// Copyright (C) 2022 Marius Schellenberger

package fs

import (
	"context"
	"errors"
	"io"
	stdfs "io/fs"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"

	"github.com/go-logr/logr"
)

type FS struct {
	log     logr.Logger
	cancel  func()
	NoCache http.Handler
	src     string
	dst     string
	dc      *DirCache
	sc      *StatCache

	q  *Quota
	mh *MetadataHandler
	ph *PreloadHandler
}

func NewFS(quota int64, max int, src, dst, metadata string, log logr.Logger) (fs *FS, err error) {
	if !filepath.IsAbs(src) {
		return nil, errors.New("src path is not absolute")
	}
	if !filepath.IsAbs(dst) {
		return nil, errors.New("dst path is not absolute")
	}
	if src == dst {
		return nil, errors.New("src and dst path can not be equal")
	}

	ctx, cancel := context.WithCancel(context.Background())

	fs = &FS{
		log:     log,
		cancel:  cancel,
		NoCache: http.FileServer(http.Dir(src)),
		src:     src,
		dst:     dst,
		dc:      NewDirCache(),
	}

	fs.mh, err = NewMetadataHandler(ctx, fs, metadata, dst, log.WithName("metadata"))
	if err != nil {
		return
	}
	fs.q, err = NewQuota(fs.mh.Size(), quota, fs, log.WithName("quota"))
	if err != nil {
		return
	}
	fs.ph = NewPreloadHandler(ctx, fs, max, log.WithName("preload"))
	fs.sc = NewStatCache(ctx)
	return
}

func (fs *FS) Stat(name string) (fi stdfs.FileInfo, err error) {
	sp, dp := fs.paths(name)
	fi, err = fs.sc.Get(name)
	if err == nil {
		return
	}
	fi, err = os.Stat(sp)
	if err == nil {
		fs.sc.Set(name, fi)
		return
	}
	fi, err = os.Stat(dp)
	return
}

func (fs *FS) RemoveDst(name string) error {
	_, dp := fs.paths(name)
	return os.Remove(dp)
}

func (fs *FS) StatDst(name string) (fi stdfs.FileInfo, err error) {
	fi, err = fs.sc.Get(name)
	if err == nil {
		return
	}
	return fs.statDst(name)
}

func (fs *FS) statDst(name string) (stdfs.FileInfo, error) {
	_, dp := fs.paths(name)
	return os.Stat(dp)
}

func (fs *FS) OpenDst(name string) (f http.File, err error) {
	log := fs.log.WithValues("file", name)
	_, dp := fs.paths(name)
	fi, err := fs.StatDst(name)
	if err != nil {
		if !skipLog(name) {
			log.Error(err, "error stat cache file")
		}
		return
	}
	file, err := os.Open(dp)
	if err != nil {
		if !skipLog(name) {
			log.Error(err, "error opening cache file")
		}
		return
	}
	if fi.IsDir() {
		f = &Dir{log: log.WithName("dir"), f: file, dc: fs.dc}
		return
	}
	md := fs.mh.Metadata(name, fi.Size())
	f = &File{
		log:     log.WithName("file"),
		f:       file,
		md:      md,
		offline: true,
	}
	return
}

func (fs *FS) QuotaUsage() (cur, max int64) {
	return fs.q.Usage()
}

func (fs *FS) CancelPreload(name string) {
	fs.ph.CancelPreload(name)
}

func (fs *FS) Preloads() Preloads {
	return fs.ph.Preloads()
}

func (fs *FS) Preload(name string) {
	fs.ph.Preload(name)
}

func skipLog(name string) bool {
	return strings.HasSuffix(name, "index.html") || strings.HasSuffix(name, "favicon.ico")
}

func (fs *FS) paths(name string) (sp string, dp string) {
	p := filepath.FromSlash(path.Clean("/" + name))
	sp = filepath.Join(fs.src, p)
	dp = filepath.Join(fs.dst, p)
	return
}

func (fs *FS) open(name, sp, dp string) (f *os.File, fi os.FileInfo, offline bool, err error) {
	f, err = os.Open(sp)
	if err == nil {
		fi, err = f.Stat()
		if err == nil {
			return
		}
		f.Close()
	}
	f, err = os.Open(dp)
	if err != nil {
		return
	}
	fi, err = f.Stat()
	if err != nil {
		f.Close()
	}
	offline = true
	return
}

func (fs *FS) Open(name string) (f http.File, err error) {
	log := fs.log.WithValues("file", name)
	sp, dp := fs.paths(name)
	file, fi, offline, err := fs.open(name, sp, dp)
	if err != nil {
		if !skipLog(name) {
			log.Error(err, "error opening source file")
		}
		return
	}
	if fi.IsDir() {
		if offline {
			log.V(2).Info("dir offline mode", "path", dp)
		}
		f = &Dir{log: log.WithName("dir"), f: file, dc: fs.dc}
		return
	}
	if offline {
		log.V(2).Info("file offline mode", "path", dp)
	}
	md := fs.mh.Metadata(name, fi.Size())
	f = &File{
		log:     log.WithName("file"),
		f:       file,
		md:      md,
		offline: offline,
	}
	return
}

func (fs *FS) openCacheFile(name string, size int64) (df *os.File, err error) {
	_, dp := fs.paths(name)
	log := fs.log
	if i := strings.LastIndex(dp, "/"); i > 0 {
		dir := dp[:i]
		_, err = os.Stat(dir)
		if errors.Is(err, os.ErrNotExist) {
			err = os.MkdirAll(dir, 0o755)
			if err != nil {
				log.Error(err, "error creating cache dir", "dir", dp)
				return
			}
		}
	}
	_, err = os.Stat(dp)
	truncate := errors.Is(err, os.ErrNotExist)
	df, err = os.OpenFile(dp, os.O_RDWR|os.O_CREATE, 0o644)
	if err != nil {
		log.Error(err, "error opening cache file")
		return
	}
	if truncate {
		err = df.Truncate(size)
		if err != nil {
			log.Error(err, "error truncating cache file")
			return
		}
		err = df.Sync()
		if err != nil {
			log.Error(err, "error syncing cache file")
			return
		}
	}
	return
}

func (fs *FS) CacheStatus(name string) int {
	return fs.mh.CacheStatus(name)
}

func (fs *FS) Close() {
	fs.cancel()
}

func dirEmpty(name string) (bool, error) {
	f, err := os.Open(name)
	if err != nil {
		return false, err
	}
	_, err = f.ReadDir(1)
	if err == io.EOF {
		f.Close()
		return true, nil
	}
	f.Close()
	return false, err
}