import {Resolver, promises as dnsPromises} from 'dns';
import {Agent} from 'http';

type AsyncResolver = dnsPromises.Resolver;

export type IPFamily = 4 | 6;

type TPromise<T> = T | Promise<T>;

export interface CacheInstance {
	set(hostname: string, entries: EntryObject[], ttl: number): TPromise<void | boolean>;
	get(hostname: string): TPromise<EntryObject[] | undefined>;
	delete(hostname: string): TPromise<boolean>;
	clear(): TPromise<void>;
}

export interface Options {
	/**
	 * Custom cache instance. If `undefined`, it will create a new one.
	 * @default undefined
	 */
	cache?: CacheInstance;
	/**
	 * Limits the cache time (TTL). If set to `0`, it will make a new DNS query each time.
	 * @default Infinity
	 */
	maxTtl?: number;
	/**
	 * DNS Resolver used to make DNS queries.
	 * @default new dns.promises.Resolver()
	 */
	resolver?: Resolver | AsyncResolver;
	/**
	 * The full path to the `hosts` file. Set this to `false` to prevent loading entries from the `hosts` file.
	 * @default '/etc/hosts'
	 */
	customHostsPath?: string | false;
	/**
	 * The lifetime of the entries received from the OS (TTL in seconds).
	 *
	 * **Note**: This option is independent, `options.maxTtl` does not affect this.
	 * @default 1
	 */
	fallbackTtl?: number;
	/**
	 * The time how long it needs to remember failed queries (TTL in seconds).
	 *
	 * **Note**: This option is independent, `options.maxTtl` does not affect this.
	 * @default 0.15
	 */
	errorTtl?: number;
}

export interface EntryObject {
	/**
	 * The IP address (can be an IPv4 or IPv5 address).
	 */
	readonly address: string;
	/**
	 * The IP family.
	 */
	readonly family: IPFamily;
	/**
	 * The original TTL.
	 */
	readonly ttl: number;
	/**
	 * The expiration timestamp.
	 */
	readonly expires: number;
}

export interface LookupOptions {
	/**
	 * One or more supported getaddrinfo flags. Multiple flags may be passed by bitwise ORing their values.
	 */
	hints?: number;
	/**
	 * The record family. Must be `4` or `6`. IPv4 and IPv6 addresses are both returned by default.
	 */
	family?: IPFamily;
	/**
	 * When `true`, the callback returns all resolved addresses in an array. Otherwise, returns a single address.
	 * @default false
	 */
	all?: boolean;
}

export default class CacheableLookup {
	constructor(options?: Options);
	/**
	 * DNS servers used to make the query. Can be overridden - then the new servers will be used.
	 */
	servers: string[];
	/**
	 * @see https://nodejs.org/api/dns.html#dns_dns_lookup_hostname_options_callback
	 */
	lookup(hostname: string, family: IPFamily, callback: (error: NodeJS.ErrnoException, address: string, family: IPFamily) => void): void;
	lookup(hostname: string, callback: (error: NodeJS.ErrnoException, address: string, family: IPFamily) => void): void;
	lookup(hostname: string, options: LookupOptions & {all: true}, callback: (error: NodeJS.ErrnoException, result: ReadonlyArray<EntryObject>) => void): void;
	lookup(hostname: string, options: LookupOptions, callback: (error: NodeJS.ErrnoException, address: string, family: IPFamily) => void): void;
	/**
	 * The asynchronous version of `dns.lookup(…)`.
	 */
	lookupAsync(hostname: string, options: LookupOptions & {all: true}): Promise<ReadonlyArray<EntryObject>>;
	lookupAsync(hostname: string, options: LookupOptions): Promise<EntryObject>;
	lookupAsync(hostname: string): Promise<EntryObject>;
	lookupAsync(hostname: string, family: IPFamily): Promise<EntryObject>;
	/**
	 * An asynchronous function which returns cached DNS lookup entries. This is the base for `lookupAsync(hostname, options)` and `lookup(hostname, options, callback)`.
	 */
	query(hostname: string): Promise<ReadonlyArray<EntryObject>>;
	/**
	 * An asynchronous function which makes a new DNS lookup query and updates the database. This is used by `query(hostname, family)` if no entry in the database is present. Returns an array of objects with `address`, `family`, `ttl` and `expires` properties.
	 */
	queryAndCache(hostname: string): Promise<ReadonlyArray<EntryObject>>;
	/**
	 * Returns an entry from the array for the given hostname.
	 * Useful to implement a round-robin algorithm.
	 */
	_getEntry(entries: ReadonlyArray<EntryObject>, hostname: string): EntryObject;
	/**
	 * Removes outdated entries.
	 */
	tick(): void;
	/**
	 * Attaches itself to an Agent instance.
	 */
	install(agent: Agent): void;
	/**
	 * Removes itself from an Agent instance.
	 */
	uninstall(agent: Agent): void;
	/**
	 * Updates interface info. For example, you need to run this when you plug or unplug your WiFi driver.
	 */
	updateInterfaceInfo(): void;
	/**
	 * Clears the cache for the given hostname. If the hostname argument is not present, the entire cache will be cleared.
	 */
	clear(hostname?: string): void;
}