package model

import (
	"crypto/rand"
	"cwtch.im/cwtch/protocol/groups"
	"encoding/base32"
	"encoding/hex"
	"encoding/json"
	"errors"
	"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()
	// TODO: More Robust V3 Onion Handling
	decodedPub, _ := base32.StdEncoding.DecodeString(strings.ToUpper(onion[:56]))
	profile.Ed25519PublicKey = ed25519.PublicKey(decodedPub[:32])
	p.Contacts[onion] = profile
	p.lock.Unlock()
}

// 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) {
	p.lock.Lock()
	defer p.lock.Unlock()

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

// AckSentMessageToPeer sets mesage to a peer as acknowledged
func (p *Profile) AckSentMessageToPeer(onion string, eventID string) {
	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)
		}
	}
}

// AddGroupSentMessageError searches matching groups for the message by sig and marks it as an error
func (p *Profile) AddGroupSentMessageError(groupServer string, signature string, error string) {
	for _, group := range p.Groups {
		if group.GroupServer == groupServer {
			if group.ErrorSentMessage([]byte(signature), error) {
				break
			}
		}
	}
}

// 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 onion, message and signature.
func (p *Profile) VerifyGroupMessage(onion string, groupID string, message string, timestamp int32, ciphertext []byte, signature []byte) bool {

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

	if onion == p.Onion {
		m := groupID + group.GroupServer + string(ciphertext)
		return ed25519.Verify(p.Ed25519PublicKey, []byte(m), signature)
	}

	m := groupID + group.GroupServer + string(ciphertext)
	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 []byte, err error) {
	return p.StartGroupWithMessage(server, []byte{})
}

// StartGroupWithMessage when given a server, and an initial message 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) StartGroupWithMessage(server string, initialMessage []byte) (groupID string, invite []byte, err error) {
	group, err := NewGroup(server)
	if err != nil {
		return "", nil, err
	}
	groupID = group.GroupID
	group.Owner = p.Onion
	signedGroupID := p.SignMessage(groupID + server)
	group.SignGroup(signedGroupID)
	invite, err = group.Invite(initialMessage)
	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 adds a new group invite to the profile. returns the new group ID
func (p *Profile) ProcessInvite(invite string, peerHostname string) (string, error) {
	var gci groups.GroupInvite
	err := json.Unmarshal([]byte(invite), &gci)
	if err == nil {
		group := new(Group)
		group.Version = CurrentGroupVersion
		group.GroupID = gci.GroupName
		group.LocalID = GenerateRandomID()
		group.SignedGroupID = gci.SignedGroupID
		copy(group.GroupKey[:], gci.SharedKey[:])
		group.GroupServer = gci.ServerHost
		group.InitialMessage = []byte(gci.InitialMessage)
		group.Accepted = false
		group.Owner = peerHostname
		group.Attributes = make(map[string]string)
		p.AddGroup(group)
		return group.GroupID, nil
	}
	return "", err
}

// AddGroup is a convenience method for adding a group to a profile.
func (p *Profile) AddGroup(group *Group) {
	_, exists := p.Groups[group.GroupID]
	if !exists {
		p.lock.Lock()
		defer p.lock.Unlock()
		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, bool) {
	for _, group := range p.Groups {
		success, dgm := group.DecryptMessage(ciphertext)
		if success {
			verified := p.VerifyGroupMessage(dgm.Onion, group.GroupID, dgm.Text, int32(dgm.Timestamp), 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, false
			}
			message, seen := group.AddMessage(dgm, signature)
			return true, group.GroupID, message, seen
		}
	}

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

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()

		var prevSig []byte
		if len(group.Timeline.Messages) > 0 {
			prevSig = group.Timeline.Messages[len(group.Timeline.Messages)-1].Signature
		} else {
			prevSig = group.SignedGroupID
		}

		lenPadding := MaxGroupMessageLength - len(message)
		padding := make([]byte, lenPadding)
		getRandomness(&padding)

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

		ciphertext, err := group.EncryptMessage(dm)
		if err != nil {
			return nil, nil, err
		}
		signature := p.SignMessage(groupID + group.GroupServer + string(ciphertext))
		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
}