/**
 * Wayland clipboard image reader.
 *
 * wl-paste only. No xclip, no PowerShell, no pngpaste, no native addon — this
 * extension targets a strict Wayland session, and every extra backend is a
 * spawn that can hang on a machine that will never use it.
 */

import { spawnSync } from "node:child_process";

/** Formats the Kitty graphics protocol and pi both accept without conversion. */
const PREFERRED = ["image/png", "image/jpeg", "image/webp", "image/gif"] as const;

export interface ClipboardImage {
	bytes: Buffer;
	mimeType: string;
}

function baseMime(mimeType: string): string {
	return mimeType.split(";")[0]?.trim().toLowerCase() ?? mimeType.toLowerCase();
}

export function extensionForMime(mimeType: string): string {
	switch (baseMime(mimeType)) {
		case "image/png":
			return "png";
		case "image/jpeg":
			return "jpg";
		case "image/webp":
			return "webp";
		case "image/gif":
			return "gif";
		default:
			return "bin";
	}
}

function run(args: string[], timeoutMs: number): Buffer | null {
	const result = spawnSync("wl-paste", args, {
		timeout: timeoutMs,
		maxBuffer: 64 * 1024 * 1024,
	});
	if (result.error || result.status !== 0) return null;
	return Buffer.isBuffer(result.stdout) ? result.stdout : null;
}

/** MIME types currently on the clipboard, lowercased. */
export function clipboardTypes(): string[] {
	const out = run(["--list-types"], 1_000);
	if (!out) return [];
	return out
		.toString("utf-8")
		.split(/\r?\n/)
		.map((t) => t.trim())
		.filter(Boolean);
}

function pickType(types: string[]): string | null {
	const normalized = types.map((raw) => ({ raw, base: baseMime(raw) }));
	for (const preferred of PREFERRED) {
		const match = normalized.find((t) => t.base === preferred);
		if (match) return match.raw;
	}
	// Any other image/* is still worth trying; the terminal may cope, and if it
	// does not the caller gets a clear error rather than a silent no-op.
	return normalized.find((t) => t.base.startsWith("image/"))?.raw ?? null;
}

/**
 * Read an image off the Wayland clipboard.
 *
 * Returns null when the clipboard holds no image — that is the normal case
 * (text copied), not an error. Throws only when wl-paste itself is missing.
 */
export function readClipboardImage(): ClipboardImage | null {
	const types = clipboardTypes();
	if (types.length === 0) {
		// Distinguish "wl-paste absent/broken" from "clipboard is empty".
		const probe = spawnSync("wl-paste", ["--version"], { timeout: 1_000 });
		if (probe.error) {
			throw new Error("wl-paste not found. Install wl-clipboard.");
		}
		return null;
	}

	const selected = pickType(types);
	if (!selected) return null;

	// --no-newline: wl-paste appends one for text types and would corrupt binary.
	const bytes = run(["--type", selected, "--no-newline"], 5_000);
	if (!bytes || bytes.length === 0) return null;

	return { bytes, mimeType: baseMime(selected) };
}