package cli

import (
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"sync"
	"time"

	"github.com/creack/pty"
	"iop/apps/node/internal/adapters/cli/status"
)

type terminalSessionOptions struct {
	Command string
	Args    []string
	Env     []string
}

type terminalSessionCore struct {
	cmd      *exec.Cmd
	input    io.WriteCloser
	output   io.ReadCloser
	tail     *status.TailBuffer
	outputCh chan cliOutput
	doneCh   chan error
	closed   bool
	mu       sync.Mutex
}

func startTerminalSessionCore(ctx context.Context, opts terminalSessionOptions) (*terminalSessionCore, error) {
	cmd := exec.Command(opts.Command, opts.Args...)
	if len(opts.Env) > 0 {
		cmd.Env = append(cmd.Environ(), opts.Env...)
	}
	ptmx, err := pty.StartWithSize(cmd, &pty.Winsize{
		Rows: terminalRows,
		Cols: terminalCols,
	})
	if err != nil {
		return nil, fmt.Errorf("pty start: %w", err)
	}

	core := &terminalSessionCore{
		cmd:      cmd,
		input:    ptmx,
		output:   ptmx,
		tail:     status.NewTailBuffer(2048),
		outputCh: make(chan cliOutput, 1024),
		doneCh:   make(chan error, 1),
	}

	go core.readLoop()

	return core, nil
}

func (s *terminalSessionCore) readLoop() {
	buf := make([]byte, 4096)
	for {
		n, err := s.output.Read(buf)
		if n > 0 {
			text := string(buf[:n])
			s.tail.Append(text)
			s.outputCh <- cliOutput{text: text}
		}
		if err != nil {
			s.doneCh <- s.cmd.Wait()
			close(s.outputCh)
			return
		}
	}
}

func (s *terminalSessionCore) WritePrompt(ctx context.Context, prompt string) error {
	s.mu.Lock()
	if s.closed {
		s.mu.Unlock()
		return errors.New("terminal session core closed")
	}
	s.mu.Unlock()

	for _, r := range prompt {
		s.mu.Lock()
		if s.closed {
			s.mu.Unlock()
			return errors.New("terminal session core closed")
		}
		_, err := io.WriteString(s.input, string(r))
		s.mu.Unlock()
		if err != nil {
			return err
		}
		timer := time.NewTimer(terminalInputDelay)
		select {
		case <-ctx.Done():
			timer.Stop()
			return ctx.Err()
		case <-timer.C:
		}
	}

	s.mu.Lock()
	defer s.mu.Unlock()
	if s.closed {
		return errors.New("terminal session core closed")
	}
	_, err := io.WriteString(s.input, "\r")
	return err
}

func (s *terminalSessionCore) Snapshot() status.Snapshot {
	return status.Snapshot{
		Tail: s.tail.String(),
	}
}

func (s *terminalSessionCore) Resize(rows, cols uint16) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.closed {
		return errors.New("terminal session core closed")
	}
	if rows == 0 || cols == 0 {
		return errors.New("invalid terminal size: rows and cols must be greater than 0")
	}
	f, ok := s.input.(*os.File)
	if !ok {
		return errors.New("terminal input is not a file")
	}
	return pty.Setsize(f, &pty.Winsize{Rows: rows, Cols: cols})
}

func (s *terminalSessionCore) WriteInput(ctx context.Context, data []byte) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.closed {
		return errors.New("terminal session core closed")
	}
	_, err := s.input.Write(data)
	return err
}

func (s *terminalSessionCore) Signal(sig os.Signal) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.closed {
		return errors.New("terminal session core closed")
	}
	if s.cmd == nil || s.cmd.Process == nil {
		return errors.New("no process to signal")
	}
	return s.cmd.Process.Signal(sig)
}

func (s *terminalSessionCore) Close() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.closed {
		return nil
	}
	s.closed = true
	err := s.input.Close()
	if s.cmd != nil && s.cmd.Process != nil {
		_ = s.cmd.Process.Kill()
	}
	if isAlreadyClosedError(err) {
		return nil
	}
	return err
}