slog/writers.go

package slog

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"
)

// LoggerWriter is the common sink interface used by Logger.
type LoggerWriter interface {
	Close() error
	Write(p []byte) (n int, err error)
	Print(level LogLevel, prefix string, traceback []*MethodTraceback, messages ...any) error
}

// LoggerTextWriter writes human-readable log records to an io.Writer.
type LoggerTextWriter struct {
	LoggerWriter
	writer         io.Writer
	closer         io.Closer
	printTraceback bool
	printTime      bool
}

// Write forwards raw bytes to the underlying writer.
func (w *LoggerTextWriter) Write(p []byte) (n int, err error) {
	return w.writer.Write(p)
}

// Print formats the provided record as text and writes it to the underlying writer.
func (w *LoggerTextWriter) Print(level LogLevel, prefix string, _ []*MethodTraceback, messages ...any) error {
	s := BuildString(level, prefix, w.printTime, w.printTraceback, messages...)
	_, err := w.Write([]byte(s))
	return err
}

// Close closes the owned writer, if any.
func (w *LoggerTextWriter) Close() error {
	if w.closer == nil {
		return nil
	}
	return w.closer.Close()
}

// LoggerJsonWriter writes structured log records as JSON.
type LoggerJsonWriter struct {
	LoggerWriter
	writer io.Writer
	closer io.Closer
	pretty bool
}

// LoggerJsonMessage is the JSON payload emitted by LoggerJsonWriter.
type LoggerJsonMessage struct {
	Time      time.Time          `json:"time"`
	Level     string             `json:"level"`
	Prefix    string             `json:"prefix"`
	Message   string             `json:"message"`
	Traceback []*MethodTraceback `json:"traceback"`
}

// Write forwards raw bytes to the underlying writer.
func (w *LoggerJsonWriter) Write(data []byte) (int, error) {
	return w.writer.Write(data)
}

// Print encodes the provided record as JSON and writes it to the underlying writer.
func (w *LoggerJsonWriter) Print(level LogLevel, prefix string, traceback []*MethodTraceback, messages ...any) error {
	msg := Map(messages, func(el any) string {
		return fmt.Sprintf("%v", el)
	})

	newline := false
	if msg[len(msg)-1] == "\n" {
		newline = true
		msg = msg[:len(msg)-1]
	}

	m := LoggerJsonMessage{
		Time:      time.Now(),
		Level:     level.GetName(),
		Prefix:    prefix,
		Message:   strings.TrimSpace(strings.Join(msg, " ")),
		Traceback: traceback,
	}
	var data []byte
	var err error
	if w.pretty {
		data, err = json.MarshalIndent(m, "", "  ")
	} else {
		data, err = json.Marshal(m)
	}
	if err != nil {
		return err
	}
	if newline {
		data = append(data, '\n')
	}
	_, err = w.Write(data)
	return err
}

// Close closes the owned writer, if any.
func (w *LoggerJsonWriter) Close() error {
	if w.closer == nil {
		return nil
	}
	return w.closer.Close()
}

// CreateTextWriter wraps an external writer for text output without taking
// ownership of it.
func CreateTextWriter(w io.Writer, printTraceback, printTime bool) *LoggerTextWriter {
	writer := &LoggerTextWriter{
		writer: w, printTraceback: printTraceback, printTime: printTime,
	}
	return writer
}

// CreateTextFileWriter creates a text writer for path, creating parent
// directories as needed. The returned writer owns the opened file.
func CreateTextFileWriter(path string, printTraceback, printTime bool) (*LoggerTextWriter, error) {
	err := os.MkdirAll(filepath.Dir(path), os.ModePerm)
	if err != nil {
		return nil, err
	}
	file, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return nil, err
	}
	writer := CreateTextWriter(file, printTraceback, printTime)
	writer.closer = file
	return writer, nil
}

// CreateTextStdoutWriter creates a text writer for os.Stdout without taking
// ownership of stdout.
func CreateTextStdoutWriter(printTraceback, printTime bool) *LoggerTextWriter {
	writer := CreateTextWriter(os.Stdout, printTraceback, printTime)
	writer.closer = nil
	return writer
}

// CreateJsonWriter wraps an external writer for JSON output without taking
// ownership of it.
func CreateJsonWriter(w io.Writer, pretty bool) *LoggerJsonWriter {
	writer := &LoggerJsonWriter{
		writer: w, pretty: pretty,
	}
	return writer
}

// CreateJsonStdoutWriter creates a JSON writer for os.Stdout without taking
// ownership of stdout.
func CreateJsonStdoutWriter(pretty bool) *LoggerJsonWriter {
	writer := CreateJsonWriter(os.Stdout, pretty)
	writer.closer = nil
	return writer
}

// CreateJsonFileWriter creates a JSON writer for path, creating parent
// directories as needed. The returned writer owns the opened file.
func CreateJsonFileWriter(path string, pretty bool) (*LoggerJsonWriter, error) {
	err := os.MkdirAll(filepath.Dir(path), os.ModePerm)
	if err != nil {
		return nil, err
	}
	file, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return nil, err
	}
	writer := CreateJsonWriter(file, pretty)
	writer.closer = file
	return writer, nil
}