package disk

import (
	"fmt"
	"os"
	"path/filepath"
	"s1d3sw1ped/SteamCache2/steamcache/logger"
	"s1d3sw1ped/SteamCache2/vfs"
	"s1d3sw1ped/SteamCache2/vfs/vfserror"
	"strings"
	"sync"
	"time"

	"github.com/docker/go-units"
)

// Ensure DiskFS implements VFS.
var _ vfs.VFS = (*DiskFS)(nil)

// DiskFS is a virtual file system that stores files on disk.
type DiskFS struct {
	root string

	info     map[string]*vfs.FileInfo
	capacity int64
	mu       sync.Mutex
	sg       sync.WaitGroup
}

// New creates a new DiskFS.
func new(root string, capacity int64, skipinit bool) *DiskFS {
	if capacity <= 0 {
		panic("disk capacity must be greater than 0") // panic if the capacity is less than or equal to 0
	}

	if root == "" {
		panic("disk root must not be empty") // panic if the root is empty
	}

	fi, err := os.Stat(root)
	if err != nil {
		if !os.IsNotExist(err) {
			panic(err) // panic if the error is something other than not found
		}
	}
	if !fi.IsDir() {
		panic("disk root must be a directory") // panic if the root is not a directory
	}

	dfs := &DiskFS{
		root:     root,
		info:     make(map[string]*vfs.FileInfo),
		capacity: capacity,
		mu:       sync.Mutex{},
		sg:       sync.WaitGroup{},
	}

	os.MkdirAll(dfs.root, 0755)

	if !skipinit {
		dfs.init()
	}

	return dfs
}

func New(root string, capacity int64) *DiskFS {
	return new(root, capacity, false)
}

func NewSkipInit(root string, capacity int64) *DiskFS {
	return new(root, capacity, true)
}

func (d *DiskFS) init() {
	// logger.Logger.Info().Str("name", d.Name()).Str("root", d.root).Str("capacity", units.HumanSize(float64(d.capacity))).Msg("init")

	tstart := time.Now()

	d.walk(d.root)
	d.sg.Wait()

	logger.Logger.Info().
		Str("name", d.Name()).
		Str("root", d.root).
		Str("capacity", units.HumanSize(float64(d.capacity))).
		Str("size", units.HumanSize(float64(d.Size()))).
		Str("files", fmt.Sprint(len(d.info))).
		Str("duration", time.Since(tstart).String()).
		Msg("init")
}

func (d *DiskFS) walk(path string) {
	d.sg.Add(1)
	go func() {
		defer d.sg.Done()
		filepath.Walk(path, func(npath string, info os.FileInfo, err error) error {
			if path == npath {
				return nil
			}

			if err != nil {
				return err
			}

			if info.IsDir() {
				d.walk(npath)
				return filepath.SkipDir
			}

			d.mu.Lock()
			k := strings.ReplaceAll(npath[len(d.root)+1:], "\\", "/")
			logger.Logger.Debug().Str("name", k).Str("root", d.root).Msg("walk")
			d.info[k] = vfs.NewFileInfoFromOS(info, k)
			d.mu.Unlock()

			// logger.Logger.Debug().Str("name", d.Name()).Str("root", d.root).Str("capacity", units.HumanSize(float64(d.capacity))).Str("path", npath).Msg("init")
			return nil
		})
	}()
}

func (d *DiskFS) Capacity() int64 {
	return d.capacity
}

func (d *DiskFS) Name() string {
	return "DiskFS"
}

func (d *DiskFS) Size() int64 {
	d.mu.Lock()
	defer d.mu.Unlock()

	var size int64
	for _, v := range d.info {
		size += v.Size()
	}
	return size
}

func (d *DiskFS) Set(key string, src []byte) error {
	if key == "" {
		return vfserror.ErrInvalidKey
	}
	if key[0] == '/' {
		return vfserror.ErrInvalidKey
	}

	if d.capacity > 0 {
		if size := d.Size() + int64(len(src)); size > d.capacity {
			return vfserror.ErrDiskFull
		}
	}

	logger.Logger.Debug().Str("name", key).Str("root", d.root).Msg("set")

	if _, err := d.Stat(key); err == nil {
		logger.Logger.Debug().Str("name", key).Str("root", d.root).Msg("delete")
		d.Delete(key)
	}

	d.mu.Lock()
	defer d.mu.Unlock()
	os.MkdirAll(d.root+"/"+filepath.Dir(key), 0755)
	if err := os.WriteFile(d.root+"/"+key, src, 0644); err != nil {
		return err
	}

	fi, err := os.Stat(d.root + "/" + key)
	if err != nil {
		panic(err)
	}

	d.info[key] = vfs.NewFileInfoFromOS(fi, key)

	return nil
}

// Delete deletes the value of key.
func (d *DiskFS) Delete(key string) error {
	if key == "" {
		return vfserror.ErrInvalidKey
	}
	if key[0] == '/' {
		return vfserror.ErrInvalidKey
	}

	_, err := d.Stat(key)
	if err != nil {
		return err
	}

	d.mu.Lock()
	defer d.mu.Unlock()

	delete(d.info, key)
	if err := os.Remove(filepath.Join(d.root, key)); err != nil {
		return err
	}

	return nil
}

// Get gets the value of key and returns it.
func (d *DiskFS) Get(key string) ([]byte, error) {
	if key == "" {
		return nil, vfserror.ErrInvalidKey
	}
	if key[0] == '/' {
		return nil, vfserror.ErrInvalidKey
	}

	_, err := d.Stat(key)
	if err != nil {
		return nil, err
	}

	d.mu.Lock()
	defer d.mu.Unlock()

	data, err := os.ReadFile(filepath.Join(d.root, key))
	if err != nil {
		return nil, err
	}

	return data, nil
}

// Stat returns the FileInfo of key. If key is not found in the cache, it will stat the file on disk. If the file is not found on disk, it will return vfs.ErrNotFound.
func (d *DiskFS) Stat(key string) (*vfs.FileInfo, error) {
	if key == "" {
		return nil, vfserror.ErrInvalidKey
	}
	if key[0] == '/' {
		return nil, vfserror.ErrInvalidKey
	}

	logger.Logger.Debug().Str("name", key).Str("root", d.root).Msg("stat")

	d.mu.Lock()
	defer d.mu.Unlock()

	if fi, ok := d.info[key]; !ok {
		return nil, vfserror.ErrNotFound
	} else {
		return fi, nil
	}
}

func (m *DiskFS) StatAll() []*vfs.FileInfo {
	m.mu.Lock()
	defer m.mu.Unlock()

	// hard copy the file info to prevent modification of the original file info or the other way around
	files := make([]*vfs.FileInfo, 0, len(m.info))
	for _, v := range m.info {
		fi := *v
		files = append(files, &fi)
	}

	return files
}