1 files changed, 110 insertions, 0 deletions

diff --git a/lib/ledger.ml b/lib/ledger.ml
new file mode 100644
index 0000000..fd1b2a9
--- /dev/null
+++ b/lib/ledger.ml
@@ -0,0 +1,110 @@
+open Core
+
+type account_type = Asset | Equity | Liability | Expense | Income
+
+type tx_type =
+  | Interest_tx
+  | Online_banking_tx
+  | Recurrent_direct_tx
+  | Payment_terminal_tx
+  | Cash_payment_tx
+  | Atm_tx
+  | Auto_save_rounding_tx
+  | Batch_tx
+  | Direct_debit_tx
+  | Periodic_tx
+
+type iban_tag = Account_tag | Counterparty_iban_tag [@@deriving compare]
+
+type unit_tag = Filed_tag | GooglePay_tag | AutoRoundSavings_tag
+[@@deriving compare]
+
+type string_tag =
+  | Desc_tag
+  | User_tag
+  | Counterparty_name_tag
+  | Reference_tag
+  | Mandate_id_tag
+  | Creditor_id_tag
+  | Other_party_tag
+  | Transaction_tag
+  | Terminal_tag
+  | Card_seq_no_tag
+  | Savings_account_tag
+[@@deriving compare]
+
+module Label = struct
+  type 'a t =
+    | Iban_label : iban_tag -> Iban.t t
+    | String_label : string_tag -> string t
+    | Timestamp_label : Time_ns.t t
+    | Unit_label : unit_tag -> unit t
+
+  let int_to_cmp x : ('a, 'a) Dmap.cmp =
+    if x < 0 then Lt else if x > 0 then Gt else Eq
+
+  let compare (type a1 a2) (v1 : a1 t) (v2 : a2 t) : (a1, a2) Dmap.cmp =
+    match (v1, v2) with
+    | Iban_label t1, Iban_label t2 -> int_to_cmp @@ [%compare: iban_tag] t1 t2
+    | String_label t1, String_label t2 ->
+        int_to_cmp @@ [%compare: string_tag] t1 t2
+    | Timestamp_label, Timestamp_label -> Eq
+    | Unit_label t1, Unit_label t2 -> int_to_cmp @@ [%compare: unit_tag] t1 t2
+    | Iban_label _, _ -> Lt
+    | String_label _, Iban_label _ -> Gt
+    | String_label _, _ -> Lt
+    | Timestamp_label, Unit_label _ -> Lt
+    | Timestamp_label, _ -> Gt
+    | Unit_label _, _ -> Gt
+end
+
+module Labels = Dmap.Make (Label)
+
+module Money : sig
+  type t
+
+  val equal : t -> t -> bool
+  val compare : t -> t -> int
+  val of_z : Z.t -> t
+  val to_z : t -> Z.t
+  val ( + ) : t -> t -> t
+  val ( - ) : t -> t -> t
+end = struct
+  type t = Z.t
+
+  let equal = Z.equal
+  let compare = Z.compare
+  let of_z = Fn.id
+  let to_z = Fn.id
+  let ( + ) x y = Z.(x + y)
+  let ( - ) x y = Z.(x - y)
+end
+
+type scalar = Amount of Money.t | Rate of Z.t [@@deriving equal, compare]
+type account_id = string list
+type commodity_id = string (* TODO: consider making this UUID *)
+
+type account = {
+  id : account_id;
+  description : string list;
+  commodity_id : commodity_id;
+  balance : Money.t;
+}
+
+type bal_assert = { account : account_id; amount : Money.t; labels : Labels.t }
+
+module Account_id_key = struct
+  type t = account_id
+  type comparator_witness
+end
+
+type tx = {
+  cleared : Date.t option;
+  commodity_id : commodity_id;
+  debit : scalar Map.M(Account_id_key).t;
+  credit : scalar Map.M(Account_id_key).t;
+  labels : Labels.t;
+}
+
+type item = Tx_item of tx | Bal_assert_item of bal_assert
+type ledger = Ledger of item list