package appstate

import (
	"fmt"
	"slices"
	"strings"

	"git.julianfamily.org/keepassgo/vault"
	"git.julianfamily.org/keepassgo/webdav"
)

type Section string

const (
	SectionEntries    Section = ""
	SectionTemplates  Section = "templates"
	SectionRecycleBin Section = "recycle-bin"
)

type CurrentSession interface {
	Current() (vault.Model, error)
}

type MutableSession interface {
	CurrentSession
	Replace(vault.Model)
}

type LockableSession interface {
	CurrentSession
	Lock() error
	Unlock(vault.MasterKey) error
}

type SaveableSession interface {
	CurrentSession
	Save() error
}

type CreateableSession interface {
	CurrentSession
	Create(vault.Model, vault.MasterKey) error
}

type OpenableSession interface {
	CurrentSession
	Open(string, vault.MasterKey) error
}

type SaveAsSession interface {
	CurrentSession
	SaveAs(string) error
}

type RemoteOpenableSession interface {
	CurrentSession
	OpenRemote(webdav.Client, string, vault.MasterKey) error
}

type State struct {
	Session         CurrentSession
	Section         Section
	CurrentPath     []string
	SearchQuery     string
	SelectedEntryID string
	Dirty           bool
}

func (s *State) VisibleEntries() ([]vault.Entry, error) {
	model, err := s.currentModel()
	if err != nil {
		return nil, err
	}

	entries := s.entriesForSection(model)
	if strings.TrimSpace(s.SearchQuery) != "" {
		return filterEntries(entries, s.SearchQuery), nil
	}

	if s.Section == SectionEntries {
		return model.EntriesInPath(s.CurrentPath), nil
	}
	if s.Section == SectionRecycleBin || len(s.CurrentPath) == 0 {
		return entries, nil
	}

	return entriesInPath(entries, s.CurrentPath), nil
}

func (s *State) ChildGroups() ([]string, error) {
	if strings.TrimSpace(s.SearchQuery) != "" {
		return nil, nil
	}

	model, err := s.currentModel()
	if err != nil {
		return nil, err
	}

	if s.Section != SectionEntries {
		if s.Section == SectionTemplates && len(s.CurrentPath) == 0 {
			return childGroups(s.entriesForSection(model), []string{"Templates"}), nil
		}
		return childGroups(s.entriesForSection(model), s.CurrentPath), nil
	}

	return model.ChildGroups(s.CurrentPath), nil
}

func (s *State) SelectVisibleIndex(index int) error {
	entries, err := s.VisibleEntries()
	if err != nil {
		return err
	}
	if index < 0 || index >= len(entries) {
		return fmt.Errorf("visible index %d out of range", index)
	}

	s.SelectedEntryID = entries[index].ID
	return nil
}

func (s *State) ToggleVisibleIndex(index int) error {
	entries, err := s.VisibleEntries()
	if err != nil {
		return err
	}
	if index < 0 || index >= len(entries) {
		return fmt.Errorf("visible index %d out of range", index)
	}

	if s.SelectedEntryID == entries[index].ID {
		s.SelectedEntryID = ""
		return nil
	}

	s.SelectedEntryID = entries[index].ID
	return nil
}

func (s *State) currentModel() (vault.Model, error) {
	if s.Session == nil {
		return vault.Model{}, nil
	}
	return s.Session.Current()
}

func (s *State) entriesForSection(model vault.Model) []vault.Entry {
	switch s.Section {
	case SectionTemplates:
		return slices.Clone(model.Templates)
	case SectionRecycleBin:
		return slices.Clone(model.RecycleBin)
	default:
		return slices.Clone(model.Entries)
	}
}

func entriesInPath(entries []vault.Entry, path []string) []vault.Entry {
	var out []vault.Entry
	for _, entry := range entries {
		if slices.Equal(entry.Path, path) {
			out = append(out, entry)
		}
	}
	slices.SortFunc(out, func(a, b vault.Entry) int {
		switch {
		case a.Title < b.Title:
			return -1
		case a.Title > b.Title:
			return 1
		default:
			return 0
		}
	})
	return out
}

func filterEntries(entries []vault.Entry, query string) []vault.Entry {
	query = strings.TrimSpace(strings.ToLower(query))
	if query == "" {
		return nil
	}

	var out []vault.Entry
	for _, entry := range entries {
		haystack := strings.ToLower(
			entry.Title + " " +
				entry.Username + " " +
				entry.URL + " " +
				strings.Join(entry.Path, " "),
		)
		if !strings.Contains(haystack, query) {
			continue
		}
		out = append(out, entry)
	}
	slices.SortFunc(out, func(a, b vault.Entry) int {
		switch {
		case a.Title < b.Title:
			return -1
		case a.Title > b.Title:
			return 1
		default:
			return 0
		}
	})
	return out
}

func childGroups(entries []vault.Entry, path []string) []string {
	seen := map[string]bool{}
	var groups []string
	for _, entry := range entries {
		if len(path) > len(entry.Path) {
			continue
		}
		if !slices.Equal(entry.Path[:len(path)], path) {
			continue
		}
		if len(entry.Path) == len(path) {
			continue
		}
		group := entry.Path[len(path)]
		if seen[group] {
			continue
		}
		seen[group] = true
		groups = append(groups, group)
	}
	slices.Sort(groups)
	return groups
}

func (s *State) DeleteSelectedEntry() error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	if err := model.DeleteEntry(s.SelectedEntryID); err != nil {
		return err
	}

	session.Replace(model)
	s.SelectedEntryID = ""
	s.Dirty = true
	return nil
}

func (s *State) RestoreEntry(id string) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	if err := model.RestoreEntry(id); err != nil {
		return err
	}

	session.Replace(model)
	s.Dirty = true
	return nil
}

func (s *State) UpsertEntry(entry vault.Entry) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	model.UpsertEntry(entry)
	session.Replace(model)
	s.SelectedEntryID = entry.ID
	s.Dirty = true
	return nil
}

func (s *State) UpsertTemplate(entry vault.Entry) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	model.UpsertTemplate(entry)
	session.Replace(model)
	s.SelectedEntryID = entry.ID
	s.Dirty = true
	return nil
}

func (s *State) InstantiateTemplate(templateID string, overrides vault.Entry) (vault.Entry, error) {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return vault.Entry{}, fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return vault.Entry{}, err
	}

	entry, err := model.InstantiateTemplate(templateID, overrides)
	if err != nil {
		return vault.Entry{}, err
	}

	session.Replace(model)
	s.SelectedEntryID = entry.ID
	s.Dirty = true
	return entry, nil
}

func (s *State) DeleteTemplate(id string) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	if err := model.DeleteTemplate(id); err != nil {
		return err
	}

	session.Replace(model)
	if s.SelectedEntryID == id {
		s.SelectedEntryID = ""
	}
	s.Dirty = true
	return nil
}

func (s *State) DuplicateSelectedEntry(duplicateID string) (vault.Entry, error) {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return vault.Entry{}, fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return vault.Entry{}, err
	}

	duplicate, err := model.DuplicateEntry(s.SelectedEntryID, duplicateID)
	if err != nil {
		return vault.Entry{}, err
	}

	session.Replace(model)
	s.SelectedEntryID = duplicate.ID
	s.Dirty = true
	return duplicate, nil
}

func (s *State) RestoreSelectedEntryVersion(historyIndex int) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	if err := model.RestoreEntryVersion(s.SelectedEntryID, historyIndex); err != nil {
		return err
	}

	session.Replace(model)
	s.Dirty = true
	return nil
}

func (s *State) Lock() error {
	session, ok := s.Session.(LockableSession)
	if !ok {
		return fmt.Errorf("session is not lockable")
	}

	if err := session.Lock(); err != nil {
		return err
	}

	s.SelectedEntryID = ""
	return nil
}

func (s *State) Unlock(key vault.MasterKey) error {
	session, ok := s.Session.(LockableSession)
	if !ok {
		return fmt.Errorf("session is not lockable")
	}

	return session.Unlock(key)
}

func (s *State) EnterGroup(name string) {
	s.CurrentPath = append(append([]string(nil), s.CurrentPath...), name)
	s.SelectedEntryID = ""
}

func (s *State) NavigateToPath(path []string) {
	s.CurrentPath = append([]string(nil), path...)
	s.SelectedEntryID = ""
}

func (s *State) Save() error {
	session, ok := s.Session.(SaveableSession)
	if !ok {
		return fmt.Errorf("session is not saveable")
	}

	if err := session.Save(); err != nil {
		return err
	}

	s.Dirty = false
	return nil
}

func (s *State) CreateVault(key vault.MasterKey) error {
	session, ok := s.Session.(CreateableSession)
	if !ok {
		return fmt.Errorf("session is not createable")
	}

	if err := session.Create(vault.Model{}, key); err != nil {
		return err
	}

	s.CurrentPath = nil
	s.SelectedEntryID = ""
	s.Dirty = false
	return nil
}

func (s *State) OpenVault(path string, key vault.MasterKey) error {
	session, ok := s.Session.(OpenableSession)
	if !ok {
		return fmt.Errorf("session is not openable")
	}

	if err := session.Open(path, key); err != nil {
		return err
	}

	s.CurrentPath = nil
	s.SelectedEntryID = ""
	s.Dirty = false
	return nil
}

func (s *State) SaveAs(path string) error {
	session, ok := s.Session.(SaveAsSession)
	if !ok {
		return fmt.Errorf("session is not save-as capable")
	}

	if err := session.SaveAs(path); err != nil {
		return err
	}

	s.Dirty = false
	return nil
}

func (s *State) OpenRemoteVault(client webdav.Client, path string, key vault.MasterKey) error {
	session, ok := s.Session.(RemoteOpenableSession)
	if !ok {
		return fmt.Errorf("session is not remote-openable")
	}

	if err := session.OpenRemote(client, path, key); err != nil {
		return err
	}

	s.CurrentPath = nil
	s.SelectedEntryID = ""
	s.Dirty = false
	return nil
}

func (s *State) CreateGroup(name string) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	model.CreateGroup(s.CurrentPath, name)
	session.Replace(model)
	s.Dirty = true
	return nil
}

func (s *State) RenameCurrentGroup(newName string) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	if err := model.RenameGroup(s.CurrentPath, newName); err != nil {
		return err
	}

	session.Replace(model)
	if len(s.CurrentPath) > 0 {
		s.CurrentPath = append(append([]string(nil), s.CurrentPath[:len(s.CurrentPath)-1]...), newName)
	}
	s.Dirty = true
	return nil
}

func (s *State) MoveSelectedEntry(path []string) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	if err := model.MoveEntry(s.SelectedEntryID, path); err != nil {
		return err
	}

	session.Replace(model)
	s.Dirty = true
	return nil
}

func (s *State) AddAttachmentToSelectedEntry(name string, content []byte) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	for i := range model.Entries {
		if model.Entries[i].ID != s.SelectedEntryID {
			continue
		}
		if model.Entries[i].Attachments == nil {
			model.Entries[i].Attachments = map[string][]byte{}
		}
		model.Entries[i].Attachments[name] = append([]byte(nil), content...)
		session.Replace(model)
		s.Dirty = true
		return nil
	}

	return vault.ErrEntryNotFound
}

func (s *State) DeleteAttachmentFromSelectedEntry(name string) error {
	session, ok := s.Session.(MutableSession)
	if !ok {
		return fmt.Errorf("session is not mutable")
	}

	model, err := session.Current()
	if err != nil {
		return err
	}

	for i := range model.Entries {
		if model.Entries[i].ID != s.SelectedEntryID {
			continue
		}
		delete(model.Entries[i].Attachments, name)
		if len(model.Entries[i].Attachments) == 0 {
			model.Entries[i].Attachments = nil
		}
		session.Replace(model)
		s.Dirty = true
		return nil
	}

	return vault.ErrEntryNotFound
}