// Copyright (c) Acrosync LLC. All rights reserved.
// Licensed under the Fair Source License 0.9 (https://fair.io/)
// User Limitation: 5 users

package duplicacy

import (
    "os"
    "fmt"
    "path"
    "io"
    "io/ioutil"
    "time"
    "math/rand"
)

// FileStorage is a local on-disk file storage implementing the Storage interface.
type FileStorage struct {
    RateLimitedStorage

    storageDir string
    numberOfThreads int
}

// CreateFileStorage creates a file storage.
func CreateFileStorage(storageDir string, threads int) (storage *FileStorage, err error) {

    var stat os.FileInfo

    stat, err = os.Stat(storageDir)
    if os.IsNotExist(err) {
        err = os.MkdirAll(storageDir, 0744)
        if err != nil {
            return nil, err
        }
    } else {
        if !stat.IsDir() {
            return nil, fmt.Errorf("The storage path %s is a file", storageDir)
        }
    }

    for storageDir[len(storageDir) - 1] ==  '/' {
        storageDir = storageDir[:len(storageDir) - 1]
    }

    storage = &FileStorage {
        storageDir : storageDir,
        numberOfThreads: threads,
    }

    // Random number fo generating the temporary chunk file suffix.
    rand.Seed(time.Now().UnixNano())

    return storage, nil
}

// ListFiles return the list of files and subdirectories under 'dir' (non-recursively).
func (storage *FileStorage) ListFiles(threadIndex int, dir string) (files []string, sizes []int64, err error) {

    fullPath := path.Join(storage.storageDir, dir)

    list, err := ioutil.ReadDir(fullPath)
    if err != nil {
        if os.IsNotExist(err) {
            return nil, nil, nil
        }
        return nil, nil, err
    }

    for _, f := range list {
        name := f.Name()
        if f.IsDir() && name[len(name) - 1] != '/' {
            name += "/"
        }
        files = append(files, name)
        sizes = append(sizes, f.Size())
    }

    return files, sizes, nil
}

// DeleteFile deletes the file or directory at 'filePath'.
func (storage *FileStorage) DeleteFile(threadIndex int, filePath string) (err error) {
    err = os.Remove(path.Join(storage.storageDir, filePath))
    if err == nil || os.IsNotExist(err) {
        return nil
    } else {
        return err
    }
}

// MoveFile renames the file.
func (storage *FileStorage) MoveFile(threadIndex int, from string, to string) (err error) {
    return os.Rename(path.Join(storage.storageDir, from), path.Join(storage.storageDir, to))
}

// CreateDirectory creates a new directory.
func (storage *FileStorage) CreateDirectory(threadIndex int, dir string) (err error) {
    err = os.Mkdir(path.Join(storage.storageDir, dir), 0744)
    if err != nil && os.IsExist(err) {
        return nil
    } else {
        return err
    }
}

// GetFileInfo returns the information about the file or directory at 'filePath'.
func (storage *FileStorage) GetFileInfo(threadIndex int, filePath string) (exist bool, isDir bool, size int64, err error) {
    stat, err := os.Stat(path.Join(storage.storageDir, filePath))
    if err != nil {
        if os.IsNotExist(err) {
            return false, false, 0, nil
        } else {
            return false, false, 0, err
        }
    }

    return true, stat.IsDir(), stat.Size(), nil
}

// FindChunk finds the chunk with the specified id.  If 'isFossil' is true, it will search for chunk files with the
// suffix '.fsl'.
func (storage *FileStorage) FindChunk(threadIndex int, chunkID string, isFossil bool) (filePath string, exist bool, size int64, err error) {
     dir := path.Join(storage.storageDir, "chunks")

    suffix := ""
    if isFossil {
        suffix = ".fsl"
    }

    // The minimum level of directories to dive into before searching for the chunk file.
    minimumLevel := 2

    for level := 0; level * 2 < len(chunkID); level ++ {
        if level >= minimumLevel {
            filePath = path.Join(dir, chunkID[2 * level:]) + suffix
            if stat, err := os.Stat(filePath); err == nil && !stat.IsDir() {
                return filePath[len(storage.storageDir) + 1:], true, stat.Size(), nil
            } else if err == nil && stat.IsDir() {
                return filePath[len(storage.storageDir) + 1:], true, 0, fmt.Errorf("The path %s is a directory", filePath)
            }
        }

        // Find the subdirectory the chunk file may reside.
        subDir := path.Join(dir, chunkID[2 * level: 2 * level + 2])
        stat, err := os.Stat(subDir)
        if err == nil && stat.IsDir() {
            dir = subDir
            continue
        }

        if level < minimumLevel {
            // Create the subdirectory if it doesn't exist.

            if err == nil && !stat.IsDir() {
                return "", false, 0, fmt.Errorf("The path %s is not a directory", subDir)
            }

            err = os.Mkdir(subDir, 0744)
            if err != nil {
                return "", false, 0, err
            }

            dir = subDir
            continue
        }

        // The chunk must be under this subdirectory but it doesn't exist.
        return path.Join(dir, chunkID[2 * level:])[len(storage.storageDir) + 1:] + suffix, false, 0, nil

    }

    LOG_FATAL("CHUNK_FIND", "Chunk %s is still not found after having searched a maximum level of directories",
              chunkID)
    return "", false, 0, nil

}

// DownloadFile reads the file at 'filePath' into the chunk.
func (storage *FileStorage) DownloadFile(threadIndex int, filePath string, chunk *Chunk) (err error) {

    file, err := os.Open(path.Join(storage.storageDir, filePath))

    if err != nil {
        return err
    }

    defer file.Close()
    if _, err = RateLimitedCopy(chunk, file, storage.DownloadRateLimit / storage.numberOfThreads); err != nil {
        return err
    }

    return nil

}

// UploadFile writes 'content' to the file at 'filePath'
func (storage *FileStorage) UploadFile(threadIndex int, filePath string, content []byte) (err error) {

    fullPath := path.Join(storage.storageDir, filePath)

    letters := "abcdefghijklmnopqrstuvwxyz"
    suffix := make([]byte, 8)
    for i := range suffix {
        suffix[i] = letters[rand.Intn(len(letters))]
    }

    temporaryFile := fullPath + "." + string(suffix) + ".tmp"

    file, err := os.OpenFile(temporaryFile, os.O_WRONLY | os.O_CREATE | os.O_TRUNC, 0644)
    if err != nil {
        return err
    }

    reader := CreateRateLimitedReader(content, storage.UploadRateLimit / storage.numberOfThreads)
    _, err = io.Copy(file, reader)
    if err != nil {
        file.Close()
        return err
    }

    file.Close()

    err = os.Rename(temporaryFile, fullPath)
    if err != nil {

        if _, e := os.Stat(fullPath); e == nil {
            os.Remove(temporaryFile)
            return nil
        } else {
            return err
        }
    }

    return nil
}

// If a local snapshot cache is needed for the storage to avoid downloading/uploading chunks too often when
// managing snapshots.
func (storage *FileStorage) IsCacheNeeded () (bool) { return false }

// If the 'MoveFile' method is implemented.
func (storage *FileStorage) IsMoveFileImplemented() (bool) { return true }

// If the storage can guarantee strong consistency.
func (storage *FileStorage) IsStrongConsistent() (bool) { return true }

// If the storage supports fast listing of files names.
func (storage *FileStorage) IsFastListing() (bool) { return false }

// Enable the test mode.
func (storage *FileStorage) EnableTestMode() {}