// src/lib/pathProcessor.ts

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

/** Result structure used by map.ts to bind SVG path strings */
export interface PathResult {
	mainPathD: string; // SVG String
	backwashPathD: string; // SVG String
	pureCleanPathD: string; // SVG String
	mopPathD: string; // SVG String
	// Arrays for Canvas drawing (used by mapCreator)
	mainPath: PathPoint[][];
	backwashPath: PathPoint[][];
	pureCleanPath: PathPoint[][];
	mopPath: PathPoint[][];
}

interface PointConverter {
	(robotPoint: [number, number], params: any): PathPoint;
}

// --------------------
// Helpers
// --------------------

/** Builds SVG path string segment (M/L) */
function buildPathString(x: number, y: number, lastX: number, lastY: number, pathString: string, thresholdSq: number): [string, number, number] {
	if (lastX === -1 || pathString === "") {
		pathString += `M${x},${y}`;
	} else {
		const isJump = (x - lastX) ** 2 + (y - lastY) ** 2 > thresholdSq;
		pathString += isJump ? `M${x},${y}` : `L${x},${y}`;
	}
	return [pathString, x, y];
}

/** Appends point to segment array (for Canvas) */
function appendPoint(pathSegments: PathPoint[][], currentPoint: PathPoint, lastPoint: PathPoint | null): PathPoint {
	if (!lastPoint || !pathSegments.length || pathSegments[pathSegments.length - 1].length === 0) {
		pathSegments.push([]);
	}
	pathSegments[pathSegments.length - 1].push(currentPoint);
	return currentPoint;
}

// --------------------
// Main Processor
// --------------------

export function processPaths(points: [number, number][], flags: number[], converter: PointConverter, scale: number, params: any): PathResult {
	// SVG Accumulators
	let mainPathD = "",
		backwashPathD = "",
		pureCleanPathD = "",
		mopPathD = "";

	// Canvas Accumulators
	const mainPath: PathPoint[][] = [[]];
	const backwashPath: PathPoint[][] = [[]];
	const pureCleanPath: PathPoint[][] = [[]];
	const mopPath: PathPoint[][] = [[]];

	// Pen Lift States (SVG)
	let lastX_main = -1,
		lastY_main = -1;
	let lastX_backwash = -1,
		lastY_backwash = -1;
	let lastX_pure = -1,
		lastY_pure = -1;
	let lastX_mop = -1,
		lastY_mop = -1;

	// Pen Lift States (Canvas)
	let lp_main: PathPoint | null = null;
	let lp_backwash: PathPoint | null = null;
	let lp_pure: PathPoint | null = null;
	let lp_mop: PathPoint | null = null;

	const thresholdSq = 10 * scale * (10 * scale);
	const len = Math.min(points.length, flags.length);

	for (let i = 0; i < len; i++) {
		const robotPoint: [number, number] = points[i];
		const pt = converter(robotPoint, params); // Scaled Pixel Point
		const x = pt.x;
		const y = pt.y;
		const flag = flags[i];

		// Bit Logic
		const isBackwash = ((flag >> 1) & 1) === 1 || ((flag >> 3) & 1) === 1;
		const isPureClean = ((flag >> 2) & 1) === 1;
		const isMop = (flag & 1) === 1;

		// Reset Pen Lifts for Exclusive Paths
		const prevX_main = lastX_main;
		const prevLP_main = lp_main;
		const prevX_backwash = lastX_backwash;
		const prevLP_backwash = lp_backwash;
		const prevX_pure = lastX_pure;
		const prevLP_pure = lp_pure;

		lastX_main = -1;
		lp_main = null;
		lastX_backwash = -1;
		lp_backwash = null;
		lastX_pure = -1;
		lp_pure = null;

		// --- 1. EXCLUSIVE PATHS ---
		if (isBackwash) {
			[backwashPathD, lastX_backwash, lastY_backwash] = buildPathString(x, y, prevX_backwash, lastY_backwash, backwashPathD, thresholdSq);
			lp_backwash = appendPoint(backwashPath, pt, prevLP_backwash);
		} else if (isPureClean) {
			[pureCleanPathD, lastX_pure, lastY_pure] = buildPathString(x, y, prevX_pure, lastY_pure, pureCleanPathD, thresholdSq);
			lp_pure = appendPoint(pureCleanPath, pt, prevLP_pure);
		} else {
			[mainPathD, lastX_main, lastY_main] = buildPathString(x, y, prevX_main, lastY_main, mainPathD, thresholdSq);
			lp_main = appendPoint(mainPath, pt, prevLP_main);
		}

		// --- 2. OVERLAY PATH (Bit 0) ---
		if (isMop) {
			[mopPathD, lastX_mop, lastY_mop] = buildPathString(x, y, lastX_mop, lastY_mop, mopPathD, thresholdSq);
			lp_mop = appendPoint(mopPath, pt, lp_mop);
		} else {
			lastX_mop = -1;
			lp_mop = null;
		}
	}

	const filterEmpty = (arr: PathPoint[][]) => arr.filter((sub) => sub.length > 0);

	return {
		mainPathD,
		backwashPathD,
		pureCleanPathD,
		mopPathD,
		mainPath: filterEmpty(mainPath),
		backwashPath: filterEmpty(backwashPath),
		pureCleanPath: filterEmpty(pureCleanPath),
		mopPath: filterEmpty(mopPath),
	};
}