package client

import (
	"crypto"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net"
	"strings"
	"time"

	"github.com/cbeuw/Cloak/internal/common"
	log "github.com/sirupsen/logrus"

	"github.com/cbeuw/Cloak/internal/ecdh"
	mux "github.com/cbeuw/Cloak/internal/multiplex"
)

// RawConfig represents the fields in the config json file
// jsonOptional means if the json's empty, its value will be set from environment variables or commandline args
// but it mustn't be empty when ProcessRawConfig is called
type RawConfig struct {
	// Required fields
	// ServerName is the domain you appear to be visiting
	// to your Firewall or ISP
	ServerName string
	// ProxyMethod is the name of the underlying proxy you wish
	// to connect to, as determined by your server. The value can
	// be any string whose UTF-8 ENCODED byte length is no greater than
	// 12 bytes
	ProxyMethod string
	// UID is a 16-byte secret string unique to an authorised user
	// The same UID can be used by the same user for multiple Cloak connections
	UID []byte
	// PublicKey is the 32-byte public Curve25519 ECDH key of your server
	PublicKey []byte
	// RemoteHost is the Cloak server's hostname or IP address
	RemoteHost string // jsonOptional

	// Optional Fields
	// EncryptionMethod is the cryptographic algorithm used to
	// encrypt data on the wire.
	// Valid values are `aes-128-gcm`, `aes-256-gcm`, `chacha20-poly1305`, and `plain`
	// Defaults to `aes-256-gcm`
	EncryptionMethod string
	// NumConn is the amount of underlying TLS connections to establish with Cloak server.
	// Cloak multiplexes any number of incoming connections to a fixed number of underlying TLS connections.
	// If set to 0, a special singleplex mode is enabled: each incoming connection will correspond to exactly one
	// TLS connection
	// Defaults to 4
	NumConn *int
	// UDP enables UDP semantics, where packets must fit into one unit of message (below 16000 bytes by default),
	// and packets can be received out of order. Though reliable delivery is still guaranteed.
	UDP bool
	// BrowserSig is the browser signature to be used. Options are `chrome` and `firefox`
	// Defaults to `chrome`
	BrowserSig string
	// Transport is either `direct` or `cdn`. Under `direct`, the client connects to a Cloak server directly.
	// Under `cdn`, the client connects to a CDN provider such as Amazon Cloudfront, which in turn connects
	// to a Cloak server.
	// Defaults to `direct`
	Transport string
	// CDNOriginHost is the CDN Origin's (i.e. Cloak server) real hostname or IP address, which is encrypted between
	// the client and the CDN server, and therefore hidden to ISP or firewalls. This only has effect when Transport
	// is set to `cdn`
	// Defaults to RemoteHost
	CDNOriginHost string
	// StreamTimeout is the duration, in seconds, for a stream to be automatically closed after the last write.
	// Defaults to 300
	StreamTimeout int
	// KeepAlive is the interval between TCP KeepAlive packets to be sent over the underlying TLS connections
	// Defaults to -1, which means no TCP KeepAlive is ever sent
	KeepAlive int
	// RemotePort is the port Cloak server is listening to
	// Defaults to 443
	RemotePort string

	// LocalHost is the hostname or IP address to listen for incoming proxy client connections
	LocalHost string // jsonOptional
	// LocalPort is the port to listen for incomig proxy client connections
	LocalPort string // jsonOptional
	// AlternativeNames is a list of ServerName Cloak may randomly pick from for different sessions
	AlternativeNames []string
}

type RemoteConnConfig struct {
	Singleplex     bool
	NumConn        int
	KeepAlive      time.Duration
	RemoteAddr     string
	TransportMaker func() transports.Transport
}

type LocalConnConfig struct {
	LocalAddr      string
	Timeout        time.Duration
	MockDomainList []string
}

type AuthInfo = transports.AuthInfo

// semi-colon separated value. This is for Android plugin options
func ssvToJson(ssv string) (ret []byte) {
	elem := func(val string, lst []string) bool {
		for _, v := range lst {
			if val == v {
				return true
			}
		}
		return false
	}
	unescape := func(s string) string {
		r := strings.Replace(s, `\\`, `\`, -1)
		r = strings.Replace(r, `\=`, `=`, -1)
		r = strings.Replace(r, `\;`, `;`, -1)
		return r
	}
	unquoted := []string{"NumConn", "StreamTimeout", "KeepAlive", "UDP"}
	lines := strings.Split(unescape(ssv), ";")
	ret = []byte("{")
	for _, ln := range lines {
		if ln == "" {
			break
		}
		sp := strings.SplitN(ln, "=", 2)
		if len(sp) < 2 {
			log.Errorf("Malformed config option: %v", ln)
			continue
		}
		key := sp[0]
		value := sp[1]
		if strings.HasPrefix(key, "AlternativeNames") {
			switch strings.Contains(value, ",") {
			case true:
				domains := strings.Split(value, ",")
				for index, domain := range domains {
					domains[index] = `"` + domain + `"`
				}
				value = strings.Join(domains, ",")
				ret = append(ret, []byte(`"`+key+`":[`+value+`],`)...)
			case false:
				ret = append(ret, []byte(`"`+key+`":["`+value+`"],`)...)
			}
			continue
		}
		// JSON doesn't like quotation marks around int and bool
		// This is extremely ugly but it's still better than writing a tokeniser
		if elem(key, unquoted) {
			ret = append(ret, []byte(`"`+key+`":`+value+`,`)...)
		} else {
			ret = append(ret, []byte(`"`+key+`":"`+value+`",`)...)
		}
	}
	ret = ret[:len(ret)-1] // remove the last comma
	ret = append(ret, '}')
	return ret
}

func ParseConfig(conf string) (raw *RawConfig, err error) {
	var content []byte
	// Checking if it's a path to json or a ssv string
	if strings.Contains(conf, ";") && strings.Contains(conf, "=") {
		content = ssvToJson(conf)
	} else {
		content, err = ioutil.ReadFile(conf)
		if err != nil {
			return
		}
	}

	raw = new(RawConfig)
	err = json.Unmarshal(content, &raw)
	if err != nil {
		return
	}
	return
}

func (raw *RawConfig) ProcessRawConfig(worldState common.WorldState) (local LocalConnConfig, remote RemoteConnConfig, auth AuthInfo, err error) {
	nullErr := func(field string) (local LocalConnConfig, remote RemoteConnConfig, auth AuthInfo, err error) {
		err = fmt.Errorf("%v cannot be empty", field)
		return
	}

	auth.UID = raw.UID
	auth.Unordered = raw.UDP
	if raw.ServerName == "" {
		return nullErr("ServerName")
	}
	auth.MockDomain = raw.ServerName

	var filteredAlternativeNames []string
	for _, alternativeName := range raw.AlternativeNames {
		if len(alternativeName) > 0 {
			filteredAlternativeNames = append(filteredAlternativeNames, alternativeName)
		}
	}
	raw.AlternativeNames = filteredAlternativeNames

	local.MockDomainList = raw.AlternativeNames
	local.MockDomainList = append(local.MockDomainList, auth.MockDomain)
	if raw.ProxyMethod == "" {
		return nullErr("ServerName")
	}
	auth.ProxyMethod = raw.ProxyMethod
	if len(raw.UID) == 0 {
		return nullErr("UID")
	}

	// static public key
	if len(raw.PublicKey) == 0 {
		return nullErr("PublicKey")
	}
	pub, ok := ecdh.Unmarshal(raw.PublicKey)
	if !ok {
		err = fmt.Errorf("failed to unmarshal Public key")
		return
	}
	auth.ServerPubKey = pub
	auth.WorldState = worldState

	// Encryption method
	switch strings.ToLower(raw.EncryptionMethod) {
	case "plain":
		auth.EncryptionMethod = mux.EncryptionMethodPlain
	case "aes-gcm", "aes-256-gcm":
		auth.EncryptionMethod = mux.EncryptionMethodAES256GCM
	case "aes-128-gcm":
		auth.EncryptionMethod = mux.EncryptionMethodAES128GCM
	case "chacha20-poly1305":
		auth.EncryptionMethod = mux.EncryptionMethodChaha20Poly1305
	case "":
		auth.EncryptionMethod = mux.EncryptionMethodAES256GCM
	default:
		err = fmt.Errorf("unknown encryption method %v", raw.EncryptionMethod)
		return
	}

	if raw.RemoteHost == "" {
		return nullErr("RemoteHost")
	}
	var remotePort string
	if raw.RemotePort == "" {
		remotePort = "443"
	} else {
		remotePort = raw.RemotePort
	}
	remote.RemoteAddr = net.JoinHostPort(raw.RemoteHost, remotePort)
	if raw.NumConn == nil {
		remote.NumConn = 4
		remote.Singleplex = false
	} else if *raw.NumConn <= 0 {
		remote.NumConn = 1
		remote.Singleplex = true
	} else {
		remote.NumConn = *raw.NumConn
		remote.Singleplex = false
	}

	// Transport and (if TLS mode), browser
	switch strings.ToLower(raw.Transport) {
	case "cdn":
		cdnPort := raw.RemotePort
		var cdnHost string
		if raw.CDNOriginHost == "" {
			cdnHost = raw.RemoteHost
		} else {
			cdnHost = raw.CDNOriginHost
		}

		remote.TransportMaker = func() transports.Transport {
			return &transports.WSOverTLS{
				CDNHost: cdnHost,
				CDNPort: cdnPort,
			}
		}
	case "direct":
		fallthrough
	default:
		var browser browser
		switch strings.ToLower(raw.BrowserSig) {
		case "firefox":
			browser = firefox
		case "safari":
			browser = safari
		case "chrome":
			fallthrough
		default:
			browser = chrome
		}
		remote.TransportMaker = func() transports.Transport {
			return &transports.DirectTLS{
				Browser: browser,
			}
		}
	}

	// KeepAlive
	if raw.KeepAlive <= 0 {
		remote.KeepAlive = -1
	} else {
		remote.KeepAlive = remote.KeepAlive * time.Second
	}

	if raw.LocalHost == "" {
		return nullErr("LocalHost")
	}
	if raw.LocalPort == "" {
		return nullErr("LocalPort")
	}
	local.LocalAddr = net.JoinHostPort(raw.LocalHost, raw.LocalPort)
	// stream no write timeout
	if raw.StreamTimeout == 0 {
		local.Timeout = 300 * time.Second
	} else {
		local.Timeout = time.Duration(raw.StreamTimeout) * time.Second
	}

	return
}