/* -------------------------------------------------------------------------- */
/*           Provider error classification + friendly messaging               */
/*                                                                            */
/* Table-driven: adding a recognized failure mode = one row below. No control */
/* flow changes required.                                                     */
/* -------------------------------------------------------------------------- */

export type ProviderErrorInfo = {
  status?: number;
  code?: string;
  providerMessage?: string;
  apiMessage?: string;
};

/** Explicit provider error codes -> user-friendly message. */
const CODE_MESSAGES: Record<string, (pm?: string) => string> = {
  context_length_exceeded: () => "Prompt too long: exceeds the model's context limit. Start a new chat or reduce context.",
  capacity_exhausted: () => "Server out of memory. Try again later or reduce context size.",
  authentication_error: () => "Invalid or missing API key. Check your settings.",
  model_not_found: (pm) => `Model not found. Check the model name in settings.${pm ? ` (${pm})` : ""}`,
  engine_recovering: () => "Server is recovering. Try again in a few seconds.",
  engine_failed: () => "Server engine failed. The server needs to be restarted.",
  frontend_overloaded: () => "Server is overloaded. Try again in a few seconds.",
  resource_timeout: () => "Server ran out of memory while processing. Try again or reduce context.",
  mask_timeout: () => "Server internal timeout. Try again.",
  runtime_busy: () => "Server is busy. Try again in a few seconds.",
  runtime_unavailable: () => "Server runtime unavailable. Try again in a few seconds.",
  request_timeout: () => "Request timed out. Try reducing context or increasing timeout.",
  request_too_large: () => "Request body too large. Reduce the prompt/request size.",
  server_shutdown: () => "Server is shutting down. Try again later.",
  forbidden: (pm) => `Access forbidden. ${pm ?? "Check server --allowed-host / --allowed-origin settings."}`,
  model_result_invalid: () => "Model produced an invalid result. Try again.",
};

/** HTTP status codes -> user-friendly message (consulted when no explicit code is present). */
const STATUS_MESSAGES: Record<number, (pm?: string) => string> = {
  401: () => "Invalid or missing API key. Check your settings.",
  403: (pm) => `Access forbidden. ${pm ?? ""}`,
  404: (pm) => `Not found. ${pm ?? "Check the model name."}`,
  413: () => "Request too large.",
  429: (pm) => `Rate limit exceeded. Try again later.${pm ? ` (${pm})` : ""}`,
  500: (pm) => `Server error. ${pm ?? "Try again later."}`,
  503: (pm) => `Server unavailable. ${pm ?? "Try again later."}`,
  504: () => "Request timed out.",
};

/** Narrow an unknown value to a plain object record, or null. */
function asPlainObject(value: unknown): Record<string, unknown> | null {
  return value !== null && typeof value === "object" ? (value as Record<string, unknown>) : null;
}

/** Extract a non-empty string, else undefined. */
function readString(value: unknown): string | undefined {
  return typeof value === "string" && value.length > 0 ? value : undefined;
}

/** Extract a finite number, else undefined. */
function readNumber(value: unknown): number | undefined {
  return typeof value === "number" && Number.isFinite(value) ? value : undefined;
}

/**
 * Best-effort extraction of structured error info from an opaque thrown value.
 * Probes the common envelope shapes used by OpenAI-compatible gateways. Operates purely on
 * `unknown` with guarded readers — no `any` escapes at the boundary.
 */
export function extractProviderError(error: unknown): ProviderErrorInfo {
  const root = asPlainObject(error);
  const response = asPlainObject(root?.response);
  const responseData = asPlainObject(response?.data);
  const errorObj =
    asPlainObject(root?.error) ?? asPlainObject(responseData?.error) ?? asPlainObject(response?.error);

  const status = readNumber(root?.status) ?? readNumber(response?.status) ?? readNumber(root?.code);
  const apiMessage = readString(root?.message);
  const providerMessage =
    readString(errorObj?.message) ?? readString(responseData?.message) ?? apiMessage;
  const code = readString(errorObj?.code) ?? readString(asPlainObject(responseData?.error)?.code);

  return { status, code, providerMessage, apiMessage };
}

/** Map classified error info onto a concise, actionable message. */
export function formatErrorMessage(info: ProviderErrorInfo): string {
  if (info.code && CODE_MESSAGES[info.code]) return CODE_MESSAGES[info.code](info.providerMessage);
  if (info.status != null && STATUS_MESSAGES[info.status]) return STATUS_MESSAGES[info.status](info.providerMessage);
  return `API error: ${info.providerMessage ?? info.apiMessage ?? "Unknown error"}`;
}

/* -------------------------------------------------------------------------- */
/*           Provider error classification + friendly messaging               */
/*                                                                            */
/* Table-driven: adding a recognized failure mode = one row below. No control */
/* flow changes required.                                                     */
/* -------------------------------------------------------------------------- */

export type ProviderErrorInfo = {
  status?: number;
  code?: string;
  providerMessage?: string;
  apiMessage?: string;
};

/** Explicit provider error codes -> user-friendly message. */
const CODE_MESSAGES: Record<string, (pm?: string) => string> = {
  context_length_exceeded: () => "Prompt too long: exceeds the model's context limit. Start a new chat or reduce context.",
  capacity_exhausted: () => "Server out of memory. Try again later or reduce context size.",
  authentication_error: () => "Invalid or missing API key. Check your settings.",
  model_not_found: (pm) => `Model not found. Check the model name in settings.${pm ? ` (${pm})` : ""}`,
  engine_recovering: () => "Server is recovering. Try again in a few seconds.",
  engine_failed: () => "Server engine failed. The server needs to be restarted.",
  frontend_overloaded: () => "Server is overloaded. Try again in a few seconds.",
  resource_timeout: () => "Server ran out of memory while processing. Try again or reduce context.",
  mask_timeout: () => "Server internal timeout. Try again.",
  runtime_busy: () => "Server is busy. Try again in a few seconds.",
  runtime_unavailable: () => "Server runtime unavailable. Try again in a few seconds.",
  request_timeout: () => "Request timed out. Try reducing context or increasing timeout.",
  request_too_large: () => "Request body too large. Reduce the prompt/request size.",
  server_shutdown: () => "Server is shutting down. Try again later.",
  forbidden: (pm) => `Access forbidden. ${pm ?? "Check server --allowed-host / --allowed-origin settings."}`,
  model_result_invalid: () => "Model produced an invalid result. Try again.",
};

/** HTTP status codes -> user-friendly message (consulted when no explicit code is present). */
const STATUS_MESSAGES: Record<number, (pm?: string) => string> = {
  401: () => "Invalid or missing API key. Check your settings.",
  403: (pm) => `Access forbidden. ${pm ?? ""}`,
  404: (pm) => `Not found. ${pm ?? "Check the model name."}`,
  413: () => "Request too large.",
  429: (pm) => `Rate limit exceeded. Try again later.${pm ? ` (${pm})` : ""}`,
  500: (pm) => `Server error. ${pm ?? "Try again later."}`,
  503: (pm) => `Server unavailable. ${pm ?? "Try again later."}`,
  504: () => "Request timed out.",
};

/** Narrow an unknown value to a plain object record, or null. */
function asPlainObject(value: unknown): Record<string, unknown> | null {
  return value !== null && typeof value === "object" ? (value as Record<string, unknown>) : null;
}

/** Extract a non-empty string, else undefined. */
function readString(value: unknown): string | undefined {
  return typeof value === "string" && value.length > 0 ? value : undefined;
}

/** Extract a finite number, else undefined. */
function readNumber(value: unknown): number | undefined {
  return typeof value === "number" && Number.isFinite(value) ? value : undefined;
}

/**
 * Best-effort extraction of structured error info from an opaque thrown value.
 * Probes the common envelope shapes used by OpenAI-compatible gateways. Operates purely on
 * `unknown` with guarded readers — no `any` escapes at the boundary.
 */
export function extractProviderError(error: unknown): ProviderErrorInfo {
  const root = asPlainObject(error);
  const response = asPlainObject(root?.response);
  const responseData = asPlainObject(response?.data);
  const errorObj =
    asPlainObject(root?.error) ?? asPlainObject(responseData?.error) ?? asPlainObject(response?.error);

  const status = readNumber(root?.status) ?? readNumber(response?.status) ?? readNumber(root?.code);
  const apiMessage = readString(root?.message);
  const providerMessage =
    readString(errorObj?.message) ?? readString(responseData?.message) ?? apiMessage;
  const code = readString(errorObj?.code) ?? readString(asPlainObject(responseData?.error)?.code);

  return { status, code, providerMessage, apiMessage };
}

/** Map classified error info onto a concise, actionable message. */
export function formatErrorMessage(info: ProviderErrorInfo): string {
  if (info.code && CODE_MESSAGES[info.code]) return CODE_MESSAGES[info.code](info.providerMessage);
  if (info.status != null && STATUS_MESSAGES[info.status]) return STATUS_MESSAGES[info.status](info.providerMessage);
  return `API error: ${info.providerMessage ?? info.apiMessage ?? "Unknown error"}`;
}