feat: add logger package and tests

Signed-off-by: Kit Patella <[email protected]>

src/pkg/logger/logger.go

@@ -0,0 +1,143 @@
+package logger
+
+import (
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"strings"
+)
+
+// Level declares each supported log level. These are 1:1 what log/slog supports by default.
+type Level int
+
+var (
+	Debug = Level(slog.LevelDebug) // -4
+	// Info is the default log level.
+	Info  = Level(slog.LevelInfo)  // 0
+	Warn  = Level(slog.LevelWarn)  // 4
+	Error = Level(slog.LevelError) // 8
+)
+
+// validLevels is a set that provides an ergonomic way to check if a level is a member of the set.
+var validLevels = map[Level]bool{
+	Debug: true,
+	Info:  true,
+	Warn:  true,
+	Error: true,
+}
+
+// strLevels maps a string to its Level.
+var strLevels = map[string]Level{
+	"debug": Debug,
+	"info":  Info,
+	"warn":  Warn,
+	"error": Error,
+}
+
+// ParseLevel takes a string representation of a Level, ensure it exists, and then converts it into a Level.
+func ParseLevel(s string) (Level, error) {
+	k := strings.ToLower(s)
+	l, ok := strLevels[k]
+	if !ok {
+		return 0, fmt.Errorf("invalid log level: %s", k)
+	}
+	return l, nil
+}
+
+// Format declares the kind of logging handler to use.
+type Format string
+
+// ToLower takes a Format string and converts it to lowercase for case-agnostic validation. Users shouldn't have to care
+// about "json" vs. "JSON" for example - they should both work.
+func (f Format) ToLower() Format {
+	return Format(strings.ToLower(string(f)))
+}
+
+// TODO(mkcp): Add dev format
+var (
+	// FormatEmpty means no format was supplied. This is equivalent to a default, or "Text".
+	FormatEmpty Format = ""
+	// FormatText uses the standard slog TextHandler
+	FormatText Format = "text"
+	// FormatJSON uses the standard slog JSONHandler
+	FormatJSON Format = "json"
+	// FormatNone sends log writes to DestinationNone / io.Discard
+	FormatNone Format = "none"
+)
+
+// More printers would be great, like dev format https://github.com/golang-cz/devslog
+// and a pretty console slog https://github.com/phsym/console-slog
+
+type Destination io.Writer
+
+var (
+	// DestinationDefault points to Stderr
+	DestinationDefault Destination = os.Stderr
+	// DestinationNone discards logs as they are received
+	DestinationNone Destination = io.Discard
+)
+
+// Config is configuration for a logger.
+type Config struct {
+	// Level sets the log level. An empty value corresponds to Info aka 0.
+	Level
+	Format
+	Destination
+}
+
+// ConfigDefault returns a Config with defaults like Text formatting at Info level writing to Stderr.
+func ConfigDefault() Config {
+	return Config{
+		Level:       Info,
+		Format:      FormatText,
+		Destination: DestinationDefault, // Stderr
+	}
+}
+
+// New takes a Config and returns a validated logger.
+func New(cfg Config) (*slog.Logger, error) {
+	var handler slog.Handler
+	opts := slog.HandlerOptions{}
+
+	if cfg.Destination == nil {
+		cfg.Destination = DestinationDefault
+	}
+
+	// Check that we have a valid log level.
+	if !validLevels[cfg.Level] {
+		return nil, fmt.Errorf("unsupported log level: %d", cfg.Level)
+	}
+	opts.Level = slog.Level(cfg.Level)
+
+	switch cfg.Format.ToLower() {
+	// Use Text handler if no format provided, e.g. "" for Empty
+	case FormatEmpty, FormatText:
+		handler = slog.NewTextHandler(cfg.Destination, &opts)
+	case FormatJSON:
+		handler = slog.NewJSONHandler(cfg.Destination, &opts)
+	// TODO(mkcp): Add dev format
+	// case FormatDev:
+	// 	handler = slog.NewTextHandler(DestinationNone, &slog.HandlerOptions{
+	//		AddSource: true,
+	//	})
+	case FormatNone:
+		handler = slog.NewTextHandler(DestinationNone, &slog.HandlerOptions{})
+	// Format not found, let's error out
+	default:
+		return nil, fmt.Errorf("unsupported log format: %s", cfg.Format)
+	}
+
+	log := slog.New(handler)
+	return log, nil
+}
+
+// Default gets a logger from the atomic slog default.
+func Default() *slog.Logger {
+	return slog.Default()
+}
+
+// SetDefault takes a logger and sets it as the atomic slog default.
+func SetDefault(l *slog.Logger) {
+	slog.SetDefault(l)
+}

src/pkg/logger/logger_test.go

@@ -0,0 +1,211 @@
+package logger
+
+import (
+	"github.com/stretchr/testify/assert"
+	"os"
+	"testing"
+)
+
+func Test_New(t *testing.T) {
+	t.Parallel()
+
+	tt := []struct {
+		name string
+		cfg  Config
+	}{
+		{
+			name: "Empty level, format, and destination are ok",
+			cfg:  Config{},
+		},
+		{
+			name: "Default config is ok",
+			cfg:  ConfigDefault(),
+		},
+		{
+			name: "Debug logs are ok",
+			cfg: Config{
+				Level: Debug,
+			},
+		},
+		{
+			name: "Info logs are ok",
+			cfg: Config{
+				Level: Info,
+			},
+		},
+		{
+			name: "Warn logs are ok",
+			cfg: Config{
+				Level: Warn,
+			},
+		},
+		{
+			name: "Error logs are ok",
+			cfg: Config{
+				Level: Error,
+			},
+		},
+		{
+			name: "Text format is supported",
+			cfg: Config{
+				Format: FormatText,
+			},
+		},
+		{
+			name: "JSON format is supported",
+			cfg: Config{
+				Format: FormatJSON,
+			},
+		},
+		{
+			name: "FormatNone is supported to disable logs",
+			cfg: Config{
+				Format: FormatNone,
+			},
+		},
+		{
+			name: "DestinationNone is supported to disable logs",
+			cfg: Config{
+				Destination: DestinationNone,
+			},
+		},
+		{
+			name: "users can send logs to any io.Writer",
+			cfg: Config{
+				Destination: os.Stdout,
+			},
+		},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			res, err := New(tc.cfg)
+			assert.NoError(t, err)
+			assert.NotNil(t, res)
+		})
+	}
+}
+
+func Test_NewErrors(t *testing.T) {
+	t.Parallel()
+
+	tt := []struct {
+		name string
+		cfg  Config
+	}{
+		{
+			name: "unsupported log level errors",
+			cfg: Config{
+				Level: 3,
+			},
+		},
+		{
+			name: "wildly unsupported log level errors",
+			cfg: Config{
+				Level: 42389412389213489,
+			},
+		},
+		{
+			name: "unsupported format errors",
+			cfg: Config{
+				Format: "foobar",
+			},
+		},
+		{
+			name: "wildly unsupported format errors",
+			cfg: Config{
+				Format: "^\\w+([-+.']\\w+)*@\\w+([-.]\\w+)*\\.\\w+([-.]\\w+)*$ lorem ipsum dolor sit amet 243897 )*&($#",
+			},
+		},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			res, err := New(tc.cfg)
+			assert.Error(t, err)
+			assert.Nil(t, res)
+		})
+	}
+}
+
+func Test_ParseLevel(t *testing.T) {
+	t.Parallel()
+
+	tt := []struct {
+		name   string
+		s      string
+		expect Level
+	}{
+		{
+			name:   "can parse debug",
+			s:      "debug",
+			expect: Debug,
+		},
+		{
+			name:   "can parse info",
+			s:      "Info",
+			expect: Info,
+		},
+		{
+			name:   "can parse warn",
+			s:      "warn",
+			expect: Warn,
+		},
+		{
+			name:   "can parse error",
+			s:      "error",
+			expect: Error,
+		},
+		{
+			name:   "can handle uppercase",
+			s:      "ERROR",
+			expect: Error,
+		},
+		{
+			name:   "can handle inconsistent uppercase",
+			s:      "errOR",
+			expect: Error,
+		},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			res, err := ParseLevel(tc.s)
+			assert.NoError(t, err)
+			assert.Equal(t, tc.expect, res)
+		})
+	}
+}
+
+func Test_ParseLevelErrors(t *testing.T) {
+	t.Parallel()
+
+	tt := []struct {
+		name string
+		s    string
+	}{
+		{
+			name: "errors out on unknown level",
+			s:    "SUPER-DEBUG-10x-supremE",
+		},
+		{
+			name: "is precise about character variations",
+			s:    "érrør",
+		},
+		{
+			name: "does not partial match level",
+			s:    "error-info",
+		},
+		{
+			name: "does not partial match level 2",
+			s:    "info-error",
+		},
+		{
+			name: "does not partial match level 3",
+			s:    "info2",
+		},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := ParseLevel(tc.s)
+			assert.Error(t, err)
+		})
+	}
+}