// Copyright 2023, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

package shellapi

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"os"
	"os/exec"
	"os/user"
	"path"
	"path/filepath"
	"regexp"
	"runtime"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/alessio/shellescape"
	"github.com/creack/pty"
	"github.com/wavetermdev/waveterm/waveshell/pkg/base"
	"github.com/wavetermdev/waveterm/waveshell/pkg/packet"
	"github.com/wavetermdev/waveterm/waveshell/pkg/shellutil"
)

const GetStateTimeout = 5 * time.Second
const GetGitBranchCmdStr = `printf "GITBRANCH %s\x00" "$(git rev-parse --abbrev-ref HEAD 2>/dev/null)"`
const RunCommandFmt = `%s`
const DebugState = false

var userShellRegexp = regexp.MustCompile(`^UserShell: (.*)$`)

var cachedMacUserShell string
var macUserShellOnce = &sync.Once{}

const DefaultMacOSShell = "/bin/bash"

type RunCommandOpts struct {
	Sudo              bool
	SudoWithPass      bool
	MaxFdNum          int // needed for Sudo
	CommandFdNum      int // needed for Sudo
	PwFdNum           int // needed for SudoWithPass
	CommandStdinFdNum int // needed for SudoWithPass
}

type ShellApi interface {
	GetShellType() string
	MakeExitTrap(fdNum int) string
	GetLocalMajorVersion() string
	GetLocalShellPath() string
	GetRemoteShellPath() string
	MakeRunCommand(cmdStr string, opts RunCommandOpts) string
	MakeShExecCommand(cmdStr string, rcFileName string, usePty bool) *exec.Cmd
	GetShellState() (*packet.ShellState, error)
	GetBaseShellOpts() string
	ParseShellStateOutput(output []byte) (*packet.ShellState, error)
	MakeRcFileStr(pk *packet.RunPacketType) string
	MakeShellStateDiff(oldState *packet.ShellState, oldStateHash string, newState *packet.ShellState) (*packet.ShellStateDiff, error)
	ApplyShellStateDiff(oldState *packet.ShellState, diff *packet.ShellStateDiff) (*packet.ShellState, error)
}

func DetectLocalShellType() string {
	shellPath := GetMacUserShell()
	if shellPath == "" {
		shellPath = os.Getenv("SHELL")
	}
	if shellPath == "" {
		return packet.ShellType_bash
	}
	_, file := filepath.Split(shellPath)
	if strings.HasPrefix(file, "zsh") {
		return packet.ShellType_zsh
	}
	return packet.ShellType_bash
}

func HasShell(shellType string) bool {
	if shellType == packet.ShellType_bash {
		_, err := exec.LookPath("bash")
		return err != nil
	}
	if shellType == packet.ShellType_zsh {
		_, err := exec.LookPath("zsh")
		return err != nil
	}
	return false
}

func MakeShellApi(shellType string) (ShellApi, error) {
	if shellType == "" || shellType == packet.ShellType_bash {
		return &bashShellApi{}, nil
	}
	if shellType == packet.ShellType_zsh {
		return &zshShellApi{}, nil
	}
	return nil, fmt.Errorf("shell type not supported: %s", shellType)
}

func GetMacUserShell() string {
	if runtime.GOOS != "darwin" {
		return ""
	}
	macUserShellOnce.Do(func() {
		cachedMacUserShell = internalMacUserShell()
	})
	return cachedMacUserShell
}

// dscl . -read /User/[username] UserShell
// defaults to /bin/bash
func internalMacUserShell() string {
	osUser, err := user.Current()
	if err != nil {
		return DefaultMacOSShell
	}
	ctx, cancelFn := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancelFn()
	userStr := "/Users/" + osUser.Username
	out, err := exec.CommandContext(ctx, "dscl", ".", "-read", userStr, "UserShell").CombinedOutput()
	if err != nil {
		return DefaultMacOSShell
	}
	outStr := strings.TrimSpace(string(out))
	m := userShellRegexp.FindStringSubmatch(outStr)
	if m == nil {
		return DefaultMacOSShell
	}
	return m[1]
}

const FirstExtraFilesFdNum = 3

// returns output(stdout+stderr), extraFdOutput, error
func RunCommandWithExtraFd(ecmd *exec.Cmd, extraFdNum int) ([]byte, []byte, error) {
	ecmd.Env = os.Environ()
	shellutil.UpdateCmdEnv(ecmd, shellutil.MShellEnvVars(shellutil.DefaultTermType))
	cmdPty, cmdTty, err := pty.Open()
	if err != nil {
		return nil, nil, fmt.Errorf("opening new pty: %w", err)
	}
	defer cmdTty.Close()
	defer cmdPty.Close()
	pty.Setsize(cmdPty, &pty.Winsize{Rows: shellutil.DefaultTermRows, Cols: shellutil.DefaultTermCols})
	ecmd.Stdin = cmdTty
	ecmd.Stdout = cmdTty
	ecmd.Stderr = cmdTty
	ecmd.SysProcAttr = &syscall.SysProcAttr{}
	ecmd.SysProcAttr.Setsid = true
	ecmd.SysProcAttr.Setctty = true
	pipeReader, pipeWriter, err := os.Pipe()
	if err != nil {
		return nil, nil, fmt.Errorf("could not create pipe: %w", err)
	}
	defer pipeWriter.Close()
	defer pipeReader.Close()
	extraFiles := make([]*os.File, extraFdNum+1)
	extraFiles[extraFdNum] = pipeWriter
	ecmd.ExtraFiles = extraFiles[FirstExtraFilesFdNum:]
	defer pipeReader.Close()
	ecmd.Start()
	cmdTty.Close()
	pipeWriter.Close()
	if err != nil {
		return nil, nil, err
	}
	var outputWg sync.WaitGroup
	var outputBuf bytes.Buffer
	var extraFdOutputBuf bytes.Buffer
	outputWg.Add(2)
	go func() {
		// ignore error (/dev/ptmx has read error when process is done)
		defer outputWg.Done()
		io.Copy(&outputBuf, cmdPty)
	}()
	go func() {
		defer outputWg.Done()
		io.Copy(&extraFdOutputBuf, pipeReader)
	}()
	exitErr := ecmd.Wait()
	if exitErr != nil {
		return nil, nil, exitErr
	}
	outputWg.Wait()
	return outputBuf.Bytes(), extraFdOutputBuf.Bytes(), nil
}

func RunSimpleCmdInPty(ecmd *exec.Cmd) ([]byte, error) {
	ecmd.Env = os.Environ()
	shellutil.UpdateCmdEnv(ecmd, shellutil.MShellEnvVars(shellutil.DefaultTermType))
	cmdPty, cmdTty, err := pty.Open()
	if err != nil {
		return nil, fmt.Errorf("opening new pty: %w", err)
	}
	pty.Setsize(cmdPty, &pty.Winsize{Rows: shellutil.DefaultTermRows, Cols: shellutil.DefaultTermCols})
	ecmd.Stdin = cmdTty
	ecmd.Stdout = cmdTty
	ecmd.Stderr = cmdTty
	ecmd.SysProcAttr = &syscall.SysProcAttr{}
	ecmd.SysProcAttr.Setsid = true
	ecmd.SysProcAttr.Setctty = true
	err = ecmd.Start()
	cmdTty.Close()
	if err != nil {
		cmdPty.Close()
		return nil, err
	}
	defer cmdPty.Close()
	ioDone := make(chan bool)
	var outputBuf bytes.Buffer
	go func() {
		// ignore error (/dev/ptmx has read error when process is done)
		io.Copy(&outputBuf, cmdPty)
		close(ioDone)
	}()
	exitErr := ecmd.Wait()
	if exitErr != nil {
		return nil, exitErr
	}
	<-ioDone
	return outputBuf.Bytes(), nil
}

func parsePVarOutput(pvarBytes []byte, isZsh bool) map[string]*DeclareDeclType {
	declMap := make(map[string]*DeclareDeclType)
	pvars := bytes.Split(pvarBytes, []byte{0})
	for _, pvarBA := range pvars {
		pvarStr := string(pvarBA)
		pvarFields := strings.SplitN(pvarStr, " ", 2)
		if len(pvarFields) != 2 {
			continue
		}
		if pvarFields[0] == "" {
			continue
		}
		decl := &DeclareDeclType{IsZshDecl: isZsh, Args: "x"}
		decl.Name = "PROMPTVAR_" + pvarFields[0]
		decl.Value = shellescape.Quote(pvarFields[1])
		declMap[decl.Name] = decl
	}
	return declMap
}

// for debugging (not for production use)
func writeStateToFile(shellType string, outputBytes []byte) error {
	msHome := base.GetMShellHomeDir()
	stateFileName := path.Join(msHome, shellType+"-state.txt")
	os.WriteFile(stateFileName, outputBytes, 0644)
	return nil
}