// Author: Simon-Pierre Boucher
// Contact: contact@spboucher.ai
// Project: chat.spboucher.ai

export type AIErrorCode =
  | "AUTHENTICATION_ERROR"
  | "RATE_LIMIT"
  | "MODEL_UNAVAILABLE"
  | "PROVIDER_UNAVAILABLE"
  | "CONTEXT_TOO_LARGE"
  | "INVALID_REQUEST"
  | "CONTENT_REJECTED"
  | "TIMEOUT"
  | "NETWORK_ERROR"
  | "UNKNOWN";

export interface NormalizedAIError {
  code: AIErrorCode;
  message: string;
  retryable: boolean;
  modelId?: string;
  status?: number;
}

export class AIError extends Error implements NormalizedAIError {
  code: AIErrorCode;
  retryable: boolean;
  modelId?: string;
  status?: number;

  constructor(err: NormalizedAIError) {
    super(err.message);
    this.name = "AIError";
    this.code = err.code;
    this.retryable = err.retryable;
    this.modelId = err.modelId;
    this.status = err.status;
  }
}

/** Map an HTTP status + upstream message to a normalized error. Never leaks internals. */
export function normalizeHttpError(status: number, upstreamMessage: string, modelId?: string): AIError {
  const msg = (upstreamMessage || "").slice(0, 500);
  switch (status) {
    case 401:
    case 403:
      return new AIError({
        code: "AUTHENTICATION_ERROR",
        message: "The gateway rejected the server credentials. Check the OpenRouter key.",
        retryable: false,
        modelId,
        status,
      });
    case 402:
      return new AIError({
        code: "AUTHENTICATION_ERROR",
        message: "OpenRouter account has insufficient credits.",
        retryable: false,
        modelId,
        status,
      });
    case 404:
      return new AIError({
        code: "MODEL_UNAVAILABLE",
        message: "This model is not available right now. Pick another model.",
        retryable: false,
        modelId,
        status,
      });
    case 408:
      return new AIError({ code: "TIMEOUT", message: "The model timed out. Try again.", retryable: true, modelId, status });
    case 413:
      return new AIError({
        code: "CONTEXT_TOO_LARGE",
        message: "The conversation exceeds this model's context window. Trim it or switch to a larger-context model.",
        retryable: false,
        modelId,
        status,
      });
    case 429:
      return new AIError({
        code: "RATE_LIMIT",
        message: "Rate limited upstream. Wait a moment and retry.",
        retryable: true,
        modelId,
        status,
      });
    case 502:
    case 503:
      return new AIError({
        code: "PROVIDER_UNAVAILABLE",
        message: "The upstream provider is unavailable. Retry, or switch models.",
        retryable: true,
        modelId,
        status,
      });
    default:
      if (status >= 500) {
        return new AIError({
          code: "PROVIDER_UNAVAILABLE",
          message: "Upstream failure. Retry, or switch models.",
          retryable: true,
          modelId,
          status,
        });
      }
      if (/moderation|flagged|content policy/i.test(msg)) {
        return new AIError({
          code: "CONTENT_REJECTED",
          message: "The provider rejected this content.",
          retryable: false,
          modelId,
          status,
        });
      }
      if (/context length|maximum context|too many tokens/i.test(msg)) {
        return new AIError({
          code: "CONTEXT_TOO_LARGE",
          message: "The conversation exceeds this model's context window. Trim it or switch to a larger-context model.",
          retryable: false,
          modelId,
          status,
        });
      }
      return new AIError({
        code: "INVALID_REQUEST",
        message: msg || "The request was rejected.",
        retryable: false,
        modelId,
        status,
      });
  }
}

export function normalizeNetworkError(err: unknown, modelId?: string): AIError {
  if (err instanceof AIError) return err;
  if (err instanceof Error && err.name === "AbortError") {
    return new AIError({ code: "TIMEOUT", message: "The request was cancelled.", retryable: false, modelId });
  }
  return new AIError({
    code: "NETWORK_ERROR",
    message: "Could not reach the model gateway. Check connectivity and retry.",
    retryable: true,
    modelId,
  });
}