import { omitUndefinedKeys } from "./omitUndefinedKeys.ts";

/**
 * Full UTM configuration object.
 */
export type UtmParams = {
  /**
   * The website/platform the visitor is coming from.
   */
  source: string;

  /**
   * The type of marketing channel (e.g. cpc, email, affiliate, social,
   * or similar).
   */
  medium: string;

  /**
   * The name of the campaign or product description. In our case, this is
   * usually the name of the app.
   */
  campaign: string;

  /**
   * Optionally, provide an identifier for the place from which the link was
   * clicked. E.g. footer, join, etc.
   */
  content?: string;

  /**
   * Optionally, identify paid keywords. We usually do not use this.
   */
  term?: string;
};

/**
 * UTM Params configuration that is appropriate to set at the link level,
 * if app-level defaults have been set.
 */
export type LinkUtmParams = Pick<UtmParams, "content" | "term">;

/**
 * Returns URL Search params with provided UTM configuration.
 *
 * Most of the time, you probably want to set up some defaults using
 * {@link createUtm}. This function is intended for special cases.
 */
export function utm(params: UtmParams) {
  return new URLSearchParams(
    omitUndefinedKeys({
      utm_source: params.source,
      utm_medium: params.medium,
      utm_campaign: params.campaign,
      utm_content: params.content,
      utm_term: params.term,
    }),
  );
}

/**
 * A factory for the {@link utm} function. Use it to set sensible defaults for
 * further use of the returned function.
 *
 * @example
 * ```ts
 * const utm = createUtm({
 *   source: "indietabletopclub",
 *   medium: "referral",
 *   campaign: "spacegitsapp",
 * });
 *
 * utm() // => URLSearchParams that inlude the above config
 *
 * utm({ campaign: "foo", content: "bar" }) // Sets optional fiels and overrides
 * ```
 */
export function createUtm(defaults: UtmParams) {
  return function (params?: Partial<UtmParams>) {
    return utm({
      ...defaults,
      ...(params && omitUndefinedKeys(params)),
    });
  };
}