OmniRoute/open-sse/services/errorClassifier.ts

import {
  isAccountDeactivated,
  isCreditsExhausted,
  isDailyQuotaExhausted,
  isOAuthInvalidToken,
} from "./accountFallback.ts";
import { getProviderCategory } from "../config/providerRegistry.ts";

// Terminal stop signals where an empty content payload is still a legitimate,
// successful completion (truncated at the token limit, or a tool-call turn) —
// NOT a silent "fake success" failure. Used to avoid rewriting a valid HTTP 200
// (e.g. a Claude Code `max_tokens: 1` connectivity ping) into a synthetic 502.
const LEGIT_EMPTY_CLAUDE_STOP = new Set(["max_tokens", "tool_use"]);
const LEGIT_EMPTY_OPENAI_FINISH = new Set(["length", "tool_calls"]);

export function isEmptyContentResponse(responseBody: unknown): boolean {
  if (!responseBody || typeof responseBody !== "object") return false;

  const body = responseBody as Record<string, unknown>;

  if (Array.isArray(body.choices)) {
    const firstChoice = body.choices[0] as Record<string, unknown> | undefined;
    if (!firstChoice) return true;

    const message = firstChoice.message as Record<string, unknown> | undefined;
    const delta = firstChoice.delta as Record<string, unknown> | undefined;

    const content = message?.content ?? delta?.content;
    const reasoningContent = message?.reasoning_content ?? delta?.reasoning_content;
    const hasToolCalls =
      (Array.isArray(message?.tool_calls) && (message.tool_calls as unknown[]).length > 0) ||
      (Array.isArray(delta?.tool_calls) && (delta.tool_calls as unknown[]).length > 0);

    const hasContent = content !== null && content !== undefined && content !== "";
    const hasReasoning =
      reasoningContent !== null && reasoningContent !== undefined && reasoningContent !== "";

    // A response truncated at the token limit (finish_reason "length") is a valid,
    // successful completion even with empty text — do not flag it as a fake success.
    const finishReason =
      typeof firstChoice.finish_reason === "string" ? firstChoice.finish_reason : "";
    if (LEGIT_EMPTY_OPENAI_FINISH.has(finishReason)) return false;

    return !hasContent && !hasReasoning && !hasToolCalls;
  }

  if (Array.isArray(body.content)) {
    if (body.content.length > 0) return false;
    // Empty content array: a response truncated at max_tokens (or one that stopped
    // to emit a tool_use block) is a legitimate terminal state, not a silent
    // failure. Only flag empty content when no such terminal stop_reason is present.
    const stopReason = typeof body.stop_reason === "string" ? body.stop_reason : "";
    return !LEGIT_EMPTY_CLAUDE_STOP.has(stopReason);
  }

  if (typeof body.text === "string") {
    return body.text.trim() === "";
  }

  if ("content" in body) {
    const content = body.content;
    return content === null || content === undefined || content === "";
  }

  return false;
}

export const PROVIDER_ERROR_TYPES = {
  RATE_LIMITED: "rate_limited",
  UNAUTHORIZED: "unauthorized",
  ACCOUNT_DEACTIVATED: "account_deactivated",
  FORBIDDEN: "forbidden",
  SERVER_ERROR: "server_error",
  QUOTA_EXHAUSTED: "quota_exhausted",
  PROJECT_ROUTE_ERROR: "project_route_error",
  CONTEXT_OVERFLOW: "context_overflow",
  OAUTH_INVALID_TOKEN: "oauth_invalid_token",
  EMPTY_CONTENT: "empty_content",
};

export const CONTEXT_OVERFLOW_SIGNALS = [
  "context overflow",
  "prompt too large",
  "context window",
  "maximum context",
  "exceeds context",
  "input too long",
  "token limit",
  "too many tokens",
  "context length",
  "exceed.*context",
  "messages exceed",
];

export const CONTEXT_OVERFLOW_REGEX = new RegExp(CONTEXT_OVERFLOW_SIGNALS.join("|"), "i");

export function isContextOverflow(errorText: string): boolean {
  return CONTEXT_OVERFLOW_REGEX.test(String(errorText || ""));
}

function responseBodyToString(responseBody: unknown): string {
  if (typeof responseBody === "string") return responseBody;
  if (responseBody !== null && typeof responseBody === "object") {
    try {
      return JSON.stringify(responseBody);
    } catch {
      return "";
    }
  }
  return "";
}

function shouldPreserveQuotaSignalsFor429(provider?: string | null): boolean {
  if (!provider) return true;
  return getProviderCategory(provider) === "oauth";
}

export function classifyProviderError(
  statusCode: number,
  responseBody: unknown,
  provider?: string | null
): string | null {
  const bodyStr = responseBodyToString(responseBody);
  const creditsExhausted = isCreditsExhausted(bodyStr);
  const accountDeactivated = isAccountDeactivated(bodyStr);
  const oauthInvalid = isOAuthInvalidToken(bodyStr);
  const preserveQuota429 = shouldPreserveQuotaSignalsFor429(provider);

  if (creditsExhausted && [400, 402, 403].includes(statusCode)) {
    return PROVIDER_ERROR_TYPES.QUOTA_EXHAUSTED;
  }

  if (creditsExhausted && statusCode === 429 && preserveQuota429) {
    return PROVIDER_ERROR_TYPES.QUOTA_EXHAUSTED;
  }

  // API-key providers route 429 cooldowns through the resilience-aware fallback layer.
  // OAuth providers keep their existing quota semantics because some of them encode
  // longer quota windows as 429 responses.
  if (statusCode === 429) {
    if (preserveQuota429 && isDailyQuotaExhausted(bodyStr)) {
      return PROVIDER_ERROR_TYPES.QUOTA_EXHAUSTED;
    }
    return PROVIDER_ERROR_TYPES.RATE_LIMITED;
  }

  if (statusCode === 401) {
    if (oauthInvalid) {
      return PROVIDER_ERROR_TYPES.OAUTH_INVALID_TOKEN;
    }
    return accountDeactivated
      ? PROVIDER_ERROR_TYPES.ACCOUNT_DEACTIVATED
      : PROVIDER_ERROR_TYPES.UNAUTHORIZED;
  }

  if (statusCode === 402) return PROVIDER_ERROR_TYPES.QUOTA_EXHAUSTED;
  if (statusCode === 403 && accountDeactivated) {
    return PROVIDER_ERROR_TYPES.ACCOUNT_DEACTIVATED;
  }
  if (statusCode === 403) {
    if (bodyStr.includes("has not been used in project")) {
      return PROVIDER_ERROR_TYPES.PROJECT_ROUTE_ERROR;
    }
    if (provider && getProviderCategory(provider) === "apikey") {
      return null;
    }
    return PROVIDER_ERROR_TYPES.FORBIDDEN;
  }
  if (statusCode >= 500) return PROVIDER_ERROR_TYPES.SERVER_ERROR;

  if (statusCode === 400 && isContextOverflow(bodyStr)) {
    return PROVIDER_ERROR_TYPES.CONTEXT_OVERFLOW;
  }

  return null;
}