/*
 * Minio Cloud Storage, (C) 2015, 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 (
	"encoding/hex"
	"fmt"
	"io"
	"path"
	"regexp"
	"runtime"
	"strings"
	"unicode/utf8"

	"github.com/skyrings/skyring-common/tools/uuid"
)

const (
	// Minio meta bucket.
	minioMetaBucket = ".minio.sys"
	// Multipart meta prefix.
	mpartMetaPrefix = "multipart"
	// Minio Multipart meta prefix.
	minioMetaMultipartBucket = minioMetaBucket + "/" + mpartMetaPrefix
	// Minio Tmp meta prefix.
	minioMetaTmpBucket = minioMetaBucket + "/tmp"
)

// validBucket regexp.
var validBucket = regexp.MustCompile(`^[a-z0-9][a-z0-9\.\-]{1,61}[a-z0-9]$`)
var isIPAddress = regexp.MustCompile(`^(\d+\.){3}\d+$`)

// isMinioBucket returns true if given bucket is a Minio internal
// bucket and false otherwise.
func isMinioMetaBucketName(bucket string) bool {
	return bucket == minioMetaBucket ||
		bucket == minioMetaMultipartBucket ||
		bucket == minioMetaTmpBucket
}

// IsValidBucketName verifies a bucket name in accordance with Amazon's
// requirements. It must be 3-63 characters long, can contain dashes
// and periods, but must begin and end with a lowercase letter or a number.
// See: http://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html
func IsValidBucketName(bucket string) bool {
	// Special case when bucket is equal to one of the meta buckets.
	if isMinioMetaBucketName(bucket) {
		return true
	}
	if len(bucket) < 3 || len(bucket) > 63 {
		return false
	}
	if bucket[0] == '.' || bucket[len(bucket)-1] == '.' {
		return false
	}
	return (validBucket.MatchString(bucket) &&
		!isIPAddress.MatchString(bucket) &&
		!strings.Contains(bucket, ".."))
}

// IsValidObjectName verifies an object name in accordance with Amazon's
// requirements. It cannot exceed 1024 characters and must be a valid UTF8
// string.
//
// See:
// http://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html
//
// You should avoid the following characters in a key name because of
// significant special handling for consistency across all
// applications.
//
// Rejects strings with following characters.
//
// - Backslash ("\")
//
// additionally minio does not support object names with trailing "/".
func IsValidObjectName(object string) bool {
	if len(object) == 0 {
		return false
	}
	if hasSuffix(object, slashSeparator) {
		return false
	}
	if hasPrefix(object, slashSeparator) {
		return false
	}
	return IsValidObjectPrefix(object)
}

// IsValidObjectPrefix verifies whether the prefix is a valid object name.
// Its valid to have a empty prefix.
func IsValidObjectPrefix(object string) bool {
	if len(object) > 1024 {
		return false
	}
	if !utf8.ValidString(object) {
		return false
	}
	// Reject unsupported characters in object name.
	if strings.ContainsAny(object, "\\") {
		return false
	}
	return true
}

// Slash separator.
const slashSeparator = "/"

// retainSlash - retains slash from a path.
func retainSlash(s string) string {
	return strings.TrimSuffix(s, slashSeparator) + slashSeparator
}

// pathJoin - like path.Join() but retains trailing "/" of the last element
func pathJoin(elem ...string) string {
	trailingSlash := ""
	if len(elem) > 0 {
		if hasSuffix(elem[len(elem)-1], slashSeparator) {
			trailingSlash = "/"
		}
	}
	return path.Join(elem...) + trailingSlash
}

// mustGetUUID - get a random UUID.
func mustGetUUID() string {
	uuid, err := uuid.New()
	if err != nil {
		panic(fmt.Sprintf("Random UUID generation failed. Error: %s", err))
	}

	return uuid.String()
}

// Create an s3 compatible MD5sum for complete multipart transaction.
func getCompleteMultipartMD5(parts []completePart) (string, error) {
	var finalMD5Bytes []byte
	for _, part := range parts {
		md5Bytes, err := hex.DecodeString(part.ETag)
		if err != nil {
			return "", traceError(err)
		}
		finalMD5Bytes = append(finalMD5Bytes, md5Bytes...)
	}
	s3MD5 := fmt.Sprintf("%s-%d", getMD5Hash(finalMD5Bytes), len(parts))
	return s3MD5, nil
}

// Prefix matcher string matches prefix in a platform specific way.
// For example on windows since its case insensitive we are supposed
// to do case insensitive checks.
func hasPrefix(s string, prefix string) bool {
	if runtime.GOOS == globalWindowsOSName {
		return strings.HasPrefix(strings.ToLower(s), strings.ToLower(prefix))
	}
	return strings.HasPrefix(s, prefix)
}

// Suffix matcher string matches suffix in a platform specific way.
// For example on windows since its case insensitive we are supposed
// to do case insensitive checks.
func hasSuffix(s string, suffix string) bool {
	if runtime.GOOS == globalWindowsOSName {
		return strings.HasSuffix(strings.ToLower(s), strings.ToLower(suffix))
	}
	return strings.HasSuffix(s, suffix)
}

// Validates if two strings are equal.
func isStringEqual(s1 string, s2 string) bool {
	if runtime.GOOS == globalWindowsOSName {
		return strings.EqualFold(s1, s2)
	}
	return s1 == s2
}

// Ignores all reserved bucket names or invalid bucket names.
func isReservedOrInvalidBucket(bucketEntry string) bool {
	bucketEntry = strings.TrimSuffix(bucketEntry, slashSeparator)
	if !IsValidBucketName(bucketEntry) {
		return true
	}
	return isMinioMetaBucket(bucketEntry) || isMinioReservedBucket(bucketEntry)
}

// Returns true if input bucket is a reserved minio meta bucket '.minio.sys'.
func isMinioMetaBucket(bucketName string) bool {
	return bucketName == minioMetaBucket
}

// Returns true if input bucket is a reserved minio bucket 'minio'.
func isMinioReservedBucket(bucketName string) bool {
	return bucketName == minioReservedBucket
}

// byBucketName is a collection satisfying sort.Interface.
type byBucketName []BucketInfo

func (d byBucketName) Len() int           { return len(d) }
func (d byBucketName) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
func (d byBucketName) Less(i, j int) bool { return d[i].Name < d[j].Name }

// rangeReader returns a Reader that reads from r
// but returns error after Max bytes read as errDataTooLarge.
// but returns error if reader exits before reading Min bytes
// errDataTooSmall.
type rangeReader struct {
	Reader io.Reader // underlying reader
	Min    int64     // min bytes remaining
	Max    int64     // max bytes remaining
}

func (l *rangeReader) Read(p []byte) (n int, err error) {
	n, err = l.Reader.Read(p)
	l.Max -= int64(n)
	l.Min -= int64(n)
	if l.Max < 0 {
		// If more data is available than what is expected we return error.
		return 0, errDataTooLarge
	}
	if err == io.EOF && l.Min > 0 {
		return 0, errDataTooSmall
	}
	return
}