package main

import (
	"os"
	"sort"
	"strconv"
	"sync/atomic"
	"syscall"
	"time"

	"reflector-cleaner/atime"

	"github.com/google/gops/agent"
	"github.com/karrick/godirwalk"
	"github.com/lbryio/lbry.go/v2/extras/errors"
	"github.com/sirupsen/logrus"
)

var blobsDir string

func main() {
	if err := agent.Listen(agent.Options{}); err != nil {
		panic(err)
	}
	if len(os.Args) != 2 {
		panic("you must pass 1 argument: the path of the blobs directory")
	}
	blobsDir = os.Args[1]
	thresholdStr := os.Getenv("DISK_THRESHOLD")
	threshold := 0.90
	var err error
	if thresholdStr != "" {
		threshold, err = strconv.ParseFloat(thresholdStr, 64)
		if err != nil {
			panic(err)
		}
	}
	if _, err := os.Stat(blobsDir); os.IsNotExist(err) {
		panic(errors.Err("directory doesn't exist: %s", blobsDir))
	}
	used, err := getUsedSpace()
	if err != nil {
		logrus.Errorln(err.Error())
		return
	}
	logrus.Infof("disk usage: %.2f%%\n", used*100)
	if used > threshold {
		logrus.Infof("over %.2f%%, cleaning up", threshold*100)
		err = WipeOldestBlobs()
		if err != nil {
			logrus.Errorln(err.Error())
			return
		}
		used, err := getUsedSpace()
		if err != nil {
			logrus.Errorln(err.Error())
			return
		}
		logrus.Infof("disk usage: %.2f%%\n", used*100)
		logrus.Infoln("Done cleaning up")
	}
}

// GetUsedSpace returns a value between 0 and 1, with 0 being completely empty and 1 being full, for the disk that holds the provided path
func getUsedSpace() (float64, error) {
	var stat syscall.Statfs_t
	err := syscall.Statfs(blobsDir, &stat)
	if err != nil {
		return 0, err
	}
	// Available blocks * size per block = available space in bytes
	all := stat.Blocks * uint64(stat.Bsize)
	free := stat.Bfree * uint64(stat.Bsize)
	used := all - free

	return float64(used) / float64(all), nil
}

func WipeOldestBlobs() (err error) {
	type datedFile struct {
		Atime    time.Time
		FullPath string
	}
	datedFiles := make([]datedFile, 0, 5000)
	checkedBlobs := int32(0)
	err = godirwalk.Walk(blobsDir, &godirwalk.Options{
		Callback: func(osPathname string, de *godirwalk.Dirent) error {
			if !de.IsDir() {
				i := atomic.AddInt32(&checkedBlobs, 1)
				if i%100 == 0 {
					logrus.Infof("checked %d blobs", i)
				}
				if de.IsRegular() {
					stat, err := os.Stat(osPathname)
					if err != nil {
						return err
					}
					datedFiles = append(datedFiles, datedFile{
						Atime:    atime.Atime(stat),
						FullPath: osPathname,
					})
				}
			}
			return nil
		},
		Unsorted: true, // (optional) set true for faster yet non-deterministic enumeration (see godoc)
	})
	if err != nil {
		return err
	}

	sort.Slice(datedFiles, func(i, j int) bool {
		return datedFiles[i].Atime.Before(datedFiles[j].Atime)
	})
	//delete the first 5000 blobs
	for i, df := range datedFiles {
		if i >= 5000 {
			break
		}
		if i%100 == 0 {
			logrus.Infof("[%s] would delete %s", df.Atime.String(), df.FullPath)
		}
		//err = os.Remove(df.FullPath)
		//if err != nil {
		//	return err
		//}
	}
	return nil
}