docs: incorporate latest changes into readme

README.md

@@ -37,7 +37,8 @@ import { OCPP16, OCPP20 } from 'typed-ocpp';
 ```
 
 Both namespaces export identical APIs while typings and schemas differ
-according to the differences in the respective OCPP versions.
+according to the differences in the respective OCPP versions. All of the
+examples below apply to both namespaces.
 
 ### `parse()`
 
@@ -81,7 +82,7 @@ As returned values are fully-typed, the TS compiler can use known types to
 infer others:
 
 ```typescript
-if (parsed[0] === OCPP16.MessageType.CALL) {
+if (OCPP16.isCall(parsed)) {
  parsed[2]; // TS gives type "OCPP.Action" 
  if (parsed[2] === OCPP16.Action.BootNotification) {
  // TS infers the shape of the call payload based on the action
@@ -91,18 +92,35 @@ if (parsed[0] === OCPP16.MessageType.CALL) {
 }
 ```
 
+### `isCall()`, `isCallResult()` and `isCallError()`
+
+The `isCall()`, `isCallResult()` and `isCallError()` functions are utility type
+guards that facilitates identifying the type of a parsed message: 
+
+```typescript
+const parsed = OCPP16.parse(message);
+
+if (OCPP16.isCall(parsed)) {
+ // TS infers that parsed is of type OCPP16.Call
+}
+
+if (OCPP16.isCallResult(message)) {
+ // TS infers that parsed is of type OCPP16.UncheckedCallResult
+}
+
+if (OCPP16.isCallError(message)) {
+// TS infers that parsed is of type OCPP16.CallError
+}
+```
+
 ### `checkCallResult()`
 
-Call Result messages are first returned as having type `UncheckedCallResult`
-and must be checked against the originating messages of type `Call` for further
+Call Result messages are returned by `parse()` as the `UncheckedCallResult`
+type and must be checked against the originating `Call` messages for further
 validation and type-awareness.
 
 If `checkCallResult()` does not throw the returned values are guaranteed to be
-valid `CallResult` objects _matching the provided `Call` objects_.
-
-While `CallResult` type is the union of all Call Result message types, the TS
-compiler will infer the specific type of Call Result based on the action of the
-provided `Call`:
+valid `CallResult` objects _matching the provided `Call` objects_:
 
 ```typescript
 const call = '[2,"test","BootNotification",{"chargePointModel":"model","chargePointVendor":"vendor"}]';
@@ -111,16 +129,22 @@ const result = '[3, "test", { status: "Accepted", currentTime: "1970-01-01T00:00
 const parsedCall = OCPP16.parse(call);
 const parsedResult = OCPP16.parse(result);
 
-if (parsedCall[0] === OCPP16.MessageType.CALL && parsedResult[0] === OCPP16.MessageType.CALLRESULT) {
- if (parsedCall[2] === OCPP16.Action.BootNotification) {
- const checkedResult = OCPP16.checkCallResult(parsedResult, parsedCall);
- checkedResult[2].status; // TS gives type "Accepted"|"Pending"|"Rejected"
+if (OCPP16.isCall(parsedCall)) { // Narrows parsedCall to OCPP16.Call
+ if (OCPP16.isCallResult(parsedResult)) { // Narrows parsedResult to OCPP16.UncheckedCallResult
+ if (parsedCall[2] === OCPP16.Action.BootNotification) { // Narrows parsedCall to OCPP16.BootNotificationCall
+ const checkedResult = OCPP16.checkCallResult( // checkedResult inferred as having type
+ parsedResult, parsedCall // OCPP16.BootNotificationCallResult
+ );
+ checkedResult[2].status; // Inferred as "Accepted" | "Pending" | "Rejected"
+ }
  }
 }
 ```
 
-The `checkCallResult()` function returns values of the
-`CheckedCallResult<C extends Call>` type, which may also be used on its own to
+The `checkCallResult()` function returns values of the generic type
+`CheckedCallResult<C extends Call>` which resolves to the type of Call Result
+message that corresponds to the type of Call messages provided as the `C` type
+argument. `CheckedCallResult<C extends Call>` may also be used on its own to
 model Call Result messages matching a specific Call message. See below.
 
 ### `stringify()`
@@ -150,17 +174,19 @@ OCPP16.Call // union type of all Call message types
 OCPP16.CallResult // union type of all Call Result message types
 OCPP16.CallError // type of Call Error messages
 OCPP16.UncheckedCallResult // type of unchecked Call Result messages
-OCPP16.CheckedCallResult // generic type for Call Result messages matching
- // a specific type of Call messages
+OCPP16.CheckedCallResult< // generic type of that resolves to the specific
+ C extends OCPP16.Call> // type of Call Result message matching the
+ // provided type of Call message "C"
 ``` 
 
 ```typescript
-OCPP20.Call // union type of all Call message types
-OCPP20.CallResult // union type of all Call Result message types
-OCPP20.CallError // type of Call Error messages
-OCPP20.UncheckedCallResult // type of unchecked Call Result messages
-OCPP20.CheckedCallResult // generic type for Call Result messages matching
- // a specific type of Call messages
+OCPP20.Call // union type of all Call message types
+OCPP20.CallResult // union type of all Call Result message types
+OCPP20.CallError // type of Call Error messages
+OCPP20.UncheckedCallResult // type of unchecked Call Result messages
+OCPP20.CheckedCallResult< // generic type of that resolves to the specific
+ C extends OCPP20.Call> // type of Call Result message matching the
+ // provided type of Call message "C"
 ```
 
 #### Message-specific types
@@ -183,10 +209,9 @@ OCPP20.MeterValuesCallResult
 
 #### The `CheckedCallResult<C extends Call>` type
 
-The `checkCallResult()` function returns values of the generic
-`CheckedCallResult<C extends Call>` type, which can also be used
-on its own to model a Call Result message after a known type of
-Call message:
+The generic `CheckedCallResult<C extends Call>` type can also be used on its
+own to model a Call Result message after a known or inferred type of Call
+message:
 
 ```typescript
 const result: OCPP16.CheckedCallResult<OCPP16.GetConfigurationCall> = [
@@ -221,7 +246,7 @@ OCPP20.ErrorCode // enum of error code in Call Error messages ("NotIm
 
 #### Utility types for OCPP 1.6
 
-Additionally, the following types may be used to model value descriptors within
+The following types may be used to model value descriptors within
 `MeterValues` Call messages:
 
 ```typescript
@@ -235,6 +260,20 @@ OCPP16.SampledValue // individual entry of the "sampledValue" array
 OCPP16.MeterValue // individual entry of the "meterValue" array
 ```
 
+The following types may be used to model value descriptors within
+`StatusNotification` Call messages:
+
+```typescript
+OCPP16.Status // status ("Available", "Reserved", ...)
+```
+
+#### Utility types for OCPP 2.0.1
+
+```typescript
+OCPP20.ConnectorStatus // connector status ("Available", "Occupied", ...)
+OCPP20.ChargingState // charging status ("Charging", "EVConnected", ...)
+```
+
 ### JSON Schema(s) 
 
 Both the `OCPP16` and the `OCPP20` namespaces export the official JSON Schema