/*
 * Minio Client (C) 2015, 2016, 2017 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 (
	"crypto/tls"
	"errors"
	"io"
	"math/rand"
	"os"
	"runtime"
	"sort"
	"strings"
	"time"

	"github.com/minio/minio-go"
	"github.com/minio/minio-go/pkg/encrypt"

	"github.com/minio/mc/pkg/console"
	"github.com/minio/mc/pkg/probe"
)

func isErrIgnored(err *probe.Error) (ignored bool) {
	// For all non critical errors we can continue for the remaining files.
	switch err.ToGoError().(type) {
	// Handle these specifically for filesystem related errors.
	case BrokenSymlink, TooManyLevelsSymlink, PathNotFound, PathInsufficientPermission:
		ignored = true
	// Handle these specifically for object storage related errors.
	case BucketNameEmpty, ObjectMissing, ObjectAlreadyExists:
		ignored = true
	case ObjectAlreadyExistsAsDirectory, BucketDoesNotExist, BucketInvalid, ObjectOnGlacier:
		ignored = true
	default:
		ignored = false
	}
	return ignored
}

const (
	letterBytes   = "abcdefghijklmnopqrstuvwxyz01234569"
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

// UTCNow - returns current UTC time.
func UTCNow() time.Time {
	return time.Now().UTC()
}

var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

// newRandomID generates a random id of regular lower case and uppercase english characters.
func newRandomID(n int) string {
	rand.Seed(UTCNow().UnixNano())
	sid := make([]rune, n)
	for i := range sid {
		sid[i] = letters[rand.Intn(len(letters))]
	}
	return string(sid)
}

// randString generates random names and prepends them with a known prefix.
func randString(n int, src rand.Source, prefix string) string {
	b := make([]byte, n)
	// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			b[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}
	return prefix + string(b[0:30-len(prefix)])
}

// dumpTlsCertificates prints some fields of the certificates received from the server.
// Fields will be inspected by the user, so they must be conscise and useful
func dumpTLSCertificates(t *tls.ConnectionState) {
	for _, cert := range t.PeerCertificates {
		console.Debugln("TLS Certificate found: ")
		if len(cert.Issuer.Country) > 0 {
			console.Debugln(" >> Country: " + cert.Issuer.Country[0])
		}
		if len(cert.Issuer.Organization) > 0 {
			console.Debugln(" >> Organization: " + cert.Issuer.Organization[0])
		}
		console.Debugln(" >> Expires: " + cert.NotAfter.String())
	}
}

// isStdIO checks if the input parameter is one of the standard input/output streams
func isStdIO(reader io.Reader) bool {
	return reader == os.Stdin || reader == os.Stdout || reader == os.Stderr
}

// splitStr splits a string into n parts, empty strings are added
// if we are not able to reach n elements
func splitStr(path, sep string, n int) []string {
	splits := strings.SplitN(path, sep, n)
	// Add empty strings if we found elements less than nr
	for i := n - len(splits); i > 0; i-- {
		splits = append(splits, "")
	}
	return splits
}

// newS3Config simply creates a new Config struct using the passed
// parameters.
func newS3Config(urlStr string, hostCfg *hostConfigV9) *Config {
	// We have a valid alias and hostConfig. We populate the
	// credentials from the match found in the config file.
	s3Config := new(Config)

	s3Config.AppName = "mc"
	s3Config.AppVersion = Version
	s3Config.AppComments = []string{os.Args[0], runtime.GOOS, runtime.GOARCH}
	s3Config.Debug = globalDebug
	s3Config.Insecure = globalInsecure

	s3Config.HostURL = urlStr
	if hostCfg != nil {
		s3Config.AccessKey = hostCfg.AccessKey
		s3Config.SecretKey = hostCfg.SecretKey
		s3Config.Signature = hostCfg.API
	}
	s3Config.Lookup = getLookupType(hostCfg.Lookup)
	return s3Config
}

// lineTrunc - truncates a string to the given maximum length by
// adding ellipsis in the middle
func lineTrunc(content string, maxLen int) string {
	runes := []rune(content)
	rlen := len(runes)
	if rlen <= maxLen {
		return content
	}
	halfLen := maxLen / 2
	fstPart := string(runes[0:halfLen])
	sndPart := string(runes[rlen-halfLen:])
	return fstPart + "…" + sndPart
}

// isOlder returns true if the passed object is older than olderRef
func isOlder(c *clientContent, olderRef int) bool {
	objectAge := UTCNow().Sub(c.Time)
	return objectAge < (time.Duration(olderRef) * Day)
}

// isNewer returns true if the passed object is newer than newerRef
func isNewer(c *clientContent, newerRef int) bool {
	objectAge := UTCNow().Sub(c.Time)
	return objectAge > (time.Duration(newerRef) * Day)
}

// getLookupType returns the minio.BucketLookupType for lookup
// option entered on the command line
func getLookupType(l string) minio.BucketLookupType {
	l = strings.ToLower(l)
	switch l {
	case "dns":
		return minio.BucketLookupDNS
	case "path":
		return minio.BucketLookupPath
	}
	return minio.BucketLookupAuto
}

// struct representing object prefix and sse keys association.
type prefixSSEPair struct {
	Prefix string
	SSE    encrypt.ServerSide
}

// parse and validate encryption keys entered on command line
func parseAndValidateEncryptionKeys(sseKeys string, sse string) (encMap map[string][]prefixSSEPair, err *probe.Error) {
	encMap, err = parseEncryptionKeys(sseKeys)
	if err != nil {
		return nil, err
	}
	if sse != "" {
		for _, prefix := range strings.Split(sse, ",") {
			alias, _ := url2Alias(prefix)
			encMap[alias] = append(encMap[alias], prefixSSEPair{
				Prefix: prefix,
				SSE:    encrypt.NewSSE(),
			})
		}
	}
	for alias, ps := range encMap {
		if hostCfg := mustGetHostConfig(alias); hostCfg == nil {
			for _, p := range ps {
				return nil, probe.NewError(errors.New("SSE prefix " + p.Prefix + " has invalid alias"))
			}
		}
	}
	return encMap, nil
}

// parse list of comma separated alias/prefix=sse key values entered on command line and
// construct a map of alias to prefix and sse pairs.
func parseEncryptionKeys(sseKeys string) (encMap map[string][]prefixSSEPair, err *probe.Error) {
	encMap = make(map[string][]prefixSSEPair)
	if sseKeys == "" {
		return
	}
	prefix := ""
	index := 0 // start index of prefix
	vs := 0    // start index of sse-c key
	sseKeyLen := 32
	delim := 1
	k := len(sseKeys)
	for index < k {
		i := strings.Index(sseKeys[index:], "=")
		if i == -1 {
			return nil, probe.NewError(errors.New("SSE-C prefix should be of the form prefix1=key1,... "))
		}
		prefix = sseKeys[index : index+i]
		alias, _ := url2Alias(prefix)
		vs = i + 1 + index
		if vs+32 > k {
			return nil, probe.NewError(errors.New("SSE-C key should be 32 bytes long"))
		}
		if (vs+sseKeyLen < k) && sseKeys[vs+sseKeyLen] != ',' {
			return nil, probe.NewError(errors.New("SSE-C prefix=secret should be delimited by , and secret should be 32 bytes long"))
		}
		sseKey := sseKeys[vs : vs+sseKeyLen]
		if _, ok := encMap[alias]; !ok {
			encMap[alias] = make([]prefixSSEPair, 0)
		}
		sse, e := encrypt.NewSSEC([]byte(sseKey))
		if e != nil {
			return nil, probe.NewError(e)
		}
		encMap[alias] = append(encMap[alias], prefixSSEPair{
			Prefix: prefix,
			SSE:    sse,
		})
		// advance index sseKeyLen + delim bytes for the next key start
		index = vs + sseKeyLen + delim
	}

	// Sort encryption keys in descending order of prefix length
	for _, encKeys := range encMap {
		sort.Sort(byPrefixLength(encKeys))
	}

	// Success.
	return encMap, nil
}

// byPrefixLength implements sort.Interface.
type byPrefixLength []prefixSSEPair

func (p byPrefixLength) Len() int { return len(p) }
func (p byPrefixLength) Less(i, j int) bool {
	return len(p[i].Prefix) > len(p[j].Prefix)
}
func (p byPrefixLength) Swap(i, j int) { p[i], p[j] = p[j], p[i] }

// get SSE Key if object prefix matches with given resource.
func getSSE(resource string, encKeys []prefixSSEPair) encrypt.ServerSide {
	for _, k := range encKeys {
		if strings.HasPrefix(resource, k.Prefix) {
			return k.SSE
		}
	}
	return nil
}

// Return true if target url is a part of a source url such as:
// alias/bucket/ and alias/bucket/dir/, however
func isURLContains(srcURL, tgtURL, sep string) bool {
	// Add a separator to source url if not found
	if !strings.HasSuffix(srcURL, sep) {
		srcURL += sep
	}
	if !strings.HasSuffix(tgtURL, sep) {
		tgtURL += sep
	}
	// Check if we are going to copy a directory into itself
	if strings.HasPrefix(tgtURL, srcURL) {
		return true
	}
	return false
}
