/**
 * src/core/errors/index.ts — Error taxonomy professionale
 *
 * Ogni errore AI/network ha un codice, un messaggio user-facing,
 * e una severity. Usare sempre questi invece di string generici.
 *
 * Checklist 1.3 — error taxonomy
 */

// ─── Error codes ────────────────────────────────────────────────────────────
export enum ErrorCode {
  NETWORK_ERROR      = "NETWORK_ERROR",
  RATE_LIMIT         = "RATE_LIMIT",
  INVALID_KEY        = "INVALID_KEY",
  MODEL_UNAVAILABLE  = "MODEL_UNAVAILABLE",
  EXECUTION_FAILED   = "EXECUTION_FAILED",
  MEMORY_ERROR       = "MEMORY_ERROR",
  OFFLINE_MODE       = "OFFLINE_MODE",
  TIMEOUT            = "TIMEOUT",
  QUOTA_EXCEEDED     = "QUOTA_EXCEEDED",
  PROVIDER_SWITCHING = "PROVIDER_SWITCHING",
  UNKNOWN_ERROR      = "UNKNOWN_ERROR",
}

export type ErrorSeverity = "info" | "warn" | "error" | "fatal";

// ─── Structured app error ───────────────────────────────────────────────────
export interface AppError {
  code:      ErrorCode;
  message:   string;         // user-facing (breve)
  detail?:   string;         // tecnico / debug
  provider?: string;         // es. "Groq", "Gemini"
  severity:  ErrorSeverity;
  retryable: boolean;
  timestamp: number;
}

// ─── Factory ─────────────────────────────────────────────────────────────────
export function createError(
  code: ErrorCode,
  opts: Partial<Omit<AppError, "code" | "timestamp">> = {},
): AppError {
  return {
    code,
    message:   opts.message   ?? ERROR_MESSAGES[code],
    detail:    opts.detail,
    provider:  opts.provider,
    severity:  opts.severity  ?? ERROR_SEVERITY[code],
    retryable: opts.retryable ?? ERROR_RETRYABLE[code],
    timestamp: Date.now(),
  };
}

// ─── Default user-facing messages ────────────────────────────────────────────
const ERROR_MESSAGES: Record<ErrorCode, string> = {
  [ErrorCode.NETWORK_ERROR]:      "Errore di rete — controlla la connessione",
  [ErrorCode.RATE_LIMIT]:         "Limite richieste raggiunto — ritento automaticamente",
  [ErrorCode.INVALID_KEY]:        "Chiave API non valida — verifica nelle Impostazioni",
  [ErrorCode.MODEL_UNAVAILABLE]:  "Modello non disponibile — passo al prossimo",
  [ErrorCode.EXECUTION_FAILED]:   "Esecuzione fallita",
  [ErrorCode.MEMORY_ERROR]:       "Errore di memoria — prova a liberare spazio",
  [ErrorCode.OFFLINE_MODE]:       "Modalità offline — funzionalità limitate",
  [ErrorCode.TIMEOUT]:            "Timeout — la risposta ha impiegato troppo",
  [ErrorCode.QUOTA_EXCEEDED]:     "Quota esaurita — cambio provider",
  [ErrorCode.PROVIDER_SWITCHING]: "Provider non disponibile — cambio in corso",
  [ErrorCode.UNKNOWN_ERROR]:      "Errore sconosciuto",
};

// ─── Default severity ────────────────────────────────────────────────────────
const ERROR_SEVERITY: Record<ErrorCode, ErrorSeverity> = {
  [ErrorCode.NETWORK_ERROR]:      "warn",
  [ErrorCode.RATE_LIMIT]:         "warn",
  [ErrorCode.INVALID_KEY]:        "error",
  [ErrorCode.MODEL_UNAVAILABLE]:  "warn",
  [ErrorCode.EXECUTION_FAILED]:   "error",
  [ErrorCode.MEMORY_ERROR]:       "error",
  [ErrorCode.OFFLINE_MODE]:       "info",
  [ErrorCode.TIMEOUT]:            "warn",
  [ErrorCode.QUOTA_EXCEEDED]:     "warn",
  [ErrorCode.PROVIDER_SWITCHING]: "info",
  [ErrorCode.UNKNOWN_ERROR]:      "error",
};

// ─── Default retryable ───────────────────────────────────────────────────────
const ERROR_RETRYABLE: Record<ErrorCode, boolean> = {
  [ErrorCode.NETWORK_ERROR]:      true,
  [ErrorCode.RATE_LIMIT]:         true,
  [ErrorCode.INVALID_KEY]:        false,
  [ErrorCode.MODEL_UNAVAILABLE]:  true,
  [ErrorCode.EXECUTION_FAILED]:   false,
  [ErrorCode.MEMORY_ERROR]:       false,
  [ErrorCode.OFFLINE_MODE]:       false,
  [ErrorCode.TIMEOUT]:            true,
  [ErrorCode.QUOTA_EXCEEDED]:     true,
  [ErrorCode.PROVIDER_SWITCHING]: true,
  [ErrorCode.UNKNOWN_ERROR]:      false,
};

// ─── Classifier: HTTP status + body → ErrorCode ──────────────────────────────
export function classifyHttpError(status: number, body = ""): ErrorCode {
  const b = body.toLowerCase();
  if (status === 401 || status === 403)               return ErrorCode.INVALID_KEY;
  if (status === 429 || status === 402)               return ErrorCode.RATE_LIMIT;
  if (status === 404)                                 return ErrorCode.MODEL_UNAVAILABLE;
  if (status === 408)                                 return ErrorCode.TIMEOUT;
  if (b.includes("quota") || b.includes("exceeded")) return ErrorCode.QUOTA_EXCEEDED;
  if (b.includes("rate limit"))                       return ErrorCode.RATE_LIMIT;
  if (b.includes("model not found"))                  return ErrorCode.MODEL_UNAVAILABLE;
  if (status >= 500)                                  return ErrorCode.NETWORK_ERROR;
  return ErrorCode.UNKNOWN_ERROR;
}

// ─── Classifier: catch(err) → ErrorCode ─────────────────────────────────────
export function classifyJsError(err: unknown): ErrorCode {
  if (!err) return ErrorCode.UNKNOWN_ERROR;
  const e = err as { name?: string; message?: string; status?: number; body?: string };
  if (e.name === "AbortError")                           return ErrorCode.TIMEOUT;
  if (e.message?.includes("completion-timeout"))         return ErrorCode.TIMEOUT;
  if (e.message?.toLowerCase().includes("network"))      return ErrorCode.NETWORK_ERROR;
  if (e.message?.toLowerCase().includes("offline"))      return ErrorCode.OFFLINE_MODE;
  if (e.status && e.body !== undefined)                  return classifyHttpError(e.status, e.body);
  return ErrorCode.UNKNOWN_ERROR;
}

// ─── Format for display ──────────────────────────────────────────────────────
export function formatErrorBanner(err: AppError): string {
  const prefix = err.provider ? `${err.provider}: ` : "";
  return `${prefix}${err.message}`;
}