/**
 * The one registry of Chopin's keyboard shortcuts. Handlers, tooltip hints, menus,
 * and the shortcuts sheet all read from here so a chord is never described in two places.
 */

export type ShortcutPlatform = "mac" | "other";

export type ShortcutId =
	| "search"
	| "new-document"
	| "toggle-sidebar"
	| "toggle-chat"
	| "shortcuts"
	| "bold"
	| "italic"
	| "link"
	| "undo"
	| "redo";

export type Shortcut = {
	id: ShortcutId;
	label: string;
	group: "General" | "Editing";
	key: string;
	/** ⌘ on a Mac, Ctrl elsewhere. */
	mod?: boolean;
	alt?: boolean;
	shift?: boolean;
	/** Physical fallback when the layout cannot report a printable ASCII character. */
	code?: string;
	/** Listed in the sheet only; the editor owns the key. */
	display?: boolean;
};

export const SHORTCUTS: readonly Shortcut[] = [
	{
		id: "search",
		label: "Search documents",
		group: "General",
		key: "k",
		code: "KeyK",
		mod: true,
	},
	{
		id: "new-document",
		label: "New document",
		group: "General",
		key: "n",
		code: "KeyN",
		alt: true,
	},
	{
		id: "toggle-sidebar",
		label: "Show or hide sidebar",
		group: "General",
		key: "\\",
		code: "Backslash",
		mod: true,
	},
	{
		id: "toggle-chat",
		label: "Show or hide chat",
		group: "General",
		key: ".",
		code: "Period",
		mod: true,
	},
	{ id: "shortcuts", label: "Keyboard shortcuts", group: "General", key: "?" },
	{ id: "bold", label: "Bold", group: "Editing", key: "b", mod: true, display: true },
	{ id: "italic", label: "Italic", group: "Editing", key: "i", mod: true, display: true },
	{ id: "link", label: "Link selected text", group: "Editing", key: "k", mod: true, display: true },
	{ id: "undo", label: "Undo", group: "Editing", key: "z", mod: true, display: true },
	{ id: "redo", label: "Redo", group: "Editing", key: "z", mod: true, shift: true, display: true },
];

export function shortcutPlatform(userAgent: string, platform?: string): ShortcutPlatform {
	// Native editing commands follow the OS platform even when the browser spoofs its user agent.
	return /Mac|iPhone|iPad|iPod/.test(platform || userAgent) ? "mac" : "other";
}

export function currentShortcutPlatform(): ShortcutPlatform {
	return typeof navigator === "undefined"
		? "other"
		: shortcutPlatform(navigator.userAgent, navigator.platform);
}

function shortcut(id: ShortcutId): Shortcut {
	return SHORTCUTS.find(entry => entry.id === id)!;
}

function keyName(key: string): string {
	return key.length === 1 ? key.toUpperCase() : key;
}

/** The separate keys of a chord, as printed on keycaps. */
export function shortcutKeys(id: ShortcutId, platform: ShortcutPlatform): string[] {
	let entry = shortcut(id);
	let keys: string[] = [];
	if (entry.mod) keys.push(platform === "mac" ? "⌘" : "Ctrl");
	if (entry.alt) keys.push(platform === "mac" ? "⌥" : "Alt");
	if (entry.shift) keys.push(platform === "mac" ? "⇧" : "Shift");
	keys.push(keyName(entry.key));
	return keys;
}

/** A chord as one string: `⌘K` on a Mac, `Ctrl+K` elsewhere. */
export function shortcutLabel(id: ShortcutId, platform: ShortcutPlatform): string {
	return shortcutKeys(id, platform).join(platform === "mac" ? "" : "+");
}

export type ShortcutKey = {
	key: string;
	code?: string;
	metaKey: boolean;
	ctrlKey: boolean;
	altKey: boolean;
	shiftKey: boolean;
	isComposing?: boolean;
};

export type ShortcutContext = {
	/** Focus is in a text field, contenteditable, or a menu with its own keys. */
	typing: boolean;
	/** A modal dialog or drawer owns the keyboard. */
	modal: boolean;
};

/**
 * Single keys and Alt chords never fire while typing. Command/Control chords may
 * fire in fields unless the editor claims and prevents the event first.
 */
export function matchShortcut(
	event: ShortcutKey,
	platform: ShortcutPlatform,
	context: ShortcutContext,
): ShortcutId | undefined {
	if (event.isComposing || context.modal) return;
	let mod = platform === "mac" ? event.metaKey : event.ctrlKey;
	let other = platform === "mac" ? event.ctrlKey : event.metaKey;
	if (other) return;
	let key = event.key.toLowerCase();
	// Prefer the typed character, including ASCII punctuation. The physical key is only
	// a fallback for dead keys, unidentified keys, and non-ASCII layouts.
	let physicalFallback = !/^[\x20-\x7e]$/.test(event.key) && !event.shiftKey;
	for (let entry of SHORTCUTS) {
		if (entry.display || !!entry.mod !== mod || !!entry.alt !== event.altKey) continue;
		if (!entry.mod && context.typing) continue;
		// Punctuation needs Shift on some layouts (`.` on AZERTY, `?` nearly everywhere), so
		// Shift only distinguishes letter chords.
		if (/^[a-z0-9]$/.test(entry.key) && !!entry.shift !== event.shiftKey) continue;
		if (
			key === entry.key
			|| (physicalFallback && entry.code !== undefined && event.code === entry.code)
		) {
			return entry.id;
		}
	}
	return;
}