package main

import (
	"flag"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	logger "git.site.quack-lab.dev/dave/cylogger"
	"github.com/bmatcuk/doublestar/v4"
	"github.com/djherbis/times"
)

type Constants struct {
	ROOT                string
	ROOT_ARCHIVE        string
	IGNORED_DIRECTORIES []string
	ARCHIVE_THRESHOLD   int64 // ms
	DELETE_THRESHOLD    int64 // ms
	SCAN_INTERVAL       time.Duration
	USE_MODTIME         bool
}

var (
	constants        Constants
	timeUnits        = map[string]int64{"ms": 1, "s": 1000, "m": 60_000, "h": 3_600_000, "d": 86_400_000, "M": 2_592_000_000, "y": 31_536_000_000}
	valueRegex       = regexp.MustCompile(`\d+`)
	unitRegex        = regexp.MustCompile(`[a-zA-Z]+`)
	numFilesArchived = 0
	numFilesDeleted  = 0
)

func parseDurationMS(expr string) int64 {
	expr = strings.TrimSpace(expr)
	if expr == "" {
		return 0
	}
	var total int64
	for _, p := range strings.Split(expr, "_") {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		v := valueRegex.FindString(p)
		u := unitRegex.FindString(p)
		if v == "" || u == "" {
			logger.Warning("Invalid duration part: %q", p)
			continue
		}
		unit, ok := timeUnits[u]
		if !ok {
			logger.Warning("Invalid duration unit: %q", u)
			continue
		}
		n, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			logger.Warning("Invalid duration value: %q: %v", v, err)
			continue
		}
		total += n * unit
	}
	return total
}

func getenv(key, def string) string {
	if v, ok := os.LookupEnv(key); ok {
		return v
	}
	return def
}

func loadConfig() Constants {
	flag.Parse()
	logger.InitFlag()

	root := filepath.ToSlash(strings.TrimSpace(getenv("ROOT", "/tmp")))
	archive := filepath.ToSlash(strings.TrimSpace(getenv("ROOT_ARCHIVE", root+"/archive")))
	_ = os.MkdirAll(archive, os.ModePerm)

	// TODO: This just doesn't really work or do what it says it does
	// Fix it...
	// Right now we don't care because we're not using it
	// But we might want to...
	ignored := []string{}
	if ig := strings.TrimSpace(getenv("IGNORED_DIRECTORIES", "")); ig != "" {
		for _, s := range strings.Split(ig, ",") {
			if t := strings.TrimSpace(s); t != "" {
				ignored = append(ignored, filepath.ToSlash(t))
			}
		}
	}

	archiveMs := parseDurationMS(getenv("ARCHIVE_THRESHOLD", "1d"))
	deleteMs := parseDurationMS(getenv("DELETE_THRESHOLD", "12h"))
	interval := time.Duration(parseDurationMS(getenv("SCAN_INTERVAL", "1m"))) * time.Millisecond
	useMod := strings.EqualFold(strings.TrimSpace(getenv("USE_MODTIME", "false")), "true")

	logger.Info("Config:")
	logger.Info("  ROOT: %s", root)
	logger.Info("  ROOT_ARCHIVE: %s", archive)
	logger.Info("  IGNORED_DIRECTORIES: %v", ignored)
	logger.Info("  ARCHIVE_THRESHOLD(ms): %d", archiveMs)
	logger.Info("  DELETE_THRESHOLD(ms): %d", deleteMs)
	logger.Info("  SCAN_INTERVAL(ms): %d", interval.Milliseconds())
	logger.Info("  USE_MODTIME: %t", useMod)

	return Constants{
		ROOT:                root,
		ROOT_ARCHIVE:        archive,
		IGNORED_DIRECTORIES: ignored,
		ARCHIVE_THRESHOLD:   archiveMs,
		DELETE_THRESHOLD:    deleteMs,
		SCAN_INTERVAL:       interval,
		USE_MODTIME:         useMod,
	}
}

func shouldIgnore(path string) bool {
	log := logger.Default.WithPrefix("shouldIgnore").WithPrefix(path)
	// Match against slash-normalized full path
	path = filepath.ToSlash(path)
	for _, pat := range constants.IGNORED_DIRECTORIES {
		patLog := log.WithPrefix(pat)
		ok, err := doublestar.Match(pat, path)
		if err != nil {
			patLog.Warning("Ignore pattern error %q vs %q: %v", pat, path, err)
			continue
		}
		if ok {
			patLog.Debug("ignore due to doublestar %q", pat)
			return true
		}
	}
	return false
}

func fileTime(info os.FileInfo) int64 {
	t := times.Get(info)
	if constants.USE_MODTIME {
		return t.ModTime().UnixMilli()
	}
	// If AccessTime is not supported, it returns ModTime; times handles that internally.
	return t.AccessTime().UnixMilli()
}

func archiveCandidate(path string, info os.FileInfo) {
	log := logger.Default.WithPrefix("archiveCandidate")
	if info.IsDir() {
		return
	}
	now := time.Now().UnixMilli()
	ft := fileTime(info)
	log.Debug("now %s filetime %s", time.UnixMilli(now).Format(time.RFC3339), time.UnixMilli(ft).Format(time.RFC3339))
	if now-ft <= constants.ARCHIVE_THRESHOLD {
		log.Debug("skip")
		return
	}

	rel, err := filepath.Rel(constants.ROOT, path)
	if err != nil {
		log.Warning("rel ROOT->%s: %v", path, err)
		return
	}
	if strings.HasPrefix(rel, "archive") {
		log.Debug("refusing to archive a file that's already archived")
		return
	}
	log.Debug("rel %q", rel)
	dst := filepath.Join(constants.ROOT_ARCHIVE, rel)
	log.Debug("dst %q", dst)

	if err := os.MkdirAll(filepath.Dir(dst), os.ModePerm); err != nil {
		log.Error("mkdir %s: %v", filepath.Dir(dst), err)
		return
	}

	if err := os.Rename(path, dst); err != nil {
		log.Error("archive %s -> %s: %v", path, dst, err)
		return
	}
	numFilesArchived++
	log.Info("Archived: %s -> %s", path, dst)
}

func deleteCandidate(path string, info os.FileInfo) {
	log := logger.Default.WithPrefix("deleteCandidate").WithPrefix(path)
	if info.IsDir() {
		return
	}
	now := time.Now().UnixMilli()
	ft := fileTime(info)
	log.Debug("now %s filetime %s", time.UnixMilli(now).Format(time.RFC3339), time.UnixMilli(ft).Format(time.RFC3339))
	if now-ft <= constants.DELETE_THRESHOLD {
		log.Debug("skip")
		return
	}
	log.Debug("delete")
	if err := os.Remove(path); err != nil {
		log.Error("delete %s: %v", path, err)
		return
	}
	numFilesDeleted++
	log.Info("Deleted: %s", path)
}

func scanRoot() {
	log := logger.Default.WithPrefix("scanRoot")
	root := constants.ROOT

	// doublestar.Glob with os.DirFS(root) returns relative paths
	log.Debug("glob %s", root)
	paths, err := doublestar.Glob(os.DirFS(root), "**")
	if err != nil {
		log.Error("glob %s: %v", root, err)
		return
	}
	log.Info("Found %d files in root", len(paths))
	for _, rel := range paths {
		pathLog := log.WithPrefix(rel)
		full := filepath.Join(root, rel)
		pathLog.Debug("full %s", full)
		if shouldIgnore(full) {
			pathLog.Debug("ignore")
			continue
		}
		info, err := os.Stat(full)
		pathLog.Trace("stat %+v", info)
		if err != nil {
			log.Warning("stat %s: %v", full, err)
			continue
		}
		archiveCandidate(full, info)
	}
}

func scanArchive() {
	log := logger.Default.WithPrefix("scanArchive")
	base := constants.ROOT_ARCHIVE

	paths, err := doublestar.Glob(os.DirFS(base), "**")
	if err != nil {
		log.Error("glob %s: %v", base, err)
		return
	}
	for _, rel := range paths {
		full := filepath.Join(base, rel)
		info, err := os.Stat(full)
		if err != nil {
			log.Warning("stat %s: %v", full, err)
			continue
		}
		deleteCandidate(full, info)
	}
}

func cleanEmptyDirs() {
	log := logger.Default.WithPrefix("cleanEmptyDirs")
	root := constants.ROOT

	paths, err := doublestar.Glob(os.DirFS(root), "**")
	if err != nil {
		log.Error("glob %s: %v", root, err)
		return
	}
	// Remove empty dirs; iterate deepest first by sorting longer paths first
	// Build a slice of directory paths
	var dirs []string
	for _, rel := range paths {
		full := filepath.Join(root, rel)
		info, err := os.Stat(full)
		if err != nil || !info.IsDir() {
			continue
		}
		if shouldIgnore(full) {
			continue
		}
		dirs = append(dirs, full)
	}
	// Simple length-based reverse to try delete children before parents
	for i := 0; i < len(dirs)-1; i++ {
		for j := i + 1; j < len(dirs); j++ {
			if len(dirs[i]) < len(dirs[j]) {
				dirs[i], dirs[j] = dirs[j], dirs[i]
			}
		}
	}
	for _, d := range dirs {
		empty, err := isDirEmpty(d)
		if err != nil {
			log.Warning("check empty %s: %v", d, err)
			continue
		}
		if empty {
			if err := os.Remove(d); err == nil {
				log.Info("Removed empty dir: %s", d)
			} else {
				log.Warning("remove %s: %v", d, err)
			}
		}
	}
}

func isDirEmpty(dir string) (bool, error) {
	f, err := os.Open(dir)
	if err != nil {
		return false, err
	}
	defer f.Close()
	// Read at most one entry; if none, it's empty
	_, err = f.Readdirnames(1)
	if err == os.ErrNotExist {
		// For older Go versions, fall back
		return true, nil
	}
	if err != nil {
		// io.EOF indicates empty for Readdirnames
		return true, nil
	}
	return false, nil
}

func doRun() {
	scanRoot()
	scanArchive()
	cleanEmptyDirs()
	logger.Info("Cycle summary: archived=%d deleted=%d", numFilesArchived, numFilesDeleted)
	numFilesArchived, numFilesDeleted = 0, 0
}

func main() {
	flag.Parse()
	logger.InitFlag()

	logger.Info("Starting directory cleaner")
	constants = loadConfig()
	logger.Info("Ready. First scan in %s", constants.SCAN_INTERVAL)

	// Run immediately, then on interval
	doRun()
	t := time.NewTicker(constants.SCAN_INTERVAL)
	defer t.Stop()
	for range t.C {
		logger.Info("Tick %d", time.Now().UnixMilli())
		doRun()
	}
}