export const parseVersion = (version: string): number[] =>
  version.split(".").map((v) => parseInt(v));

const versionGreaterThan = (v1: string, v2: string): boolean => {
  const v1Parts = parseVersion(v1);
  const v2Parts = parseVersion(v2);
  for (let i = 0; i < v1Parts.length; i++) {
    const v1Part = v1Parts[i];
    const v2Part = v2Parts[i];
    if (v1Part > v2Part) {
      return true;
    } else if (v1Part < v2Part) {
      return false;
    }
  }
  return false;
};

const sortVersions = (versions: string[]): string[] =>
  versions?.sort((v1, v2) => {
    if (versionGreaterThan(v1, v2)) {
      return -1;
    } else if (versionGreaterThan(v2, v1)) {
      return 1;
    }
    return 0;
  });

type APIPayload = {
  dashboard: string;
  juju: string[];
};

/**
 * Avoid making multiple requests to the API by caching the response.
 */
export let cachedAPIResponse: { data: APIPayload; fetchedAt: Date } | null =
  null;
const TTL = 1000 * 60 * 60; // 1 hours

/**
 * Fetch the latest Juju versions from the API.
 */
const fetchVersions = async () => {
  if (
    cachedAPIResponse &&
    cachedAPIResponse.fetchedAt.getTime() + TTL > new Date().getTime()
  )
    return cachedAPIResponse.data;
  cachedAPIResponse = null;
  const response = await fetch("https://juju.is/latest.json");
  const data: APIPayload | undefined = await response?.json();
  if (!data) {
    return null;
  }
  cachedAPIResponse = {
    data: { ...data, juju: sortVersions(data.juju) },
    fetchedAt: new Date(),
  };
  return cachedAPIResponse.data;
};

/**
 * Check the Juju controller version against the latest available
 * version (ignores the patch version).
 * @param jujuVersion The version of the Juju controller to check
 * @returns
 */
export const jujuUpdateAvailable = async (jujuVersion: string) => {
  const jujuVersions = (await fetchVersions())?.juju;
  if (!jujuVersions) {
    return null;
  }
  const latestAvailableVersion = jujuVersions.slice(-1)[0];
  return versionGreaterThan(latestAvailableVersion, jujuVersion);
};

/**
 * Check the Juju dashboard version against the latest available
 * version (ignore the patch version).
 * @param dashboardVersion The version of the Juju dashboard to check
 * @returns
 */
export const dashboardUpdateAvailable = async (dashboardVersion: string) => {
  const latestDashboardVersion = (await fetchVersions())?.dashboard;
  if (!latestDashboardVersion) {
    return null;
  }
  return versionGreaterThan(latestDashboardVersion, dashboardVersion);
};