package api

import (
	"context"
	"errors"
	"maps"
	"os"
	"slices"
	"strings"
	"sync"

	"git.julianfamily.org/keepassgo/clipboard"
	"git.julianfamily.org/keepassgo/passwords"
	keepassgov1 "git.julianfamily.org/keepassgo/proto/keepassgo/v1"
	"git.julianfamily.org/keepassgo/session"
	"git.julianfamily.org/keepassgo/vault"
	"git.julianfamily.org/keepassgo/webdav"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/status"
)

type Server struct {
	keepassgov1.UnimplementedVaultServiceServer

	mu        sync.RWMutex
	model     vault.Model
	locked    bool
	dirty     bool
	lifecycle lifecycleBackend
	profiles  map[string]passwords.Profile
	clipboard clipboard.Writer
}

type lifecycleBackend interface {
	Current() (vault.Model, error)
	Open(string, vault.MasterKey) error
	OpenRemote(webdav.Client, string, vault.MasterKey) error
	Save() error
	Lock() error
	Unlock(vault.MasterKey) error
}

func NewServer(model vault.Model, profiles map[string]passwords.Profile, clipboardWriter clipboard.Writer) *Server {
	return &Server{
		model:     model,
		profiles:  profiles,
		clipboard: clipboardWriter,
	}
}

func NewServerWithLifecycle(model vault.Model, profiles map[string]passwords.Profile, clipboardWriter clipboard.Writer, lifecycle lifecycleBackend) *Server {
	server := NewServer(model, profiles, clipboardWriter)
	server.lifecycle = lifecycle
	return server
}

func (s *Server) GetSessionStatus(_ context.Context, _ *keepassgov1.GetSessionStatusRequest) (*keepassgov1.GetSessionStatusResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	return &keepassgov1.GetSessionStatusResponse{
		Locked:     s.locked,
		Dirty:      s.dirty,
		EntryCount: uint32(len(s.model.Entries)),
	}, nil
}

func (s *Server) OpenVault(_ context.Context, req *keepassgov1.OpenVaultRequest) (*keepassgov1.OpenVaultResponse, error) {
	if s.lifecycle == nil {
		return nil, status.Error(codes.FailedPrecondition, "vault lifecycle backend is not configured")
	}

	key := vault.MasterKey{Password: req.GetPassword(), KeyFileData: append([]byte(nil), req.GetKeyFileData()...)}
	if err := s.lifecycle.Open(req.GetPath(), key); err != nil {
		return nil, mapLifecycleError("open vault", err)
	}

	model, err := s.lifecycle.Current()
	if err != nil {
		return nil, mapLifecycleError("load opened vault", err)
	}

	s.mu.Lock()
	s.model = model
	s.locked = false
	s.dirty = false
	s.mu.Unlock()

	return &keepassgov1.OpenVaultResponse{}, nil
}

func (s *Server) OpenRemoteVault(_ context.Context, req *keepassgov1.OpenRemoteVaultRequest) (*keepassgov1.OpenRemoteVaultResponse, error) {
	if s.lifecycle == nil {
		return nil, status.Error(codes.FailedPrecondition, "vault lifecycle backend is not configured")
	}

	client := webdav.Client{
		BaseURL:  req.GetBaseUrl(),
		Username: req.GetUsername(),
		Password: req.GetPassword(),
	}
	key := vault.MasterKey{Password: req.GetMasterPassword(), KeyFileData: append([]byte(nil), req.GetKeyFileData()...)}
	if err := s.lifecycle.OpenRemote(client, req.GetPath(), key); err != nil {
		return nil, mapLifecycleError("open remote vault", err)
	}

	model, err := s.lifecycle.Current()
	if err != nil {
		return nil, mapLifecycleError("load opened remote vault", err)
	}

	s.mu.Lock()
	s.model = model
	s.locked = false
	s.dirty = false
	s.mu.Unlock()

	return &keepassgov1.OpenRemoteVaultResponse{}, nil
}

func (s *Server) SaveVault(_ context.Context, _ *keepassgov1.SaveVaultRequest) (*keepassgov1.SaveVaultResponse, error) {
	if s.lifecycle == nil {
		return nil, status.Error(codes.FailedPrecondition, "vault lifecycle backend is not configured")
	}

	if err := s.lifecycle.Save(); err != nil {
		return nil, mapLifecycleError("save vault", err)
	}

	s.mu.Lock()
	s.dirty = false
	s.mu.Unlock()

	return &keepassgov1.SaveVaultResponse{}, nil
}

func (s *Server) LockVault(_ context.Context, _ *keepassgov1.LockVaultRequest) (*keepassgov1.LockVaultResponse, error) {
	if s.lifecycle == nil {
		return nil, status.Error(codes.FailedPrecondition, "vault lifecycle backend is not configured")
	}

	if err := s.lifecycle.Lock(); err != nil {
		return nil, mapLifecycleError("lock vault", err)
	}

	s.mu.Lock()
	s.locked = true
	s.mu.Unlock()

	return &keepassgov1.LockVaultResponse{}, nil
}

func (s *Server) UnlockVault(_ context.Context, req *keepassgov1.UnlockVaultRequest) (*keepassgov1.UnlockVaultResponse, error) {
	if s.lifecycle == nil {
		return nil, status.Error(codes.FailedPrecondition, "vault lifecycle backend is not configured")
	}

	key := vault.MasterKey{Password: req.GetPassword(), KeyFileData: append([]byte(nil), req.GetKeyFileData()...)}
	if err := s.lifecycle.Unlock(key); err != nil {
		return nil, mapLifecycleError("unlock vault", err)
	}

	model, err := s.lifecycle.Current()
	if err != nil {
		return nil, mapLifecycleError("load unlocked vault", err)
	}

	s.mu.Lock()
	s.model = model
	s.locked = false
	s.mu.Unlock()

	return &keepassgov1.UnlockVaultResponse{}, nil
}

func mapLifecycleError(operation string, err error) error {
	switch {
	case errors.Is(err, os.ErrNotExist):
		return status.Errorf(codes.NotFound, "%s: %v", operation, err)
	case errors.Is(err, vault.ErrInvalidMasterKey):
		return status.Errorf(codes.InvalidArgument, "%s: %v", operation, err)
	case errors.Is(err, session.ErrLocked), errors.Is(err, session.ErrNoPath):
		return status.Errorf(codes.FailedPrecondition, "%s: %v", operation, err)
	case errors.Is(err, webdav.ErrConflict):
		return status.Errorf(codes.Aborted, "%s: %v", operation, err)
	default:
		return status.Errorf(codes.Internal, "%s: %v", operation, err)
	}
}

func (s *Server) ListEntries(_ context.Context, req *keepassgov1.ListEntriesRequest) (*keepassgov1.ListEntriesResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	var entries []vault.Entry
	if strings.TrimSpace(req.GetQuery()) != "" {
		results := s.model.Search(req.GetQuery())
		entries = make([]vault.Entry, 0, len(results))
		for _, result := range results {
			entries = append(entries, result.Entry)
		}
	} else {
		entries = s.model.EntriesInPath(req.GetPath())
	}

	resp := &keepassgov1.ListEntriesResponse{
		Entries: make([]*keepassgov1.Entry, 0, len(entries)),
	}
	for _, entry := range entries {
		resp.Entries = append(resp.Entries, entryToProto(entry))
	}

	return resp, nil
}

func (s *Server) ListGroups(_ context.Context, req *keepassgov1.ListGroupsRequest) (*keepassgov1.ListGroupsResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	return &keepassgov1.ListGroupsResponse{
		Names: s.model.ChildGroups(req.GetPath()),
	}, nil
}

func (s *Server) CreateGroup(_ context.Context, req *keepassgov1.CreateGroupRequest) (*keepassgov1.CreateGroupResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	s.model.CreateGroup(req.GetParentPath(), req.GetName())
	s.dirty = true
	return &keepassgov1.CreateGroupResponse{}, nil
}

func (s *Server) RenameGroup(_ context.Context, req *keepassgov1.RenameGroupRequest) (*keepassgov1.RenameGroupResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	if err := s.model.RenameGroup(req.GetPath(), req.GetNewName()); err != nil {
		if errors.Is(err, vault.ErrEntryNotFound) {
			return nil, status.Error(codes.NotFound, err.Error())
		}
		return nil, status.Errorf(codes.Internal, "rename group: %v", err)
	}

	s.dirty = true
	return &keepassgov1.RenameGroupResponse{}, nil
}

func (s *Server) UpsertEntry(_ context.Context, req *keepassgov1.UpsertEntryRequest) (*keepassgov1.UpsertEntryResponse, error) {
	if req.GetEntry() == nil {
		return nil, status.Error(codes.InvalidArgument, "missing entry")
	}

	entry := entryFromProto(req.GetEntry())

	s.mu.Lock()
	if s.locked {
		s.mu.Unlock()
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}
	s.model.UpsertEntry(entry)
	s.dirty = true
	s.mu.Unlock()

	return &keepassgov1.UpsertEntryResponse{Entry: entryToProto(entry)}, nil
}

func (s *Server) DeleteEntry(_ context.Context, req *keepassgov1.DeleteEntryRequest) (*keepassgov1.DeleteEntryResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	if err := s.model.DeleteEntry(req.GetId()); err != nil {
		if errors.Is(err, vault.ErrEntryNotFound) {
			return nil, status.Error(codes.NotFound, err.Error())
		}
		return nil, status.Errorf(codes.Internal, "delete entry: %v", err)
	}

	s.dirty = true
	return &keepassgov1.DeleteEntryResponse{}, nil
}

func (s *Server) RestoreEntry(_ context.Context, req *keepassgov1.RestoreEntryRequest) (*keepassgov1.RestoreEntryResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	var restored vault.Entry
	for _, entry := range s.model.RecycleBin {
		if entry.ID == req.GetId() {
			restored = entry
			break
		}
	}

	if err := s.model.RestoreEntry(req.GetId()); err != nil {
		if errors.Is(err, vault.ErrEntryNotFound) {
			return nil, status.Error(codes.NotFound, err.Error())
		}
		return nil, status.Errorf(codes.Internal, "restore entry: %v", err)
	}

	s.dirty = true
	return &keepassgov1.RestoreEntryResponse{Entry: entryToProto(restored)}, nil
}

func (s *Server) ListEntryHistory(_ context.Context, req *keepassgov1.ListEntryHistoryRequest) (*keepassgov1.ListEntryHistoryResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry, err := findEntryByID(s.model, req.GetId())
	if err != nil {
		return nil, status.Error(codes.NotFound, err.Error())
	}

	resp := &keepassgov1.ListEntryHistoryResponse{
		Entries: make([]*keepassgov1.Entry, 0, len(entry.History)),
	}
	for _, historical := range entry.History {
		resp.Entries = append(resp.Entries, entryToProto(historical))
	}
	return resp, nil
}

func (s *Server) RestoreEntryHistory(_ context.Context, req *keepassgov1.RestoreEntryHistoryRequest) (*keepassgov1.RestoreEntryHistoryResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	if err := s.model.RestoreEntryVersion(req.GetId(), int(req.GetHistoryIndex())); err != nil {
		if errors.Is(err, vault.ErrEntryNotFound) {
			return nil, status.Error(codes.NotFound, err.Error())
		}
		return nil, status.Errorf(codes.Internal, "restore entry history: %v", err)
	}

	entry, err := findEntryByID(s.model, req.GetId())
	if err != nil {
		return nil, status.Error(codes.NotFound, err.Error())
	}
	s.dirty = true
	return &keepassgov1.RestoreEntryHistoryResponse{Entry: entryToProto(entry)}, nil
}

func (s *Server) ListTemplates(_ context.Context, _ *keepassgov1.ListTemplatesRequest) (*keepassgov1.ListTemplatesResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	resp := &keepassgov1.ListTemplatesResponse{
		Templates: make([]*keepassgov1.Entry, 0, len(s.model.Templates)),
	}
	for _, template := range s.model.Templates {
		resp.Templates = append(resp.Templates, entryToProto(template))
	}

	return resp, nil
}

func (s *Server) UpsertTemplate(_ context.Context, req *keepassgov1.UpsertTemplateRequest) (*keepassgov1.UpsertTemplateResponse, error) {
	if req.GetTemplate() == nil {
		return nil, status.Error(codes.InvalidArgument, "missing template")
	}

	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry := entryFromProto(req.GetTemplate())
	s.model.UpsertTemplate(entry)
	s.dirty = true

	return &keepassgov1.UpsertTemplateResponse{Template: entryToProto(entry)}, nil
}

func (s *Server) DeleteTemplate(_ context.Context, req *keepassgov1.DeleteTemplateRequest) (*keepassgov1.DeleteTemplateResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	if err := s.model.DeleteTemplate(req.GetId()); err != nil {
		if errors.Is(err, vault.ErrEntryNotFound) {
			return nil, status.Error(codes.NotFound, err.Error())
		}
		return nil, status.Errorf(codes.Internal, "delete template: %v", err)
	}
	s.dirty = true

	return &keepassgov1.DeleteTemplateResponse{}, nil
}

func (s *Server) InstantiateTemplate(_ context.Context, req *keepassgov1.InstantiateTemplateRequest) (*keepassgov1.InstantiateTemplateResponse, error) {
	if req.GetOverrides() == nil {
		return nil, status.Error(codes.InvalidArgument, "missing overrides")
	}

	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry, err := s.model.InstantiateTemplate(req.GetTemplateId(), entryFromProto(req.GetOverrides()))
	if err != nil {
		if errors.Is(err, vault.ErrEntryNotFound) {
			return nil, status.Error(codes.NotFound, err.Error())
		}
		return nil, status.Errorf(codes.Internal, "instantiate template: %v", err)
	}

	s.dirty = true
	return &keepassgov1.InstantiateTemplateResponse{Entry: entryToProto(entry)}, nil
}

func (s *Server) ListAttachments(_ context.Context, req *keepassgov1.ListAttachmentsRequest) (*keepassgov1.ListAttachmentsResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry, err := findEntryByID(s.model, req.GetEntryId())
	if err != nil {
		return nil, status.Error(codes.NotFound, err.Error())
	}

	names := make([]string, 0, len(entry.Attachments))
	for name := range entry.Attachments {
		names = append(names, name)
	}
	slices.Sort(names)

	return &keepassgov1.ListAttachmentsResponse{Names: names}, nil
}

func (s *Server) UploadAttachment(_ context.Context, req *keepassgov1.UploadAttachmentRequest) (*keepassgov1.UploadAttachmentResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry, index, err := findMutableEntryByID(&s.model, req.GetEntryId())
	if err != nil {
		return nil, status.Error(codes.NotFound, err.Error())
	}

	if entry.Attachments == nil {
		entry.Attachments = map[string][]byte{}
	}
	entry.Attachments[req.GetName()] = append([]byte(nil), req.GetContent()...)
	s.model.Entries[index] = entry
	s.dirty = true

	return &keepassgov1.UploadAttachmentResponse{}, nil
}

func (s *Server) DownloadAttachment(_ context.Context, req *keepassgov1.DownloadAttachmentRequest) (*keepassgov1.DownloadAttachmentResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry, err := findEntryByID(s.model, req.GetEntryId())
	if err != nil {
		return nil, status.Error(codes.NotFound, err.Error())
	}

	content, ok := entry.Attachments[req.GetName()]
	if !ok {
		return nil, status.Error(codes.NotFound, "attachment not found")
	}

	return &keepassgov1.DownloadAttachmentResponse{
		Content: append([]byte(nil), content...),
	}, nil
}

func (s *Server) DeleteAttachment(_ context.Context, req *keepassgov1.DeleteAttachmentRequest) (*keepassgov1.DeleteAttachmentResponse, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	entry, index, err := findMutableEntryByID(&s.model, req.GetEntryId())
	if err != nil {
		return nil, status.Error(codes.NotFound, err.Error())
	}

	if _, ok := entry.Attachments[req.GetName()]; !ok {
		return nil, status.Error(codes.NotFound, "attachment not found")
	}

	delete(entry.Attachments, req.GetName())
	if len(entry.Attachments) == 0 {
		entry.Attachments = nil
	}
	s.model.Entries[index] = entry
	s.dirty = true

	return &keepassgov1.DeleteAttachmentResponse{}, nil
}

func (s *Server) CopyEntryField(_ context.Context, req *keepassgov1.CopyEntryFieldRequest) (*keepassgov1.CopyEntryFieldResponse, error) {
	s.mu.RLock()
	model := s.model
	locked := s.locked
	s.mu.RUnlock()

	if locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	service := clipboard.Service{Writer: s.clipboard}
	if err := service.Copy(model, req.GetId(), clipboard.Target(req.GetTarget())); err != nil {
		switch {
		case errors.Is(err, vault.ErrEntryNotFound):
			return nil, status.Error(codes.NotFound, err.Error())
		case errors.Is(err, clipboard.ErrUnsupportedTarget):
			return nil, status.Error(codes.InvalidArgument, err.Error())
		default:
			return nil, status.Errorf(codes.Internal, "copy entry field: %v", err)
		}
	}

	return &keepassgov1.CopyEntryFieldResponse{}, nil
}

func (s *Server) GeneratePassword(_ context.Context, req *keepassgov1.GeneratePasswordRequest) (*keepassgov1.GeneratePasswordResponse, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	if s.locked {
		return nil, status.Error(codes.FailedPrecondition, "vault is locked")
	}

	profile, ok := s.profiles[req.GetProfile()]
	if !ok {
		return nil, status.Errorf(codes.InvalidArgument, "unknown password profile %q", req.GetProfile())
	}

	password, err := passwords.Generate(profile)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "generate password: %v", err)
	}

	return &keepassgov1.GeneratePasswordResponse{Password: password}, nil
}

func entryToProto(entry vault.Entry) *keepassgov1.Entry {
	return &keepassgov1.Entry{
		Id:       entry.ID,
		Title:    entry.Title,
		Username: entry.Username,
		Password: entry.Password,
		Url:      entry.URL,
		Notes:    entry.Notes,
		Tags:     append([]string(nil), entry.Tags...),
		Path:     append([]string(nil), entry.Path...),
	}
}

func entryFromProto(entry *keepassgov1.Entry) vault.Entry {
	return vault.Entry{
		ID:       entry.GetId(),
		Title:    entry.GetTitle(),
		Username: entry.GetUsername(),
		Password: entry.GetPassword(),
		URL:      entry.GetUrl(),
		Notes:    entry.GetNotes(),
		Tags:     append([]string(nil), entry.GetTags()...),
		Path:     append([]string(nil), entry.GetPath()...),
	}
}

func findEntryByID(model vault.Model, id string) (vault.Entry, error) {
	for _, entry := range model.Entries {
		if entry.ID == id {
			return entry, nil
		}
	}
	return vault.Entry{}, vault.ErrEntryNotFound
}

func findMutableEntryByID(model *vault.Model, id string) (vault.Entry, int, error) {
	for i, entry := range model.Entries {
		if entry.ID == id {
			entry.Attachments = maps.Clone(entry.Attachments)
			return entry, i, nil
		}
	}
	return vault.Entry{}, -1, vault.ErrEntryNotFound
}

func BearerTokenInterceptor(expectedToken string) grpc.UnaryServerInterceptor {
	return func(
		ctx context.Context,
		req any,
		info *grpc.UnaryServerInfo,
		handler grpc.UnaryHandler,
	) (any, error) {
		md, ok := metadata.FromIncomingContext(ctx)
		if !ok {
			return nil, status.Error(codes.Unauthenticated, "missing metadata")
		}

		values := md.Get("authorization")
		if len(values) == 0 {
			return nil, status.Error(codes.Unauthenticated, "missing authorization")
		}

		if values[0] != "Bearer "+expectedToken {
			return nil, status.Error(codes.Unauthenticated, "invalid bearer token")
		}

		return handler(ctx, req)
	}
}