package store

import (
	"io/ioutil"
	"os"
	"path"
	"path/filepath"

	"github.com/lbryio/lbry.go/v2/extras/errors"
	"github.com/lbryio/lbry.go/v2/stream"

	"github.com/spf13/afero"
)

// DiskStore stores blobs on a local disk
type DiskStore struct {
	// the location of blobs on disk
	blobDir string
	// store files in subdirectories based on the first N chars in the filename. 0 = don't create subdirectories.
	prefixLength int

	// filesystem abstraction
	fs afero.Fs

	// true if initOnce ran, false otherwise
	initialized bool
}

// NewDiskStore returns an initialized file disk store pointer.
func NewDiskStore(dir string, prefixLength int) *DiskStore {
	return &DiskStore{
		blobDir:      dir,
		prefixLength: prefixLength,
		fs:           afero.NewOsFs(),
	}
}

const nameDisk = "disk"

// Name is the cache type name
func (d *DiskStore) Name() string { return nameDisk }

// Has returns T/F or Error if it the blob stored already. It will error with any IO disk error.
func (d *DiskStore) Has(hash string) (bool, error) {
	err := d.initOnce()
	if err != nil {
		return false, err
	}

	_, err = d.fs.Stat(d.path(hash))
	if err != nil {
		if os.IsNotExist(err) {
			return false, nil
		}
		return false, errors.Err(err)
	}
	return true, nil
}

// Get returns the blob or an error if the blob doesn't exist.
func (d *DiskStore) Get(hash string) (stream.Blob, error) {
	err := d.initOnce()
	if err != nil {
		return nil, err
	}

	file, err := d.fs.Open(d.path(hash))
	if err != nil {
		if os.IsNotExist(err) {
			return nil, errors.Err(ErrBlobNotFound)
		}
		return nil, err
	}
	defer file.Close()

	blob, err := ioutil.ReadAll(file)
	return blob, errors.Err(err)
}

// Put stores the blob on disk
func (d *DiskStore) Put(hash string, blob stream.Blob) error {
	err := d.initOnce()
	if err != nil {
		return err
	}

	err = d.ensureDirExists(d.dir(hash))
	if err != nil {
		return err
	}

	err = afero.WriteFile(d.fs, d.path(hash), blob, 0644)
	return errors.Err(err)
}

// PutSD stores the sd blob on the disk
func (d *DiskStore) PutSD(hash string, blob stream.Blob) error {
	return d.Put(hash, blob)
}

// Delete deletes the blob from the store
func (d *DiskStore) Delete(hash string) error {
	err := d.initOnce()
	if err != nil {
		return err
	}

	has, err := d.Has(hash)
	if err != nil {
		return err
	}
	if !has {
		return nil
	}

	err = d.fs.Remove(d.path(hash))
	return errors.Err(err)
}

// list returns a slice of blobs that already exist in the blobDir
func (d *DiskStore) list() ([]string, error) {
	dirs, err := afero.ReadDir(d.fs, d.blobDir)
	if err != nil {
		return nil, err
	}

	var existing []string

	for _, dir := range dirs {
		if dir.IsDir() {
			files, err := afero.ReadDir(d.fs, filepath.Join(d.blobDir, dir.Name()))
			if err != nil {
				return nil, err
			}
			for _, file := range files {
				if file.Mode().IsRegular() && !file.IsDir() {
					existing = append(existing, file.Name())
				}
			}
		}
	}

	return existing, nil
}

func (d *DiskStore) dir(hash string) string {
	if d.prefixLength <= 0 || len(hash) < d.prefixLength {
		return d.blobDir
	}
	return path.Join(d.blobDir, hash[:d.prefixLength])
}

func (d *DiskStore) path(hash string) string {
	return path.Join(d.dir(hash), hash)
}

func (d *DiskStore) ensureDirExists(dir string) error {
	return errors.Err(d.fs.MkdirAll(dir, 0755))
}

func (d *DiskStore) initOnce() error {
	if d.initialized {
		return nil
	}

	err := d.ensureDirExists(d.blobDir)
	if err != nil {
		return err
	}

	d.initialized = true
	return nil
}