package imaputils

import (
	"git.sr.ht/~blallo/papero/config"
	"github.com/emersion/go-imap"
)

type ListMessagesOpts struct {
	Mailbox string
	Limit   uint32
}

func ListMessages(conf *config.AccountData, opts *ListMessagesOpts, debug bool) ([]*imap.Message, error) {
	var empty []*imap.Message
	conn := NewConnection(conf)

	err := conn.Start(debug)
	if err != nil {
		return empty, err
	}
	defer conn.Close()

	return ListMessagesInSession(conn, opts)
}

func ListMessagesInSession(conn *IMAPConnection, opts *ListMessagesOpts) ([]*imap.Message, error) {
	var messages []*imap.Message
	mbox, err := conn.client.Select(opts.Mailbox, true)
	if err != nil {
		return messages, err
	}

	return getMessages(mbox, conn, opts.Limit)
}

func getMessages(mbox *imap.MailboxStatus, conn *IMAPConnection, limit uint32) ([]*imap.Message, error) {
	var start uint32
	var msgs []*imap.Message
	seqset := new(imap.SeqSet)
	messages := make(chan *imap.Message, 10)
	done := make(chan error, 1)

	switch {
	case limit == 0:
		start = 1
	case mbox.Messages > limit:
		start = mbox.Messages - limit + 1
	default:
		start = 1
	}

	seqset.AddRange(start, mbox.Messages)
	go func() {
		done <- conn.client.Fetch(seqset, []imap.FetchItem{imap.FetchEnvelope, imap.FetchFlags}, messages)
	}()

	for msg := range messages {
		msgs = append(msgs, msg)
	}

	if err := <-done; err != nil {
		return []*imap.Message{}, err
	}
	return msgs, nil
}