// Resolution-refusal vocabulary: the 503 payloads, retry-after math, and the
// outcome labels behind resolution metrics.

import { json } from "./http.js";
import type { Resolution } from "./placement.js";

export type ServeResolution =
  | Resolution
  | { kind: "not-serving" }
  | { kind: "no-hostname-workers" }
  | { kind: "binding-quarantine"; retryAfterMs: number }
  | { kind: "env-conflict" };
export type Refusal = Exclude<
  ServeResolution,
  { kind: "forward" } | { kind: "unknown-ns" }
>;

const REFUSAL_ERRORS: Record<Refusal["kind"], string> = {
  "no-backends": "no live backends for namespace",
  quarantine: "registry cold start, retry",
  "not-serving": "not the serving fleet",
  "no-hostname-workers": "no live workers for hostname",
  "binding-quarantine": "hostname binding displaced, retry",
  "env-conflict": "hostname bindings inconsistent, retry",
  "takeover-pending": "takeover in progress, retry",
  "takeover-denied": "placement held by another hostname",
};

// takeover-denied rides the takeover-pending outcome; takeovers_total
// distinguishes the strategies. "nack" counts in-band activation refusals.
export const RESOLUTION_OUTCOMES = [
  "forward",
  "unknown-ns",
  "no-backends",
  "quarantine",
  "not-serving",
  "no-hostname-workers",
  "binding-quarantine",
  "takeover-pending",
  "env-conflict",
  "nack",
] as const;

export type ResolutionCounts = Record<
  (typeof RESOLUTION_OUTCOMES)[number],
  number
>;

export const createResolutionCounts = (): ResolutionCounts =>
  Object.fromEntries(
    RESOLUTION_OUTCOMES.map((outcome) => [outcome, 0]),
  ) as ResolutionCounts;

export const resolutionOutcome = (
  kind: ServeResolution["kind"],
): (typeof RESOLUTION_OUTCOMES)[number] =>
  kind === "takeover-denied" ? "takeover-pending" : kind;

export const refusalResponse = (refusal: Refusal, now: number): Response => {
  const retryAfterSeconds =
    refusal.kind === "quarantine" || refusal.kind === "binding-quarantine"
      ? Math.max(1, Math.ceil(refusal.retryAfterMs / 1000))
      : refusal.kind === "takeover-pending"
        ? Math.max(1, Math.ceil((refusal.fenceExpiry - now) / 1000))
        : 1;
  return json(
    503,
    { error: REFUSAL_ERRORS[refusal.kind] },
    { "retry-after": String(retryAfterSeconds) },
  );
};