/*
 * Minio Cloud Storage, (C) 2016 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package main

import (
	"strings"
	"sync"
)

// Common initialization needed for both object layers.
func initObjectLayer(storageDisks ...StorageAPI) error {
	// This happens for the first time, but keep this here since this
	// is the only place where it can be made expensive optimizing all
	// other calls. Create minio meta volume, if it doesn't exist yet.
	var wg = &sync.WaitGroup{}

	// Initialize errs to collect errors inside go-routine.
	var errs = make([]error, len(storageDisks))

	// Initialize all disks in parallel.
	for index, disk := range storageDisks {
		wg.Add(1)
		go func(index int, disk StorageAPI) {
			// Indicate this wait group is done.
			defer wg.Done()

			// Attempt to create `.minio`.
			err := disk.MakeVol(minioMetaBucket)
			if err != nil {
				if err != errVolumeExists && err != errDiskNotFound {
					errs[index] = err
					return
				}
			}
			// Cleanup all temp entries upon start.
			err = cleanupDir(disk, minioMetaBucket, tmpMetaPrefix)
			if err != nil {
				errs[index] = err
				return
			}
			errs[index] = nil
		}(index, disk)
	}

	// Wait for all cleanup to finish.
	wg.Wait()

	// Return upon first error.
	for _, err := range errs {
		if err == nil {
			continue
		}
		return toObjectErr(err, minioMetaBucket, tmpMetaPrefix)
	}

	// Return success here.
	return nil
}

// Cleanup a directory recursively.
func cleanupDir(storage StorageAPI, volume, dirPath string) error {
	var delFunc func(string) error
	// Function to delete entries recursively.
	delFunc = func(entryPath string) error {
		if !strings.HasSuffix(entryPath, slashSeparator) {
			// No trailing "/" means that this is a file which can be deleted.
			return storage.DeleteFile(volume, entryPath)
		}
		// If it's a directory, list and call delFunc() for each entry.
		entries, err := storage.ListDir(volume, entryPath)
		if err != nil {
			if err == errFileNotFound {
				// if dirPath prefix never existed.
				return nil
			}
			return err
		}
		for _, entry := range entries {
			err = delFunc(pathJoin(entryPath, entry))
			if err != nil {
				return err
			}
		}
		return nil
	}
	return delFunc(retainSlash(pathJoin(dirPath)))
}