(** Eio-idiomatic errors for Matrix operations.

    This module provides error types that follow Eio conventions,
    using [Eio.Io] for IO-related errors and exceptions for
    exceptional conditions. *)

(** The source type for Matrix IO errors *)
type err =
  | Network of string  (** Network-level error *)
  | Http of { status : int; body : string }  (** HTTP error response *)
  | Json of string  (** JSON encoding/decoding error *)
  | Matrix of {
      errcode : Matrix_client.Error.errcode;
      error : string;
      retry_after_ms : int option;
    }  (** Matrix protocol error *)
  | Not_logged_in  (** Operation requires authentication *)
  | Cancelled  (** Operation was cancelled *)

type Eio.Exn.err += E of err

let err e = Eio.Exn.create (E e)

(** Pretty-print an error source *)
let pp_err fmt = function
  | Network msg -> Format.fprintf fmt "Network error: %s" msg
  | Http { status; body } -> Format.fprintf fmt "HTTP %d: %s" status body
  | Json msg -> Format.fprintf fmt "JSON error: %s" msg
  | Matrix { errcode; error; _ } ->
      Format.fprintf fmt "Matrix error %s: %s"
        (Matrix_client.Error.errcode_to_string errcode) error
  | Not_logged_in -> Format.fprintf fmt "Not logged in"
  | Cancelled -> Format.fprintf fmt "Operation cancelled"

let () = Eio.Exn.register_pp (fun fmt -> function
  | E e -> pp_err fmt e; true
  | _ -> false)

(** Convert a matrix_client error to an Eio error *)
let of_client_error = function
  | Matrix_client.Error.Matrix_error e ->
      Matrix {
        errcode = e.errcode;
        error = e.error;
        retry_after_ms = e.retry_after_ms;
      }
  | Matrix_client.Error.Network_error msg -> Network msg
  | Matrix_client.Error.Json_error msg -> Json msg
  | Matrix_client.Error.Http_error { status; body } -> Http { status; body }

(** Raise an Eio.Io exception from a matrix_client error *)
let raise_client_error e =
  raise (Eio.Exn.create (E (of_client_error e)))

(** Convert Result-based client operations to Eio-style exceptions *)
let unwrap = function
  | Ok v -> v
  | Error e -> raise_client_error e

(** Check if an error is retryable *)
let is_retryable = function
  | Network _ -> true
  | Http { status; _ } -> status >= 500 || status = 429
  | Matrix { errcode; _ } -> errcode = Matrix_client.Error.M_LIMIT_EXCEEDED
  | Json _ | Not_logged_in | Cancelled -> false

(** Get retry delay in seconds from an error, if available *)
let retry_after = function
  | Matrix { retry_after_ms = Some ms; _ } -> Some (float_of_int ms /. 1000.0)
  | Http { status = 429; _ } -> Some 1.0  (* Default retry after *)
  | _ -> None