syntax = "proto3";

package containerd.v1;

import "gogoproto/gogo.proto";
import "google/protobuf/timestamp.proto";
import "google/protobuf/empty.proto";

// Content provides access to a content addressable storage system.
service Content {
	// Info returns information about a committed object.
	//
	// This call can be used for getting the size of content and checking for
	// existence.
	rpc Info(InfoRequest) returns (InfoResponse);

	// Delete will delete the referenced object.
	rpc Delete(DeleteContentRequest) returns (google.protobuf.Empty);

	// Read allows one to read an object based on the offset into the content.
	//
	// The requested data may be returned in one or more messages.
	rpc Read(ReadRequest) returns (stream ReadResponse);

	// Status returns the status of ongoing object ingestions, started via
	// Write.
	//
	// For active ingestions, the status will be streamed until the client
	// closes the connection or all matched ingestions are committed.
	rpc Status(StatusRequest) returns (stream StatusResponse);

	// Write begins or resumes writes to a resource identified by a unique ref.
	// Only one active stream may exist at a time for each ref.
	//
	// Once a write stream has started, it may only write to a single ref, thus
	// once a stream is started, the ref may be ommitted on subsequent writes.
	//
	// For any write transaction represented by a ref, only a single write may
	// be made to a given offset. If overlapping writes occur, it is an error.
	// Writes should be sequential and implementations may throw an error if
	// this is required.
	//
	// If expected_digest is set and already part of the content store, the
	// write will fail.
	//
	// When completed, the commit flag should be set to true. If expected size
	// or digest is set, the content will be validated against those values.
	rpc Write(stream WriteRequest) returns (stream WriteResponse);
}

message InfoRequest {
	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
}

message InfoResponse {
	// Digest is the hash identity of the blob.
	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];

	// Size is the total number of bytes in the blob.
	int64 size = 2;

	// CommittedAt provides the time at which the blob was committed.
	google.protobuf.Timestamp committed_at = 3 [(gogoproto.stdtime) = true, (gogoproto.nullable) = false];
}

message DeleteContentRequest {
	// Digest specifies which content to delete.
	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
}

// ReadRequest defines the fields that make up a request to read a portion of
// data from a stored object.
message ReadRequest {
	// Digest is the hash identity to read.
	string digest = 1 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];

	// Offset specifies the number of bytes from the start at which to begin
	// the read. If zero or less, the read will be from the start. This uses
	// standard zero-indexed semantics.
	int64 offset = 2;

	// size is the total size of the read. If zero, the entire blob will be
	// returned by the service.
	int64 size = 3;
}

// ReadResponse carries byte data for a read request.
message ReadResponse {
	int64 offset = 1; // offset of the returned data
	bytes data = 2; // actual data
}


// WriteAction defines the behavior of a WriteRequest.
enum WriteAction {
	option (gogoproto.goproto_enum_prefix) = false;
	option (gogoproto.enum_customname) = "WriteAction";

	// WriteActionStat instructs the writer to return the current status while
	// holding the lock on the write.
	STAT = 0 [(gogoproto.enumvalue_customname) = "WriteActionStat"];

	// WriteActionWrite sets the action for the write request to write data.
	//
	// Any data included will be written at the provided offset. The
	// transaction will be left open for further writes.
	//
	// This is the default.
	WRITE = 1 [(gogoproto.enumvalue_customname) = "WriteActionWrite"];

	// WriteActionCommit will write any outstanding data in the message and
	// commit the write, storing it under the digest.
	//
	// This can be used in a single message to send the data, verify it and
	// commit it.
	//
	// This action will always terminate the write.
	COMMIT = 2 [(gogoproto.enumvalue_customname) = "WriteActionCommit"];

	// WriteActionAbort will release any resources associated with the write
	// and free up the ref for a completely new set of writes.
	//
	// This action will always terminate the write.
	ABORT = -1 [(gogoproto.enumvalue_customname) = "WriteActionAbort"];
}

// WriteRequest writes data to the request ref at offset. 
message WriteRequest {
	// Action sets the behavior of the write.
	//
	// When this is a write and the ref is not yet allocated, the ref will be
	// allocated and the data will be written at offset.
	//
	// If the action is write and the ref is allocated, it will accept data to
	// an offset that has not yet been written.
	//
	// If the action is write and there is no data, the current write status
	// will be returned. This works differently from status because the stream
	// holds a lock.
	WriteAction action = 1;

	// Ref identifies the pre-commit object to write to.
	string ref = 2;

	// Total can be set to have the service validate the total size of the
	// committed content.
	//
	// The latest value before or with the commit action message will be use to
	// validate the content. If the offset overflows total, the service may
	// report an error. It is only required on one message for the write.
	//
	// If the value is zero or less, no validation of the final content will be
	// performed.
	int64 total = 3;

	// Expected can be set to have the service validate the final content against
	// the provided digest.
	//
	// If the digest is already present in the object store, an AlreadyExists
	// error will be returned.
	//
	// Only the latest version will be used to check the content against the
	// digest. It is only required to include it on a single message, before or
	// with the commit action message.
	string expected = 4 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];

	// Offset specifies the number of bytes from the start at which to begin
	// the write. For most implementations, this means from the start of the
	// file. This uses standard, zero-indexed semantics.
	//
	// If the action is write, the remote may remove all previously written
	// data after the offset. Implementations may support arbitrary offsets but
	// MUST support reseting this value to zero with a write. If an
	// implementation does not support a write at a particular offset, an
	// OutOfRange error must be returned.
	int64 offset = 5;

	// Data is the actual bytes to be written.
	//
	// If this is empty and the message is not a commit, a response will be
	// returned with the current write state.
	bytes data = 6;
}

// WriteResponse is returned on the culmination of a write call.
message WriteResponse {
	// Action contains the action for the final message of the stream. A writer
	// should confirm that they match the intended result.
	WriteAction action = 1;

	// StartedAt provides the time at which the write began.
	//
	// This must be set for stat and commit write actions. All other write
	// actions may omit this.
	google.protobuf.Timestamp started_at = 2 [(gogoproto.stdtime) = true, (gogoproto.nullable) = false];

	// UpdatedAt provides the last time of a successful write.
	//
	// This must be set for stat and commit write actions. All other write
	// actions may omit this.
	google.protobuf.Timestamp updated_at = 3 [(gogoproto.stdtime) = true, (gogoproto.nullable) = false];

	// Offset is the current committed size for the write.
	int64 offset = 4;

	// Total provides the current, expected total size of the write.
	//
	// We include this to provide consistency with the Status structure on the
	// client writer.
	//
	// This is only valid on the Stat and Commit response.
	int64 total = 5;

	// Digest, if present, includes the digest up to the currently committed
	// bytes. If action is commit, this field will be set. It is implementation
	// defined if this is set for other actions, except abort. On abort, this
	// will be empty.
	string digest = 6 [(gogoproto.customtype) = "github.com/opencontainers/go-digest.Digest", (gogoproto.nullable) = false];
}

message StatusRequest {
	repeated string refs = 1;
	repeated string prefix = 2;
}

message StatusResponse {
	google.protobuf.Timestamp started_at = 1 [(gogoproto.stdtime) = true, (gogoproto.nullable) = false];
	google.protobuf.Timestamp updated_at = 2 [(gogoproto.stdtime) = true, (gogoproto.nullable) = false];
	string ref = 3;
	int64 offset = 4;
	int64 total = 5;
}