package logging

import (
	"os"
	"path/filepath"
	"sync"
	"time"
)

// DailyWriter writes log entries to <root>/<yyyy-mm-dd>/<name>. It keeps the
// file handle open for the active day and rotates on the first write after
// midnight, matching the directory layout consumed by the log viewer.
type DailyWriter struct {
	mu   sync.Mutex
	root string
	name string
	date string
	file *os.File
}

func NewDailyWriter(root, name string) *DailyWriter {
	return &DailyWriter{root: root, name: name}
}

func (w *DailyWriter) Write(value []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	date := time.Now().Format("2006-01-02")
	if w.file == nil || w.date != date {
		if w.file != nil {
			_ = w.file.Close()
		}
		directory := filepath.Join(w.root, date)
		if err := os.MkdirAll(directory, 0o755); err != nil {
			return 0, err
		}
		file, err := os.OpenFile(filepath.Join(directory, w.name), os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
		if err != nil {
			return 0, err
		}
		w.file, w.date = file, date
	}
	return w.file.Write(value)
}

func (w *DailyWriter) Close() error {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.file == nil {
		return nil
	}
	err := w.file.Close()
	w.file = nil
	return err
}