// Copyright 2024, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

package wshutil

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"os/signal"
	"sync"
	"sync/atomic"
	"syscall"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
	"github.com/wavetermdev/waveterm/pkg/wavebase"
	"github.com/wavetermdev/waveterm/pkg/wshrpc"
	"golang.org/x/term"
)

// these should both be 5 characters
const WaveOSC = "23198"
const WaveServerOSC = "23199"
const WaveOSCPrefixLen = 5 + 3 // \x1b] + WaveOSC + ; + \x07

const WaveOSCPrefix = "\x1b]" + WaveOSC + ";"
const WaveServerOSCPrefix = "\x1b]" + WaveServerOSC + ";"

const HexChars = "0123456789ABCDEF"
const BEL = 0x07
const ST = 0x9c
const ESC = 0x1b

const DefaultOutputChSize = 32
const DefaultInputChSize = 32

const WaveJwtTokenVarName = "WAVETERM_JWT"

// OSC escape types
// OSC 23198 ; (JSON | base64-JSON) ST
// JSON = must escape all ASCII control characters ([\x00-\x1F\x7F])
// we can tell the difference between JSON and base64-JSON by the first character: '{' or not

// for responses (terminal -> program), we'll use OSC 23199
// same json format

func copyOscPrefix(dst []byte, oscNum string) {
	dst[0] = ESC
	dst[1] = ']'
	copy(dst[2:], oscNum)
	dst[len(oscNum)+2] = ';'
}

func oscPrefixLen(oscNum string) int {
	return 3 + len(oscNum)
}

func makeOscPrefix(oscNum string) []byte {
	output := make([]byte, oscPrefixLen(oscNum))
	copyOscPrefix(output, oscNum)
	return output
}

func EncodeWaveOSCBytes(oscNum string, barr []byte) []byte {
	if len(oscNum) != 5 {
		panic("oscNum must be 5 characters")
	}
	hasControlChars := false
	for _, b := range barr {
		if b < 0x20 || b == 0x7F {
			hasControlChars = true
			break
		}
	}
	if !hasControlChars {
		// If no control characters, directly construct the output
		// \x1b] (2) + WaveOSC + ; (1) + message + \x07 (1)
		output := make([]byte, oscPrefixLen(oscNum)+len(barr)+1)
		copyOscPrefix(output, oscNum)
		copy(output[oscPrefixLen(oscNum):], barr)
		output[len(output)-1] = BEL
		return output
	}

	var buf bytes.Buffer
	buf.Write(makeOscPrefix(oscNum))
	escSeq := [6]byte{'\\', 'u', '0', '0', '0', '0'}
	for _, b := range barr {
		if b < 0x20 || b == 0x7f {
			escSeq[4] = HexChars[b>>4]
			escSeq[5] = HexChars[b&0x0f]
			buf.Write(escSeq[:])
		} else {
			buf.WriteByte(b)
		}
	}
	buf.WriteByte(BEL)
	return buf.Bytes()
}

func EncodeWaveOSCMessageEx(oscNum string, msg *RpcMessage) ([]byte, error) {
	if msg == nil {
		return nil, fmt.Errorf("nil message")
	}
	barr, err := json.Marshal(msg)
	if err != nil {
		return nil, fmt.Errorf("error marshalling message to json: %w", err)
	}
	return EncodeWaveOSCBytes(oscNum, barr), nil
}

var termModeLock = sync.Mutex{}
var termIsRaw bool
var origTermState *term.State
var shutdownSignalHandlersInstalled bool
var shutdownOnce sync.Once
var extraShutdownFunc atomic.Pointer[func()]

func DoShutdown(reason string, exitCode int, quiet bool) {
	shutdownOnce.Do(func() {
		defer os.Exit(exitCode)
		RestoreTermState()
		extraFn := extraShutdownFunc.Load()
		if extraFn != nil {
			(*extraFn)()
		}
		if !quiet && reason != "" {
			log.Printf("shutting down: %s\r\n", reason)
		}
	})
}

func installShutdownSignalHandlers(quiet bool) {
	termModeLock.Lock()
	defer termModeLock.Unlock()
	if shutdownSignalHandlersInstalled {
		return
	}
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGHUP, syscall.SIGTERM, syscall.SIGINT)
	go func() {
		for sig := range sigCh {
			DoShutdown(fmt.Sprintf("got signal %v", sig), 1, quiet)
			break
		}
	}()
}

func SetTermRawModeAndInstallShutdownHandlers(quietShutdown bool) {
	SetTermRawMode()
	installShutdownSignalHandlers(quietShutdown)
}

func SetExtraShutdownFunc(fn func()) {
	extraShutdownFunc.Store(&fn)
}

func SetTermRawMode() {
	termModeLock.Lock()
	defer termModeLock.Unlock()
	if termIsRaw {
		return
	}
	origState, err := term.MakeRaw(int(os.Stdin.Fd()))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error setting raw mode: %v\n", err)
		return
	}
	origTermState = origState
	termIsRaw = true
}

func RestoreTermState() {
	termModeLock.Lock()
	defer termModeLock.Unlock()
	if !termIsRaw || origTermState == nil {
		return
	}
	term.Restore(int(os.Stdin.Fd()), origTermState)
	termIsRaw = false
}

// returns (wshRpc, wrappedStdin)
func SetupTerminalRpcClient(serverImpl ServerImpl) (*WshRpc, io.Reader) {
	messageCh := make(chan []byte, DefaultInputChSize)
	outputCh := make(chan []byte, DefaultOutputChSize)
	ptyBuf := MakePtyBuffer(WaveServerOSCPrefix, os.Stdin, messageCh)
	rpcClient := MakeWshRpc(messageCh, outputCh, wshrpc.RpcContext{}, serverImpl)
	go func() {
		for msg := range outputCh {
			barr := EncodeWaveOSCBytes(WaveOSC, msg)
			os.Stdout.Write(barr)
		}
	}()
	return rpcClient, ptyBuf
}

func SetupConnRpcClient(conn net.Conn, serverImpl ServerImpl) (*WshRpc, chan error, error) {
	inputCh := make(chan []byte, DefaultInputChSize)
	outputCh := make(chan []byte, DefaultOutputChSize)
	writeErrCh := make(chan error, 1)
	go func() {
		writeErr := AdaptOutputChToStream(outputCh, conn)
		if writeErr != nil {
			writeErrCh <- writeErr
			close(writeErrCh)
		}
	}()
	go func() {
		// when input is closed, close the connection
		defer conn.Close()
		AdaptStreamToMsgCh(conn, inputCh)
	}()
	rtn := MakeWshRpc(inputCh, outputCh, wshrpc.RpcContext{}, serverImpl)
	return rtn, writeErrCh, nil
}

func SetupDomainSocketRpcClient(sockName string, serverImpl ServerImpl) (*WshRpc, error) {
	conn, err := net.Dial("unix", sockName)
	if err != nil {
		return nil, fmt.Errorf("failed to connect to Unix domain socket: %w", err)
	}
	rtn, errCh, err := SetupConnRpcClient(conn, serverImpl)
	go func() {
		defer conn.Close()
		err := <-errCh
		if err != nil && err != io.EOF {
			log.Printf("error in domain socket connection: %v\n", err)
		}
	}()
	return rtn, err
}

func MakeClientJWTToken(rpcCtx wshrpc.RpcContext, sockName string) (string, error) {
	claims := jwt.MapClaims{}
	claims["iat"] = time.Now().Unix()
	claims["iss"] = "waveterm"
	claims["sock"] = sockName
	claims["exp"] = time.Now().Add(time.Hour * 24 * 365).Unix()
	if rpcCtx.BlockId != "" {
		claims["blockid"] = rpcCtx.BlockId
	}
	if rpcCtx.TabId != "" {
		claims["tabid"] = rpcCtx.TabId
	}
	if rpcCtx.Conn != "" {
		claims["conn"] = rpcCtx.Conn
	}
	if rpcCtx.ClientType != "" {
		claims["ctype"] = rpcCtx.ClientType
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenStr, err := token.SignedString([]byte(wavebase.JwtSecret))
	if err != nil {
		return "", fmt.Errorf("error signing token: %w", err)
	}
	return tokenStr, nil
}

func ValidateAndExtractRpcContextFromToken(tokenStr string) (*wshrpc.RpcContext, error) {
	parser := jwt.NewParser(jwt.WithValidMethods([]string{jwt.SigningMethodHS256.Name}))
	token, err := parser.Parse(tokenStr, func(token *jwt.Token) (interface{}, error) {
		return []byte(wavebase.JwtSecret), nil
	})
	if err != nil {
		return nil, fmt.Errorf("error parsing token: %w", err)
	}
	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return nil, fmt.Errorf("error getting claims from token")
	}
	// validate "exp" claim
	if exp, ok := claims["exp"].(float64); ok {
		if int64(exp) < time.Now().Unix() {
			return nil, fmt.Errorf("token has expired")
		}
	} else {
		return nil, fmt.Errorf("exp claim is missing or invalid")
	}
	// validate "iss" claim
	if iss, ok := claims["iss"].(string); ok {
		if iss != "waveterm" {
			return nil, fmt.Errorf("unexpected issuer: %s", iss)
		}
	} else {
		return nil, fmt.Errorf("iss claim is missing or invalid")
	}
	return mapClaimsToRpcContext(claims), nil
}

func mapClaimsToRpcContext(claims jwt.MapClaims) *wshrpc.RpcContext {
	rpcCtx := &wshrpc.RpcContext{}
	if claims["blockid"] != nil {
		if blockId, ok := claims["blockid"].(string); ok {
			rpcCtx.BlockId = blockId
		}
	}
	if claims["tabid"] != nil {
		if tabId, ok := claims["tabid"].(string); ok {
			rpcCtx.TabId = tabId
		}
	}
	if claims["conn"] != nil {
		if conn, ok := claims["conn"].(string); ok {
			rpcCtx.Conn = conn
		}
	}
	if claims["ctype"] != nil {
		if ctype, ok := claims["ctype"].(string); ok {
			rpcCtx.ClientType = ctype
		}
	}
	return rpcCtx
}

func RunWshRpcOverListener(listener net.Listener) {
	defer log.Printf("domain socket listener shutting down\n")
	for {
		conn, err := listener.Accept()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Printf("error accepting connection: %v\n", err)
			break
		}
		log.Print("got domain socket connection\n")
		go handleDomainSocketClient(conn)
	}
}

func MakeRouteIdFromCtx(rpcCtx *wshrpc.RpcContext) (string, error) {
	if rpcCtx.ClientType != "" {
		if rpcCtx.ClientType == wshrpc.ClientType_ConnServer {
			if rpcCtx.Conn != "" {
				return MakeConnectionRouteId(rpcCtx.Conn), nil
			}
			return "", fmt.Errorf("invalid connserver connection, no conn id")
		}
		if rpcCtx.ClientType == wshrpc.ClientType_BlockController {
			if rpcCtx.BlockId != "" {
				return MakeControllerRouteId(rpcCtx.BlockId), nil
			}
			return "", fmt.Errorf("invalid block controller connection, no block id")
		}
		return "", fmt.Errorf("invalid client type: %q", rpcCtx.ClientType)
	}
	procId := uuid.New().String()
	return MakeProcRouteId(procId), nil
}

func handleDomainSocketClient(conn net.Conn) {
	var routeIdContainer atomic.Pointer[string]
	proxy := MakeRpcProxy()
	go func() {
		writeErr := AdaptOutputChToStream(proxy.ToRemoteCh, conn)
		if writeErr != nil {
			log.Printf("error writing to domain socket: %v\n", writeErr)
		}
	}()
	go func() {
		// when input is closed, close the connection
		defer func() {
			conn.Close()
			routeIdPtr := routeIdContainer.Load()
			if routeIdPtr != nil && *routeIdPtr != "" {
				DefaultRouter.UnregisterRoute(*routeIdPtr)
			}
		}()
		AdaptStreamToMsgCh(conn, proxy.FromRemoteCh)
	}()
	rpcCtx, err := proxy.HandleAuthentication()
	if err != nil {
		conn.Close()
		log.Printf("error handling authentication: %v\n", err)
		return
	}
	// now that we're authenticated, set the ctx and attach to the router
	log.Printf("domain socket connection authenticated: %#v\n", rpcCtx)
	proxy.SetRpcContext(rpcCtx)
	routeId, err := MakeRouteIdFromCtx(rpcCtx)
	if err != nil {
		conn.Close()
		log.Printf("error making route id: %v\n", err)
		return
	}
	routeIdContainer.Store(&routeId)
	DefaultRouter.RegisterRoute(routeId, proxy)
}

// only for use on client
func ExtractUnverifiedRpcContext(tokenStr string) (*wshrpc.RpcContext, error) {
	// this happens on the client who does not have access to the secret key
	// we want to read the claims without validating the signature
	token, _, err := new(jwt.Parser).ParseUnverified(tokenStr, jwt.MapClaims{})
	if err != nil {
		return nil, fmt.Errorf("error parsing token: %w", err)
	}
	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return nil, fmt.Errorf("error getting claims from token")
	}
	return mapClaimsToRpcContext(claims), nil
}

// only for use on client
func ExtractUnverifiedSocketName(tokenStr string) (string, error) {
	// this happens on the client who does not have access to the secret key
	// we want to read the claims without validating the signature
	token, _, err := new(jwt.Parser).ParseUnverified(tokenStr, jwt.MapClaims{})
	if err != nil {
		return "", fmt.Errorf("error parsing token: %w", err)
	}
	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return "", fmt.Errorf("error getting claims from token")
	}
	sockName, ok := claims["sock"].(string)
	if !ok {
		return "", fmt.Errorf("sock claim is missing or invalid")
	}
	return sockName, nil
}