/*
 * 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 cmd

import (
	"sort"
	"strings"
)

func listDirHealFactory(isLeaf isLeafFunc, disks ...StorageAPI) listDirFunc {
	// Returns sorted merged entries from all the disks.
	listDir := func(bucket, prefixDir, prefixEntry string) (mergedEntries []string, delayIsLeaf bool, err error) {
		for _, disk := range disks {
			if disk == nil {
				continue
			}
			var entries []string
			var newEntries []string
			entries, err = disk.ListDir(bucket, prefixDir)
			if err != nil {
				continue
			}
			// Listing needs to be sorted.
			sort.Strings(entries)

			// Filter entries that have the prefix prefixEntry.
			entries = filterMatchingPrefix(entries, prefixEntry)

			// isLeaf() check has to happen here so that trailing "/" for objects can be removed.
			for i, entry := range entries {
				if isLeaf(bucket, pathJoin(prefixDir, entry)) {
					entries[i] = strings.TrimSuffix(entry, slashSeparator)
				}
			}
			// Sort again after removing trailing "/" for objects as the previous sort
			// does not hold good anymore.
			sort.Strings(entries)
			if len(mergedEntries) == 0 {
				// For the first successful disk.ListDir()
				mergedEntries = entries
				sort.Strings(mergedEntries)
				continue
			}
			// find elements in entries which are not in mergedentries
			for _, entry := range entries {
				idx := sort.SearchStrings(mergedEntries, entry)
				if mergedEntries[idx] == entry {
					continue
				}
				newEntries = append(newEntries, entry)
			}
			if len(newEntries) > 0 {
				// Merge the entries and sort it.
				mergedEntries = append(mergedEntries, newEntries...)
				sort.Strings(mergedEntries)
			}
		}
		return mergedEntries, false, nil
	}
	return listDir
}

// listObjectsHeal - wrapper function implemented over file tree walk.
func (xl xlObjects) listObjectsHeal(bucket, prefix, marker, delimiter string, maxKeys int) (ListObjectsInfo, error) {
	// Default is recursive, if delimiter is set then list non recursive.
	recursive := true
	if delimiter == slashSeparator {
		recursive = false
	}

	// "heal" true for listObjectsHeal() and false for listObjects()
	heal := true
	walkResultCh, endWalkCh := xl.listPool.Release(listParams{bucket, recursive, marker, prefix, heal})
	if walkResultCh == nil {
		endWalkCh = make(chan struct{})
		isLeaf := xl.isObject
		listDir := listDirHealFactory(isLeaf, xl.storageDisks...)
		walkResultCh = startTreeWalk(bucket, prefix, marker, recursive, listDir, nil, endWalkCh)
	}

	var objInfos []ObjectInfo
	var eof bool
	var nextMarker string
	for i := 0; i < maxKeys; {
		walkResult, ok := <-walkResultCh
		if !ok {
			// Closed channel.
			eof = true
			break
		}
		// For any walk error return right away.
		if walkResult.err != nil {
			// File not found is a valid case.
			if walkResult.err == errFileNotFound {
				return ListObjectsInfo{}, nil
			}
			return ListObjectsInfo{}, toObjectErr(walkResult.err, bucket, prefix)
		}
		entry := walkResult.entry
		var objInfo ObjectInfo
		if strings.HasSuffix(entry, slashSeparator) {
			// Object name needs to be full path.
			objInfo.Bucket = bucket
			objInfo.Name = entry
			objInfo.IsDir = true
		} else {
			objInfo.Bucket = bucket
			objInfo.Name = entry
		}
		nextMarker = objInfo.Name
		objInfos = append(objInfos, objInfo)
		i++
		if walkResult.end == true {
			eof = true
			break
		}
	}

	params := listParams{bucket, recursive, nextMarker, prefix, heal}
	if !eof {
		xl.listPool.Set(params, walkResultCh, endWalkCh)
	}

	result := ListObjectsInfo{IsTruncated: !eof}
	for _, objInfo := range objInfos {
		result.NextMarker = objInfo.Name
		if objInfo.IsDir {
			result.Prefixes = append(result.Prefixes, objInfo.Name)
			continue
		}

		// Check if the current object needs healing
		objectLock := nsMutex.NewNSLock(bucket, objInfo.Name)
		objectLock.RLock()
		partsMetadata, errs := readAllXLMetadata(xl.storageDisks, bucket, objInfo.Name)
		if xlShouldHeal(partsMetadata, errs) {
			result.Objects = append(result.Objects, ObjectInfo{
				Name:    objInfo.Name,
				ModTime: objInfo.ModTime,
				Size:    objInfo.Size,
				IsDir:   false,
			})
		}
		objectLock.RUnlock()
	}
	return result, nil
}

// ListObjects - list all objects at prefix, delimited by '/'.
func (xl xlObjects) ListObjectsHeal(bucket, prefix, marker, delimiter string, maxKeys int) (ListObjectsInfo, error) {
	if err := checkListObjsArgs(bucket, prefix, marker, delimiter, xl); err != nil {
		return ListObjectsInfo{}, err
	}

	// With max keys of zero we have reached eof, return right here.
	if maxKeys == 0 {
		return ListObjectsInfo{}, nil
	}

	// For delimiter and prefix as '/' we do not list anything at all
	// since according to s3 spec we stop at the 'delimiter' along
	// with the prefix. On a flat namespace with 'prefix' as '/'
	// we don't have any entries, since all the keys are of form 'keyName/...'
	if delimiter == slashSeparator && prefix == slashSeparator {
		return ListObjectsInfo{}, nil
	}

	// Over flowing count - reset to maxObjectList.
	if maxKeys < 0 || maxKeys > maxObjectList {
		maxKeys = maxObjectList
	}

	// Initiate a list operation, if successful filter and return quickly.
	listObjInfo, err := xl.listObjectsHeal(bucket, prefix, marker, delimiter, maxKeys)
	if err == nil {
		// We got the entries successfully return.
		return listObjInfo, nil
	}

	// Return error at the end.
	return ListObjectsInfo{}, toObjectErr(err, bucket, prefix)
}