package cli

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"os"
	"strings"
	"syscall"
	"unsafe"

	"email-mcp/internal/secretstore"
)

type SetupPrompter interface {
	PromptSetup(ctx context.Context) (secretstore.Credential, error)
}

type PasswordReader interface {
	ReadPassword(prompt string) (string, error)
}

type InteractiveSetupPrompter struct {
	input          *bufio.Reader
	rawInput       io.Reader
	output         io.Writer
	passwordReader PasswordReader
}

type terminalPasswordReader struct {
	input                io.Reader
	output               io.Writer
	isTerminal           func(io.Reader) bool
	readHiddenPassword   func(*os.File) ([]byte, error)
	readFallbackPassword func(string) (string, error)
}

func NewInteractiveSetupPrompter(input io.Reader, output io.Writer) *InteractiveSetupPrompter {
	return NewInteractiveSetupPrompterWithPasswordReader(input, output, nil)
}

func NewInteractiveSetupPrompterWithPasswordReader(input io.Reader, output io.Writer, passwordReader PasswordReader) *InteractiveSetupPrompter {
	if input == nil {
		input = strings.NewReader("")
	}
	if output == nil {
		output = io.Discard
	}

	prompter := &InteractiveSetupPrompter{
		input:    bufio.NewReader(input),
		rawInput: input,
		output:   output,
	}
	if passwordReader == nil {
		passwordReader = newTerminalPasswordReader(input, output, prompter.prompt)
	}
	prompter.passwordReader = passwordReader

	return prompter
}

func (p *InteractiveSetupPrompter) PromptSetup(context.Context) (secretstore.Credential, error) {
	host, err := p.prompt("IMAP host: ")
	if err != nil {
		return secretstore.Credential{}, err
	}
	username, err := p.prompt("Username: ")
	if err != nil {
		return secretstore.Credential{}, err
	}
	password, err := p.passwordReader.ReadPassword("Password: ")
	if err != nil {
		return secretstore.Credential{}, err
	}

	cred := secretstore.Credential{
		Host:     host,
		Username: username,
		Password: password,
	}
	if err := cred.Validate(); err != nil {
		return secretstore.Credential{}, err
	}
	return cred, nil
}

func (p *InteractiveSetupPrompter) prompt(label string) (string, error) {
	if _, err := fmt.Fprint(p.output, label); err != nil {
		return "", err
	}

	value, err := p.input.ReadString('\n')
	if err != nil && err != io.EOF {
		return "", err
	}
	return strings.TrimSpace(value), nil
}

func newTerminalPasswordReader(input io.Reader, output io.Writer, fallback func(string) (string, error)) PasswordReader {
	return terminalPasswordReader{
		input:                input,
		output:               output,
		isTerminal:           isTerminalReader,
		readHiddenPassword:   readHiddenPassword,
		readFallbackPassword: fallback,
	}
}

func (r terminalPasswordReader) ReadPassword(prompt string) (string, error) {
	if r.isTerminal != nil && r.isTerminal(r.input) {
		file, ok := r.input.(*os.File)
		if ok {
			if _, err := fmt.Fprint(r.output, prompt); err != nil {
				return "", err
			}
			password, err := r.readHiddenPassword(file)
			if _, printErr := fmt.Fprintln(r.output); err == nil && printErr != nil {
				return "", printErr
			}
			if err != nil {
				return "", err
			}
			return strings.TrimSpace(string(password)), nil
		}
	}

	return r.readFallbackPassword(prompt)
}

func isTerminalReader(reader io.Reader) bool {
	file, ok := reader.(*os.File)
	if !ok {
		return false
	}
	return isTerminalFile(file)
}

func isTerminalFile(file *os.File) bool {
	_, err := getTermios(file.Fd())
	return err == nil
}

func readHiddenPassword(file *os.File) ([]byte, error) {
	state, err := getTermios(file.Fd())
	if err != nil {
		return nil, err
	}

	next := *state
	next.Lflag &^= syscall.ECHO
	if err := setTermios(file.Fd(), &next); err != nil {
		return nil, err
	}
	defer func() {
		_ = setTermios(file.Fd(), state)
	}()

	reader := bufio.NewReader(file)
	value, err := reader.ReadBytes('\n')
	if err != nil && err != io.EOF {
		return nil, err
	}
	return []byte(strings.TrimRight(string(value), "\r\n")), nil
}

func getTermios(fd uintptr) (*syscall.Termios, error) {
	state := &syscall.Termios{}
	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, fd, uintptr(syscall.TCGETS), uintptr(unsafe.Pointer(state)))
	if errno != 0 {
		return nil, errno
	}
	return state, nil
}

func setTermios(fd uintptr, state *syscall.Termios) error {
	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, fd, uintptr(syscall.TCSETS), uintptr(unsafe.Pointer(state)))
	if errno != 0 {
		return errno
	}
	return nil
}