package model

import (
	"crypto/rand"
	"cwtch.im/cwtch/model/attr"
	"cwtch.im/cwtch/model/constants"
	"cwtch.im/cwtch/protocol/groups"
	"encoding/base32"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"git.openprivacy.ca/openprivacy/connectivity/tor"
	"golang.org/x/crypto/ed25519"
	"io"
	"path/filepath"
	"strings"
	"sync"
	"time"
)

// Authorization is a type determining client assigned authorization to a peer
type Authorization string

const (
	// AuthUnknown is an initial state for a new unseen peer
	AuthUnknown Authorization = "unknown"
	// AuthApproved means the client has approved the peer, it can send messages to us, perform GetVals, etc
	AuthApproved Authorization = "approved"
	// AuthBlocked means the client has blocked the peer, it's messages and connections should be rejected
	AuthBlocked Authorization = "blocked"
)

// PublicProfile is a local copy of a CwtchIdentity
type PublicProfile struct {
	Name                   string
	Ed25519PublicKey       ed25519.PublicKey
	Authorization          Authorization
	DeprecatedBlocked      bool `json:"Blocked"`
	Onion                  string
	Attributes             map[string]string
	Timeline               Timeline `json:"-"`
	LocalID                string   // used by storage engine
	State                  string   `json:"-"`
	lock                   sync.Mutex
	UnacknowledgedMessages map[string]int
}

// Profile encapsulates all the attributes necessary to be a Cwtch Peer.
type Profile struct {
	PublicProfile
	Contacts          map[string]*PublicProfile
	Ed25519PrivateKey ed25519.PrivateKey
	Groups            map[string]*Group
}

// MaxGroupMessageLength is the maximum length of a message posted to a server group.
// TODO: Should this be per server?
const MaxGroupMessageLength = 1800

// GenerateRandomID generates a random 16 byte hex id code
func GenerateRandomID() string {
	randBytes := make([]byte, 16)
	rand.Read(randBytes)
	return filepath.Join(hex.EncodeToString(randBytes))
}

func (p *PublicProfile) init() {
	if p.Attributes == nil {
		p.Attributes = make(map[string]string)
	}
	p.UnacknowledgedMessages = make(map[string]int)
	p.LocalID = GenerateRandomID()
}

// SetAttribute allows applications to store arbitrary configuration info at the profile level.
func (p *PublicProfile) SetAttribute(name string, value string) {
	p.lock.Lock()
	defer p.lock.Unlock()
	p.Attributes[name] = value
}

// IsServer returns true if the profile is associated with a server.
func (p *PublicProfile) IsServer() (isServer bool) {
	_, isServer = p.GetAttribute(string(KeyTypeServerOnion))
	return
}

// GetAttribute returns the value of a value set with SetCustomAttribute. If no such value has been set exists is set to false.
func (p *PublicProfile) GetAttribute(name string) (value string, exists bool) {
	p.lock.Lock()
	defer p.lock.Unlock()
	value, exists = p.Attributes[name]
	return
}

// GenerateNewProfile creates a new profile, with new encryption and signing keys, and a profile name.
func GenerateNewProfile(name string) *Profile {
	p := new(Profile)
	p.init()
	p.Name = name
	pub, priv, _ := ed25519.GenerateKey(rand.Reader)
	p.Ed25519PublicKey = pub
	p.Ed25519PrivateKey = priv
	p.Onion = tor.GetTorV3Hostname(pub)

	p.Contacts = make(map[string]*PublicProfile)
	p.Contacts[p.Onion] = &p.PublicProfile
	p.Groups = make(map[string]*Group)
	return p
}

// AddContact allows direct manipulation of cwtch contacts
func (p *Profile) AddContact(onion string, profile *PublicProfile) {
	p.lock.Lock()
	profile.init()
	// We expect callers to verify addresses before we get to this point, so if this isn't a
	// valid address this is a noop.
	if tor.IsValidHostname(onion) {
		decodedPub, err := base32.StdEncoding.DecodeString(strings.ToUpper(onion[:56]))
		if err == nil {
			profile.Ed25519PublicKey = ed25519.PublicKey(decodedPub[:32])
			p.Contacts[onion] = profile
		}
	}
	p.lock.Unlock()
}

// UpdateMessageFlags updates the flags stored with a message
func (p *Profile) UpdateMessageFlags(handle string, mIdx int, flags uint64) {
	p.lock.Lock()
	defer p.lock.Unlock()
	if contact, exists := p.Contacts[handle]; exists {
		if len(contact.Timeline.Messages) > mIdx {
			contact.Timeline.Messages[mIdx].Flags = flags
		}
	} else if group, exists := p.Groups[handle]; exists {
		if len(group.Timeline.Messages) > mIdx {
			group.Timeline.Messages[mIdx].Flags = flags
		}
	}
}

// DeleteContact deletes a peer contact
func (p *Profile) DeleteContact(onion string) {
	p.lock.Lock()
	defer p.lock.Unlock()
	delete(p.Contacts, onion)
}

// DeleteGroup deletes a group
func (p *Profile) DeleteGroup(groupID string) {
	p.lock.Lock()
	defer p.lock.Unlock()
	delete(p.Groups, groupID)
}

// RejectInvite rejects and removes a group invite
func (p *Profile) RejectInvite(groupID string) {
	p.lock.Lock()
	delete(p.Groups, groupID)
	p.lock.Unlock()
}

// AddSentMessageToContactTimeline allows the saving of a message sent via a direct connection chat to the profile.
func (p *Profile) AddSentMessageToContactTimeline(onion string, messageTxt string, sent time.Time, eventID string) *Message {
	p.lock.Lock()
	defer p.lock.Unlock()

	contact, ok := p.Contacts[onion]
	if ok {
		now := time.Now()
		sig := p.SignMessage(onion + messageTxt + sent.String() + now.String())

		message := &Message{PeerID: p.Onion, Message: messageTxt, Timestamp: sent, Received: now, Signature: sig, Acknowledged: false}
		if contact.UnacknowledgedMessages == nil {
			contact.UnacknowledgedMessages = make(map[string]int)
		}
		contact.Timeline.Insert(message)
		contact.UnacknowledgedMessages[eventID] = contact.Timeline.Len() - 1
		return message
	}
	return nil
}

// AddMessageToContactTimeline allows the saving of a message sent via a direct connection chat to the profile.
func (p *Profile) AddMessageToContactTimeline(onion string, messageTxt string, sent time.Time) (message *Message) {
	p.lock.Lock()
	defer p.lock.Unlock()
	contact, ok := p.Contacts[onion]

	// We don't really need a Signature here, but we use it to maintain order
	now := time.Now()
	sig := p.SignMessage(onion + messageTxt + sent.String() + now.String())
	if ok {
		message = &Message{PeerID: onion, Message: messageTxt, Timestamp: sent, Received: now, Signature: sig, Acknowledged: true}
		contact.Timeline.Insert(message)
	}
	return
}

// ErrorSentMessageToPeer sets a sent message's error message and removes it from the unacknowledged list
func (p *Profile) ErrorSentMessageToPeer(onion string, eventID string, error string) int {
	p.lock.Lock()
	defer p.lock.Unlock()

	contact, ok := p.Contacts[onion]
	if ok {
		mIdx, ok := contact.UnacknowledgedMessages[eventID]
		if ok {
			contact.Timeline.Messages[mIdx].Error = error
			delete(contact.UnacknowledgedMessages, eventID)
			return mIdx
		}
	}
	return -1
}

// AckSentMessageToPeer sets mesage to a peer as acknowledged
func (p *Profile) AckSentMessageToPeer(onion string, eventID string) int {
	p.lock.Lock()
	defer p.lock.Unlock()

	contact, ok := p.Contacts[onion]
	if ok {
		mIdx, ok := contact.UnacknowledgedMessages[eventID]
		if ok {
			contact.Timeline.Messages[mIdx].Acknowledged = true
			delete(contact.UnacknowledgedMessages, eventID)
			return mIdx
		}
	}

	return -1
}

// AddGroupSentMessageError searches matching groups for the message by sig and marks it as an error
func (p *Profile) AddGroupSentMessageError(groupID string, signature []byte, error string) {
	p.lock.Lock()
	defer p.lock.Unlock()
	group, exists := p.Groups[groupID]
	if exists {
		group.ErrorSentMessage(signature, error)
	}
}

// AcceptInvite accepts a group invite
func (p *Profile) AcceptInvite(groupID string) (err error) {
	p.lock.Lock()
	defer p.lock.Unlock()
	group, ok := p.Groups[groupID]
	if ok {
		group.Accepted = true
	} else {
		err = errors.New("group does not exist")
	}
	return
}

// GetGroups returns an unordered list of group IDs associated with this profile.
func (p *Profile) GetGroups() []string {
	p.lock.Lock()
	defer p.lock.Unlock()
	var keys []string
	for onion := range p.Groups {
		keys = append(keys, onion)
	}
	return keys
}

// GetContacts returns an unordered list of contact onions associated with this profile.
func (p *Profile) GetContacts() []string {
	p.lock.Lock()
	defer p.lock.Unlock()
	var keys []string
	for onion := range p.Contacts {
		if onion != p.Onion {
			keys = append(keys, onion)
		}
	}
	return keys
}

// SetContactAuthorization sets the authoirization level of a peer
func (p *Profile) SetContactAuthorization(onion string, auth Authorization) (err error) {
	p.lock.Lock()
	defer p.lock.Unlock()
	contact, ok := p.Contacts[onion]
	if ok {
		contact.Authorization = auth
	} else {
		err = errors.New("peer does not exist")
	}
	return
}

// GetContactAuthorization returns the contact's authorization level
func (p *Profile) GetContactAuthorization(onion string) Authorization {
	p.lock.Lock()
	defer p.lock.Unlock()
	contact, ok := p.Contacts[onion]
	if ok {
		return contact.Authorization
	}
	return AuthUnknown
}

// ContactsAuthorizations calculates a list of Peers who are at the supplied auth levels
func (p *Profile) ContactsAuthorizations(authorizationFilter ...Authorization) map[string]Authorization {
	authorizations := map[string]Authorization{}
	for _, contact := range p.GetContacts() {
		c, _ := p.GetContact(contact)
		authorizations[c.Onion] = c.Authorization
	}
	return authorizations
}

// GetContact returns a contact if the profile has it
func (p *Profile) GetContact(onion string) (*PublicProfile, bool) {
	p.lock.Lock()
	defer p.lock.Unlock()
	contact, ok := p.Contacts[onion]
	return contact, ok
}

// VerifyGroupMessage confirms the authenticity of a message given an sender onion, message and signature.
// The goal of this function is 2-fold:
// 1. We confirm that the sender referenced in the group text is the actual sender of the message (or at least
//     knows the senders private key)
// 2. Secondly, we confirm that the sender sent the message to a particular group id on a specific server (it doesn't
//      matter if we actually received this message from the server or from a hybrid protocol, all that matters is
//      that the sender and receivers agree that this message was intended for the group
// The 2nd point is important as it prevents an attack documented in the original Cwtch paper (and later at
// https://docs.openprivacy.ca/cwtch-security-handbook/groups.html) in which a malicious profile sets up 2 groups
// on two different servers with the same key and then forwards messages between them to convince the parties in
// each group that they are actually in one big group (with the intent to later censor and/or selectively send messages
// to each group).
func (p *Profile) VerifyGroupMessage(onion string, groupID string, message string, signature []byte) bool {

	group := p.GetGroup(groupID)
	if group == nil {
		return false
	}

	// We use our group id, a known reference server and the ciphertext of the message.
	m := groupID + group.GroupServer + message

	// If the message is ostensibly from us then we check it against our public key...
	if onion == p.Onion {
		return ed25519.Verify(p.Ed25519PublicKey, []byte(m), signature)
	}

	// Otherwise we derive the public key from the sender and check it against that.
	decodedPub, err := base32.StdEncoding.DecodeString(strings.ToUpper(onion))
	if err == nil && len(decodedPub) >= 32 {
		return ed25519.Verify(decodedPub[:32], []byte(m), signature)
	}
	return false
}

// SignMessage takes a given message and returns an Ed21159 signature
func (p *Profile) SignMessage(message string) []byte {
	sig := ed25519.Sign(p.Ed25519PrivateKey, []byte(message))
	return sig
}

// StartGroup when given a server, creates a new Group under this profile and returns the group id an a precomputed
// invite which can be sent on the wire.
func (p *Profile) StartGroup(server string) (groupID string, invite string, err error) {
	group, err := NewGroup(server)
	if err != nil {
		return "", "", err
	}
	groupID = group.GroupID
	invite, err = group.Invite()
	p.lock.Lock()
	defer p.lock.Unlock()
	p.Groups[group.GroupID] = group
	return
}

// GetGroup a pointer to a Group by the group Id, returns nil if no group found.
func (p *Profile) GetGroup(groupID string) (g *Group) {
	p.lock.Lock()
	defer p.lock.Unlock()
	g = p.Groups[groupID]
	return
}

// ProcessInvite validates a group invite and adds a new group invite to the profile if it is valid.
// returns the new group ID on success, error on fail.
func (p *Profile) ProcessInvite(invite string) (string, error) {
	gci, err := ValidateInvite(invite)
	if err == nil {
		if server, exists := p.GetContact(gci.ServerHost); !exists || !server.IsServer() {
			return "", fmt.Errorf("unknown server. a server key bundle needs to be imported before this group can be verified")
		}
		group := new(Group)
		group.Version = CurrentGroupVersion
		group.GroupID = gci.GroupID
		group.LocalID = GenerateRandomID()
		copy(group.GroupKey[:], gci.SharedKey[:])
		group.GroupServer = gci.ServerHost
		group.Accepted = false
		group.Attributes = make(map[string]string)
		group.Attributes[attr.GetLocalScope(constants.Name)] = gci.GroupName
		p.AddGroup(group)
		return gci.GroupID, nil
	}
	return "", err
}

// AddGroup is a convenience method for adding a group to a profile.
func (p *Profile) AddGroup(group *Group) {
	p.lock.Lock()
	defer p.lock.Unlock()
	_, exists := p.Groups[group.GroupID]
	if !exists {
		p.Groups[group.GroupID] = group
	}
}

// AttemptDecryption takes a ciphertext and signature and attempts to decrypt it under known groups.
// If successful, adds the message to the group's timeline
func (p *Profile) AttemptDecryption(ciphertext []byte, signature []byte) (bool, string, *Message, int) {
	for _, group := range p.Groups {
		success, dgm := group.DecryptMessage(ciphertext)
		if success {

			// Attempt to serialize this message
			serialized, err := json.Marshal(dgm)

			// Someone send a message that isn't a valid Decrypted Group Message. Since we require this struct in orer
			// to verify the message, we simply ignore it.
			if err != nil {
				return false, group.GroupID, nil, -1
			}

			// This now requires knowledge of the Sender, the Onion and the Specific Decrypted Group Message (which should only
			// be derivable from the cryptographic key) which contains many unique elements such as the time and random padding
			verified := p.VerifyGroupMessage(dgm.Onion, group.GroupID, base64.StdEncoding.EncodeToString(serialized), signature)

			if !verified {
				// An earlier version of this protocol mistakenly signed the ciphertext of the message
				// instead of the serialized decrypted group message.
				// This has 2 issues:
				// 1. A server with knowledge of group members public keys AND the Group ID would be able to detect valid messages
				// 2. It made the metadata-security of a group dependent on keeping the cryptographically derived Group ID secret.
				// While not awful, it also isn't good. For Version 3 groups only we permit Cwtch to check this older signature
				// structure in a backwards compatible way for the duration of the Groups Experiment.
				// TODO: Delete this check when Groups are no long Experimental
				if group.Version == 3 {
					verified = p.VerifyGroupMessage(dgm.Onion, group.GroupID, string(ciphertext), signature)
				}
			}

			// So we have a message that has a valid group key, but the signature can't be verified.
			// The most obvious explanation for this is that the group key has been compromised (or we are in an open group and the server is being malicious)
			// Either way, someone who has the private key is being detectably bad so we are just going to throw this message away and mark the group as Compromised.
			if !verified {
				group.Compromised()
				return false, group.GroupID, nil, -1
			}
			message, index := group.AddMessage(dgm, signature)
			return true, group.GroupID, message, index
		}
	}

	// If we couldn't find a group to decrypt the message with we just return false. This is an expected case
	return false, "", nil, -1
}

func getRandomness(arr *[]byte) {
	if _, err := io.ReadFull(rand.Reader, (*arr)[:]); err != nil {
		if err != nil {
			// If we can't do randomness, just crash something is very very wrong and we are not going
			// to resolve it here....
			panic(err.Error())
		}
	}
}

// EncryptMessageToGroup when given a message and a group, encrypts and signs the message under the group and
// profile
func (p *Profile) EncryptMessageToGroup(message string, groupID string) ([]byte, []byte, error) {

	if len(message) > MaxGroupMessageLength {
		return nil, nil, errors.New("group message is too long")
	}

	group := p.GetGroup(groupID)
	if group != nil {
		timestamp := time.Now().Unix()

		// Select the latest message from the timeline as a reference point.
		var prevSig []byte
		if len(group.Timeline.Messages) > 0 {
			prevSig = group.Timeline.Messages[len(group.Timeline.Messages)-1].Signature
		} else {
			prevSig = []byte(group.GroupID)
		}

		lenPadding := MaxGroupMessageLength - len(message)
		padding := make([]byte, lenPadding)
		getRandomness(&padding)
		hexGroupID, err := hex.DecodeString(group.GroupID)
		if err != nil {
			return nil, nil, err
		}

		dm := &groups.DecryptedGroupMessage{
			Onion:              p.Onion,
			Text:               message,
			SignedGroupID:      hexGroupID,
			Timestamp:          uint64(timestamp),
			PreviousMessageSig: prevSig,
			Padding:            padding[:],
		}

		ciphertext, err := group.EncryptMessage(dm)
		if err != nil {
			return nil, nil, err
		}
		serialized, _ := json.Marshal(dm)
		signature := p.SignMessage(groupID + group.GroupServer + base64.StdEncoding.EncodeToString(serialized))
		group.AddSentMessage(dm, signature)
		return ciphertext, signature, nil
	}
	return nil, nil, errors.New("group does not exist")
}

// GetCopy returns a full deep copy of the Profile struct and its members (timeline inclusion control by arg)
func (p *Profile) GetCopy(timeline bool) *Profile {
	p.lock.Lock()
	defer p.lock.Unlock()

	newp := new(Profile)
	bytes, _ := json.Marshal(p)
	json.Unmarshal(bytes, &newp)

	if timeline {
		for groupID := range newp.Groups {
			newp.Groups[groupID].Timeline = *p.Groups[groupID].Timeline.GetCopy()
		}

		for peerID := range newp.Contacts {
			newp.Contacts[peerID].Timeline = *p.Contacts[peerID].Timeline.GetCopy()
		}
	}

	return newp
}