export enum ErrorCode {
  // Provider errors
  PROVIDER_ERROR = "PROVIDER_ERROR",

  // Tool errors
  TOOL_ERROR = "TOOL_ERROR",

  // Permission errors
  PERMISSION_DENIED = "PERMISSION_DENIED",

  // Config errors
  CONFIG_ERROR = "CONFIG_ERROR",

  // Daemon errors
  DAEMON_ERROR = "DAEMON_ERROR",

  // Platform-specific errors (clipboard, unsupported OS features)
  PLATFORM_ERROR = "PLATFORM_ERROR",

  // WASM integrity check failures
  INTEGRITY_ERROR = "INTEGRITY_ERROR",

  // Internal/unexpected errors
  INTERNAL_ERROR = "INTERNAL_ERROR",
}

// ── Root ──────────────────────────────────────────────────────────────────────

/** Root base class for all named Vellum errors. */
export class VellumError extends Error {
  constructor(message: string, options?: ErrorOptions) {
    super(message, options);
    this.name = "VellumError";
  }
}

// ── Backend errors ────────────────────────────────────────────────────────────

/**
 * Errors originating from infrastructure or external service calls.
 * Catch this when you want to handle any backend failure uniformly.
 */
export class BackendError extends VellumError {
  constructor(message: string, options?: ErrorOptions) {
    super(message, options);
    this.name = "BackendError";
  }
}

/**
 * The embedding or vector-search backend is not configured or not reachable.
 * Thrown before attempting an embedding operation so callers can skip or defer.
 */
export class BackendUnavailableError extends BackendError {
  constructor(reason: string) {
    super(reason);
    this.name = "BackendUnavailableError";
  }
}

/**
 * A request or token-budget quota was exceeded.
 * Thrown by the provider rate-limiter and by domain-specific clients (e.g. DoorDash).
 */
export class RateLimitError extends BackendError {
  constructor(message: string) {
    super(message);
    this.name = "RateLimitError";
  }
}

// ── User errors ───────────────────────────────────────────────────────────────

/**
 * Errors caused by user input, policy violations, or user-facing constraints.
 * Catch this when you want to present an actionable message to the user.
 */
export class UserError extends VellumError {
  constructor(message: string, options?: ErrorOptions) {
    super(message, options);
    this.name = "UserError";
  }
}

// ── AssistantError subtree ────────────────────────────────────────────────────

/**
 * Base class for errors originating from assistant logic (providers, tools,
 * permissions, config). Extends VellumError and carries a structured ErrorCode.
 */
export class AssistantError extends VellumError {
  constructor(
    message: string,
    public readonly code: ErrorCode,
    options?: { cause?: unknown },
  ) {
    super(message, options);
    this.name = "AssistantError";
  }
}

/**
 * Semantic classification of a provider failure, stamped by the provider layer
 * at the throw site (from status + body signals) so downstream consumers
 * (`daemon/conversation-error.ts`, `providers/retry.ts`) can switch on intent
 * instead of re-deriving it from status codes and message regex. Co-located
 * with `ProviderError` — a leaf module — for the same reason as `abortReason`:
 * no import cost. `unknown` (and an absent `reason`) defers to the existing
 * status/regex fallback.
 */
export type ProviderErrorReason =
  | "invalid_credentials"
  | "model_restricted"
  | "model_not_found"
  | "insufficient_credits"
  | "daily_limit_reached"
  | "rate_limited"
  | "overloaded"
  | "context_overflow"
  | "vision_unsupported"
  | "bad_request"
  | "server_error"
  | "network_error"
  | "unknown";

export type ProviderCredentialSource =
  | "byok"
  | "no-auth"
  | "oauth-subscription"
  | "vellum-managed";

export interface ProviderRouteAttribution {
  connectionName?: string;
  profileName?: string;
  isManagedRoute?: boolean;
  /**
   * Credential surface used for this request. Finer than `isManagedRoute`:
   * it separates personal provider keys, keyless endpoints, and subscription
   * logins from each other so error copy can name what the user must fix.
   */
  credentialSource?: ProviderCredentialSource;
}

export class ProviderError extends AssistantError {
  /** Delay (in ms) suggested by the server's Retry-After header, if present. */
  public readonly retryAfterMs?: number;
  /** Upstream provider error metadata, parsed from the raw non-2xx body. */
  public readonly apiErrorCode?: string;
  public readonly apiErrorType?: string;
  public readonly apiErrorParam?: string;
  public readonly requestId?: string;
  /**
   * Verbatim upstream non-2xx body (possibly truncated). Persisted so the
   * inspector's Raw tab can show the actual provider error payload, not just
   * the extracted fields.
   */
  public readonly rawBody?: string;
  /**
   * Tagged daemon-owned abort reason carried over from the AbortSignal that
   * triggered this error. Untyped here to avoid a daemon→util import cycle;
   * `AbortReason` from `util/abort-reasons.ts` is the only producer and
   * `isAbortReason` is the canonical type guard for consumers.
   */
  public readonly abortReason?: unknown;
  /** Semantic failure classification stamped at the throw site. */
  public readonly reason?: ProviderErrorReason;
  /** Transport route selected for the failed provider call. */
  public routeAttribution?: ProviderRouteAttribution;

  constructor(
    message: string,
    public readonly provider: string,
    public readonly statusCode?: number,
    options?: {
      cause?: unknown;
      retryAfterMs?: number;
      abortReason?: unknown;
      apiErrorCode?: string;
      apiErrorType?: string;
      apiErrorParam?: string;
      requestId?: string;
      rawBody?: string;
      reason?: ProviderErrorReason;
    },
  ) {
    super(message, ErrorCode.PROVIDER_ERROR, options);
    this.name = "ProviderError";
    this.retryAfterMs = options?.retryAfterMs;
    this.apiErrorCode = options?.apiErrorCode;
    this.apiErrorType = options?.apiErrorType;
    this.apiErrorParam = options?.apiErrorParam;
    this.requestId = options?.requestId;
    this.rawBody = options?.rawBody;
    this.abortReason = options?.abortReason;
    this.reason = options?.reason;
  }

  attachRouteAttribution(attribution: ProviderRouteAttribution): void {
    this.routeAttribution = {
      ...attribution,
      ...this.routeAttribution,
    };
  }
}

export class ToolError extends AssistantError {
  constructor(
    message: string,
    public readonly toolName: string,
  ) {
    super(message, ErrorCode.TOOL_ERROR);
    this.name = "ToolError";
  }
}

export class PermissionDeniedError extends AssistantError {
  constructor(
    message: string,
    public readonly toolName: string,
  ) {
    super(message, ErrorCode.PERMISSION_DENIED);
    this.name = "PermissionDeniedError";
  }
}

export class ConfigError extends AssistantError {
  constructor(message: string, options?: { cause?: unknown }) {
    super(message, ErrorCode.CONFIG_ERROR, options);
    this.name = "ConfigError";
  }
}

export class ProviderNotConfiguredError extends ConfigError {
  /**
   * Optional name of the `provider_connections` row whose credential was
   * missing. Surfaced through `ConversationErrorEvent.connectionName` so
   * the macOS chat banner can render "API key required for connection
   * <name>" instead of a generic message.
   */
  public readonly connectionName?: string;
  /**
   * Optional name of the resolved profile in play when this error was
   * thrown. Forwarded to the wire `ConversationErrorEvent.profileName`
   * for the same banner-attribution purpose as `connectionName`.
   */
  public readonly profileName?: string;

  constructor(
    public readonly requestedProvider: string,
    public readonly registeredProviders: string[],
    attribution?: { connectionName?: string; profileName?: string },
  ) {
    super(
      `No providers available. Requested: "${requestedProvider}". Registered: ${registeredProviders.join(", ") || "none"}`,
    );
    this.name = "ProviderNotConfiguredError";
    this.connectionName = attribution?.connectionName;
    this.profileName = attribution?.profileName;
  }
}

export class DaemonError extends AssistantError {
  constructor(message: string, options?: { cause?: unknown }) {
    super(message, ErrorCode.DAEMON_ERROR, options);
    this.name = "DaemonError";
  }
}

export class IntegrityError extends AssistantError {
  constructor(message: string, options?: { cause?: unknown }) {
    super(message, ErrorCode.INTEGRITY_ERROR, options);
    this.name = "IntegrityError";
  }
}