add pkg/log with zap log library (#155)

Adds a logger pkg using the zap log library.  Generally straight-
forward, though we'll have to watch out for gotchas with the
flush requirements.

src/cli/cli.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"context"
 	"fmt"
 	"os"
 
@@ -10,6 +11,7 @@ import (
 	"github.com/alcionai/corso/cli/backup"
 	"github.com/alcionai/corso/cli/config"
 	"github.com/alcionai/corso/cli/repo"
+	"github.com/alcionai/corso/pkg/logger"
 )
 
 // The root-level command.
@@ -58,7 +60,10 @@ func Handle() {
 	repo.AddCommands(corsoCmd)
 	backup.AddCommands(corsoCmd)
 
-	if err := corsoCmd.Execute(); err != nil {
+	ctx, log := logger.Seed(context.Background())
+	defer log.Sync() // flush all logs in the buffer
+
+	if err := corsoCmd.ExecuteContext(ctx); err != nil {
 		fmt.Println(err)
 		os.Exit(1)
 	}

src/cli/repo/s3.go

@@ -10,6 +10,7 @@ import (
 	"github.com/alcionai/corso/cli/config"
 	"github.com/alcionai/corso/cli/utils"
 	"github.com/alcionai/corso/pkg/credentials"
+	"github.com/alcionai/corso/pkg/logger"
 	"github.com/alcionai/corso/pkg/repository"
 	"github.com/alcionai/corso/pkg/storage"
 )
@@ -52,20 +53,21 @@ var s3InitCmd = &cobra.Command{
 
 // initializes a s3 repo.
 func initS3Cmd(cmd *cobra.Command, args []string) error {
+	log := logger.Ctx(cmd.Context())
+
 	m365 := credentials.GetM365()
 	s3Cfg, commonCfg, err := makeS3Config()
 	if err != nil {
 		return err
 	}
 
-	fmt.Printf(
-		"Called - %s\n\tbucket:\t%s\n\tkey:\t%s\n\t356Client:\t%s\n\tfound 356Secret:\t%v\n\tfound awsSecret:\t%v\n",
-		cmd.CommandPath(),
-		s3Cfg.Bucket,
-		s3Cfg.AccessKey,
-		m365.ClientID,
-		len(m365.ClientSecret) > 0,
-		len(s3Cfg.SecretKey) > 0)
+	log.Debugw(
+		"Called - "+cmd.CommandPath(),
+		"bucket", s3Cfg.Bucket,
+		"clientID", m365.ClientID,
+		"hasClientSecret", len(m365.ClientSecret) > 0,
+		"accessKey", s3Cfg.AccessKey,
+		"hasSecretKey", len(s3Cfg.SecretKey) > 0)
 
 	a := repository.Account{
 		TenantID:     m365.TenantID,
@@ -102,20 +104,21 @@ var s3ConnectCmd = &cobra.Command{
 
 // connects to an existing s3 repo.
 func connectS3Cmd(cmd *cobra.Command, args []string) error {
+	log := logger.Ctx(cmd.Context())
+
 	m365 := credentials.GetM365()
 	s3Cfg, commonCfg, err := makeS3Config()
 	if err != nil {
 		return err
 	}
 
-	fmt.Printf(
-		"Called - %s\n\tbucket:\t%s\n\tkey:\t%s\n\t356Client:\t%s\n\tfound 356Secret:\t%v\n\tfound awsSecret:\t%v\n",
-		cmd.CommandPath(),
-		s3Cfg.Bucket,
-		s3Cfg.AccessKey,
-		m365.ClientID,
-		len(m365.ClientSecret) > 0,
-		len(s3Cfg.SecretKey) > 0)
+	log.Debugw(
+		"Called - "+cmd.CommandPath(),
+		"bucket", s3Cfg.Bucket,
+		"clientID", m365.ClientID,
+		"hasClientSecret", len(m365.ClientSecret) > 0,
+		"accessKey", s3Cfg.AccessKey,
+		"hasSecretKey", len(s3Cfg.SecretKey) > 0)
 
 	// TODO: Merge/Validate any local configuration here to make sure there are no conflicts
 	// For now - just reading/logging the local config here (a successful repo connect will overwrite)

src/pkg/logger/logger.go

@@ -0,0 +1,55 @@
+package logger
+
+import (
+	"context"
+	"os"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+var logCore *zapcore.Core
+
+func coreSingleton() *zapcore.Core {
+	if logCore == nil {
+		// level handling
+		highPriority := zap.LevelEnablerFunc(func(lvl zapcore.Level) bool {
+			return lvl >= zapcore.ErrorLevel
+		})
+		lowPriority := zap.LevelEnablerFunc(func(lvl zapcore.Level) bool {
+			return lvl < zapcore.ErrorLevel
+		})
+		// level-based output
+		consoleDebugging := zapcore.Lock(os.Stdout)
+		consoleErrors := zapcore.Lock(os.Stderr)
+		// encoder type
+		consoleEncoder := zapcore.NewConsoleEncoder(zap.NewDevelopmentEncoderConfig())
+		// combine into a logger core
+		core := zapcore.NewTee(
+			zapcore.NewCore(consoleEncoder, consoleErrors, highPriority),
+			zapcore.NewCore(consoleEncoder, consoleDebugging, lowPriority),
+		)
+		logCore = &core
+	}
+	return logCore
+}
+
+type loggingKey string
+
+const ctxKey loggingKey = "corsoLogger"
+
+// Seed embeds a logger into the context for later retrieval.
+func Seed(ctx context.Context) (context.Context, *zap.SugaredLogger) {
+	l := zap.New(*coreSingleton())
+	s := l.Sugar()
+	return context.WithValue(ctx, ctxKey, s), s
+}
+
+// Ctx retrieves the logger embedded in the context.
+func Ctx(ctx context.Context) *zap.SugaredLogger {
+	l := ctx.Value(ctxKey)
+	if l == nil {
+		return zap.New(*coreSingleton()).Sugar()
+	}
+	return l.(*zap.SugaredLogger)
+}