import { realpathSync, readFileSync } from "node:fs";
import { join, relative, isAbsolute } from "node:path";
import { pathToFileURL } from "node:url";

// Resolve through the switched version, never the old launcher's captured pins.
export async function resolveStartupRelaunch(input: {
	root: string; home: string; platform: NodeJS.Platform; env: NodeJS.ProcessEnv; argv: string[];
}): Promise<{ command: string; args: string[]; env: NodeJS.ProcessEnv }> {
	const { activeVersion, prefixLayout } = await import("../scripts/bundled-install.mjs");
	const layout = prefixLayout(input);
	const id = activeVersion(layout);
	if (!id) throw new Error("No active Gentle Shell after upgrade");
	const versions = realpathSync(layout.versions);
	const version = realpathSync(join(versions, id));
	const inside = (root: string, file: string) => {
		const path = relative(root, file);
		return path !== "" && !path.startsWith("..") && !isAbsolute(path);
	};
	if (!inside(versions, version) || readFileSync(join(version, ".gentle-shell-version"), "utf8") !== `${id}\n`) {
		throw new Error("Invalid active Gentle Shell version");
	}
	const pkg = join(version, "node_modules", "gentle-pi");
	const modulePath = realpathSync(join(pkg, "scripts", "bundled-install.mjs"));
	const entry = realpathSync(join(pkg, "bin", "gentle-shell.mjs"));
	if (!inside(version, modulePath) || !inside(version, entry)) throw new Error("Active launcher escaped its version");
	const release = await import(pathToFileURL(modulePath).href);
	const next = release.prefixLayout(input);
	return { command: next.node, args: [entry, ...input.argv], env: { ...input.env, GENTLE_SHELL_SKIP_STARTUP_UPDATE: "1" } };
}

// Only an explicit update selection may cross the existing upgrade boundary.
export async function applyStartupChoice(choice: "update" | "skip" | "omit" | "cancel", effects: {
	omit: () => void;
	upgrade: () => Promise<number>;
	relaunch: () => Promise<number>;
	warn?: (message: string) => void;
}): Promise<number | undefined> {
	if (choice === "cancel") return 130;
	if (choice === "omit") {
		try { effects.omit(); }
		catch { effects.warn?.("Could not remember the skipped release; continuing without saving."); }
	}
	if (choice !== "update") return undefined;
	if (await effects.upgrade() !== 0) return undefined;
	// A failed relaunch must not fall through to the captured old packageRoot.
	return effects.relaunch();
}

export function omitStartupVersion(read: () => string | undefined, write: (text: string) => void, version: string): void {
	const text = read();
	const config = text === undefined ? {} : JSON.parse(text);
	if (config === null || typeof config !== "object" || Array.isArray(config)) throw new Error("Invalid launcher config");
	write(`${JSON.stringify({ ...config, skippedStartupRelease: version }, null, 2)}\n`);
}