export const COOKIE_ACCESS = "ap_at";
export const COOKIE_ID = "ap_it";
export const COOKIE_REFRESH = "ap_rt";
export const COOKIE_OAUTH = "ap_oauth";
export const COOKIE_SESSION_HINT = "ap_sess";

export const ACCESS_MAX_AGE_SEC = 60 * 60;
export const REFRESH_MAX_AGE_SEC = 8 * 60 * 60;
export const OAUTH_MAX_AGE_SEC = 10 * 60;

export type CookieEvent = {
  cookies?: string[];
  headers?: Record<string, string | undefined>;
};

export type OauthCookie = {
  state: string;
  verifier: string;
  returnTo: string;
};

export type CookieNames = {
  access: string;
  id: string;
  refresh: string;
  oauth: string;
  hint: string;
};

export type SessionHint = {
  displayName: string;
  email: string;
};

export function cookieNames(stage: string): CookieNames {
  const prefix = stage === "local" ? "" : "__Host-";
  return {
    access: `${prefix}${COOKIE_ACCESS}`,
    id: `${prefix}${COOKIE_ID}`,
    refresh: `${prefix}${COOKIE_REFRESH}`,
    oauth: `${prefix}${COOKIE_OAUTH}`,
    hint: `${prefix}${COOKIE_SESSION_HINT}`,
  };
}

export function parseCookies(event: CookieEvent): Record<string, string> {
  const parsed: Record<string, string> = {};
  for (const part of cookieParts(event)) {
    const eq = part.indexOf("=");
    if (eq <= 0) continue;
    const name = part.slice(0, eq).trim();
    const value = part.slice(eq + 1).trim();
    if (!name) continue;
    if (Object.prototype.hasOwnProperty.call(parsed, name)) continue;
    parsed[name] = decodeCookieValue(value);
  }
  return parsed;
}

export function cookieValue(event: CookieEvent, name: string): string | undefined {
  const value = parseCookies(event)[name];
  return value ? value : undefined;
}

export function sessionCookieValue(
  event: CookieEvent,
  kind: keyof CookieNames,
  stage: string,
): string | undefined {
  return cookieValue(event, cookieNames(stage)[kind]);
}

export function serializeCookie(
  name: string,
  value: string,
  options: { maxAge: number; stage: string; path?: string; httpOnly?: boolean },
): string {
  const hostPrefixed = name.startsWith("__Host-");
  const path = hostPrefixed ? "/" : (options.path ?? "/");
  const parts = [
    `${name}=${encodeURIComponent(value)}`,
    `Path=${path}`,
    "SameSite=Lax",
    `Max-Age=${options.maxAge}`,
  ];
  if (options.httpOnly !== false) parts.splice(2, 0, "HttpOnly");
  if (hostPrefixed || options.stage !== "local") parts.push("Secure");
  return parts.join("; ");
}

export function clearCookie(
  name: string,
  stage: string,
  options: { httpOnly?: boolean } = {},
): string {
  return serializeCookie(name, "", {
    maxAge: 0,
    stage,
    path: cookiePath(name),
    httpOnly: options.httpOnly,
  });
}

export function tokenCookies(
  tokens: { accessToken: string; idToken: string; refreshToken?: string },
  stage: string,
): string[] {
  const names = cookieNames(stage);
  const cookies = [
    serializeCookie(names.access, tokens.accessToken, { maxAge: ACCESS_MAX_AGE_SEC, stage }),
    serializeCookie(names.id, tokens.idToken, { maxAge: ACCESS_MAX_AGE_SEC, stage }),
  ];
  if (tokens.refreshToken) {
    cookies.push(
      serializeCookie(names.refresh, tokens.refreshToken, {
        maxAge: REFRESH_MAX_AGE_SEC,
        stage,
        path: cookiePath(names.refresh),
      }),
    );
  }
  cookies.push(
    serializeCookie(names.hint, sessionHintValue(tokens.idToken), {
      maxAge: REFRESH_MAX_AGE_SEC,
      stage,
      httpOnly: false,
    }),
  );
  cookies.push(clearCookie(names.oauth, stage));
  return cookies;
}

export function clearedSessionCookies(stage: string): string[] {
  const names = cookieNames(stage);
  const cookies = [
    clearCookie(names.access, stage),
    clearCookie(names.id, stage),
    clearCookie(names.refresh, stage),
    clearCookie(names.oauth, stage),
    clearCookie(names.hint, stage, { httpOnly: false }),
  ];
  if (stage !== "local") {
    const legacy = cookieNames("local");
    cookies.push(
      serializeCookie(legacy.access, "", { maxAge: 0, stage, path: "/" }),
      serializeCookie(legacy.id, "", { maxAge: 0, stage, path: "/" }),
      serializeCookie(legacy.refresh, "", { maxAge: 0, stage, path: "/" }),
      serializeCookie(legacy.oauth, "", { maxAge: 0, stage, path: "/" }),
      serializeCookie(legacy.hint, "", { maxAge: 0, stage, path: "/", httpOnly: false }),
    );
  }
  return cookies;
}

export function serializeOauthCookie(payload: OauthCookie, stage: string): string {
  const names = cookieNames(stage);
  return serializeCookie(names.oauth, encodeOauth(payload), { maxAge: OAUTH_MAX_AGE_SEC, stage });
}

export function readOauthCookie(event: CookieEvent, stage: string): OauthCookie | undefined {
  const raw = sessionCookieValue(event, "oauth", stage);
  if (!raw) return undefined;
  try {
    const parsed = JSON.parse(raw) as Partial<OauthCookie>;
    if (
      typeof parsed.state !== "string" ||
      !parsed.state ||
      typeof parsed.verifier !== "string" ||
      !parsed.verifier ||
      typeof parsed.returnTo !== "string"
    ) {
      return undefined;
    }
    return { state: parsed.state, verifier: parsed.verifier, returnTo: parsed.returnTo };
  } catch {
    return undefined;
  }
}

export function headerFrom(event: CookieEvent, name: string): string | undefined {
  const headers = event.headers ?? {};
  const needle = name.toLowerCase();
  for (const [key, value] of Object.entries(headers)) {
    if (key.toLowerCase() === needle) return value;
  }
  return undefined;
}

export function cookieEventFromHeader(cookieHeader: string | undefined): CookieEvent {
  return { headers: { cookie: cookieHeader } };
}

export function sessionHintFromIdToken(token: string): SessionHint | null {
  const parts = token.split(".");
  if (parts.length !== 3) return null;
  try {
    const claims = JSON.parse(Buffer.from(parts[1], "base64url").toString("utf8")) as Record<
      string,
      unknown
    >;
    const email =
      typeof claims.email === "string" && claims.email.includes("@") ? claims.email : "";
    if (!email) return null;
    const displayName =
      (typeof claims.name === "string" && claims.name) ||
      (typeof claims.given_name === "string" && claims.given_name) ||
      email;
    return { email, displayName };
  } catch {
    return null;
  }
}

function cookiePath(name: string): string {
  if (name.startsWith("__Host-")) return "/";
  return name.endsWith(COOKIE_REFRESH) ? "/api/auth" : "/";
}

function sessionHintValue(idToken: string): string {
  const hint = sessionHintFromIdToken(idToken);
  return hint ? JSON.stringify(hint) : "1";
}

function cookieParts(event: CookieEvent): string[] {
  const parts: string[] = [];
  for (const cookie of event.cookies ?? []) {
    parts.push(cookie);
  }
  const header = headerFrom(event, "cookie");
  if (header) {
    for (const part of header.split(";")) {
      if (part.trim()) parts.push(part);
    }
  }
  return parts;
}

function decodeCookieValue(value: string): string {
  try {
    return decodeURIComponent(value);
  } catch {
    return value;
  }
}

function encodeOauth(payload: OauthCookie): string {
  return JSON.stringify(payload);
}