sjansen/mecha

package main

import (
    "fmt"
    "os"

    "github.com/alecthomas/kingpin/v2"
    "go.uber.org/zap"
    "go.uber.org/zap/zapcore"
)

var (
    verbose = kingpin.Flag("verbose", "Verbose mode.").Short('v').Counter()
    trace   = kingpin.Flag("trace", "Enable trace logging.").Bool()
)

func main() {
    kingpin.Parse()

    var level zapcore.Level
    switch {
    case *verbose >= 3:
        level = zapcore.DebugLevel
    case *verbose == 2:
        level = zapcore.InfoLevel
    case *verbose == 1:
        level = zapcore.WarnLevel
    default:
        level = zapcore.ErrorLevel
    }

    var logger *zap.SugaredLogger
    if *trace {
        tmpfile, err := os.CreateTemp("", "zap-demo")
        if err != nil {
            fmt.Fprintln(os.Stderr, "unable to open trace log:", err)
        }
        fmt.Fprintln(os.Stderr, "logging to:", tmpfile.Name())
        logger = NewLogger(level, tmpfile).Sugar()
    } else {
        logger = NewLogger(level, nil).Sugar()
    }
    defer logger.Sync()

    logger.Errorw("an error",
        "metavar", "foo")
    logger.Warnw("a warning",
        "metavar", "bar",
        "question", "6 * 9")
    logger.With(
        "metavar", "baz").
        Infow(
            "some info",
            "answer", 42)
    logger.With(
        "hint", "The secret is to bang the rocks together, guys.").
        Debugf("debug=%d", *verbose)
}

func NewLogger(level zapcore.Level, traceLog zapcore.WriteSyncer) *zap.Logger {
    core := zapcore.NewCore(
        zapcore.NewConsoleEncoder(zapcore.EncoderConfig{
            MessageKey:     "msg",
            NameKey:        "logger",
            EncodeTime:     zapcore.ISO8601TimeEncoder,
            EncodeDuration: zapcore.StringDurationEncoder,
        }),
        os.Stderr,
        level,
    )
    if traceLog != nil {
        trace := zapcore.NewCore(
            zapcore.NewConsoleEncoder(zapcore.EncoderConfig{
                MessageKey:     "msg",
                LevelKey:       "level",
                NameKey:        "logger",
                TimeKey:        "time",
                EncodeLevel:    zapcore.CapitalLevelEncoder,
                EncodeTime:     zapcore.ISO8601TimeEncoder,
                EncodeDuration: zapcore.StringDurationEncoder,
            }),
            traceLog,
            zapcore.DebugLevel,
        )
        core = zapcore.NewTee(core, trace)
    }
    return zap.New(core)
}