPointToLocal({
	point,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
}: {
	point: { x: number; y: number };
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
}): { x: number; y: number } {
	const center = getFreeformCenterCanvasPoint({ centerX, centerY, bounds });
	const translated = {
		x: point.x - center.x,
		y: point.y - center.y,
	};
	const rotated = rotatePoint({
		x: translated.x,
		y: translated.y,
		rotationDegrees: -rotation,
	});

	return {
		x: bounds.width === 0 ? 0 : rotated.x / (bounds.width * scale),
		y: bounds.height === 0 ? 0 : rotated.y / (bounds.height * scale),
	};
}

export function getFreeformCanvasGeometry({
	points,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
}: {
	points: FreeformPathPoint[];
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
}) {
	const anchors = points.map((point) => ({
		id: point.id,
		anchor: freeformLocalPointToCanvas({
			point: { x: point.x, y: point.y },
			centerX,
			centerY,
			rotation,
			scale,
			bounds,
		}),
		inHandle: freeformLocalPointToCanvas({
			point: { x: point.x + point.inX, y: point.y + point.inY },
			centerX,
			centerY,
			rotation,
			scale,
			bounds,
		}),
		outHandle: freeformLocalPointToCanvas({
			point: { x: point.x + point.outX, y: point.y + point.outY },
			centerX,
			centerY,
			rotation,
			scale,
			bounds,
		}),
	}));

	const geometryPoints = anchors.flatMap((point) => [
		point.anchor,
		point.inHandle,
		point.outHandle,
	]);
	if (geometryPoints.length === 0) {
		return {
			anchors,
			bounds: null,
		};
	}

	const geometryBounds = getCanvasPointBounds({
		points: geometryPoints,
	});

	return {
		anchors,
		bounds: geometryBounds,
	};
}

export interface CanvasPoint {
	x: number;
	y: number;
}

function getCanvasPointBounds({ points }: { points: CanvasPoint[] }): {
	minX: number;
	maxX: number;
	minY: number;
	maxY: number;
	width: number;
	height: number;
	centerX: number;
	centerY: number;
} | null {
	if (points.length === 0) {
		return null;
	}

	const [firstPoint, ...restPoints] = points;
	let minX = firstPoint.x;
	let maxX = firstPoint.x;
	let minY = firstPoint.y;
	let maxY = firstPoint.y;

	for (const point of restPoints) {
		minX = Math.min(minX, point.x);
		maxX = Math.max(maxX, point.x);
		minY = Math.min(minY, point.y);
		maxY = Math.max(maxY, point.y);
	}

	return {
		minX,
		maxX,
		minY,
		maxY,
		width: Math.max(1, maxX - minX),
		height: Math.max(1, maxY - minY),
		centerX: (minX + maxX) / 2,
		centerY: (minY + maxY) / 2,
	};
}

export interface FreeformCanvasSegment {
	index: number;
	startPointId: string;
	endPointId: string;
	start: CanvasPoint;
	startOut: CanvasPoint;
	endIn: CanvasPoint;
	end: CanvasPoint;
	pathData: string;
}

function clampUnit(value: number): number {
	return Math.min(1, Math.max(0, value));
}

function getDistanceSquared({
	a,
	b,
}: {
	a: CanvasPoint;
	b: CanvasPoint;
}): number {
	const dx = a.x - b.x;
	const dy = a.y - b.y;
	return dx * dx + dy * dy;
}

function lerpPoint({
	a,
	b,
	t,
}: {
	a: CanvasPoint;
	b: CanvasPoint;
	t: number;
}): CanvasPoint {
	return {
		x: a.x + (b.x - a.x) * t,
		y: a.y + (b.y - a.y) * t,
	};
}

function evaluateCubicBezier({
	p0,
	p1,
	p2,
	p3,
	t,
}: {
	p0: CanvasPoint;
	p1: CanvasPoint;
	p2: CanvasPoint;
	p3: CanvasPoint;
	t: number;
}): CanvasPoint {
	const oneMinusT = 1 - t;
	return {
		x:
			oneMinusT ** 3 * p0.x +
			3 * oneMinusT ** 2 * t * p1.x +
			3 * oneMinusT * t ** 2 * p2.x +
			t ** 3 * p3.x,
		y:
			oneMinusT ** 3 * p0.y +
			3 * oneMinusT ** 2 * t * p1.y +
			3 * oneMinusT * t ** 2 * p2.y +
			t ** 3 * p3.y,
	};
}

function getFreeformSegmentIndices({
	points,
	segmentIndex,
	closed,
}: {
	points: FreeformPathPoint[];
	segmentIndex: number;
	closed: boolean;
}): { startIndex: number; endIndex: number } | null {
	const segmentCount = getFreeformSegmentCount({ points, closed });
	if (segmentIndex < 0 || segmentIndex >= segmentCount) {
		return null;
	}

	return {
		startIndex: segmentIndex,
		endIndex: (segmentIndex + 1) % points.length,
	};
}

export function getFreeformSegmentCount({
	points,
	closed,
}: {
	points: FreeformPathPoint[];
	closed: boolean;
}): number {
	if (points.length < 2) {
		return 0;
	}
	return closed ? points.length : points.length - 1;
}

export function getFreeformCanvasSegments({
	points,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
	closed,
}: {
	points: FreeformPathPoint[];
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
	closed: boolean;
}): FreeformCanvasSegment[] {
	const geometry = getFreeformCanvasGeometry({
		points,
		centerX,
		centerY,
		rotation,
		scale,
		bounds,
	});
	const segmentCount = getFreeformSegmentCount({ points, closed });

	return Array.from({ length: segmentCount }, (_, segmentIndex) => {
		const start = geometry.anchors[segmentIndex];
		const end = geometry.anchors[(segmentIndex + 1) % geometry.anchors.length];
		return {
			index: segmentIndex,
			startPointId: start.id,
			endPointId: end.id,
			start: start.anchor,
			startOut: start.outHandle,
			endIn: end.inHandle,
			end: end.anchor,
			pathData: `M ${start.anchor.x},${start.anchor.y} C ${start.outHandle.x},${start.outHandle.y} ${end.inHandle.x},${end.inHandle.y} ${end.anchor.x},${end.anchor.y}`,
		};
	});
}

export function findClosestPointOnFreeformSegment({
	points,
	segmentIndex,
	canvasPoint,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
	closed,
}: {
	points: FreeformPathPoint[];
	segmentIndex: number;
	canvasPoint: CanvasPoint;
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
	closed: boolean;
}): { t: number; point: CanvasPoint } | null {
	const segment = getFreeformCanvasSegments({
		points,
		centerX,
		centerY,
		rotation,
		scale,
		bounds,
		closed,
	}).find((candidate) => candidate.index === segmentIndex);
	if (!segment) {
		return null;
	}

	const sampleCount = 24;
	let bestT = 0;
	let bestDistanceSquared = getDistanceSquared({
		a: canvasPoint,
		b: segment.start,
	});

	for (let step = 0; step <= sampleCount; step++) {
		const t = step / sampleCount;
		const point = evaluateCubicBezier({
			p0: segment.start,
			p1: segment.startOut,
			p2: segment.endIn,
			p3: segment.end,
			t,
		});
		const distanceSquared = getDistanceSquared({ a: canvasPoint, b: point });
		if (distanceSquared < bestDistanceSquared) {
			bestDistanceSquared = distanceSquared;
			bestT = t;
		}
	}

	let searchStep = 1 / sampleCount;
	for (let iteration = 0; iteration < 8; iteration++) {
		const candidates = [bestT - searchStep, bestT, bestT + searchStep]
			.map(clampUnit)
			.map((t) => ({
				t,
				point: evaluateCubicBezier({
					p0: segment.start,
					p1: segment.startOut,
					p2: segment.endIn,
					p3: segment.end,
					t,
				}),
			}));
		for (const candidate of candidates) {
			const distanceSquared = getDistanceSquared({
				a: canvasPoint,
				b: candidate.point,
			});
			if (distanceSquared < bestDistanceSquared) {
				bestDistanceSquared = distanceSquared;
				bestT = candidate.t;
			}
		}
		searchStep /= 2;
	}

	const clampedT = Math.min(0.999, Math.max(0.001, bestT));
	return {
		t: clampedT,
		point: evaluateCubicBezier({
			p0: segment.start,
			p1: segment.startOut,
			p2: segment.endIn,
			p3: segment.end,
			t: clampedT,
		}),
	};
}

export function insertPointIntoFreeformSegment({
	points,
	segmentIndex,
	pointId,
	t,
	closed,
}: {
	points: FreeformPathPoint[];
	segmentIndex: number;
	pointId: string;
	t: number;
	closed: boolean;
}): FreeformPathPoint[] {
	const indices = getFreeformSegmentIndices({
		points,
		segmentIndex,
		closed,
	});
	if (!indices) {
		return points;
	}

	const startPoint = points[indices.startIndex];
	const endPoint = points[indices.endIndex];
	const clampedT = Math.min(0.999, Math.max(0.001, t));
	const p0 = { x: startPoint.x, y: startPoint.y };
	const p1 = {
		x: startPoint.x + startPoint.outX,
		y: startPoint.y + startPoint.outY,
	};
	const p2 = {
		x: endPoint.x + endPoint.inX,
		y: endPoint.y + endPoint.inY,
	};
	const p3 = { x: endPoint.x, y: endPoint.y };
	const p01 = lerpPoint({ a: p0, b: p1, t: clampedT });
	const p12 = lerpPoint({ a: p1, b: p2, t: clampedT });
	const p23 = lerpPoint({ a: p2, b: p3, t: clampedT });
	const p012 = lerpPoint({ a: p01, b: p12, t: clampedT });
	const p123 = lerpPoint({ a: p12, b: p23, t: clampedT });
	const splitPoint = lerpPoint({ a: p012, b: p123, t: clampedT });

	const nextPoints = [...points];
	nextPoints[indices.startIndex] = {
		...startPoint,
		outX: p01.x - startPoint.x,
		outY: p01.y - startPoint.y,
	};
	nextPoints[indices.endIndex] = {
		...endPoint,
		inX: p23.x - endPoint.x,
		inY: p23.y - endPoint.y,
	};
	nextPoints.splice(indices.endIndex, 0, {
		id: pointId,
		x: splitPoint.x,
		y: splitPoint.y,
		inX: p012.x - splitPoint.x,
		inY: p012.y - splitPoint.y,
		outX: p123.x - splitPoint.x,
		outY: p123.y - splitPoint.y,
	});
	return nextPoints;
}

export function getFreeformLocalBounds({
	points,
	bounds,
}: {
	points: FreeformPathPoint[];
	bounds: ElementBounds;
}) {
	if (points.length === 0) {
		return null;
	}

	const values = points.flatMap((point) => [
		{ x: point.x * bounds.width, y: point.y * bounds.height },
		{
			x: (point.x + point.inX) * bounds.width,
			y: (point.y + point.inY) * bounds.height,
		},
		{
			x: (point.x + point.outX) * bounds.width,
			y: (point.y + point.outY) * bounds.height,
		},
	]);

	const localBounds = getCanvasPointBounds({
		points: values,
	});
	if (!localBounds) {
		return null;
	}

	return {
		width: localBounds.width,
		height: localBounds.height,
	};
}

export function recenterFreeformPath({
	points,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
}: {
	points: FreeformPathPoint[];
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
}) {
	if (points.length === 0) {
		return { centerX, centerY, points };
	}

	const geometry = getFreeformCanvasGeometry({
		points,
		centerX,
		centerY,
		rotation,
		scale,
		bounds,
	});
	if (!geometry.bounds) {
		return { centerX, centerY, points };
	}

	const nextCenterCanvas = {
		x: geometry.bounds.centerX,
		y: geometry.bounds.centerY,
	};
	const nextCenterLocal = {
		x: bounds.width === 0 ? 0 : (nextCenterCanvas.x - bounds.cx) / bounds.width,
		y:
			bounds.height === 0
				? 0
				: (nextCenterCanvas.y - bounds.cy) / bounds.height,
	};

	const nextPoints = geometry.anchors.map((point) => {
		const anchor = freeformCanvasPointToLocal({
			point: point.anchor,
			centerX: nextCenterLocal.x,
			centerY: nextCenterLocal.y,
			rotation,
			scale,
			bounds,
		});
		const inHandle = freeformCanvasPointToLocal({
			point: point.inHandle,
			centerX: nextCenterLocal.x,
			centerY: nextCenterLocal.y,
			rotation,
			scale,
			bounds,
		});
		const outHandle = freeformCanvasPointToLocal({
			point: point.outHandle,
			centerX: nextCenterLocal.x,
			centerY: nextCenterLocal.y,
			rotation,
			scale,
			bounds,
		});

		return {
			id: point.id,
			x: anchor.x,
			y: anchor.y,
			inX: inHandle.x - anchor.x,
			inY: inHandle.y - anchor.y,
			outX: outHandle.x - anchor.x,
			outY: outHandle.y - anchor.y,
		};
	});

	return {
		centerX: nextCenterLocal.x,
		centerY: nextCenterLocal.y,
		points: nextPoints,
	};
}

export function buildFreeformPath2D({
	points,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
	closed,
}: {
	points: FreeformPathPoint[];
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
	closed: boolean;
}): Path2D {
	const path = new Path2D();
	if (points.length === 0) {
		return path;
	}

	const geometry = getFreeformCanvasGeometry({
		points,
		centerX,
		centerY,
		rotation,
		scale,
		bounds,
	});
	const anchors = geometry.anchors;
	path.moveTo(anchors[0].anchor.x, anchors[0].anchor.y);

	for (let index = 1; index < anchors.length; index++) {
		const previous = anchors[index - 1];
		const current = anchors[index];
		path.bezierCurveTo(
			previous.outHandle.x,
			previous.outHandle.y,
			current.inHandle.x,
			current.inHandle.y,
			current.anchor.x,
			current.anchor.y,
		);
	}

	if (closed && anchors.length > 1) {
		const last = anchors[anchors.length - 1];
		const first = anchors[0];
		path.bezierCurveTo(
			last.outHandle.x,
			last.outHandle.y,
			first.inHandle.x,
			first.inHandle.y,
			first.anchor.x,
			first.anchor.y,
		);
		path.closePath();
	}

	return path;
}

export function buildFreeformSvgPath({
	points,
	centerX,
	centerY,
	rotation,
	scale,
	bounds,
	closed,
}: {
	points: FreeformPathPoint[];
	centerX: number;
	centerY: number;
	rotation: number;
	scale: number;
	bounds: ElementBounds;
	closed: boolean;
}): string {
	if (points.length === 0) {
		return "";
	}

	const geometry = getFreeformCanvasGeometry({
		points,
		centerX,
		centerY,
		rotation,
		scale,
		bounds,
	});
	const anchors = geometry.anchors;
	const segments = [`M ${anchors[0].anchor.x},${anchors[0].anchor.y}`];

	for (let index = 1; index < anchors.length; index++) {
		const previous = anchors[index - 1];
		const current = anchors[index];
		segments.push(
			`C ${previous.outHandle.x},${previous.outHandle.y} ${current.inHandle.x},${current.inHandle.y} ${current.anchor.x},${current.anchor.y}`,
		);
	}

	if (closed && anchors.length > 1) {
		const last = anchors[anchors.length - 1];
		const first = anchors[0];
		segments.push(
			`C ${last.outHandle.x},${last.outHandle.y} ${first.inHandle.x},${first.inHandle.y} ${first.anchor.x},${first.anchor.y}`,
		);
		segments.push("Z");
	}

	return segments.join(" ");
}