package path

import (
	"github.com/pkg/errors"
)

var ErrorUnknownService = errors.New("unknown service string")

// ServiceType denotes what service the path corresponds to. Metadata services
// are also included though they are only used for paths that house metadata for
// Corso backups.
//
// Metadata services are not considered valid service types for resource paths
// though they can be used for metadata paths.
//
// The order of the enums below can be changed, but the string representation of
// each enum must remain the same or migration code needs to be added to handle
// changes to the string format.
type ServiceType int

//go:generate stringer -type=ServiceType -linecomment
const (
	UnknownService            ServiceType = iota
	ExchangeService                       // exchange
	OneDriveService                       // onedrive
	SharePointService                     // sharepoint
	ExchangeMetadataService               // exchangeMetadata
	OneDriveMetadataService               // onedriveMetadata
	SharePointMetadataService             // sharepointMetadata
)

func toServiceType(service string) ServiceType {
	switch service {
	case ExchangeService.String():
		return ExchangeService
	case OneDriveService.String():
		return OneDriveService
	case SharePointService.String():
		return SharePointService
	case ExchangeMetadataService.String():
		return ExchangeMetadataService
	case OneDriveMetadataService.String():
		return OneDriveMetadataService
	case SharePointMetadataService.String():
		return SharePointMetadataService
	default:
		return UnknownService
	}
}

var ErrorUnknownCategory = errors.New("unknown category string")

// CategoryType denotes what category of data the path corresponds to. The order
// of the enums below can be changed, but the string representation of each enum
// must remain the same or migration code needs to be added to handle changes to
// the string format.
type CategoryType int

//go:generate stringer -type=CategoryType -linecomment
const (
	UnknownCategory   CategoryType = iota
	EmailCategory                  // email
	ContactsCategory               // contacts
	EventsCategory                 // events
	FilesCategory                  // files
	ListsCategory                  // lists
	LibrariesCategory              // libraries
	PagesCategory                  // pages
	DetailsCategory                // details
)

func ToCategoryType(category string) CategoryType {
	switch category {
	case EmailCategory.String():
		return EmailCategory
	case ContactsCategory.String():
		return ContactsCategory
	case EventsCategory.String():
		return EventsCategory
	case FilesCategory.String():
		return FilesCategory
	case LibrariesCategory.String():
		return LibrariesCategory
	case ListsCategory.String():
		return ListsCategory
	case PagesCategory.String():
		return PagesCategory
	case DetailsCategory.String():
		return DetailsCategory
	default:
		return UnknownCategory
	}
}

// serviceCategories is a mapping of all valid service/category pairs for
// non-metadata paths.
var serviceCategories = map[ServiceType]map[CategoryType]struct{}{
	ExchangeService: {
		EmailCategory:    {},
		ContactsCategory: {},
		EventsCategory:   {},
	},
	OneDriveService: {
		FilesCategory: {},
	},
	SharePointService: {
		LibrariesCategory: {},
		ListsCategory:     {},
		PagesCategory:     {},
	},
}

func validateServiceAndCategoryStrings(s, c string) (ServiceType, CategoryType, error) {
	service := toServiceType(s)
	if service == UnknownService {
		return UnknownService, UnknownCategory, errors.Wrapf(ErrorUnknownService, "%q", s)
	}

	category := ToCategoryType(c)
	if category == UnknownCategory {
		return UnknownService, UnknownCategory, errors.Wrapf(ErrorUnknownCategory, "%q", c)
	}

	if err := validateServiceAndCategory(service, category); err != nil {
		return UnknownService, UnknownCategory, err
	}

	return service, category, nil
}

func validateServiceAndCategory(service ServiceType, category CategoryType) error {
	cats, ok := serviceCategories[service]
	if !ok {
		return errors.New("unsupported service")
	}

	if _, ok := cats[category]; !ok {
		return errors.Errorf(
			"unknown service/category combination %q/%q",
			service,
			category,
		)
	}

	return nil
}

// dataLayerResourcePath allows callers to extract information from a
// resource-specific path. This struct is unexported so that callers are
// forced to use the pre-defined constructors, making it impossible to create a
// dataLayerResourcePath with invalid service/category combinations.
//
// All dataLayerResourcePaths start with the same prefix:
// <tenant ID>/<service>/<resource owner ID>/<category>
// which allows extracting high-level information from the path. The path
// elements after this prefix represent zero or more folders and, if the path
// refers to a file or item, an item ID. A valid dataLayerResourcePath must have
// at least one folder or an item so that the resulting path has at least one
// element after the prefix.
type dataLayerResourcePath struct {
	Builder
	category CategoryType
	service  ServiceType
	hasItem  bool
}

// Tenant returns the tenant ID embedded in the dataLayerResourcePath.
func (rp dataLayerResourcePath) Tenant() string {
	return rp.Builder.elements[0]
}

// Service returns the ServiceType embedded in the dataLayerResourcePath.
func (rp dataLayerResourcePath) Service() ServiceType {
	return rp.service
}

// Category returns the CategoryType embedded in the dataLayerResourcePath.
func (rp dataLayerResourcePath) Category() CategoryType {
	return rp.category
}

// ResourceOwner returns the user ID or group ID embedded in the
// dataLayerResourcePath.
func (rp dataLayerResourcePath) ResourceOwner() string {
	return rp.Builder.elements[2]
}

func (rp dataLayerResourcePath) lastFolderIdx() int {
	endIdx := len(rp.Builder.elements)

	if rp.hasItem {
		endIdx--
	}

	return endIdx
}

// Folder returns the folder segment embedded in the dataLayerResourcePath.
func (rp dataLayerResourcePath) Folder() string {
	endIdx := rp.lastFolderIdx()
	if endIdx == 4 {
		return ""
	}

	return rp.Builder.join(4, endIdx)
}

// Folders returns the individual folder elements embedded in the
// dataLayerResourcePath.
func (rp dataLayerResourcePath) Folders() []string {
	endIdx := rp.lastFolderIdx()
	if endIdx == 4 {
		return nil
	}

	return append([]string{}, rp.elements[4:endIdx]...)
}

// Item returns the item embedded in the dataLayerResourcePath if the path
// refers to an item.
func (rp dataLayerResourcePath) Item() string {
	if rp.hasItem {
		return rp.Builder.elements[len(rp.Builder.elements)-1]
	}

	return ""
}

func (rp dataLayerResourcePath) Dir() (Path, error) {
	if len(rp.elements) <= 4 {
		return nil, errors.Errorf("unable to shorten path %q", rp)
	}

	return &dataLayerResourcePath{
		Builder:  *rp.Builder.Dir(),
		service:  rp.service,
		category: rp.category,
		hasItem:  false,
	}, nil
}

func (rp dataLayerResourcePath) Append(
	element string,
	isItem bool,
) (Path, error) {
	if rp.hasItem {
		return nil, errors.New("appending to an item path")
	}

	return &dataLayerResourcePath{
		Builder:  *rp.Builder.Append(element),
		service:  rp.service,
		category: rp.category,
		hasItem:  isItem,
	}, nil
}

func (rp dataLayerResourcePath) ToBuilder() *Builder {
	// Safe to directly return the Builder because Builders are immutable.
	return &rp.Builder
}