import * as fs from "node:fs";
import * as os from "node:os";
import * as path from "node:path";

const UNICODE_SPACES = /[\u00A0\u2000-\u200A\u202F\u205F\u3000]/g;
const NARROW_NO_BREAK_SPACE = "\u202F";

function normalizeUnicodeSpaces(str: string): string {
	return str.replace(UNICODE_SPACES, " ");
}

function tryMacOSScreenshotPath(filePath: string): string {
	return filePath.replace(/ (AM|PM)\./g, `${NARROW_NO_BREAK_SPACE}$1.`);
}

function tryNFDVariant(filePath: string): string {
	// macOS stores filenames in NFD (decomposed) form, try converting user input to NFD
	return filePath.normalize("NFD");
}

function tryCurlyQuoteVariant(filePath: string): string {
	// macOS uses U+2019 (right single quotation mark) in screenshot names like "Capture d'écran"
	// Users typically type U+0027 (straight apostrophe)
	return filePath.replace(/'/g, "\u2019");
}

function fileExists(filePath: string): boolean {
	try {
		fs.accessSync(filePath, fs.constants.F_OK);
		return true;
	} catch {
		return false;
	}
}

function normalizeAtPrefix(filePath: string): string {
	if (!filePath.startsWith("@")) return filePath;

	const withoutAt = filePath.slice(1);

	// We only treat a leading "@" as a shorthand for a small set of well-known
	// syntaxes. This avoids mangling literal paths like "@my-file.txt".
	if (
		withoutAt.startsWith("/") ||
		withoutAt === "~" ||
		withoutAt.startsWith("~/") ||
		// Windows absolute paths (drive letters / UNC / root-relative)
		path.win32.isAbsolute(withoutAt) ||
		// Internal URL shorthands
		withoutAt.startsWith("agent://") ||
		withoutAt.startsWith("artifact://") ||
		withoutAt.startsWith("skill://") ||
		withoutAt.startsWith("rule://")
	) {
		return withoutAt;
	}

	return filePath;
}

export function expandTilde(filePath: string, home?: string): string {
	const h = home ?? os.homedir();
	if (filePath === "~") return h;
	if (filePath.startsWith("~/") || filePath.startsWith("~\\")) {
		return h + filePath.slice(1);
	}
	if (filePath.startsWith("~")) {
		return path.join(h, filePath.slice(1));
	}
	return filePath;
}

export function expandPath(filePath: string): string {
	const normalized = normalizeUnicodeSpaces(normalizeAtPrefix(filePath));
	return expandTilde(normalized);
}

/**
 * Resolve a path relative to the given cwd.
 * Handles ~ expansion and absolute paths.
 */
export function resolveToCwd(filePath: string, cwd: string): string {
	const expanded = expandPath(filePath);
	if (path.isAbsolute(expanded)) {
		return expanded;
	}
	return path.resolve(cwd, expanded);
}

export function resolveReadPath(filePath: string, cwd: string): string {
	const resolved = resolveToCwd(filePath, cwd);

	if (fileExists(resolved)) {
		return resolved;
	}

	// Try macOS AM/PM variant (narrow no-break space before AM/PM)
	const amPmVariant = tryMacOSScreenshotPath(resolved);
	if (amPmVariant !== resolved && fileExists(amPmVariant)) {
		return amPmVariant;
	}

	// Try NFD variant (macOS stores filenames in NFD form)
	const nfdVariant = tryNFDVariant(resolved);
	if (nfdVariant !== resolved && fileExists(nfdVariant)) {
		return nfdVariant;
	}

	// Try curly quote variant (macOS uses U+2019 in screenshot names)
	const curlyVariant = tryCurlyQuoteVariant(resolved);
	if (curlyVariant !== resolved && fileExists(curlyVariant)) {
		return curlyVariant;
	}

	// Try combined NFD + curly quote (for French macOS screenshots like "Capture d'écran")
	const nfdCurlyVariant = tryCurlyQuoteVariant(nfdVariant);
	if (nfdCurlyVariant !== resolved && fileExists(nfdCurlyVariant)) {
		return nfdCurlyVariant;
	}

	return resolved;
}