package monitor

import (
	"fmt"
	"github.com/nxadm/tail"
	"go.uber.org/zap"
	"regexp"
)

type Monitor interface {
	Close() error
	Watch(filename string, filter *regexp.Regexp, lineChan chan<- string) error
}

func New() *LogMonitor {
	return &LogMonitor{
		cancel: make(chan interface{}),
	}
}

type LogMonitor struct {
	cancel chan interface{}
}

func (l *LogMonitor) Close() error {
	close(l.cancel)
	return nil
}

func (l *LogMonitor) Watch(filename string, filter *regexp.Regexp, lineChan chan<- string) error {
	t, err := tail.TailFile(filename, tail.Config{Follow: true, ReOpen: true, Logger: tail.DiscardingLogger})
	if err != nil {
		return fmt.Errorf("unable to begin to tail file '%s': %w", filename, err)
	}

	for {
		select {
		case line := <-t.Lines:
			if line.Err != nil {
				zap.S().Errorf("tail error: %v", err)
				continue
			}
			zap.S().Infof("new line: '%s'", line.Text)
			if filter.MatchString(line.Text) {
				lineChan <- line.Text
			}
		case <-l.cancel:
			t.Stop()
			t.Cleanup()
			return nil
		}
	}
	return nil
}