import type { Settings, SettingsPatch } from "@/lib/types";

const SECTIONS = [
	"upstream",
	"dns",
	"blocking",
	"cache",
	"web",
	"doh_server",
	"dot_server",
	"edns",
	"logging",
	"disk",
	"blocklist_update",
] as const;

/**
 * Minimal partial patch for PUT /api/settings: only fields whose edited value
 * differs from the original, grouped by section. The derived `web.auth_enabled`
 * is never emitted. A non-empty `password` passes through as `web.password`.
 * Returns null when nothing changed and no password was given.
 */
export function buildSettingsPatch(original: Settings, edited: Settings, password?: string): SettingsPatch | null {
	const patch: Record<string, Record<string, unknown>> = {};
	for (const section of SECTIONS) {
		const before = original[section] as Record<string, unknown>;
		const after = edited[section] as Record<string, unknown>;
		let changed: Record<string, unknown> | undefined;
		for (const key of Object.keys(after)) {
			if (section === "web" && key === "auth_enabled") continue;
			if (before[key] !== after[key]) (changed ??= {})[key] = after[key];
		}
		if (changed !== undefined) patch[section] = changed;
	}
	if (password !== undefined && password !== "") {
		patch["web"] = { ...patch["web"], password };
	}
	return Object.keys(patch).length === 0 ? null : (patch as SettingsPatch);
}