Flesh out the log event and log writer classes (#2175)

* Add timekeeping infrastructure.

* Add the log proto protocol.

* Flesh out the log event a bit.

* Flesh out the log writer.

* Put in comments for the log proto protocol.

* Move queue to a private header and update the TODO.

* Add comment about the QoS tier

* Fix style

Author: mikehaney24

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogClock.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** A struct to hold data pertaining to a snapshot in time. */
+typedef struct {
+  /** The current time in millis. */
+  int64_t timeMillis;
+
+  /** The device uptime in millis. */
+  int64_t uptimeMillis;
+
+  /** The timezone offset in millis. */
+  int64_t timezoneOffsetMillis;
+} GDLLogClockSnapshot;
+
+/** This class manages the device clock and produces snapshots of the current time. */
+@interface GDLLogClock : NSObject
+
+// TODO(mikehaney24): - (GDLLogClockSnapshot)snapshot;
+
+@end
+
+NS_ASSUME_NONNULL_END

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogClock.m

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import "GDLLogClock.h"
+
+@implementation GDLLogClock
+
+@end

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogEvent.h

@@ -16,6 +16,54 @@
 
 #import <Foundation/Foundation.h>
 
+#import "GDLLogClock.h"
+#import "GDLLogProto.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** The different possible log quality of service specifiers. High values indicate high priority. */
+typedef NS_ENUM(NSInteger, GDLLogQoS) {
+  /** The QoS tier wasn't set, and won't ever be sent. */
+  GDLLogQoSUnknown = 0,
+
+  /** This log is internal telemetry data that should not be sent on its own if possible. */
+  GDLLogQoSTelemetry = 1,
+
+  /** This log should be sent, but in a batch only roughly once per day. */
+  GDLLogQoSDaily = 2,
+
+  /** This log should be sent when requested by the uploader. */
+  GDLLogQosDefault = 3,
+
+  /** This log should be sent immediately along with any other data that can be batched. */
+  GDLLogQoSFast = 4
+};
+
 @interface GDLLogEvent : NSObject
 
+/** The log map identifier, to allow backends to map the extension property to a proto. */
+@property(readonly, nonatomic) NSString *logMapID;
+
+/** The log object itself, encapsulated in the transport of your choice, as long as it implements
+ * the GDLLogProto protocol. */
+@property(nonatomic) id<GDLLogProto> extension;
+
+/** The quality of service tier this log belongs to. */
+@property(nonatomic) GDLLogQoS qosTier;
+
+/** The clock snapshot at the time of logging. */
+@property(nonatomic) GDLLogClockSnapshot clockSnapshot;
+
+// Please use the designated initializer.
+- (instancetype)init NS_UNAVAILABLE;
+
+/** Initializes an instance using the given logMapID.
+ *
+ * @param logMapID The log map identifier.
+ * @return An instance of this class.
+ */
+- (instancetype)initWithLogMapID:(NSString *)logMapID NS_DESIGNATED_INITIALIZER;
+
 @end
+
+NS_ASSUME_NONNULL_END

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogEvent.m

@@ -18,4 +18,13 @@
 
 @implementation GDLLogEvent
 
+- (instancetype)initWithLogMapID:(NSString *)logMapID {
+  NSAssert(logMapID.length > 0, @"Please give a valid log map ID");
+  self = [super init];
+  if (self) {
+    _logMapID = logMapID;
+  }
+  return self;
+}
+
 @end

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogProto.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+/** This protocol defines the common interface that log protos should implement regardless of the
+ * underlying transport technology (protobuf, nanopb, etc).
+ */
+@protocol GDLLogProto <NSObject>
+
+/** Returns the serialized proto bytes of the implementing log proto.
+ *
+ * @return the serialized proto bytes of the implementing log proto.
+ */
+- (NSData *)protoBytes;
+
+@end

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogWriter.h

@@ -16,7 +16,25 @@
 
 #import <Foundation/Foundation.h>
 
+@class GDLLogEvent;
+
+@protocol GDLLogTransformer;
+
 /** Manages the writing and log-time transforming of logs. */
 @interface GDLLogWriter : NSObject
 
+/** Instantiates or returns the log writer singleton.
+ *
+ * @return The singleton instance of the log writer.
+ */
++ (instancetype)sharedInstance;
+
+/** Writes the result of applying the given transformers' -transform method on the given log.
+ *
+ * @param log The log to apply transformers on.
+ * @param logTransformers The list of transformers to apply.
+ */
+- (void)writeLog:(GDLLogEvent *)log
+    afterApplyingTransformers:(nullable NSArray<id<GDLLogTransformer>> *)logTransformers;
+
 @end

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogWriter.m

@@ -15,7 +15,46 @@
  */
 
 #import "GDLLogWriter.h"
+#import "GDLLogWriter_Private.h"
 
-@implementation GDLLogWriter : NSObject
+#import <GoogleDataLogger/GDLLogTransformer.h>
+
+#import "GDLLogStorage.h"
+
+@implementation GDLLogWriter
+
+// This class doesn't have to be a singleton, but allocating an instance for every logger could be
+// wasteful.
++ (instancetype)sharedInstance {
+  static GDLLogWriter *logWriter;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    logWriter = [[self alloc] init];
+  });
+  return logWriter;
+}
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    _logWritingQueue = dispatch_queue_create("com.google.GDLLogWriter", DISPATCH_QUEUE_SERIAL);
+  }
+  return self;
+}
+
+- (void)writeLog:(GDLLogEvent *)log
+    afterApplyingTransformers:(NSArray<id<GDLLogTransformer>> *)logTransformers {
+  NSAssert(log, @"You can't write a nil log");
+  dispatch_async(_logWritingQueue, ^{
+    GDLLogEvent *transformedLog = log;
+    for (id<GDLLogTransformer> transformer in logTransformers) {
+      transformedLog = [transformer transform:transformedLog];
+      if (!transformedLog) {
+        return;
+      }
+    }
+    // TODO(mikehaney24): [[GDLLogStorage sharedInstance] storeLog:transformedLog];
+  });
+}
 
 @end

GoogleDataLogger/GoogleDataLogger/Classes/GDLLogger.m

@@ -60,7 +60,7 @@ - (void)logDataEvent:(GDLLogEvent *)logEvent {
 }
 
 - (GDLLogEvent *)newEvent {
-  return [[GDLLogEvent alloc] init];
+  return [[GDLLogEvent alloc] initWithLogMapID:_logMapID];
 }
 
 @end

GoogleDataLogger/GoogleDataLogger/Classes/Private/GDLLogWriter_Private.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#import "GDLLogWriter.h"
+
+@interface GDLLogWriter ()
+
+/** The queue on which all work will occur. */
+@property(nonatomic) dispatch_queue_t logWritingQueue;
+
+@end

GoogleDataLogger/Tests/GDLLogEventTest.m

@@ -25,7 +25,8 @@ @interface GDLLogEventTest : XCTestCase
 @implementation GDLLogEventTest
 
 - (void)testInit {
-  XCTAssertNotNil([[GDLLogEvent alloc] init]);
+  XCTAssertNotNil([[GDLLogEvent alloc] initWithLogMapID:@"1"]);
+  XCTAssertThrows([[GDLLogEvent alloc] initWithLogMapID:@""]);
 }
 
 @end

GoogleDataLogger/Tests/GDLLogWriterTest.m

@@ -16,7 +16,23 @@
 
 #import <XCTest/XCTest.h>
 
+#import <GoogleDataLogger/GDLLogTransformer.h>
+
+#import "GDLLogEvent.h"
 #import "GDLLogWriter.h"
+#import "GDLLogWriter_Private.h"
+
+@interface GDLLogWriterTestNilingTransformer : NSObject <GDLLogTransformer>
+
+@end
+
+@implementation GDLLogWriterTestNilingTransformer
+
+- (GDLLogEvent *)transform:(GDLLogEvent *)logEvent {
+  return nil;
+}
+
+@end
 
 @interface GDLLogWriterTest : XCTestCase
 
@@ -29,4 +45,29 @@ - (void)testInit {
   XCTAssertNotNil([[GDLLogWriter alloc] init]);
 }
 
+/** Tests the pointer equality of result of the -sharedInstance method. */
+- (void)testSharedInstance {
+  XCTAssertEqual([GDLLogWriter sharedInstance], [GDLLogWriter sharedInstance]);
+}
+
+- (void)testWriteLogWithoutTransformers {
+  GDLLogWriter *writer = [GDLLogWriter sharedInstance];
+  GDLLogEvent *log = [[GDLLogEvent alloc] initWithLogMapID:@"1"];
+  XCTAssertNoThrow([writer writeLog:log afterApplyingTransformers:nil]);
+  dispatch_sync(writer.logWritingQueue, ^{
+                    // TODO(mikehaney24): Assert that storage contains the log.
+                });
+}
+
+- (void)testWriteLogWithTransformersThatNilTheLog {
+  GDLLogWriter *writer = [GDLLogWriter sharedInstance];
+  GDLLogEvent *log = [[GDLLogEvent alloc] initWithLogMapID:@"2"];
+  NSArray<id<GDLLogTransformer>> *transformers =
+      @[ [[GDLLogWriterTestNilingTransformer alloc] init] ];
+  XCTAssertNoThrow([writer writeLog:log afterApplyingTransformers:transformers]);
+  dispatch_sync(writer.logWritingQueue, ^{
+                    // TODO(mikehaney24): Assert that storage does not contain the log.
+                });
+}
+
 @end