export const DIAGNOSTIC_LEVELS = Object.freeze([
  "debug",
  "info",
  "warn",
  "error",
] as const);
export { queueSizeBucket } from "./diagnostic-buckets.ts";
export type DiagnosticLevel = (typeof DIAGNOSTIC_LEVELS)[number];

export const DIAGNOSTIC_EVENT_REGISTRY = Object.freeze({
  "app.boot.failed": Object.freeze({ level: "error" }),
  "http.request.completed": Object.freeze({ level: "info" }),
  "cache.operation.failed": Object.freeze({ level: "warn" }),
  "storage.operation.failed": Object.freeze({ level: "warn" }),
  "route.changed": Object.freeze({ level: "info" }),
  "ui.render.failed": Object.freeze({ level: "error" }),
  "release.mismatch.detected": Object.freeze({ level: "warn" }),
  "telemetry.delivery.dropped": Object.freeze({ level: "warn" }),
});
export type DiagnosticEventId = keyof typeof DIAGNOSTIC_EVENT_REGISTRY;

export const DIAGNOSTIC_CONTEXT_ALLOWLIST = Object.freeze([
  "app_version",
  "build_id",
  "release_id",
  "active_release_id",
  "config_schema_version",
  "api_contract_version",
  "route_id",
  "operation_id",
  "correlation_id",
  "error_kind",
  "outcome",
  "http_status_group",
  "attempt_count_bucket",
  "duration_bucket",
  "component_boundary",
  "mismatch_kind",
  "operation",
  "reason",
  "queue_size_bucket",
] as const);
export type DiagnosticContextKey =
  (typeof DIAGNOSTIC_CONTEXT_ALLOWLIST)[number];
export type DiagnosticContext = Readonly<
  Partial<Record<DiagnosticContextKey, string | number | boolean>>
>;

export type DiagnosticRecordInput = Readonly<{
  level: DiagnosticLevel;
  eventId: DiagnosticEventId;
  context?: Readonly<Record<string, unknown>>;
}>;

export type DiagnosticRecord = Readonly<{
  level: DiagnosticLevel;
  eventId: DiagnosticEventId;
  timestamp: string;
  context: DiagnosticContext;
}>;

const SAFE_VALUE = /^[A-Za-z0-9][A-Za-z0-9._:@/-]{0,63}$/;

function projectDiagnosticRecordUnsafe(
  input: DiagnosticRecordInput,
  now: () => number = Date.now,
):
  | Readonly<{ success: true; record: DiagnosticRecord }>
  | Readonly<{ success: false; reason: string }> {
  if (!Object.hasOwn(DIAGNOSTIC_EVENT_REGISTRY, input.eventId)) {
    return { success: false, reason: "unregistered-event" };
  }
  if (!DIAGNOSTIC_LEVELS.includes(input.level)) {
    return { success: false, reason: "invalid-level" };
  }
  const contextEntries = Object.entries(input.context ?? {});
  if (contextEntries.length > DIAGNOSTIC_CONTEXT_ALLOWLIST.length) {
    return { success: false, reason: "invalid-context" };
  }
  const projected: Partial<
    Record<DiagnosticContextKey, string | number | boolean>
  > = {};
  for (const [key, value] of contextEntries) {
    if (
      !DIAGNOSTIC_CONTEXT_ALLOWLIST.includes(key as DiagnosticContextKey)
    ) {
      return { success: false, reason: "unknown-context" };
    }
    if (typeof value === "string") {
      if (!SAFE_VALUE.test(value)) {
        return { success: false, reason: "invalid-context" };
      }
      projected[key as DiagnosticContextKey] = value;
    } else if (typeof value === "number" && Number.isFinite(value)) {
      projected[key as DiagnosticContextKey] = value;
    } else if (typeof value === "boolean") {
      projected[key as DiagnosticContextKey] = value;
    } else {
      return { success: false, reason: "invalid-context" };
    }
  }
  let timestamp: string;
  try {
    timestamp = new Date(now()).toISOString();
  } catch {
    timestamp = new Date(0).toISOString();
  }
  return {
    success: true,
    record: Object.freeze({
      level: input.level,
      eventId: input.eventId,
      timestamp,
      context: Object.freeze(projected),
    }),
  };
}

export function projectDiagnosticRecord(
  input: DiagnosticRecordInput,
  now: () => number = Date.now,
): ReturnType<typeof projectDiagnosticRecordUnsafe> {
  try {
    return projectDiagnosticRecordUnsafe(input, now);
  } catch {
    return { success: false, reason: "serialization-failure" };
  }
}

export function safeErrorKind(error: unknown): string {
  try {
    if (error && typeof error === "object") {
      const record = error as Readonly<Record<string, unknown>>;
      if (
        typeof record.kind === "string" &&
        /^[A-Z][A-Z0-9_]{0,63}$/.test(record.kind)
      ) {
        return record.kind;
      }
      if (
        typeof record.name === "string" &&
        /^[A-Za-z][A-Za-z0-9]{0,63}$/.test(record.name)
      ) {
        const normalized = record.name
          .replace(/([a-z0-9])([A-Z])/g, "$1_$2")
          .toUpperCase();
        return /^[A-Z][A-Z0-9_]{0,63}$/.test(normalized)
          ? normalized
          : "UNKNOWN_FAILURE";
      }
    }
  } catch {
    return "UNKNOWN_FAILURE";
  }
  return "UNKNOWN_FAILURE";
}

export function statusGroup(status: number | undefined): string {
  return typeof status === "number" && Number.isFinite(status)
    ? `${Math.max(0, Math.min(9, Math.floor(status / 100)))}xx`
    : "none";
}

export function attemptBucket(attemptCount: number): string {
  if (attemptCount <= 1) return "1";
  if (attemptCount === 2) return "2";
  if (attemptCount <= 4) return "3-4";
  return "5+";
}

export function durationBucket(durationMs: number): string {
  if (!Number.isFinite(durationMs) || durationMs < 0) return "unknown";
  if (durationMs < 100) return "lt100ms";
  if (durationMs < 500) return "100-499ms";
  if (durationMs < 2_000) return "500-1999ms";
  return "gte2000ms";
}