inspector/clients/web/src/components/groups/protocolUtils.ts

import type { MessageEntry, MessageMethod } from "@inspector/core/mcp/types.js";
import {
  isInputRequiredResult,
  SUBSCRIPTION_ID_META_KEY,
} from "@modelcontextprotocol/client";

export function extractMethod(entry: MessageEntry): MessageMethod {
  if ("method" in entry.message) {
    // Cast: SDK types message.method as `string`, but every entry in this
    // app's MessageEntry log originates from MCP SDK schemas.
    return entry.message.method as MessageMethod;
  }
  return "response";
}

/**
 * Request methods the Protocol Replay action can re-issue (client→server reads
 * and calls). Server→client requests (roots/list, sampling, elicitation) and
 * side-effectful methods (logging/setLevel, subscribe) are intentionally
 * excluded. Single source of truth: `ProtocolEntry` hides the Replay button for
 * anything not listed here, and App's `replayProtocolRequest` gates dispatch on
 * the same set.
 */
export const REPLAYABLE_PROTOCOL_METHODS: ReadonlySet<string> = new Set([
  "tools/call",
  "prompts/get",
  "resources/read",
  "tools/list",
  "prompts/list",
  "resources/list",
  "resources/templates/list",
  "tasks/list",
  "ping",
]);

export function isReplayableProtocolMethod(method: string): boolean {
  return REPLAYABLE_PROTOCOL_METHODS.has(method);
}

// --- Modern-era (2026-07-28) message vocabulary -----------------------------
//
// The modern era changes the over-the-wire conversation (spec §7.2–7.4): every
// result carries a `resultType`, server→client interactions become MRTR (the
// server *returns* `input_required` and the client *retries* with a new id),
// and push notifications move to a `subscriptions/listen` stream. These helpers
// read that vocabulary off the transport-level `MessageEntry` log so the
// Protocol view can render and correlate it. IMPORTANT: they classify individual
// *frames* — they must NOT be used to decide a connection's era. The modern
// probe carries the `_meta` envelope before the era is negotiated, so "saw an
// envelope/resultType" ≠ "modern negotiated" (spec §8.3). Era labeling comes
// from the negotiated `protocolEra` connection state, threaded in as a prop.

// The successful `result` object of a request entry's paired response, or
// undefined when there is no response or it was an error. (messageLogState folds
// a request's response onto the request entry by JSON-RPC id.)
function getResponseResult(
  entry: MessageEntry,
): Record<string, unknown> | undefined {
  const response = entry.response;
  if (!response || "error" in response) return undefined;
  const result = response.result;
  return result && typeof result === "object"
    ? (result as Record<string, unknown>)
    : undefined;
}

function getMessageParams(
  entry: MessageEntry,
): Record<string, unknown> | undefined {
  const msg = entry.message;
  if (!("params" in msg) || !msg.params) return undefined;
  return msg.params as Record<string, unknown>;
}

/**
 * The modern `resultType` discriminator on a request's paired result:
 * `"input_required"` (the server needs input before it can complete) or
 * `"complete"`. Undefined for legacy results (no `resultType` on the wire),
 * errors, notifications, and pending requests — so a `resultType` badge only
 * shows where the modern era actually put one.
 */
export function extractResultType(
  entry: MessageEntry,
): "complete" | "input_required" | undefined {
  const result = getResponseResult(entry);
  if (!result) return undefined;
  if (isInputRequiredResult(result)) return "input_required";
  return result.resultType === "complete" ? "complete" : undefined;
}

/**
 * The opaque MRTR `requestState` token that links the rounds of one logical
 * operation across multiple JSON-RPC ids. It appears on the `input_required`
 * *result* (original call) and is echoed back in the *params* of the retried
 * request (spec §7.3). Returns undefined for non-MRTR traffic.
 */
export function extractRequestState(entry: MessageEntry): string | undefined {
  const result = getResponseResult(entry);
  const fromResult = result?.requestState;
  if (typeof fromResult === "string" && fromResult.length > 0)
    return fromResult;
  const params = getMessageParams(entry);
  const fromParams = params?.requestState;
  if (typeof fromParams === "string" && fromParams.length > 0)
    return fromParams;
  return undefined;
}

/**
 * The `subscriptionId` a modern push notification is tagged with, carried in
 * `params._meta` under `io.modelcontextprotocol/subscriptionId` (spec §7.4).
 * Undefined for untagged frames.
 */
export function extractSubscriptionId(entry: MessageEntry): string | undefined {
  const params = getMessageParams(entry);
  const meta = params?._meta as Record<string, unknown> | undefined;
  const id = meta?.[SUBSCRIPTION_ID_META_KEY];
  return typeof id === "string" ? id : undefined;
}

/**
 * A rendered row in the Protocol list: either a single message entry, or an
 * MRTR conversation — the contiguous run of entries sharing one `requestState`
 * (original call → `input_required` → retried call → final result), grouped so
 * one logical operation renders as one expandable unit.
 */
export type ProtocolRow =
  | { kind: "single"; entry: MessageEntry }
  | { kind: "mrtr"; requestState: string; rounds: MessageEntry[] };

/**
 * Fold a (already filtered/sorted) entry list into rows, clustering contiguous
 * entries that share a non-empty `requestState` into one MRTR row. Contiguity is
 * safe because the SDK auto-fulfils MRTR input in-process (no intervening wire
 * frames) so an operation's rounds are adjacent in the log. Order is preserved;
 * everything without a `requestState` stays a `single` row.
 */
export function groupProtocolEntries(entries: MessageEntry[]): ProtocolRow[] {
  const rows: ProtocolRow[] = [];
  for (const entry of entries) {
    const requestState = extractRequestState(entry);
    if (requestState) {
      const last = rows[rows.length - 1];
      if (last?.kind === "mrtr" && last.requestState === requestState) {
        last.rounds.push(entry);
        continue;
      }
      rows.push({ kind: "mrtr", requestState, rounds: [entry] });
      continue;
    }
    rows.push({ kind: "single", entry });
  }
  return rows;
}