// Copyright (c) 2015-2024 MinIO, Inc.
//
// # This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"encoding/base64"
	"sort"
	"strconv"
	"strings"

	"github.com/minio/cli"
	"github.com/minio/mc/pkg/probe"
	"github.com/minio/minio-go/v7/pkg/encrypt"
)

type sseKeyType int

const (
	sseNone sseKeyType = iota
	sseC
	sseKMS
	sseS3
)

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

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

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

func validateAndCreateEncryptionKeys(ctx *cli.Context) (encMap map[string][]prefixSSEPair, err *probe.Error) {
	encMap = make(map[string][]prefixSSEPair, 0)

	for _, v := range ctx.StringSlice("enc-kms") {
		prefixPair, alias, err := validateAndParseKey(ctx, v, sseKMS)
		if err != nil {
			return nil, err
		}
		encMap[alias] = append(encMap[alias], *prefixPair)
	}

	for _, v := range ctx.StringSlice("enc-s3") {
		prefixPair, alias, err := validateAndParseKey(ctx, v, sseS3)
		if err != nil {
			return nil, err
		}
		encMap[alias] = append(encMap[alias], *prefixPair)
	}

	for _, v := range ctx.StringSlice("enc-c") {
		prefixPair, alias, err := validateAndParseKey(ctx, v, sseC)
		if err != nil {
			return nil, err
		}
		encMap[alias] = append(encMap[alias], *prefixPair)
	}

	for i := range encMap {
		err = validateOverLappingSSEKeys(encMap[i])
		if err != nil {
			return nil, err
		}
	}

	for alias, ps := range encMap {
		if hostCfg := mustGetHostConfig(alias); hostCfg == nil {
			for _, p := range ps {
				return nil, errSSEInvalidAlias(p.Prefix)
			}
		}
	}

	for _, encKeys := range encMap {
		sort.Sort(byPrefixLength(encKeys))
	}

	return encMap, nil
}

func validateAndParseKey(ctx *cli.Context, key string, keyType sseKeyType) (SSEPair *prefixSSEPair, alias string, perr *probe.Error) {
	matchedCount := 0
	alias, prefix, encKey, keyErr := parseSSEKey(key, keyType)
	if keyErr != nil {
		return nil, "", keyErr
	}
	if alias == "" {
		return nil, "", errSSEInvalidAlias(prefix).Trace(key)
	}

	if (keyType == sseKMS || keyType == sseC) && encKey == "" {
		return nil, "", errSSEClientKeyFormat("SSE-C/KMS key should be of the form alias/prefix=key,... ").Trace(key)
	}

	for _, arg := range ctx.Args() {
		if strings.HasPrefix(arg, alias+"/"+prefix) {
			matchedCount++
		}
	}

	if matchedCount == 0 {
		return nil, "", errSSEPrefixMatch()
	}

	ssePairPrefix := alias + "/" + prefix
	var sse encrypt.ServerSide
	var err error

	switch keyType {
	case sseC:
		sse, err = encrypt.NewSSEC([]byte(encKey))
	case sseKMS:
		sse, err = encrypt.NewSSEKMS(encKey, nil)
	case sseS3:
		sse = encrypt.NewSSE()
	}

	if err != nil {
		return nil, "", probe.NewError(err).Trace(key)
	}

	return &prefixSSEPair{
		Prefix: ssePairPrefix,
		SSE:    sse,
	}, alias, nil
}

func validateOverLappingSSEKeys(keyMap []prefixSSEPair) (err *probe.Error) {
	for i := 0; i < len(keyMap); i++ {
		for j := i + 1; j < len(keyMap); j++ {
			if strings.HasPrefix(keyMap[i].Prefix, keyMap[j].Prefix) ||
				strings.HasPrefix(keyMap[j].Prefix, keyMap[i].Prefix) {
				return errSSEOverlappingAlias(keyMap[i].Prefix, keyMap[j].Prefix)
			}
		}
	}
	return
}

func splitKey(sseKey string) (alias, prefix string) {
	x := strings.SplitN(sseKey, "/", 2)
	switch len(x) {
	case 2:
		return x[0], x[1]
	case 1:
		return x[0], ""
	}
	return "", ""
}

func parseSSEKey(sseKey string, keyType sseKeyType) (
	alias string,
	prefix string,
	key string,
	err *probe.Error,
) {
	if keyType == sseS3 {
		alias, prefix = splitKey(sseKey)
		return
	}

	var path string
	alias, path = splitKey(sseKey)
	splitPath := strings.Split(path, "=")
	if len(splitPath) == 0 {
		err = errSSEKeyMissing().Trace(sseKey)
		return
	}

	aliasPlusPrefix := strings.Join(splitPath[:len(splitPath)-1], "=")
	prefix = strings.Replace(aliasPlusPrefix, alias+"/", "", 1)
	key = splitPath[len(splitPath)-1]

	if keyType == sseC {
		keyB, de := base64.RawStdEncoding.DecodeString(key)
		if de != nil {
			err = errSSEClientKeyFormat("One of the inserted keys was " + strconv.Itoa(len(key)) + " bytes and did not have valid base64 raw encoding.").Trace(sseKey)
			return
		}
		key = string(keyB)
		if len(key) != 32 {
			err = errSSEClientKeyFormat("The plain text key was " + strconv.Itoa(len(key)) + " bytes but should be 32 bytes long").Trace(sseKey)
			return
		}
	}

	if keyType == sseKMS {
		if !validKMSKeyName(key) {
			err = errSSEKMSKeyFormat("One of the inserted keys was " + strconv.Itoa(len(key)) + " bytes and did not have a valid KMS key name.").Trace(sseKey)
			return
		}
	}

	return
}

func validKMSKeyName(s string) bool {
	if s == "" || s == "_" {
		return false
	}

	n := len(s) - 1
	for i, r := range s {
		switch {
		case r >= '0' && r <= '9':
		case r >= 'A' && r <= 'Z':
		case r >= 'a' && r <= 'z':
		case r == '-' && i > 0 && i < n:
		case r == '_':
		default:
			return false
		}
	}
	return true
}