// Package logger provides structured logging using stdlib log/slog.
//
// JSON output always, one format for every environment, TTY or not. A
// log line is a record to be queried, not prose to be read.
package logger

import (
	"fmt"
	"io"
	"log/slog"
	"path/filepath"
)

// New returns a JSON logger writing to out, at debug level when debug is
// set and at info level otherwise.
func New(out io.Writer, debug bool) *slog.Logger {
	level := slog.LevelInfo
	if debug {
		level = slog.LevelDebug
	}

	// replaceAttr simplifies the source attribute to "file.go:line".
	replaceAttr := func(_ []string, a slog.Attr) slog.Attr {
		if a.Key == slog.SourceKey {
			if src, ok := a.Value.Any().(*slog.Source); ok {
				a.Value = slog.StringValue(
					fmt.Sprintf("%s:%d", filepath.Base(src.File), src.Line),
				)
			}
		}

		return a
	}

	return slog.New(slog.NewJSONHandler(out, &slog.HandlerOptions{
		Level:       level,
		AddSource:   true,
		ReplaceAttr: replaceAttr,
	}))
}