package msg

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"regexp"
	"strings"

	"git.sr.ht/~sircmpwn/getopt"

	"git.sr.ht/~rjarry/aerc/lib"
	"git.sr.ht/~rjarry/aerc/lib/format"
	"git.sr.ht/~rjarry/aerc/logging"
	"git.sr.ht/~rjarry/aerc/models"
	"git.sr.ht/~rjarry/aerc/widgets"
	"github.com/emersion/go-message/mail"
)

type reply struct{}

func init() {
	register(reply{})
}

func (reply) Aliases() []string {
	return []string{"reply"}
}

func (reply) Complete(aerc *widgets.Aerc, args []string) []string {
	return nil
}

func (reply) Execute(aerc *widgets.Aerc, args []string) error {
	opts, optind, err := getopt.Getopts(args, "aqT:")
	if err != nil {
		return err
	}
	if optind != len(args) {
		return errors.New("Usage: reply [-aq -T <template>]")
	}
	var (
		quote    bool
		replyAll bool
		template string
	)
	for _, opt := range opts {
		switch opt.Option {
		case 'a':
			replyAll = true
		case 'q':
			quote = true
		case 'T':
			template = opt.Value
		}
	}

	widget := aerc.SelectedTabContent().(widgets.ProvidesMessage)
	acct := widget.SelectedAccount()

	if acct == nil {
		return errors.New("No account selected")
	}
	conf := acct.AccountConfig()
	from, err := mail.ParseAddress(conf.From)
	if err != nil {
		return err
	}
	var aliases []*mail.Address
	if conf.Aliases != "" {
		aliases, err = mail.ParseAddressList(conf.Aliases)
		if err != nil {
			return err
		}
	}

	store := widget.Store()
	if store == nil {
		return errors.New("Cannot perform action. Messages still loading")
	}
	msg, err := widget.SelectedMessage()
	if err != nil {
		return err
	}

	// figure out the sending from address if we have aliases
	if len(aliases) != 0 {
		rec := newAddrSet()
		rec.AddList(msg.Envelope.To)
		rec.AddList(msg.Envelope.Cc)
		// test the from first, it has priority over any present alias
		if rec.Contains(from) {
			// do nothing
		} else {
			for _, a := range aliases {
				if rec.Contains(a) {
					from = a
					break
				}
			}
		}
	}

	var (
		to []*mail.Address
		cc []*mail.Address
	)

	recSet := newAddrSet() // used for de-duping

	if len(msg.Envelope.ReplyTo) != 0 {
		to = msg.Envelope.ReplyTo
	} else {
		to = msg.Envelope.From
	}

	if !aerc.Config().Compose.ReplyToSelf {
		for i, v := range to {
			if v.Address == from.Address {
				to = append(to[:i], to[i+1:]...)
				break
			}
		}
		if len(to) == 0 {
			to = msg.Envelope.To
		}
	}

	recSet.AddList(to)

	if replyAll {
		// order matters, due to the deduping
		// in order of importance, first parse the To, then the Cc header

		// we add our from address, so that we don't self address ourselves
		recSet.Add(from)

		envTos := make([]*mail.Address, 0, len(msg.Envelope.To))
		for _, addr := range msg.Envelope.To {
			if recSet.Contains(addr) {
				continue
			}
			envTos = append(envTos, addr)
		}
		recSet.AddList(envTos)
		to = append(to, envTos...)

		for _, addr := range msg.Envelope.Cc {
			// dedupe stuff from the to/from headers
			if recSet.Contains(addr) {
				continue
			}
			cc = append(cc, addr)
		}
		recSet.AddList(cc)
	}

	subject := "Re: " + trimLocalizedRe(msg.Envelope.Subject)

	h := &mail.Header{}
	h.SetAddressList("to", to)
	h.SetAddressList("cc", cc)
	h.SetAddressList("from", []*mail.Address{from})
	h.SetSubject(subject)
	h.SetMsgIDList("in-reply-to", []string{msg.Envelope.MessageId})
	err = setReferencesHeader(h, msg.RFC822Headers)
	if err != nil {
		aerc.PushError(fmt.Sprintf("could not set references: %v", err))
	}
	original := models.OriginalMail{
		From:          format.FormatAddresses(msg.Envelope.From),
		Date:          msg.Envelope.Date,
		RFC822Headers: msg.RFC822Headers,
	}

	addTab := func() error {
		composer, err := widgets.NewComposer(aerc, acct, aerc.Config(),
			acct.AccountConfig(), acct.Worker(), template, h, original)
		if err != nil {
			aerc.PushError("Error: " + err.Error())
			return err
		}

		if args[0] == "reply" {
			composer.FocusTerminal()
		}

		tab := aerc.NewTab(composer, subject)
		composer.OnHeaderChange("Subject", func(subject string) {
			if subject == "" {
				tab.Name = "New email"
			} else {
				tab.Name = subject
			}
			tab.Content.Invalidate()
		})

		composer.OnClose(func(c *widgets.Composer) {
			if c.Sent() {
				store.Answered([]uint32{msg.Uid}, true, nil)
			}
		})

		return nil
	}

	if quote {
		if template == "" {
			template = aerc.Config().Templates.QuotedReply
		}

		part := lib.FindPlaintext(msg.BodyStructure, nil)
		if part == nil {
			// mkey... let's get the first thing that isn't a container
			// if that's still nil it's either not a multipart msg (ok) or
			// broken (containers only)
			part = lib.FindFirstNonMultipart(msg.BodyStructure, nil)
		}

		err = addMimeType(msg, part, &original)
		if err != nil {
			return err
		}

		store.FetchBodyPart(msg.Uid, part, func(reader io.Reader) {
			buf := new(bytes.Buffer)
			_, err := buf.ReadFrom(reader)
			if err != nil {
				logging.Warnf("failed to fetch bodypart: %v", err)
			}
			original.Text = buf.String()
			err = addTab()
			if err != nil {
				logging.Warnf("failed to add tab: %v", err)
			}
		})
		return nil
	} else {
		if template == "" {
			template = aerc.Config().Templates.NewMessage
		}
		return addTab()
	}
}

type addrSet map[string]struct{}

func newAddrSet() addrSet {
	s := make(map[string]struct{})
	return addrSet(s)
}

func (s addrSet) Add(a *mail.Address) {
	s[a.Address] = struct{}{}
}

func (s addrSet) AddList(al []*mail.Address) {
	for _, a := range al {
		s[a.Address] = struct{}{}
	}
}

func (s addrSet) Contains(a *mail.Address) bool {
	_, ok := s[a.Address]
	return ok
}

// setReferencesHeader adds the references header to target based on parent
// according to RFC2822
func setReferencesHeader(target, parent *mail.Header) error {
	refs, err := parent.MsgIDList("references")
	if err != nil {
		return err
	}
	if len(refs) == 0 {
		// according to the RFC we need to fall back to in-reply-to only if
		// References is not set
		refs, err = parent.MsgIDList("in-reply-to")
		if err != nil {
			return err
		}
	}
	msgID, err := parent.MessageID()
	if err != nil {
		return err
	}
	refs = append(refs, msgID)
	target.SetMsgIDList("references", refs)
	return nil
}

// addMimeType adds the proper mime type of the part to the originalMail struct
func addMimeType(msg *models.MessageInfo, part []int,
	orig *models.OriginalMail,
) error {
	// caution, :forward uses the code as well, keep that in mind when modifying
	bs, err := msg.BodyStructure.PartAtIndex(part)
	if err != nil {
		return err
	}
	orig.MIMEType = fmt.Sprintf("%s/%s", bs.MIMEType, bs.MIMESubType)
	return nil
}

// trimLocalizedRe removes known localizations of Re: commonly used by Outlook.
func trimLocalizedRe(subject string) string {
	return strings.TrimPrefix(subject, localizedRe.FindString(subject))
}

// localizedRe contains a list of known translations for the common Re:
var localizedRe = regexp.MustCompile(`(?i)^((AW|RE|SV|VS|ODP|R): ?)+`)