package dag import ( "github.com/MichaelMure/git-bug/entity" "github.com/MichaelMure/git-bug/identity" ) // Operation is a piece of data defining a change to reflect on the state of an Entity. // What this Operation or Entity's state looks like is not of the resort of this package as it only deals with the // data structure and storage. type Operation interface { // Id return the Operation identifier // // Some care need to be taken to define a correct Id derivation and enough entropy in the data used to avoid // collisions. Notably: // - the Id of the first Operation will be used as the Id of the Entity. Collision need to be avoided across entities // of the same type (example: no collision within the "bug" namespace). // - collisions can also happen within the set of Operations of an Entity. Simple Operation might not have enough // entropy to yield unique Ids (example: two "close" operation within the same second, same author). // If this is a concern, it is recommended to include a piece of random data in the operation's data, to guarantee // a minimal amount of entropy and avoid collision. // // Author's note: I tried to find a clever way around that inelegance (stuffing random useless data into the stored // structure is not exactly elegant) but I failed to find a proper way. Essentially, anything that would reuse some // other data (parent operation's Id, lamport clock) or the graph structure (depth) impose that the Id would only // make sense in the context of the graph and yield some deep coupling between Entity and Operation. This in turn // make the whole thing even less elegant. // // A common way to derive an Id will be to use the entity.DeriveId() function on the serialized operation data. Id() entity.Id // Validate check if the Operation data is valid Validate() error // Author returns the author of this operation Author() identity.Interface }