Add message decoder implementation.

Restrict the Message module interface to the message types and decoder function.

2 files changed, 50 insertions, 15 deletions

diff --git a/src/message.ml b/src/message.ml
index ec28922..673d5e8 100644
--- a/src/message.ml
+++ b/src/message.ml
@@ -1,12 +1,49 @@
 exception Invalid_operation of string
+exception Invalid_message of string
 
-type operation = {
+type operation =
+    | Set of string list
+    | Delete of string list
+    | Show of (string list option) * ((string * string) list option)
+
+type message = {
+    session_id: string;
+    ops: operation list
+}
+
+type raw_operation = {
     method_name: string;
     path: string list option;
     options: (string * string) list option
 } [@@deriving yojson]
 
-type message = {
-    session_id: string;
-    ops: operation list;
+type raw_message = {
+    raw_session_id: string;
+    raw_ops: raw_operation list;
 } [@@deriving yojson]
+
+
+let value_of_path p =
+    match p with
+    | Some p -> p
+    | None -> raise (Invalid_operation "Operation requires a path")
+
+let decode_operation op =
+    let op_name = op.method_name in
+    match op_name with
+    | "set" -> Set (value_of_path op.path)
+    | "delete" -> Delete (value_of_path op.path)
+    | "show" -> Show (op.path, op.options)
+    | _ -> raise (Invalid_operation "Invalid operation name")
+
+let decode_message msg =
+    let id = msg.raw_session_id in
+    let ops = List.map decode_operation msg.raw_ops in
+    {session_id = id; ops = ops}
+
+let decode j =
+    let msg = raw_message_of_yojson j in
+    match msg with
+    | `Ok msg -> decode_message msg
+    | `Error str -> raise (Invalid_message str)
+    
diff --git a/src/message.mli b/src/message.mli
index af92d67..2688b8c 100644
--- a/src/message.mli
+++ b/src/message.mli
@@ -1,16 +1,14 @@
-type operation = {
-    method_name: string;
-    path: string list option;
-    options: (string * string) list option
-}
+exception Invalid_operation of string
+exception Invalid_message of string
+
+type operation =
+    | Set of string list
+    | Delete of string list
+    | Show of (string list option) * ((string * string) list option)
 
 type message = {
     session_id: string;
-    ops: operation list;
+    ops: operation list
 }
 
-val operation_to_yojson : operation -> Yojson.Safe.json
-val operation_of_yojson : Yojson.Safe.json -> [ `Error of bytes | `Ok of operation ]
-
-val message_to_yojson : message -> Yojson.Safe.json
-val message_of_yojson : Yojson.Safe.json -> [ `Error of bytes | `Ok of message ]
+val decode : Yojson.Safe.json -> message