package session

import (
	"fmt"
	"time"
)

// Input error sentinels. These replace the TIMEOUT and NO_CARRIER
// return codes that the original TAG-BBS passed through every function.
// In Go, we use the context for cancellation and return these as errors
// only when the caller needs to distinguish the reason.
var (
	ErrTimeout      = fmt.Errorf("input timeout")
	ErrDisconnected = fmt.Errorf("disconnected")
)

// ReadChar reads a single byte from the client with a timeout.
// This is the direct replacement for ReadChar() in CONSOLE.C, which
// was the central input function that Wait()'d on serial, console,
// and timer signals simultaneously.
//
// In Go, the equivalent is a select on the input channel (fed by the
// readLoop goroutine), a timer, and the context's Done channel.
//
// A timeout of 0 means no timeout (wait forever, or until disconnect).
func (s *Session) ReadChar(timeout time.Duration) (byte, error) {
	// Check context first — if the session is already cancelled,
	// don't block on input.
	select {
	case <-s.ctx.Done():
		return 0, ErrDisconnected
	default:
	}

	if timeout == 0 {
		// No timeout — block until input or disconnect
		select {
		case b, ok := <-s.inputCh:
			if !ok {
				return 0, ErrDisconnected
			}
			return b, nil
		case <-s.ctx.Done():
			return 0, ErrDisconnected
		}
	}

	// With timeout — the original used SetTimer() and waited on
	// TimerSig alongside the input signals. Same concept here.
	timer := time.NewTimer(timeout)
	defer timer.Stop()

	select {
	case b, ok := <-s.inputCh:
		if !ok {
			return 0, ErrDisconnected
		}
		return b, nil
	case <-timer.C:
		return 0, ErrTimeout
	case <-s.ctx.Done():
		return 0, ErrDisconnected
	}
}

// ReadLine reads a full line of input (terminated by Enter) with echo
// and basic line editing. Returns the entered string, or an error on
// timeout/disconnect.
//
// This replaces LineInput() from the original, which handled echo,
// backspace, and had a pre-fill capability (the first argument was
// a default string displayed in the input field). We keep the same
// semantics.
//
// maxLen limits the input length (like the original's fixed char arrays).
// A value of 0 means no limit.
// timeout is the idle timeout — resets on each keypress.
func (s *Session) ReadLine(prefill string, maxLen int, timeout time.Duration) (string, error) {
	buf := []byte(prefill)

	// Display the prefill text if any
	if len(prefill) > 0 {
		if err := s.WriteString(prefill); err != nil {
			return "", err
		}
	}

	for {
		ch, err := s.ReadChar(timeout)
		if err != nil {
			return string(buf), err
		}

		switch {
		case ch == '\r' || ch == '\n':
			// Enter — return the line
			s.WriteString("\r\n")
			return string(buf), nil

		case ch == 127 || ch == 8:
			// Backspace or DEL — erase last character
			// Same as the original: PutStr("\b \b")
			if len(buf) > 0 {
				buf = buf[:len(buf)-1]
				s.WriteString("\b \b")
			}

		case ch == 24: // Ctrl-X — erase entire line
			// Same as the original editor's line-kill
			for len(buf) > 0 {
				buf = buf[:len(buf)-1]
				s.WriteString("\b \b")
			}

		case ch == 23: // Ctrl-W — erase last word
			// Delete trailing spaces first, then back to previous space.
			// Same logic as the original EDIT.C's Ctrl-W handler.
			for len(buf) > 0 && buf[len(buf)-1] == ' ' {
				buf = buf[:len(buf)-1]
				s.WriteString("\b \b")
			}
			for len(buf) > 0 && buf[len(buf)-1] != ' ' {
				buf = buf[:len(buf)-1]
				s.WriteString("\b \b")
			}

		case ch >= 32 && ch < 127:
			// Printable character
			if maxLen > 0 && len(buf) >= maxLen {
				continue // At limit, ignore
			}
			buf = append(buf, ch)
			s.Write([]byte{ch})

		default:
			// Control characters — ignore
			continue
		}
	}
}

// ReadLineNoEcho reads a line of input without echoing characters.
// Used for password entry. Displays asterisks instead of the actual
// characters.
func (s *Session) ReadLineNoEcho(maxLen int, timeout time.Duration) (string, error) {
	var buf []byte

	for {
		ch, err := s.ReadChar(timeout)
		if err != nil {
			return string(buf), err
		}

		switch {
		case ch == '\r' || ch == '\n':
			s.WriteString("\r\n")
			return string(buf), nil

		case ch == 127 || ch == 8:
			if len(buf) > 0 {
				buf = buf[:len(buf)-1]
				s.WriteString("\b \b")
			}

		case ch >= 32 && ch < 127:
			if maxLen > 0 && len(buf) >= maxLen {
				continue
			}
			buf = append(buf, ch)
			s.Write([]byte{'*'})

		default:
			continue
		}
	}
}

// ReadKey reads a single keypress and returns it immediately without
// waiting for Enter. Used for single-character menu selections.
// This is the classic BBS "press a key" input — the original's
// ReadChar(120L) in the menu dispatch loops.
func (s *Session) ReadKey(timeout time.Duration) (byte, error) {
	for {
		ch, err := s.ReadChar(timeout)
		if err != nil {
			return 0, err
		}

		// Skip null bytes (can come from function key sequences)
		if ch == 0 {
			continue
		}

		return ch, nil
	}
}

// WaitForKey displays a prompt and waits for any keypress.
// The classic "Press any key to continue..." pattern.
func (s *Session) WaitForKey(prompt string, timeout time.Duration) error {
	if prompt != "" {
		if err := s.WriteString(prompt); err != nil {
			return err
		}
	}
	_, err := s.ReadKey(timeout)
	return err
}

// Confirm asks a yes/no question and returns the result.
// Keeps prompting until Y or N is pressed.
func (s *Session) Confirm(prompt string, timeout time.Duration) (bool, error) {
	s.WriteString(prompt)
	for {
		ch, err := s.ReadKey(timeout)
		if err != nil {
			return false, err
		}

		switch ch {
		case 'y', 'Y':
			s.WriteString("Yes\r\n")
			return true, nil
		case 'n', 'N', '\r', '\n':
			s.WriteString("No\r\n")
			return false, nil
		}
	}
}