import type { LanguageShare } from "./languages";

const CARD_LANGUAGES = 6;

/** The card's language strip: the largest languages as whole percents (at least 1), the rest as "Other". */
export function cardLanguages(languages: readonly LanguageShare[]): Array<{ name: string; percent: number }> {
  const total = languages.reduce((sum, language) => sum + language.bytes, 0);
  if (total === 0) return [];
  const shares = languages.map((language) => ({ name: language.name, bytes: language.bytes }));
  const kept = shares.filter((language) => language.name !== "Other").slice(0, CARD_LANGUAGES);
  const rest = total - kept.reduce((sum, language) => sum + language.bytes, 0);
  if (rest > 0) kept.push({ name: "Other", bytes: rest });
  return kept.map((language) => ({
    name: language.name,
    percent: Math.max(1, Math.round((language.bytes / total) * 100)),
  }));
}

/** Social card URLs and their version hashes; shared by page heads (client and server) and the /og handler. */

/** Bump when a card layout changes so every cached card URL changes with it. */
export const OG_RENDERER_VERSION = "2";
export const OG_WIDTH = 1200;
export const OG_HEIGHT = 630;
export const OG_PREFIX = "/og/";
export const SITE_OG_PATH = "/og/site.png";
export const SITE_DESCRIPTION =
  "gitfor hosts Git repositories with pull requests, Actions-style CI, issues, security scanning and sites. Open source under 0BSD, and you can run your own instance.";
export const SITE_OG_ALT = "gitfor: open-source Git hosting, code review and CI";

/** FNV-1a 32-bit over the joined fields: cheap, sync and stable on both sides; it only needs to change, not resist collisions. */
export function ogVersion(fields: ReadonlyArray<string | number | null | undefined>): string {
  const input = [
    OG_RENDERER_VERSION,
    ...fields.map((field) => (field === null || field === undefined ? "" : String(field))),
  ].join("\u0000");
  let hash = 0x811c9dc5;
  for (let index = 0; index < input.length; index++) {
    hash ^= input.charCodeAt(index);
    hash = Math.imul(hash, 0x01000193);
  }
  return (hash >>> 0).toString(16).padStart(8, "0");
}

export type RepoCardData = {
  owner: string;
  name: string;
  description: string | null;
  stars: number;
  forks: number;
  openIssues: number;
  openPulls: number;
  avatarKey: string | null;
  latestRelease: string | null;
  topics: string[];
  /** Whole-percent shares, so pushes that barely move the mix keep the card's URL. */
  languages: Array<{ name: string; percent: number }>;
};

export type AccountCardData = {
  name: string;
  kind: "user" | "org";
  displayName: string | null;
  bio: string | null;
  avatarKey: string | null;
  publicRepos: number;
};

export function repoCardVersion(repo: RepoCardData): string {
  return ogVersion([
    "repo",
    repo.owner,
    repo.name,
    repo.description,
    repo.stars,
    repo.forks,
    repo.openIssues,
    repo.openPulls,
    repo.avatarKey,
    repo.latestRelease,
    repo.topics.join(","),
    repo.languages.map((language) => `${language.name}:${language.percent}`).join(","),
  ]);
}

export function accountCardVersion(account: AccountCardData): string {
  return ogVersion([
    "account",
    account.name,
    account.kind,
    account.displayName,
    account.bio,
    account.avatarKey,
    account.publicRepos,
  ]);
}

export function featureCardVersion(slug: string, title: string, lede: string): string {
  return ogVersion(["feature", slug, title, lede]);
}

export function siteCardVersion(): string {
  return ogVersion(["site"]);
}

export function repoOgPath(repo: RepoCardData): string {
  return `/og/${encodeURIComponent(repo.owner)}/${encodeURIComponent(repo.name)}.png?v=${repoCardVersion(repo)}`;
}

export function accountOgPath(account: AccountCardData): string {
  return `/og/${encodeURIComponent(account.name)}.png?v=${accountCardVersion(account)}`;
}

export function featureOgPath(slug: string, title: string, lede: string): string {
  return `/og/feature/${encodeURIComponent(slug)}.png?v=${featureCardVersion(slug, title, lede)}`;
}

export function siteOgPath(): string {
  return `${SITE_OG_PATH}?v=${siteCardVersion()}`;
}