syntax = "proto3";

package cosmos.app.v1alpha1;

import "google/protobuf/descriptor.proto";

extend google.protobuf.MessageOptions {
  // module indicates that this proto type is a config object for an app module
  // and optionally provides other descriptive information about the module.
  // It is recommended that a new module config object and go module is versioned
  // for every state machine breaking version of a module. The recommended
  // pattern for doing this is to put module config objects in a separate proto
  // package from the API they expose. Ex: the cosmos.group.v1 API would be
  // exposed by module configs cosmos.group.module.v1, cosmos.group.module.v2, etc.
  ModuleDescriptor module = 57193479;
}

// ModuleDescriptor describes an app module.
message ModuleDescriptor {
  // go_import names the package that should be imported by an app to load the
  // module in the runtime module registry. It is required to make debugging
  // of configuration errors easier for users.
  string go_import = 1;

  // use_package refers to a protobuf package that this module
  // uses and exposes to the world. In an app, only one module should "use"
  // or own a single protobuf package. It is assumed that the module uses
  // all of the .proto files in a single package.
  repeated PackageReference use_package = 2;

  // can_migrate_from defines which module versions this module can migrate
  // state from. The framework will check that one module version is able to
  // migrate from a previous module version before attempting to update its
  // config. It is assumed that modules can transitively migrate from earlier
  // versions. For instance if v3 declares it can migrate from v2, and v2
  // declares it can migrate from v1, the framework knows how to migrate
  // from v1 to v3, assuming all 3 module versions are registered at runtime.
  repeated MigrateFromInfo can_migrate_from = 3;
}

// PackageReference is a reference to a protobuf package used by a module.
message PackageReference {
  // name is the fully-qualified name of the package.
  string name = 1;

  // revision is the optional revision of the package that is being used.
  // Protobuf packages used in Cosmos should generally have a major version
  // as the last part of the package name, ex. foo.bar.baz.v1.
  // The revision of a package can be thought of as the minor version of a
  // package which has additional backwards compatible definitions that weren't
  // present in a previous version.
  //
  // A package should indicate its revision with a source code comment
  // above the package declaration in one of its files containing the
  // text "Revision N" where N is an integer revision. All packages start
  // at revision 0 the first time they are released in a module.
  //
  // When a new version of a module is released and items are added to existing
  // .proto files, these definitions should contain comments of the form
  // "Since: Revision N" where N is an integer revision.
  //
  // When the module runtime starts up, it will check the pinned proto
  // image and panic if there are runtime protobuf definitions that are not
  // in the pinned descriptor which do not have
  // a "Since Revision N" comment or have a "Since Revision N" comment where
  // N is <= to the revision specified here. This indicates that the protobuf
  // files have been updated, but the pinned file descriptor hasn't.
  //
  // If there are items in the pinned file descriptor with a revision
  // greater than the value indicated here, this will also cause a panic
  // as it may mean that the pinned descriptor for a legacy module has been
  // improperly updated or that there is some other versioning discrepancy.
  // Runtime protobuf definitions will also be checked for compatibility
  // with pinned file descriptors to make sure there are no incompatible changes.
  //
  // This behavior ensures that:
  // * pinned proto images are up-to-date
  // * protobuf files are carefully annotated with revision comments which
  //   are important good client UX
  // * protobuf files are changed in backwards and forwards compatible ways
  uint32 revision = 2;
}

// MigrateFromInfo is information on a module version that a newer module
// can migrate from.
message MigrateFromInfo {

  // module is the fully-qualified protobuf name of the module config object
  // for the previous module version, ex: "cosmos.group.module.v1.Module".
  string module = 1;
}
