//+build notmuch

package notmuch

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"

	"git.sr.ht/~sircmpwn/aerc/models"
	"git.sr.ht/~sircmpwn/aerc/worker/lib"
	"github.com/emersion/go-message"
	_ "github.com/emersion/go-message/charset"
	notmuch "github.com/zenhack/go.notmuch"
)

type Message struct {
	uid     uint32
	key     string
	msg     *notmuch.Message
	rwDB    func() (*notmuch.DB, error) // used to open a db for writing
	refresh func(*Message) error        // called after msg modification
}

// NewReader reads a message into memory and returns an io.Reader for it.
func (m *Message) NewReader() (io.Reader, error) {
	f, err := os.Open(m.msg.Filename())
	if err != nil {
		return nil, err
	}
	defer f.Close()
	b, err := ioutil.ReadAll(f)
	if err != nil {
		return nil, err
	}
	return bytes.NewReader(b), nil
}

// MessageInfo populates a models.MessageInfo struct for the message.
func (m *Message) MessageInfo() (*models.MessageInfo, error) {
	return lib.MessageInfo(m)
}

// NewBodyPartReader creates a new io.Reader for the requested body part(s) of
// the message.
func (m *Message) NewBodyPartReader(requestedParts []int) (io.Reader, error) {
	f, err := os.Open(m.msg.Filename())
	if err != nil {
		return nil, err
	}
	defer f.Close()
	msg, err := message.Read(f)
	if err != nil {
		return nil, fmt.Errorf("could not read message: %v", err)
	}
	return lib.FetchEntityPartReader(msg, requestedParts)
}

// MarkRead either adds or removes the maildir.FlagSeen flag from the message.
func (m *Message) MarkRead(seen bool) error {
	haveUnread := false
	for _, t := range m.tags() {
		if t == "unread" {
			haveUnread = true
			break
		}
	}
	if (haveUnread && !seen) || (!haveUnread && seen) {
		// we already have the desired state
		return nil
	}

	if haveUnread {
		err := m.RemoveTag("unread")
		if err != nil {
			return err
		}
		return nil
	}

	err := m.AddTag("unread")
	if err != nil {
		return err
	}
	return nil
}

// tags returns the notmuch tags of a message
func (m *Message) tags() []string {
	ts := m.msg.Tags()
	var tags []string
	var tag *notmuch.Tag
	for ts.Next(&tag) {
		tags = append(tags, tag.Value)
	}
	return tags
}

func (m *Message) modify(cb func(*notmuch.Message) error) error {
	db, err := m.rwDB()
	if err != nil {
		return err
	}
	defer db.Close()
	msg, err := db.FindMessage(m.key)
	if err != nil {
		return err
	}
	err = cb(msg)
	if err != nil {
		return err
	}
	// we need to explicitly close here, else we don't commit
	dcerr := db.Close()
	if dcerr != nil && err == nil {
		err = dcerr
	}
	// next we need to refresh the notmuch msg, else we serve stale tags
	rerr := m.refresh(m)
	if rerr != nil && err == nil {
		err = rerr
	}
	return err
}

func (m *Message) AddTag(tag string) error {
	err := m.modify(func(msg *notmuch.Message) error {
		return msg.AddTag(tag)
	})
	return err
}

func (m *Message) AddTags(tags []string) error {
	err := m.modify(func(msg *notmuch.Message) error {
		ierr := msg.Atomic(func(msg *notmuch.Message) {
			for _, t := range tags {
				msg.AddTag(t)
			}
		})
		return ierr
	})
	return err
}

func (m *Message) RemoveTag(tag string) error {
	err := m.modify(func(msg *notmuch.Message) error {
		return msg.RemoveTag(tag)
	})
	return err
}

func (m *Message) RemoveTags(tags []string) error {
	err := m.modify(func(msg *notmuch.Message) error {
		ierr := msg.Atomic(func(msg *notmuch.Message) {
			for _, t := range tags {
				msg.RemoveTag(t)
			}
		})
		return ierr
	})
	return err
}

func (m *Message) ModelFlags() ([]models.Flag, error) {
	var flags []models.Flag
	seen := true

	for _, tag := range m.tags() {
		switch tag {
		case "replied":
			flags = append(flags, models.AnsweredFlag)
		case "flagged":
			flags = append(flags, models.FlaggedFlag)
		case "unread":
			seen = false
		default:
			continue
		}
	}
	if seen {
		flags = append(flags, models.SeenFlag)
	}
	return flags, nil
}

func (m *Message) UID() uint32 {
	return m.uid
}