/**
 * State of the workspace panel (file tree + Preview / Editor / Terminal
 * tabs), kept apart from the chat state: the two evolve independently.
 *
 * @example
 * openPreview("README.md");   // opens the panel on the preview tab
 * useWorkspace((w) => w.tab); // inside a component
 */

import { create } from "zustand";

export type WorkspaceTab = "preview" | "editor" | "terminal";

/** Default width of the file tree column, in pixels (14rem at 16px). */
export const DEFAULT_FILE_TREE_WIDTH = 224;
/** Narrowest width the file tree column can be dragged to, in pixels. */
export const MIN_FILE_TREE_WIDTH = 120;
/** Widest width the file tree column can be dragged to, in pixels. */
export const MAX_FILE_TREE_WIDTH = 800;
/** localStorage key under which the chosen width is remembered. */
export const FILE_TREE_WIDTH_KEY = "ori.fileTreeWidth";

export interface WorkspaceState {
	/** Whether the right-hand panel is visible. */
	open: boolean;
	/** The active tab. */
	tab: WorkspaceTab;
	/** File shown in the preview tab, if any. */
	previewPath: string | null;
	/** File opened in the editor tab, if any. */
	editorPath: string | null;
	/** Width of the file tree column, in pixels, always within the bounds. */
	fileTreeWidth: number;
}

const initialWorkspace: WorkspaceState = {
	open: false,
	tab: "preview",
	previewPath: null,
	editorPath: null,
	fileTreeWidth: loadFileTreeWidth(),
};

/** React hook over the workspace store. */
export const useWorkspace = create<WorkspaceState>(() => initialWorkspace);

/** toggleWorkspace shows or hides the panel. */
export function toggleWorkspace(): void {
	useWorkspace.setState((state) => ({ open: !state.open }));
}

/** showTab activates a tab (and opens the panel if needed). */
export function showTab(tab: WorkspaceTab): void {
	useWorkspace.setState({ open: true, tab });
}

/** openPreview shows a file in the preview tab. */
export function openPreview(path: string): void {
	useWorkspace.setState({ open: true, tab: "preview", previewPath: path });
}

/** openEditor opens a file in the editor tab. */
export function openEditor(path: string): void {
	useWorkspace.setState({ open: true, tab: "editor", editorPath: path });
}

/**
 * clampFileTreeWidth brings a width back within the allowed bounds; a
 * non-finite value (NaN, Infinity) falls back to the default width.
 *
 * @example
 * clampFileTreeWidth(50);   // 120
 * clampFileTreeWidth(300);  // 300
 * clampFileTreeWidth(NaN);  // 224
 */
export function clampFileTreeWidth(width: number): number {
	if (!Number.isFinite(width)) {
		return DEFAULT_FILE_TREE_WIDTH;
	}
	return Math.min(
		MAX_FILE_TREE_WIDTH,
		Math.max(MIN_FILE_TREE_WIDTH, Math.round(width)),
	);
}

/**
 * setFileTreeWidth resizes the file tree column and remembers the width in
 * localStorage so it survives a page reload.
 *
 * @example
 * setFileTreeWidth(320);
 * useWorkspace.getState().fileTreeWidth; // 320
 */
export function setFileTreeWidth(width: number): void {
	const clamped = clampFileTreeWidth(width);
	useWorkspace.setState({ fileTreeWidth: clamped });
	saveFileTreeWidth(clamped);
}

/** resetFileTreeWidth restores the default width (and forgets the stored one). */
export function resetFileTreeWidth(): void {
	setFileTreeWidth(DEFAULT_FILE_TREE_WIDTH);
}

/**
 * loadFileTreeWidth reads the remembered width. Storage can be missing or
 * throw (private browsing, blocked site data, non-browser test runs), so any
 * failure or unusable value yields the default.
 */
function loadFileTreeWidth(): number {
	try {
		const stored = globalThis.localStorage?.getItem(FILE_TREE_WIDTH_KEY);
		if (stored === null || stored === undefined) {
			return DEFAULT_FILE_TREE_WIDTH;
		}
		return clampFileTreeWidth(Number(stored));
	} catch {
		return DEFAULT_FILE_TREE_WIDTH;
	}
}

function saveFileTreeWidth(width: number): void {
	try {
		globalThis.localStorage?.setItem(FILE_TREE_WIDTH_KEY, String(width));
	} catch {
		// Storage unavailable: the width still applies for this page.
	}
}

/** resetWorkspace restores the initial state; meant for tests. */
export function resetWorkspace(): void {
	useWorkspace.setState(
		{ ...initialWorkspace, fileTreeWidth: DEFAULT_FILE_TREE_WIDTH },
		true,
	);
}