syntax = "proto3";

package seen;
option go_package = "./proto;seen";
import "google/protobuf/timestamp.proto";

// Seen is a service to keep track of which resources a user has seen (read). For example, it can
// be used to keep track of what notifications have been seen by a user, or what messages they've 
// read in a chat.
service Seen {
	// Set a resource as seen by a user. If no timestamp is provided, the current time is used.
	rpc Set(SetRequest) returns (SetResponse);
	// Unset a resource as seen, used in cases where a user viewed a resource but wants to override
	// this so they remember to action it in the future, e.g. "Mark this as unread".
	rpc Unset(UnsetRequest) returns (UnsetResponse);
	// Read returns the timestamps at which various resources were seen by a user. If no timestamp
	// is returned for a given resource_id, it indicates that resource has not yet been seen by the 
	// user. 
	rpc Read(ReadRequest) returns (ReadResponse);
}

message Resource {
	string type = 1;
	string id = 2;
}

message SetRequest {
	string user_id = 1;
	string resource_type = 2;
	string resource_id = 3;
	google.protobuf.Timestamp timestamp = 4;
}

message SetResponse {}

message UnsetRequest {
	string user_id = 1;
	string resource_type = 2;
	string resource_id = 3;
}

message UnsetResponse {}

message ReadRequest {
	string user_id = 1;
	string resource_type = 2;
	repeated string resource_ids = 3;
}

message ReadResponse {
	map<string, google.protobuf.Timestamp> timestamps = 1;
}