import { browser } from '$app/environment';

/**
 * View-level UI preferences. Persisted to localStorage so collapse state,
 * thumb size, etc. survive a refresh. Same module is reused by the
 * timeline page and the preview overlay so the sidebar toggle stays in
 * sync across views (matches mule-image's "intelligent preview recall").
 */
const STORAGE_KEY = 'mule_view';

/**
 * Mirrors mule-image's mule-image-viewSettingsStore thumbnail presets so the
 * UX scales the same way: five steps with `M` as the default. Labels are
 * cosmetic; the numbers feed the `minmax(<size>px, 1fr)` grid template.
 */
export const THUMBNAIL_SIZE_PRESETS = [96, 128, 160, 208, 272] as const;
export type ThumbnailSize = (typeof THUMBNAIL_SIZE_PRESETS)[number];
export const THUMBNAIL_SIZE_LABELS = ['XS', 'S', 'M', 'L', 'XL'] as const;
export const DEFAULT_THUMBNAIL_SIZE: ThumbnailSize = 160;

interface Persisted {
	rightSidebarCollapsed?: boolean;
	leftSidebarCollapsed?: boolean;
	thumbnailSize?: ThumbnailSize;
	leftSidebarWidth?: number;
	rightSidebarWidth?: number;
	tagsBrowserWidth?: number;
	tagsBrowserCollapsed?: boolean;
	/**
	 * Per-section expanded state for the right-sidebar metadata panel
	 * (GPS, Credits, File). Keyed by section id; missing entries use a
	 * static default supplied by the component, so the user's chosen
	 * collapse state stays put as they navigate between photos.
	 */
	metadataSections?: Record<string, boolean>;
}

export const MIN_LEFT_WIDTH = 180;
export const MAX_LEFT_WIDTH = 480;
export const DEFAULT_LEFT_WIDTH = 224;
export const MIN_RIGHT_WIDTH = 220;
export const MAX_RIGHT_WIDTH = 480;
export const DEFAULT_RIGHT_WIDTH = 280;
export const MIN_TAGS_BROWSER_WIDTH = 180;
export const MAX_TAGS_BROWSER_WIDTH = 480;
export const DEFAULT_TAGS_BROWSER_WIDTH = 240;

function clamp(n: number, lo: number, hi: number): number {
	return Math.min(hi, Math.max(lo, n));
}

function isThumbnailSize(n: unknown): n is ThumbnailSize {
	return (
		typeof n === 'number' &&
		(THUMBNAIL_SIZE_PRESETS as readonly number[]).includes(n)
	);
}

function loadInitial(): Persisted {
	if (!browser) return {};
	try {
		const raw = localStorage.getItem(STORAGE_KEY);
		return raw ? (JSON.parse(raw) as Persisted) : {};
	} catch {
		return {};
	}
}

const initial = loadInitial();

export const view = $state<{
	rightSidebarCollapsed: boolean;
	leftSidebarCollapsed: boolean;
	thumbnailSize: ThumbnailSize;
	leftSidebarWidth: number;
	rightSidebarWidth: number;
	tagsBrowserWidth: number;
	tagsBrowserCollapsed: boolean;
	/**
	 * Ephemeral: true while the full-screen preview modal is open. Not
	 * persisted — a refresh always returns to the grid.
	 */
	previewOpen: boolean;
	metadataSections: Record<string, boolean>;
}>({
	rightSidebarCollapsed: initial.rightSidebarCollapsed ?? false,
	leftSidebarCollapsed: initial.leftSidebarCollapsed ?? false,
	thumbnailSize: isThumbnailSize(initial.thumbnailSize)
		? initial.thumbnailSize
		: DEFAULT_THUMBNAIL_SIZE,
	leftSidebarWidth: clamp(
		typeof initial.leftSidebarWidth === 'number' ? initial.leftSidebarWidth : DEFAULT_LEFT_WIDTH,
		MIN_LEFT_WIDTH,
		MAX_LEFT_WIDTH
	),
	rightSidebarWidth: clamp(
		typeof initial.rightSidebarWidth === 'number' ? initial.rightSidebarWidth : DEFAULT_RIGHT_WIDTH,
		MIN_RIGHT_WIDTH,
		MAX_RIGHT_WIDTH
	),
	tagsBrowserWidth: clamp(
		typeof initial.tagsBrowserWidth === 'number'
			? initial.tagsBrowserWidth
			: DEFAULT_TAGS_BROWSER_WIDTH,
		MIN_TAGS_BROWSER_WIDTH,
		MAX_TAGS_BROWSER_WIDTH
	),
	tagsBrowserCollapsed: initial.tagsBrowserCollapsed ?? false,
	previewOpen: false,
	metadataSections:
		initial.metadataSections && typeof initial.metadataSections === 'object'
			? { ...initial.metadataSections }
			: {}
});

function persist(): void {
	if (!browser) return;
	const payload: Persisted = {
		rightSidebarCollapsed: view.rightSidebarCollapsed,
		leftSidebarCollapsed: view.leftSidebarCollapsed,
		thumbnailSize: view.thumbnailSize,
		leftSidebarWidth: view.leftSidebarWidth,
		rightSidebarWidth: view.rightSidebarWidth,
		tagsBrowserWidth: view.tagsBrowserWidth,
		tagsBrowserCollapsed: view.tagsBrowserCollapsed,
		metadataSections: view.metadataSections
	};
	localStorage.setItem(STORAGE_KEY, JSON.stringify(payload));
}

export function setLeftSidebarWidth(px: number): void {
	view.leftSidebarWidth = clamp(Math.round(px), MIN_LEFT_WIDTH, MAX_LEFT_WIDTH);
	persist();
}

export function setRightSidebarWidth(px: number): void {
	view.rightSidebarWidth = clamp(Math.round(px), MIN_RIGHT_WIDTH, MAX_RIGHT_WIDTH);
	persist();
}

export function setTagsBrowserWidth(px: number): void {
	view.tagsBrowserWidth = clamp(
		Math.round(px),
		MIN_TAGS_BROWSER_WIDTH,
		MAX_TAGS_BROWSER_WIDTH
	);
	persist();
}

export function toggleTagsBrowser(): void {
	view.tagsBrowserCollapsed = !view.tagsBrowserCollapsed;
	persist();
}

export function openPreview(): void {
	view.previewOpen = true;
}

export function closePreview(): void {
	view.previewOpen = false;
}

export function togglePreview(): void {
	view.previewOpen = !view.previewOpen;
}

export function setThumbnailSize(size: ThumbnailSize): void {
	view.thumbnailSize = size;
	persist();
}

export function toggleRightSidebar(): void {
	view.rightSidebarCollapsed = !view.rightSidebarCollapsed;
	persist();
}

export function setRightSidebarCollapsed(collapsed: boolean): void {
	view.rightSidebarCollapsed = collapsed;
	persist();
}

export function toggleLeftSidebar(): void {
	view.leftSidebarCollapsed = !view.leftSidebarCollapsed;
	persist();
}

/**
 * Read the persisted expanded state for a right-sidebar metadata
 * section, falling back to `defaultOpen` when the user has never
 * toggled it. `defaultOpen` should be a *static* value — using a
 * per-photo data-driven default would change between photos, fire a
 * programmatic `toggle` event, and silently overwrite the user's
 * preference.
 */
export function getMetadataSectionOpen(id: string, defaultOpen: boolean): boolean {
	const v = view.metadataSections[id];
	return typeof v === 'boolean' ? v : defaultOpen;
}

/** Record the user's explicit collapse/expand choice for a metadata
 *  section. Persists immediately so a reload keeps the layout the
 *  user picked. */
export function setMetadataSection(id: string, open: boolean): void {
	view.metadataSections[id] = open;
	persist();
}