package mbox

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	mb "github.com/emersion/go-mbox"
	"github.com/emersion/go-message"

	"git.sr.ht/~sircmpwn/aerc/lib/uidstore"
	"git.sr.ht/~sircmpwn/aerc/models"
	"git.sr.ht/~sircmpwn/aerc/worker/handlers"
	"git.sr.ht/~sircmpwn/aerc/worker/types"
)

func init() {
	handlers.RegisterWorkerFactory("mbox", NewWorker)
}

var errUnsupported = fmt.Errorf("unsupported command")

type Worker struct {
	worker   *types.Worker
	basedir  string
	selected string
	uids     *uidstore.Store
}

func NewWorker(worker *types.Worker) (types.Backend, error) {
	return &Worker{
		worker: worker,
		uids:   uidstore.NewStore(),
	}, nil
}

// Run starts the worker's message handling loop.
func (w *Worker) Run() {
	for {
		action := <-w.worker.Actions
		w.handleAction(action)
	}
}

func (w *Worker) handleAction(action types.WorkerMessage) {
	msg := w.worker.ProcessAction(action)
	if err := w.handleMessage(msg); err == errUnsupported {
		w.worker.PostMessage(&types.Unsupported{
			Message: types.RespondTo(msg),
		}, nil)
	} else if err != nil {
		w.worker.PostMessage(&types.Error{
			Message: types.RespondTo(msg),
			Error:   err,
		}, nil)
	} else {
		w.worker.PostMessage(&types.Done{types.RespondTo(msg)}, nil)
	}
}

func (w *Worker) handleMessage(msg types.WorkerMessage) error {
	switch msg := msg.(type) {
	case *types.Unsupported:
		// No-op
	case *types.Configure:
		return w.handleConfigure(msg)
	case *types.Connect:
		return w.handleConnect(msg)
	case *types.ListDirectories:
		return w.handleListDirectories(msg)
	case *types.OpenDirectory:
		return w.handleOpenDirectory(msg)
	case *types.FetchDirectoryContents:
		return w.handleFetchDirectoryContents(msg)
	case *types.CreateDirectory:
		return w.handleCreateDirectory(msg)
	case *types.FetchMessageHeaders:
		return w.handleFetchMessageHeaders(msg)
	case *types.FetchMessageBodyPart:
		return w.handleFetchMessageBodyPart(msg)
	case *types.FetchFullMessages:
		return w.handleFetchFullMessages(msg)
	case *types.DeleteMessages:
		return w.handleDeleteMessages(msg)
	case *types.ReadMessages:
		return w.handleReadMessages(msg)
	case *types.CopyMessages:
		return w.handleCopyMessages(msg)
	case *types.AppendMessage:
		return w.handleAppendMessage(msg)
	case *types.SearchDirectory:
		return w.handleSearchDirectory(msg)
	}
	return errUnsupported
}

func (w *Worker) handleConfigure(msg *types.Configure) error {
	u, err := url.Parse(msg.Config.Source)
	if err != nil {
		w.worker.Logger.Printf("error configuring maildir worker: %v", err)
		return err
	}
	w.basedir = u.Path
	if u.Host == "~" {
		home, err := os.UserHomeDir()
		if err != nil {
			return fmt.Errorf("could not resolve home directory: %v", err)
		}
		w.basedir = filepath.Join(home, u.Path)
	}
	w.worker.Logger.Printf("configured base dir: %s", w.basedir)
	return nil
}

func (w *Worker) handleConnect(msg *types.Connect) error {
	return nil
}

func (w *Worker) handleListDirectories(msg *types.ListDirectories) error {
	dirs, err := ioutil.ReadDir(w.basedir)
	if err != nil {
		w.worker.Logger.Printf("error listing directories: %v", err)
		return err
	}
	for _, dir := range dirs {
		name := dir.Name()
		// TODO: more flexibility? better heuristics?
		if strings.HasPrefix(name, ".") {
			continue
		}
		w.worker.PostMessage(&types.Directory{
			Message: types.RespondTo(msg),
			Dir:     &models.Directory{Name: name},
		}, nil)
	}
	return nil
}

func (w *Worker) handleOpenDirectory(msg *types.OpenDirectory) error {
	w.worker.Logger.Printf("opening %s", msg.Directory)
	w.selected = msg.Directory
	// TODO: why does this need to be sent twice??
	info := &types.DirectoryInfo{
		Info: &models.DirectoryInfo{
			Name:     msg.Directory,
			Flags:    []string{},
			ReadOnly: false,
			// total messages
			Exists: 0,
			// new messages since mailbox was last opened
			Recent: 0,
			// total unread
			Unseen: 0,
		},
	}
	w.worker.PostMessage(info, nil)
	w.worker.PostMessage(info, nil)
	return nil
}

func (w *Worker) scanUIDs() ([]uint32, error) {
	f, err := os.Open(filepath.Join(w.basedir, w.selected))
	if err != nil {
		w.worker.Logger.Printf("could not open mbox: %v", err)
		return nil, err
	}
	defer f.Close()
	br := mb.NewReader(f)
	uids := []uint32{}
	for {
		mr, err := br.NextMessage()
		if err == io.EOF {
			return uids, nil
		} else if err != nil {
			return nil, err
		}
		msg, err := message.Read(mr)
		if err != nil {
			return nil, err
		}
		mid, err := msg.Header.Text("message-id")
		if err != nil {
			return nil, err
		}
		uids = append(uids, w.uids.GetOrInsert(mid))
	}
}

func (w *Worker) handleFetchDirectoryContents(msg *types.FetchDirectoryContents) error {
	uids, err := w.scanUIDs()
	if err != nil {
		w.worker.Logger.Printf("error scanning uids: %v", err)
		return err
	}
	w.worker.PostMessage(&types.DirectoryContents{
		Message: types.RespondTo(msg),
		Uids:    uids,
	}, nil)
	return nil
}

func (w *Worker) handleCreateDirectory(msg *types.CreateDirectory) error {
	return errUnsupported
}

func (w *Worker) handleFetchMessageHeaders(msg *types.FetchMessageHeaders) error {
	// for _, uid := range msg.Uids {
	// 	m, err := w.c.Message(*w.selected, uid)
	// 	if err != nil {
	// 		w.worker.Logger.Printf("could not get message: %v", err)
	// 		w.err(msg, err)
	// 		continue
	// 	}
	// 	info, err := m.MessageInfo()
	// 	if err != nil {
	// 		w.worker.Logger.Printf("could not get message info: %v", err)
	// 		w.err(msg, err)
	// 		continue
	// 	}
	// 	w.worker.PostMessage(&types.MessageInfo{
	// 		Message: types.RespondTo(msg),
	// 		Info:    info,
	// 	}, nil)
	// }
	return nil
}

func (w *Worker) handleFetchMessageBodyPart(msg *types.FetchMessageBodyPart) error {

	// // get reader
	// m, err := w.c.Message(*w.selected, msg.Uid)
	// if err != nil {
	// 	w.worker.Logger.Printf("could not get message %d: %v", msg.Uid, err)
	// 	return err
	// }
	// r, err := m.NewBodyPartReader(msg.Part)
	// if err != nil {
	// 	w.worker.Logger.Printf(
	// 		"could not get body part reader for message=%d, parts=%#v: %v",
	// 		msg.Uid, msg.Part, err)
	// 	return err
	// }
	// w.worker.PostMessage(&types.MessageBodyPart{
	// 	Message: types.RespondTo(msg),
	// 	Part: &models.MessageBodyPart{
	// 		Reader: r,
	// 		Uid:    msg.Uid,
	// 	},
	// }, nil)

	// // mark message as read
	// if err := m.MarkRead(true); err != nil {
	// 	w.worker.Logger.Printf("could not mark message as read: %v", err)
	// 	return err
	// }

	// // send updated flags to ui
	// info, err := m.MessageInfo()
	// if err != nil {
	// 	w.worker.Logger.Printf("could not fetch message info: %v", err)
	// 	return err
	// }
	// w.worker.PostMessage(&types.MessageInfo{
	// 	Message: types.RespondTo(msg),
	// 	Info:    info,
	// }, nil)

	return nil
}

func (w *Worker) handleFetchFullMessages(msg *types.FetchFullMessages) error {
	// for _, uid := range msg.Uids {
	// 	m, err := w.c.Message(*w.selected, uid)
	// 	if err != nil {
	// 		w.worker.Logger.Printf("could not get message %d: %v", uid, err)
	// 		return err
	// 	}
	// 	r, err := m.NewReader()
	// 	if err != nil {
	// 		w.worker.Logger.Printf("could not get message reader: %v", err)
	// 		return err
	// 	}
	// 	w.worker.PostMessage(&types.FullMessage{
	// 		Message: types.RespondTo(msg),
	// 		Content: &models.FullMessage{
	// 			Uid:    uid,
	// 			Reader: r,
	// 		},
	// 	}, nil)
	// }
	return nil
}

func (w *Worker) handleDeleteMessages(msg *types.DeleteMessages) error {
	// deleted, err := w.c.DeleteAll(*w.selected, msg.Uids)
	// if len(deleted) > 0 {
	// 	w.worker.PostMessage(&types.MessagesDeleted{
	// 		Message: types.RespondTo(msg),
	// 		Uids:    deleted,
	// 	}, nil)
	// }
	// if err != nil {
	// 	w.worker.Logger.Printf("error removing some messages: %v", err)
	// 	return err
	// }
	return nil
}

func (w *Worker) handleReadMessages(msg *types.ReadMessages) error {
	// for _, uid := range msg.Uids {
	// 	m, err := w.c.Message(*w.selected, uid)
	// 	if err != nil {
	// 		w.worker.Logger.Printf("could not get message: %v", err)
	// 		w.err(msg, err)
	// 		continue
	// 	}
	// 	if err := m.MarkRead(msg.Read); err != nil {
	// 		w.worker.Logger.Printf("could not mark message as read: %v", err)
	// 		w.err(msg, err)
	// 		continue
	// 	}
	// 	info, err := m.MessageInfo()
	// 	if err != nil {
	// 		w.worker.Logger.Printf("could not get message info: %v", err)
	// 		w.err(msg, err)
	// 		continue
	// 	}
	// 	w.worker.PostMessage(&types.MessageInfo{
	// 		Message: types.RespondTo(msg),
	// 		Info:    info,
	// 	}, nil)
	// }
	return nil
}

func (w *Worker) handleCopyMessages(msg *types.CopyMessages) error {
	// dest := w.c.Dir(msg.Destination)
	// err := w.c.CopyAll(dest, *w.selected, msg.Uids)
	// if err != nil {
	// 	return err
	// }
	return nil
}

func (w *Worker) handleAppendMessage(msg *types.AppendMessage) error {
	// dest := w.c.Dir(msg.Destination)
	// delivery, err := dest.NewDelivery()
	// if err != nil {
	// 	w.worker.Logger.Printf("could not deliver message to %s: %v",
	// 		msg.Destination, err)
	// 	return err
	// }
	// defer delivery.Close()
	// if _, err := io.Copy(delivery, msg.Reader); err != nil {
	// 	w.worker.Logger.Printf("could not write message to destination: %v", err)
	// 	return err
	// }
	return nil
}

func (w *Worker) handleSearchDirectory(msg *types.SearchDirectory) error {
	return errUnsupported
}