controller

const (
	// Not an error; returned on success
	//
	// HTTP Mapping: 200 OK
	Ok HTTPCode = iota

	// The operation was cancelled, typically by the caller.
	//
	// HTTP Mapping: 499 Client Closed Request
	Cancelled

	// Unknown error.  For example, this error may be returned when
	// a `Status` value received from another address space belongs to
	// an error space that is not known in this address space.  Also
	// errors raised by APIs that do not return enough error information
	// may be converted to this error.
	//
	// HTTP Mapping: 500 Internal Server Error
	Unknown

	// The client specified an invalid argument.  Note that this differs
	// from `FAILED_PRECONDITION`.  `INVALID_ARGUMENT` indicates arguments
	// that are problematic regardless of the state of the system
	// (e.g., a malformed file name).
	//
	// HTTP Mapping: 400 Bad Request
	InvalidArgument

	// The deadline expired before the operation could complete. For operations
	// that change the state of the system, this error may be returned
	// even if the operation has completed successfully.  For example, a
	// successful response from a server could have been delayed long
	// enough for the deadline to expire.
	//
	// HTTP Mapping: 504 Gateway Timeout
	DeadlineExceeded

	// Some requested entity (e.g., file or directory) was not found.
	//
	// Note to server developers: if a request is denied for an entire class
	// of users, such as gradual feature rollout or undocumented whitelist,
	// `NOT_FOUND` may be used. If a request is denied for some users within
	// a class of users, such as user-based access control, `PERMISSION_DENIED`
	// must be used.
	//
	// HTTP Mapping: 404 Not Found
	NotFound

	// The entity that a client attempted to create (e.g., file or directory)
	// already exists.
	//
	// HTTP Mapping: 409 Conflict
	AlreadyExists

	// The caller does not have permission to execute the specified
	// operation. `PERMISSION_DENIED` must not be used for rejections
	// caused by exhausting some resource (use `RESOURCE_EXHAUSTED`
	// instead for those errors). `PERMISSION_DENIED` must not be
	// used if the caller can not be identified (use `UNAUTHENTICATED`
	// instead for those errors). This error code does not imply the
	// request is valid or the requested entity exists or satisfies
	// other pre-conditions.
	//
	// HTTP Mapping: 403 Forbidden
	PermissionDenied

	// The request does not have valid authentication credentials for the
	// operation.
	//
	// HTTP Mapping: 401 Unauthorized
	Unauthenticated

	// Some resource has been exhausted, perhaps a per-user quota, or
	// perhaps the entire file system is out of space.
	//
	// HTTP Mapping: 429 Too Many Requests
	ResourceExhausted

	// The operation was rejected because the system is not in a state
	// required for the operation's execution.  For example, the directory
	// to be deleted is non-empty, an rmdir operation is applied to
	// a non-directory, etc.
	//
	// Service implementors can use the following guidelines to decide
	// between `FAILED_PRECONDITION`, `ABORTED`, and `UNAVAILABLE`:
	//  (a) Use `UNAVAILABLE` if the client can retry just the failing call.
	//  (b) Use `ABORTED` if the client should retry at a higher level
	//      (e.g., when a client-specified test-and-set fails, indicating the
	//      client should restart a read-modify-write sequence).
	//  (c) Use `FAILED_PRECONDITION` if the client should not retry until
	//      the system state has been explicitly fixed.  E.g., if an "rmdir"
	//      fails because the directory is non-empty, `FAILED_PRECONDITION`
	//      should be returned since the client should not retry unless
	//      the files are deleted from the directory.
	//
	// HTTP Mapping: 400 Bad Request
	FailedPrecondition

	// The operation was aborted, typically due to a concurrency issue such as
	// a sequencer check failure or transaction abort.
	//
	// See the guidelines above for deciding between `FAILED_PRECONDITION`,
	// `ABORTED`, and `UNAVAILABLE`.
	//
	// HTTP Mapping: 409 Conflict
	Aborted

	// The operation was attempted past the valid range.  E.g., seeking or
	// reading past end-of-file.
	//
	// Unlike `INVALID_ARGUMENT`, this error indicates a problem that may
	// be fixed if the system state changes. For example, a 32-bit file
	// system will generate `INVALID_ARGUMENT` if asked to read at an
	// offset that is not in the range [0,2^32-1], but it will generate
	// `OUT_OF_RANGE` if asked to read from an offset past the current
	// file size.
	//
	// There is a fair bit of overlap between `FAILED_PRECONDITION` and
	// `OUT_OF_RANGE`.  We recommend using `OUT_OF_RANGE` (the more specific
	// error) when it applies so that callers who are iterating through
	// a space can easily look for an `OUT_OF_RANGE` error to detect when
	// they are done.
	//
	// HTTP Mapping: 400 Bad Request
	OutOfRange

	// The operation is not implemented or is not supported/enabled in this
	// service.
	//
	// HTTP Mapping: 501 Not Implemented
	Unimplemented

	// Internal errors.  This means that some invariants expected by the
	// underlying system have been broken.  This error code is reserved
	// for serious errors.
	//
	// HTTP Mapping: 500 Internal Server Error
	Internal

	// The service is currently unavailable.  This is most likely a
	// transient condition, which can be corrected by retrying with
	// a backoff. Note that it is not always safe to retry
	// non-idempotent operations.
	//
	// See the guidelines above for deciding between `FAILED_PRECONDITION`,
	// `ABORTED`, and `UNAVAILABLE`.
	//
	// HTTP Mapping: 503 Service Unavailable
	Unavailable

	// Unrecoverable data loss or corruption.
	//
	// HTTP Mapping: 500 Internal Server Error
	DataLoss
)

const (
	RecentOrder  Order = "recent"
	PopularOrder       = "count"
)