Enable token storage in asset wallet notebooks

Expose and use the necessary interfaces for tokens to be included in
wallet notebooks. The big benefit of this is that all "ownership"
functions can now be handled through the same interface whether they
are fungible assets (like marbles) or non-fungible assets (like
tokens).

Needed to support the "get_balance" method in the token contract (we
already support many of the other issuer methods through
tokens). Added better support for the balance and transfer in the
plugins.

And... most notably, added an "issuer" reference in the context
file. Context references turn out to be rather useful. This creates a
reference to the specific token object in the collections file. So now
there is a canonical reference point for accessing issuer functions.

Signed-off-by: Mic Bowman <mic.bowman@intel.com>

exchange-contract/contracts/token_object.cpp

@@ -93,6 +93,7 @@ contract_method_reference_t contract_method_dispatch_table[] = {
     CONTRACT_METHOD(echo),
 
     // object transfer, escrow & claim methods
+    CONTRACT_METHOD2(get_balance,ww::exchange::token_object::get_balance),
     CONTRACT_METHOD2(transfer,ww::exchange::token_object::transfer),
     CONTRACT_METHOD2(escrow,ww::exchange::token_object::escrow),
     CONTRACT_METHOD2(escrow_attestation,ww::exchange::token_object::escrow_attestation),

exchange-contract/docs/notebooks/templates/token.py

@@ -135,8 +135,11 @@ def token_transfer(new_owner) :
 # free to change the file name as well. The default uses the asset name.
 
 # %%
+# this adds a reference key to "issuer" which makes the wallets work with tokens
+context.set('issuer', '@{.token_object.' + token_name + '}')
+
 contract_identifier = '{}_{}'.format(token_class, instance_identifier)
-contexts = ['asset_type', 'vetting', 'guardian', 'token_issuer', 'token_object']
+contexts = ['asset_type', 'issuer', 'vetting', 'guardian', 'token_issuer', 'token_object']
 contract_files = {
     'token' : token_context.get('save_file'),
 }

exchange-contract/exchange/contracts/token_object.cpp

@@ -139,6 +139,30 @@ bool ww::exchange::token_object::initialize(
     return rsp.success(true);
 }
 
+// -----------------------------------------------------------------
+// METHOD: get_balance
+//
+// JSON PARAMETERS:
+//   none
+//
+// RETURNS:
+//   current number of assets assigned to the requestor
+// -----------------------------------------------------------------
+bool ww::exchange::token_object::get_balance(const Message& msg, const Environment& env, Response& rsp)
+{
+    ASSERT_INITIALIZED(rsp);
+
+    int count = 0;
+    std::string owner;
+
+    ASSERT_SUCCESS(rsp, ww::contract::base::get_owner(owner), "failed to retrieve owner");
+    if (env.originator_id_ == owner)
+        count = 1;
+
+    ww::value::Number balance(count);
+    return rsp.value(balance, false);
+}
+
 // -----------------------------------------------------------------
 // transfer
 // -----------------------------------------------------------------

exchange-contract/exchange/token_object.h

@@ -62,6 +62,7 @@ namespace token_object
     bool initialize(const Message& msg, const Environment& env, Response& rsp);
 
     // the interface for these methods is copied from issuer contract
+    bool get_balance(const Message& msg, const Environment& env, Response& rsp);
     bool transfer(const Message& msg, const Environment& env, Response& rsp);
     bool escrow(const Message& msg, const Environment& env, Response& rsp);
     bool escrow_attestation(const Message& msg, const Environment& env, Response& rsp);

exchange-contract/pdo/exchange/plugins/token_object.py

@@ -41,6 +41,7 @@
     'op_get_asset_type_identifier',
     'op_get_issuer_authority',
     'op_get_authority',
+    'op_get_balance',
     'op_transfer',
     'op_escrow',
     'op_release',
@@ -59,6 +60,7 @@
 op_get_asset_type_identifier = asset_type.op_get_asset_type_identifier
 op_get_issuer_authority = vetting.op_get_issuer_authority
 op_get_authority = issuer.op_get_authority
+op_get_balance = issuer.op_get_balance
 op_transfer = issuer.op_transfer
 op_escrow = issuer.op_escrow
 op_release = issuer.op_release
@@ -312,6 +314,13 @@ def invoke(cls, state, context, new_owner, **kwargs) :
         with open (keyfile, "r") as myfile:
             verifying_key = myfile.read()
 
+        # in case count was specified, it must be 1 and we must remove it since it is set explicitly
+        # in the op invocation below
+        if 'count' in kwargs :
+            if kwargs['count'] != 1 :
+                raise ValueError('unexpected count for token transfer')
+            kwargs.pop('count')
+
         session = pbuilder.SessionParameters(save_file=save_file)
         pcontract.invoke_contract_op(issuer.op_transfer, state, context, session, verifying_key, 1, **kwargs)
 
@@ -372,6 +381,7 @@ def invoke(cls, state, context, message, **kwargs) :
     op_get_asset_type_identifier,
     op_get_issuer_authority,
     op_get_authority,
+    op_get_balance,
     op_transfer,
     op_escrow,
     op_release,