package storage

import (
	"errors"
	"fmt"
	"strconv"

	"code.ewintr.nl/gte/internal/task"
	"code.ewintr.nl/gte/pkg/mstore"
)

var (
	ErrMStoreError    = errors.New("mstore gave error response")
	ErrInvalidTask    = errors.New("invalid task")
	ErrInvalidMessage = errors.New("task contains invalid message")
)

type RemoteRepository struct {
	mstore mstore.MStorer
}

func NewRemoteRepository(ms mstore.MStorer) *RemoteRepository {
	return &RemoteRepository{
		mstore: ms,
	}
}

func (rr *RemoteRepository) FindAll(folder string) ([]*task.Task, error) {
	msgs, err := rr.mstore.Messages(folder)
	if err != nil {
		return []*task.Task{}, fmt.Errorf("%w: %v", ErrMStoreError, err)
	}

	tasks := []*task.Task{}
	for _, msg := range msgs {
		if msg.Valid() {
			tasks = append(tasks, task.NewFromMessage(msg))
		}
	}

	return tasks, nil
}

func (rr *RemoteRepository) Update(t *task.Task) error {
	if t == nil {
		return ErrInvalidTask
	}

	// add new
	if err := rr.Add(t); err != nil {
		return err
	}

	// remove old
	if err := rr.mstore.Remove(t.Message); err != nil {
		return fmt.Errorf("%w: %s", ErrMStoreError, err)
	}

	return nil
}

func (rr *RemoteRepository) Add(t *task.Task) error {
	if t == nil {
		return ErrInvalidTask
	}

	msg := t.NextMessage()
	if err := rr.mstore.Add(msg.Folder, msg.Subject, msg.Body); err != nil {
		return fmt.Errorf("%w: %v", ErrMStoreError, err)
	}

	return nil
}

// Cleanup removes older versions of tasks
func (rr *RemoteRepository) CleanUp() error {
	// loop through folders, get all task version info
	type msgInfo struct {
		Version int
		Message *mstore.Message
	}
	msgsSet := make(map[string][]msgInfo)

	for _, folder := range task.KnownFolders {
		msgs, err := rr.mstore.Messages(folder)
		if err != nil {
			return fmt.Errorf("%w: %v", ErrMStoreError, err)
		}

		for _, msg := range msgs {
			id := task.FieldFromBody(task.FIELD_ID, msg.Body)
			versionStr := task.FieldFromBody(task.FIELD_VERSION, msg.Body)
			version, _ := strconv.Atoi(versionStr)
			if _, ok := msgsSet[id]; !ok {
				msgsSet[id] = []msgInfo{}
			}
			msgsSet[id] = append(msgsSet[id], msgInfo{
				Version: version,
				Message: msg,
			})
		}
	}

	// determine which ones need to be gone
	var tobeRemoved []*mstore.Message
	for _, mInfos := range msgsSet {
		maxVersion := 0
		for _, mInfo := range mInfos {
			if mInfo.Version > maxVersion {
				maxVersion = mInfo.Version
			}
		}
		for _, mInfo := range mInfos {
			if mInfo.Version < maxVersion {
				tobeRemoved = append(tobeRemoved, mInfo.Message)
			}
		}
	}

	// remove them
	for _, msg := range tobeRemoved {
		if err := rr.mstore.Remove(msg); err != nil {
			return err
		}
	}

	return nil
}

func (rr *RemoteRepository) Remove(tasks []*task.Task) error {
	tMap := map[string]*task.Task{}
	for _, t := range tasks {
		tMap[t.Id] = t
	}

	var toBeRemoved []*mstore.Message
	for _, folder := range task.KnownFolders {
		msgs, err := rr.mstore.Messages(folder)
		if err != nil {
			return fmt.Errorf("%w: %v", ErrMStoreError, err)
		}

		for _, msg := range msgs {
			id := task.FieldFromBody(task.FIELD_ID, msg.Body)
			if _, ok := tMap[id]; ok {
				toBeRemoved = append(toBeRemoved, msg)
			}
		}
	}

	for _, msg := range toBeRemoved {
		if err := rr.mstore.Remove(msg); err != nil {
			return fmt.Errorf("%w: %v", ErrMStoreError, err)
		}
	}

	return nil
}