/*
 * 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

// Returns function "listDir" of the type listDirFunc.
// isLeaf - is used by listDir function to check if an entry is a leaf or non-leaf entry.
// disks - used for doing disk.ListDir(). FS passes single disk argument, XL passes a list of disks.
func listDirFactory(isLeaf isLeafFunc, treeWalkIgnoredErrs []error, disks ...StorageAPI) listDirFunc {
	// listDir - lists all the entries at a given prefix and given entry in the prefix.
	listDir := func(bucket, prefixDir, prefixEntry string) (entries []string, delayIsLeaf bool, err error) {
		for _, disk := range disks {
			if disk == nil {
				continue
			}
			entries, err = disk.ListDir(bucket, prefixDir)
			if err == nil {
				entries, delayIsLeaf = filterListEntries(bucket, prefixDir, entries, prefixEntry, isLeaf)
				return entries, delayIsLeaf, nil
			}
			// For any reason disk was deleted or goes offline, continue
			// and list from other disks if possible.
			if isErrIgnored(err, treeWalkIgnoredErrs...) {
				continue
			}
			break
		}
		// Return error at the end.
		return nil, false, traceError(err)
	}
	return listDir
}

// listObjects - wrapper function implemented over file tree walk.
func (xl xlObjects) listObjects(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 := false // true only for xl.ListObjectsHeal
	walkResultCh, endWalkCh := xl.listPool.Release(listParams{bucket, recursive, marker, prefix, heal})
	if walkResultCh == nil {
		endWalkCh = make(chan struct{})
		isLeaf := xl.isObject
		listDir := listDirFactory(isLeaf, xlTreeWalkIgnoredErrs, xl.getLoadBalancedDisks()...)
		walkResultCh = startTreeWalk(bucket, prefix, marker, recursive, listDir, isLeaf, 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 errorCause(walkResult.err) == errFileNotFound {
				return ListObjectsInfo{}, nil
			}
			return ListObjectsInfo{}, toObjectErr(walkResult.err, bucket, prefix)
		}
		entry := walkResult.entry
		var objInfo ObjectInfo
		if hasSuffix(entry, slashSeparator) {
			// Object name needs to be full path.
			objInfo.Bucket = bucket
			objInfo.Name = entry
			objInfo.IsDir = true
		} else {
			// Set the Mode to a "regular" file.
			var err error
			objInfo, err = xl.getObjectInfo(bucket, entry)
			if err != nil {
				// Ignore errFileNotFound
				if errorCause(err) == errFileNotFound {
					continue
				}
				return ListObjectsInfo{}, toObjectErr(err, bucket, prefix)
			}
		}
		nextMarker = objInfo.Name
		objInfos = append(objInfos, objInfo)
		i++
		if walkResult.end {
			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
		}
		result.Objects = append(result.Objects, objInfo)
	}
	return result, nil
}

// ListObjects - list all objects at prefix, delimited by '/'.
func (xl xlObjects) ListObjects(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.listObjects(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)
}