[Reason] Chapter FA2 basic + fungible_token exercise

src/frontend/src/pages/Chapters/Reason/ChapterFA20/caller.religo

@@ -0,0 +1,60 @@
+// Fa2 Client contract
+#include "tzip-12/fa2_interface.religo"
+
+type storage = {
+  rep : list(balanceOfResponseMichelson)
+}
+
+type request_balance_of_param = {
+    at : address,
+    requests : list(balanceOfRequest)
+}
+
+type receive_balance_of_param = list(balanceOfResponseMichelson)
+
+type entry_points =
+  | Request_balance (request_balance_of_param)
+  | Receive_balance (receive_balance_of_param)
+
+let request_balance = ((req, s) : (request_balance_of_param, storage)) : (list(operation), storage) =>
+{
+    // Get the TZIP-12 contract instance 'from' the chain 
+    let token_contract_balance_entrypoint_opt : option(contract(balanceOfParameterMichelson)) = Tezos.get_entrypoint_opt ("%balance_of", req.at) ;
+    let token_contract_balance_entrypoint : contract(balanceOfParameterMichelson) = switch (token_contract_balance_entrypoint_opt) {
+        | Some (ci) => ci
+        | None => (failwith("Entrypoint not found"): contract(balanceOfParameterMichelson))
+    };
+
+    // Callback (contract) for Balance_of will be the current contract's Receive_balance entrypoint 
+    let balance_of_callback_contract_opt : option(contract(receive_balance_of_param)) = Tezos.get_entrypoint_opt ("%receive_balance", Tezos.self_address);
+    let balance_of_callback_contract : contract(receive_balance_of_param) = switch (balance_of_callback_contract_opt) {
+        | Some (ci) => ci
+        | None => (failwith("Entrypoint not found"): contract(receive_balance_of_param))
+    };
+
+    // Set up the parameter w/ data required for the Balance_of entrypoint
+    let convert = (i : balanceOfRequest) : balanceOfRequestMichelson => Layout.convert_to_right_comb(i); 
+    let request_michelson : list(balanceOfRequestMichelson) = List.map (convert, req.requests);
+    let balance_of_operation_param : balanceOfParameterAuxiliary = {
+        requests : request_michelson,
+        callback : balance_of_callback_contract,
+    };
+    let reqPayload : balanceOfParameterMichelson = Layout.convert_to_right_comb(balance_of_operation_param);
+    // Forge an internal transaction to the TZIP-12 contract from balance_of_operation_param. We're sending 0mutez as part of this transaction
+    let balance_of_operation : operation = Tezos.transaction (reqPayload, 0mutez, token_contract_balance_entrypoint);
+    ([ balance_of_operation ], s)
+}
+
+let receive_balance = ((received, s): (receive_balance_of_param, storage)) : (list(operation), storage) =>
+{
+    let new_store : storage = { ...s, rep : received };
+    (([] :list( operation)), new_store)
+}
+
+let main = ((param, s) : (entry_points , storage)) : (list(operation), storage) =>
+{
+  switch (param) {
+    | Request_balance request_balance_of_param => request_balance ((request_balance_of_param, s))
+    | Receive_balance receive_balance_of_param => receive_balance ((receive_balance_of_param, s))
+  }
+}

src/frontend/src/pages/Chapters/Reason/ChapterFA20/course.md

@@ -43,10 +43,6 @@ type parameter =
 | Update_operators(updateOperatorsParameter)
 ```
 
-
-
-
-
 ### Balance of
 
 The FA2 client (contracts using our token) may need to know the balance of a owner. The FA2 standard specifies an entry point _Balance of_ which use a callback in order to send the balance information to the calling contract. 
@@ -208,20 +204,24 @@ Error mnemonic - Description
 
 ## Your mission
 
-<!-- prettier-ignore -->We are working on a fungible/multi-asset token compliant with the FA2 standard. We want you to complete the existing implementation of token. The *Total\_supply* entry point is not yet implemented , please finish the job !
+<!-- prettier-ignore -->We are working on a fungible token compliant with the FA2 standard. We want you to complete the existing implementation of token. The *Balance\_Of* entry point is not yet implemented , please finish the job !
+
+<!-- prettier-ignore -->The function *balanceOfRequestsIterator* is responsible for processing each request and providing a response to each request.As you can see, a request is of type *balanceOfRequestMichelson*
+
 
-<!-- prettier-ignore -->1 - Modify the *get\_total\_supply* lambda function in order to retrieve the *total\_supply* information related to the given *token\_id* list.
+<!-- prettier-ignore -->1- First, we need to retieve information from the request. convert the request *balanceOfRequestMichelson* into a vairiable named *balanceOfRequest* of type _balanceOfRequest_. You can use the *convert\_from\_right\_comb* function (seen in Chapter Interop)
 
-<!-- prettier-ignore -->2 - the *get\_total\_supply* lambda function For each given *token\_id*, find the given *token\_id* in the *tokens* map and retrieve the *total\_supply* associated to a given *token\_id* in the *tokens* map.
+<!-- prettier-ignore -->2- Now that request is readable, call the *getTokenBalance* function in order to retrieve the balance of the specified owner. Store the result in a variable *tokenBalance* of type _tokenBalance_. 
 
-<!-- prettier-ignore -->3 -If a given *token\_id* is found then the function *get\_total\_supply* must return a *total\_supply\_response* record for each given *token\_id*. As seen in the interface the *total\_supply\_response* record contains *token\_id* and *total\_supply* fields. (use v as temporary variable for the match with instruction)
+<!-- prettier-ignore -->3- Now, we need to build a response for the balanceOfRequest. Declare a variable *balanceOfResponseAuxiliary* ot type _balanceOfResponseAuxiliary_ which contains the request and the retrieved balance *tokenBalance* (defined in the previous line).
 
-<!-- prettier-ignore -->4 -If a given *token\_id* is not found then the function *get\_total\_supply* must throw an exception with the predefined error messsage *token\_undefined*.
+<!-- prettier-ignore -->4- Convert this response of type _balanceOfResponseAuxiliary_ into a variable *balanceOfResponseMichelson* of type _balanceOfResponseMichelson_. You can use the *convert\_from\_right\_comb* function (seen in Chapter Interop)
 
 
 
 
 
+## WIP
 
 ### Metadata