"use client";

import { useEffect, useId, useMemo, useRef, useState } from "react";
import { MaximizeIcon, MinusIcon, PlusIcon, XIcon } from "lucide-react";
import { cn } from "@/lib/utils";
import type { PlanBlockData, PlanNodeStatus, PlanTree } from "@/src/core";
import { derivedNodeStatus, derivePlanStatuses } from "@/src/core";

/**
 * PLAN BLOCKS — the plan lives in the chat (wave 4): persisted
 * `data-plan-block` parts render as DAG blocks in the transcript flow, and
 * the right sidebar is retired.
 *
 * - kind "full": the whole DAG, BORDERLESS — no wrapping chrome, the SVG
 *   scales to the full column width (viewBox = layout extent, so the
 *   leftmost/rightmost nodes hug the edges), natural height, no cap.
 * - kind "neighborhood": the fragment in its own small container, labeled
 *   as a FRAGMENT (clearly not the whole plan), the current node glowing.
 * - Clicking either opens the full plan in a full-screen popup overlay —
 *   the LIVE plan: the latest tree from the transcript with statuses
 *   derived at click time (contracts/plan.ts derivePlanStatuses). Blocks
 *   are frozen snapshots rendered exactly as carried (never re-derived);
 *   the popup is the live view (user decision, 2026-09).
 *
 * Hand-built SVG everywhere (user decision): a deterministic layered
 * layout fills exactly and stays SSR-testable — no force simulation, no
 * coupling to the graph stream's sigma internals. Pan/zoom in the popup
 * is harvested from the retired tree panel's graph (fit-floor semantics:
 * fully zoomed out IS the fit; panning locks at the floor).
 */

// ─── Layout constants + pure helpers (exported for tests) ────────────────────

export const NODE_W = 160;
export const NODE_H = 44;
export const GAP_X = 24;
export const GAP_Y = 48;

/** A node for layout purposes — the payload's shape and the tree's shape agree. */
export interface LayoutNode {
	id: string;
	title: string;
}

/** Topological order + longest-path depth (Kahn, authoring tie-break). */
export function topoFor(nodes: readonly LayoutNode[], edges: ReadonlyArray<{ from: string; to: string }>) {
	const index = new Map(nodes.map((n, i) => [n.id, i] as const));
	const indegree = new Map<string, number>(nodes.map((n) => [n.id, 0] as const));
	const dependents = new Map<string, string[]>();
	for (const e of edges) {
		if (!index.has(e.from) || !index.has(e.to)) continue; // defensive: dangling ids
		indegree.set(e.to, (indegree.get(e.to) ?? 0) + 1);
		const list = dependents.get(e.from);
		if (list) list.push(e.to);
		else dependents.set(e.from, [e.to]);
	}
	const ready = nodes.filter((n) => (indegree.get(n.id) ?? 0) === 0).map((n) => n.id);
	const order: LayoutNode[] = [];
	const depth = new Map<string, number>();
	const byId = new Map(nodes.map((n) => [n.id, n] as const));
	while (ready.length > 0) {
		ready.sort((a, b) => (index.get(a) ?? 0) - (index.get(b) ?? 0));
		const id = ready.shift()!;
		const node = byId.get(id);
		if (node) order.push(node);
		const d = depth.get(id) ?? 0;
		depth.set(id, d);
		for (const t of dependents.get(id) ?? []) {
			if ((depth.get(t) ?? -1) < d + 1) depth.set(t, d + 1);
			const left = (indegree.get(t) ?? 0) - 1;
			indegree.set(t, left);
			if (left === 0) ready.push(t);
		}
	}
	for (const n of nodes) {
		if (!depth.has(n.id)) {
			order.push(n);
			depth.set(n.id, 0);
		}
	}
	return { order, depth };
}

/** Layered positions: depth = row (top-down), authoring order within the
 *  row, each row centered on the widest one. */
export function blockLayout(nodes: readonly LayoutNode[], edges: ReadonlyArray<{ from: string; to: string }>) {
	const { order, depth } = topoFor(nodes, edges);
	const layers: LayoutNode[][] = [];
	for (const n of order) {
		const d = depth.get(n.id) ?? 0;
		if (!layers[d]) layers[d] = [];
		layers[d].push(n);
	}
	const rowWidth = (l: LayoutNode[]) => l.length * NODE_W + (l.length - 1) * GAP_X;
	let maxWidth = 0;
	for (const l of layers) maxWidth = Math.max(maxWidth, rowWidth(l));
	const x = new Map<string, number>();
	const y = new Map<string, number>();
	layers.forEach((l, d) => {
		const start = (maxWidth - rowWidth(l)) / 2;
		l.forEach((n, i) => {
			x.set(n.id, start + i * (NODE_W + GAP_X));
			y.set(n.id, d * (NODE_H + GAP_Y));
		});
	});
	const height = layers.length * NODE_H + Math.max(0, layers.length - 1) * GAP_Y;
	return { x, y, width: maxWidth, height };
}

/** Greedy word wrap to ≤ maxLines lines of ≤ maxChars; overflow ends in an
 *  ellipsis, a single oversized word is hard-clamped. Pure. */
export function wrapTitle(title: string, maxChars = 20, maxLines = 2): string[] {
	const words = title.trim().split(/\s+/).filter(Boolean);
	if (words.length === 0) return [""];
	const lines: string[] = [];
	for (const w of words) {
		const last = lines[lines.length - 1];
		const fits = last !== undefined && last.length + 1 + w.length <= maxChars;
		if (fits) {
			lines[lines.length - 1] = `${last} ${w}`;
		} else if (lines.length < maxLines) {
			lines.push(w.length > maxChars ? `${w.slice(0, maxChars - 1)}…` : w);
		} else {
			const lastLine = lines[lines.length - 1];
			if (lastLine !== undefined && !lastLine.endsWith("…")) {
				lines[lines.length - 1] =
					lastLine.length >= maxChars ? `${lastLine.slice(0, maxChars - 1)}…` : `${lastLine}…`;
			}
		}
	}
	return lines;
}

// ─── Status styling (the retired panel's color language, unchanged) ──────────

const BOX: Record<PlanNodeStatus, string> = {
	done: "fill-phase-teach/10 stroke-phase-teach/50",
	current: "fill-primary/10 stroke-primary",
	upcoming: "fill-card stroke-border",
};
const TEXT: Record<PlanNodeStatus, string> = {
	done: "fill-muted-foreground text-xs",
	current: "fill-foreground text-xs font-medium",
	upcoming: "fill-muted-foreground/80 text-xs",
};

/** The diagram itself: positioned nodes + bezier edges. Pure-ish render —
 *  every input is data, so SSR render tests pin the whole thing. */
function PlanDiagram({
	nodes,
	edges,
	statusOf,
	glowId,
	markerId,
}: {
	nodes: readonly LayoutNode[];
	edges: ReadonlyArray<{ from: string; to: string }>;
	statusOf: (id: string) => PlanNodeStatus;
	glowId?: string | null;
	markerId: string;
}) {
	const layout = useMemo(() => blockLayout(nodes, edges), [nodes, edges]);
	return (
		<svg
			viewBox={`0 0 ${Math.max(layout.width, 1)} ${Math.max(layout.height, 1)}`}
			className="block h-auto w-full"
			role="img"
			aria-label="Plan diagram"
		>
			<defs>
				<marker
					id={markerId}
					viewBox="0 0 8 8"
					refX="7"
					refY="4"
					markerWidth="6"
					markerHeight="6"
					orient="auto-start-reverse"
				>
					<path d="M0,1 L7,4 L0,7 z" className="fill-muted-foreground/50" />
				</marker>
			</defs>
			{edges.map((e) => {
				const x1 = (layout.x.get(e.from) ?? 0) + NODE_W / 2;
				const y1 = (layout.y.get(e.from) ?? 0) + NODE_H;
				const x2 = (layout.x.get(e.to) ?? 0) + NODE_W / 2;
				const y2 = layout.y.get(e.to) ?? 0;
				const mid = (y1 + y2) / 2;
				return (
					<path
						key={`${e.from}->${e.to}`}
						d={`M ${x1} ${y1} C ${x1} ${mid}, ${x2} ${mid}, ${x2} ${y2}`}
						className="fill-none stroke-muted-foreground/40"
						strokeWidth={1.5}
						markerEnd={`url(#${markerId})`}
					/>
				);
			})}
			{nodes.map((n) => {
				const status = statusOf(n.id);
				const glow = n.id === glowId;
				const lines = wrapTitle(n.title);
				return (
					<g
						key={n.id}
						transform={`translate(${layout.x.get(n.id) ?? 0}, ${layout.y.get(n.id) ?? 0})`}
						data-testid={`plan-node-${n.id}`}
						data-status={status}
					>
						{glow && (
							// The glow target: a soft primary halo breathing around the box.
							<rect
								x={-4}
								y={-4}
								width={NODE_W + 8}
								height={NODE_H + 8}
								rx={12}
								className="fill-none stroke-primary/70 animate-pulse"
								strokeWidth={1.5}
							/>
						)}
						<rect width={NODE_W} height={NODE_H} rx={10} className={BOX[status]} strokeWidth={1.5} />
						{lines.map((line, i) => (
							<text key={i} x={12} y={lines.length === 1 ? 27 : 18 + i * 13} className={TEXT[status]}>
								{line}
							</text>
						))}
					</g>
				);
			})}
		</svg>
	);
}

// ─── The transcript block ─────────────────────────────────────────────────────

/**
 * A persisted plan-block part, rendered as carried (snapshot statuses,
 * never re-derived). Full = borderless and column-filling; neighborhood =
 * a labeled fragment container with the current node glowing. Either
 * opens the live plan popup.
 */
export function PlanBlock({ data, onOpen }: { data: PlanBlockData; onOpen: () => void }) {
	const markerId = useId().replace(/[^a-zA-Z0-9-]/g, "");
	const statusMap = useMemo(() => new Map(data.nodes.map((n) => [n.id, n.status] as const)), [data]);
	const statusOf = (id: string): PlanNodeStatus => statusMap.get(id) ?? "upcoming";

	if (data.kind === "full") {
		return (
			<button
				type="button"
				data-testid="plan-block-full"
				onClick={onOpen}
				title="Open the full plan"
				className="block w-full text-left"
			>
				<PlanDiagram nodes={data.nodes} edges={data.edges} statusOf={statusOf} markerId={markerId} />
			</button>
		);
	}
	return (
		<div data-testid="plan-block-neighborhood" className="rounded-xl border bg-card/60 p-2.5">
			<div className="mb-1.5 px-0.5 text-[10px] font-medium uppercase tracking-wide text-muted-foreground">
				Plan fragment
			</div>
			<button type="button" onClick={onOpen} title="Open the full plan" className="block w-full text-left">
				<PlanDiagram
					nodes={data.nodes}
					edges={data.edges}
					statusOf={statusOf}
					glowId={data.current}
					markerId={markerId}
				/>
			</button>
		</div>
	);
}

// ─── The live plan popup ──────────────────────────────────────────────────────

/** Minimal structural message slice (same trick as phases.ts). */
export interface PopupMessage {
	parts: ReadonlyArray<{ type: string; state?: string; input?: unknown; output?: unknown }>;
}

/** The latest plan tree in the transcript (latest tool-plan_ output). */
function latestTree(messages: readonly PopupMessage[]): PlanTree | null {
	for (let m = messages.length - 1; m >= 0; m--) {
		const parts = messages[m]?.parts;
		if (!parts) continue;
		for (let p = parts.length - 1; p >= 0; p--) {
			const part = parts[p]!;
			if (!part.type.startsWith("tool-plan_") || part.state !== "output-available") continue;
			const output = part.output as { tree?: PlanTree } | undefined;
			if (output?.tree && Array.isArray(output.tree.nodes)) return output.tree;
		}
	}
	return null;
}

/** Zoom bounds: never below fit (fully zoomed out IS the fit), never above 2×. */
const ZOOM_MAX = 2;
const ZOOM_FLOOR = 0.15;
const FIT_PAD = 16;
const FIT_ZOOM_MAX = 1.5;

interface GraphView {
	zoom: number;
	x: number;
	y: number;
}

function fitZoomFor(box: { w: number; h: number }, viewport: { w: number; h: number }): number {
	if (!viewport.w || !viewport.h || box.w === 0) return 1;
	return Math.max(
		ZOOM_FLOOR,
		Math.min((viewport.w - FIT_PAD) / box.w, (viewport.h - FIT_PAD) / box.h, FIT_ZOOM_MAX),
	);
}

function fitGraphView(box: { w: number; h: number }, viewport: { w: number; h: number }, zoom: number): GraphView {
	return { zoom, x: (viewport.w - box.w * zoom) / 2, y: (viewport.h - box.h * zoom) / 2 };
}

function zoomedGraphView(
	view: GraphView,
	factor: number,
	floor: number,
	focus: { x: number; y: number },
	box: { w: number; h: number },
	viewport: { w: number; h: number },
): GraphView {
	const zoom = Math.min(Math.max(view.zoom * factor, floor), ZOOM_MAX);
	if (zoom === view.zoom) return view;
	if (zoom <= floor) return fitGraphView(box, viewport, floor);
	const k = zoom / view.zoom;
	return { zoom, x: focus.x - (focus.x - view.x) * k, y: focus.y - (focus.y - view.y) * k };
}

/**
 * The full plan, live: latest tree + statuses derived at click time. Esc,
 * backdrop click, or the X close it; drag pans, wheel zooms to the cursor,
 * the zoom floor is the fit (panning locks at it — nothing to move).
 */
export function PlanPopup({ messages, onClose }: { messages: readonly PopupMessage[]; onClose: () => void }) {
	const tree = useMemo(() => latestTree(messages), [messages]);
	const statuses = useMemo(
		() => (tree ? derivePlanStatuses(tree, messages as Parameters<typeof derivePlanStatuses>[1]) : null),
		[tree, messages],
	);
	const statusOf = (id: string): PlanNodeStatus => (statuses ? derivedNodeStatus(statuses, id) : "upcoming");

	// Esc closes.
	useEffect(() => {
		const onKey = (e: KeyboardEvent) => {
			if (e.key === "Escape") onClose();
		};
		window.addEventListener("keydown", onKey);
		return () => window.removeEventListener("keydown", onKey);
	}, [onClose]);

	// ── pan/zoom viewport (harvested semantics: fit floor = the default) ──
	const viewportRef = useRef<HTMLDivElement>(null);
	const [size, setSize] = useState({ w: 0, h: 0 });
	useEffect(() => {
		const el = viewportRef.current;
		if (!el || typeof ResizeObserver === "undefined") return;
		const ro = new ResizeObserver(() => setSize({ w: el.clientWidth, h: el.clientHeight }));
		ro.observe(el);
		return () => ro.disconnect();
	}, []);

	const layout = useMemo(() => (tree ? blockLayout(tree.nodes, tree.edges) : null), [tree]);
	const box = useMemo(() => (layout ? { w: layout.width, h: layout.height } : { w: 0, h: 0 }), [layout]);
	const fitZoom = useMemo(() => fitZoomFor(box, size), [box, size]);

	const [view, setView] = useState<GraphView>({ x: 0, y: 0, zoom: 1 });
	const userAdjustedRef = useRef(false);
	const atFloor = view.zoom <= fitZoom + 1e-9;

	useEffect(() => {
		if (atFloor) userAdjustedRef.current = false;
	}, [atFloor]);
	useEffect(() => {
		if (userAdjustedRef.current || !size.w || !size.h) return;
		setView(fitGraphView(box, size, fitZoom));
	}, [fitZoom, size, box]);

	useEffect(() => {
		const el = viewportRef.current;
		if (!el) return;
		const onWheel = (e: WheelEvent) => {
			e.preventDefault();
			const dy = e.deltaMode === 1 ? e.deltaY * 16 : e.deltaY;
			const factor = Math.exp(-dy * 0.0015);
			const rect = el.getBoundingClientRect();
			setView((v) =>
				zoomedGraphView(v, factor, fitZoom, { x: e.clientX - rect.left, y: e.clientY - rect.top }, box, size),
			);
			userAdjustedRef.current = true;
		};
		el.addEventListener("wheel", onWheel, { passive: false });
		return () => el.removeEventListener("wheel", onWheel);
	}, [fitZoom, box, size]);

	const dragRef = useRef<{ px: number; py: number; x: number; y: number; moved: boolean } | null>(null);
	const startDrag = (e: React.PointerEvent<HTMLDivElement>) => {
		if (e.button !== 0) return;
		if ((e.target as HTMLElement).closest("button")) return;
		if (atFloor) return;
		dragRef.current = { px: e.clientX, py: e.clientY, x: view.x, y: view.y, moved: false };
		e.currentTarget.classList.add("cursor-grabbing");
		e.currentTarget.setPointerCapture(e.pointerId);
	};
	const moveDrag = (e: React.PointerEvent<HTMLDivElement>) => {
		const d = dragRef.current;
		if (!d) return;
		d.moved = true;
		setView((v) =>
			v.zoom <= fitZoom + 1e-9 ? v : { ...v, x: d.x + (e.clientX - d.px), y: d.y + (e.clientY - d.py) },
		);
	};
	const endDrag = (e: React.PointerEvent<HTMLDivElement>) => {
		const d = dragRef.current;
		if (d) {
			dragRef.current = null;
			if (d.moved) userAdjustedRef.current = true;
		}
		e.currentTarget.classList.remove("cursor-grabbing");
	};
	const stepZoom = (factor: number) => {
		userAdjustedRef.current = true;
		setView((v) => zoomedGraphView(v, factor, fitZoom, { x: size.w / 2, y: size.h / 2 }, box, size));
	};
	const fitView = () => {
		userAdjustedRef.current = false;
		if (!size.w || !size.h) return;
		setView(fitGraphView(box, size, fitZoom));
	};

	const markerId = useId().replace(/[^a-zA-Z0-9-]/g, "");

	return (
		<div
			data-testid="plan-popup"
			className="fixed inset-0 z-50 flex flex-col bg-background/95 p-4 backdrop-blur-sm"
			role="dialog"
			aria-modal="true"
			aria-label="The full plan"
			onClick={(e) => {
				if (e.target === e.currentTarget) onClose();
			}}
		>
			<div className="mb-2 flex items-center gap-2">
				<span className="text-sm font-medium">The plan</span>
				<span className="text-xs text-muted-foreground">live — statuses derive from your check outcomes</span>
				<button
					type="button"
					onClick={onClose}
					aria-label="Close"
					data-testid="plan-popup-close"
					className="ml-auto rounded-lg p-1.5 text-muted-foreground transition-colors hover:bg-accent hover:text-foreground"
				>
					<XIcon className="size-4" />
				</button>
			</div>
			<div
				ref={viewportRef}
				className={cn(
					"relative min-h-0 flex-1 touch-none overflow-hidden rounded-xl border select-none",
					atFloor ? "cursor-default" : "cursor-grab",
				)}
				onPointerDown={startDrag}
				onPointerMove={moveDrag}
				onPointerUp={endDrag}
				onPointerCancel={endDrag}
			>
				{tree ? (
					<>
						<div
							className="absolute top-0 left-0 origin-top-left"
							style={{ transform: `translate(${view.x}px, ${view.y}px) scale(${view.zoom})` }}
						>
							<PlanDiagram
								nodes={tree.nodes}
								edges={tree.edges}
								statusOf={statusOf}
								glowId={statuses?.current ?? null}
								markerId={markerId}
							/>
						</div>
						<div className="pointer-events-none absolute inset-x-0 bottom-0 flex items-end justify-between p-2">
							<span className="text-[10px] text-muted-foreground/60">Drag to pan · scroll to zoom</span>
							<div className="flex gap-1">
								<button
									type="button"
									title="Zoom out"
									aria-label="Zoom out"
									onClick={() => stepZoom(1 / 1.25)}
									className="pointer-events-auto flex size-7 items-center justify-center rounded-md border border-border/70 bg-card/80 text-muted-foreground backdrop-blur transition-colors hover:bg-accent hover:text-foreground"
								>
									<MinusIcon className="size-3.5" />
								</button>
								<button
									type="button"
									title="Fit plan to screen"
									aria-label="Fit plan to screen"
									onClick={fitView}
									data-testid="plan-popup-fit"
									className="pointer-events-auto flex size-7 items-center justify-center rounded-md border border-border/70 bg-card/80 text-muted-foreground backdrop-blur transition-colors hover:bg-accent hover:text-foreground"
								>
									<MaximizeIcon className="size-3.5" />
								</button>
								<button
									type="button"
									title="Zoom in"
									aria-label="Zoom in"
									onClick={() => stepZoom(1.25)}
									className="pointer-events-auto flex size-7 items-center justify-center rounded-md border border-border/70 bg-card/80 text-muted-foreground backdrop-blur transition-colors hover:bg-accent hover:text-foreground"
								>
									<PlusIcon className="size-3.5" />
								</button>
							</div>
						</div>
					</>
				) : (
					<div className="flex h-full items-center justify-center text-sm text-muted-foreground">
						No plan in this session yet.
					</div>
				)}
			</div>
		</div>
	);
}