Logger & LoggerMiddleware (#66)

* add logger middleware and logger class

* update logger level setting

packages/types/src/index.ts

@@ -3,6 +3,7 @@ export * from './client';
 export * from './credentials';
 export * from './crypto';
 export * from './http';
+export * from './logger';
 export * from './marshaller';
 export * from './middleware';
 export * from './protocol';

packages/types/src/logger.ts

@@ -0,0 +1,41 @@
+import {Shape, Member} from './protocol'
+
+/**
+ * A list of logger's log level. These levels are sorted in
+ * order of increasing severity. Each log level includes itself and all
+ * the levels behind itself.
+ * 
+ * @example new Logger({logLevel: 'warn'}) will print all the warn and error
+ * message.
+ */
+export type LogLevel = 'all' | 'log' | 'info' | 'warn' | 'error' | 'off'
+
+/**
+ * An object consumed by Logger constructor to initiate a logger object.
+ */
+export interface LoggerOptions {
+    logger?: Logger;
+    logLevel?: LogLevel;
+}
+
+/**
+ * Represents a logger object that is available in HandlerExecutionContext
+ * throughout the middleware stack.
+ */
+export interface Logger {
+    log(content: string): void;
+    info(content: string): void;
+    warn(content: string): void;
+    error(content: string): void;
+}
+
+/**
+ * A function that removes the sensitive information from input parameters
+ * and output objects being logged. Meanwhile this function will output
+ * stringified object
+ * 
+ * This function is mainly used in logging middleware.
+ */
+export interface SensitiveDataScrubber {
+    (input: any, shape: Member): string
+}

packages/types/src/middleware.ts

@@ -4,6 +4,7 @@ import {
     HttpRequest
 } from './http';
 import {OperationModel} from './protocol';
+import {Logger} from './logger'
 
 export interface HandlerArguments<
     InputType extends object,
@@ -165,7 +166,7 @@ export interface HandlerExecutionContext {
     /**
      * TODO Define a logger interface
      */
-    logger: any;
+    logger: Logger;
 
     /**
      * The serialization model for the input, output, and possible errors for