// Copyright (C) 2020 Guido Berhoerster <guido+sievemgr@berhoerster.name>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

package main

import (
	"crypto/tls"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"os"
	"runtime"
	"strings"

	"go.guido-berhoerster.org/managesieve"
	"go.guido-berhoerster.org/sievemgr/cmd/sievemgr/internal/config"
	"golang.org/x/crypto/ssh/terminal"
)

var errTooBig = errors.New("too big")

func getAccount(conf *config.Configuration, name string) (*config.Account, error) {
	if name == "" {
		if conf.Default == nil {
			return nil, fmt.Errorf("no default account configured")
		}
		return conf.Default, nil
	}
	for _, acct := range conf.Accounts {
		if acct.Name == name {
			return acct, nil
		}
	}
	return nil, fmt.Errorf("account %q does not exist", name)
}

func readPassword(acct *config.Account) error {
	if acct.Password != "" {
		return nil
	}

	var tty *os.File
	var fd int
	var w io.Writer
	if runtime.GOOS == "windows" {
		fd = int(os.Stdin.Fd())
		w = os.Stdout
	} else {
		var err error
		tty, err = os.OpenFile("/dev/tty", os.O_RDWR, 0666)
		if err != nil {
			return err
		}
		defer tty.Close()
		fd = int(tty.Fd())
		w = tty
	}

	io.WriteString(w, "Password: ")
	rawPassword, err := terminal.ReadPassword(fd)
	io.WriteString(w, "\n")
	if err != nil {
		return fmt.Errorf("failed to read password: %s", err)
	}
	password := string(rawPassword)
	if password == "" {
		return fmt.Errorf("invalid password")
	}
	acct.Password = password
	return nil
}

func lookupHostPort(acct *config.Account) error {
	if acct.Port != "" {
		return nil
	}
	// no port given, try to look up a SRV record for given domain
	// and fall back to the domain and port 4190
	services, err := managesieve.LookupService(acct.Host)
	if err != nil {
		return fmt.Errorf("failed to look up service record: %s", err)
	}
	host, port, err := net.SplitHostPort(services[0])
	if err != nil {
		return fmt.Errorf("failed to parse service record: %s", err)
	}
	acct.Host = host
	acct.Port = port
	return nil
}

func dialPlainAuth(acct *config.Account) (*managesieve.Client, error) {
	c, err := managesieve.Dial(net.JoinHostPort(acct.Host, acct.Port))
	if err != nil {
		return nil, fmt.Errorf("failed to connect: %s", err)
	}

	// switch to a TLS connection except for localhost
	if acct.Host != "localhost" && acct.Host != "127.0.0.1" &&
		acct.Host != "::1" {
		tlsConf := &tls.Config{
			ServerName:         acct.Host,
			InsecureSkipVerify: acct.Insecure,
		}
		if err := c.StartTLS(tlsConf); err != nil {
			return nil,
				fmt.Errorf("failed to start TLS connection: %s",
					err)
		}
	}

	auth := managesieve.PlainAuth("", acct.User, acct.Password, acct.Host)
	if err := c.Authenticate(auth); err != nil {
		return nil, fmt.Errorf("failed to authenticate user %s: %s",
			acct.User, err)
	}

	return c, nil
}

func readLimitedString(r io.Reader, n int64) (string, error) {
	var s strings.Builder
	_, err := io.CopyN(&s, r, n)
	if err == nil {
		// check for EOF
		_, err = io.CopyN(ioutil.Discard, r, 1)
		if err == nil {
			return s.String(), errTooBig
		}
	}
	if err != io.EOF {
		return s.String(), err
	}

	return s.String(), nil
}