internal/pipewire: implement Core::Destroy

This change also implements pending destructible check on Sync. Destruction method should always be implemented as a wrapper of destructible.destroy.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pipewire/core.go

@@ -382,6 +382,41 @@ func (s *removable) mustCheckDestroy() {
 	}
 }
 
+// destructible is embedded by proxies that can be targeted by the [CoreRemoveId] event and the
+// [CoreDestroy] method and requires no cleanup. destructible purposefully does not override
+// removable.mustCheckDestroy because it is used by unexported methods called during event handling
+// and are exempt from the destruction check.
+type destructible struct {
+	destroyed bool
+
+	removable
+}
+
+// checkDestroy overrides removable.checkDestroy to also check the destroyed field.
+func (s *destructible) checkDestroy() error {
+	if s.destroyed {
+		return ErrProxyDestroyed
+	}
+	if err := s.removable.checkDestroy(); err != nil {
+		return err
+	}
+	return nil
+}
+
+// destroy calls removable.checkDestroy then queues a [CoreDestroy] event if it succeeds.
+func (s *destructible) destroy(ctx *Context, id Int) error {
+	if err := s.checkDestroy(); err != nil {
+		return err
+	}
+	l := len(ctx.pendingDestruction)
+	ctx.pendingDestruction[id] = struct{}{}
+	if len(ctx.pendingDestruction) != l+1 {
+		return ErrProxyDestroyed
+	}
+	s.destroyed = true
+	return ctx.GetCore().destroy(id)
+}
+
 // An InconsistentIdError describes an inconsistent state where the server claims an impossible
 // proxy or global id. This is only generated by the [CoreBoundProps] event.
 type InconsistentIdError struct {
@@ -504,6 +539,10 @@ func (core *Core) Sync() error {
 		core.ctx.closeReceivedFiles()
 		return &ProxyFatalError{Err: UnacknowledgedProxyError(slices.Collect(maps.Keys(core.ctx.pendingIds))), ProxyErrs: core.ctx.cloneAsProxyErrors()}
 	}
+	if len(core.ctx.pendingDestruction) != 0 {
+		core.ctx.closeReceivedFiles()
+		return &ProxyFatalError{Err: UnacknowledgedProxyDestructionError(slices.Collect(maps.Keys(core.ctx.pendingDestruction))), ProxyErrs: core.ctx.cloneAsProxyErrors()}
+	}
 	return core.ctx.doSyncComplete()
 }
 
@@ -624,6 +663,37 @@ func (core *Core) createObject(factoryName, typeName String, version Int, props
 	)
 }
 
+// CoreDestroy is sent when the client requests to destroy an object.
+type CoreDestroy struct {
+	// The proxy id of the object to destroy.
+	ID Int `json:"id"`
+}
+
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreDestroy) Opcode() byte { return PW_CORE_METHOD_DESTROY }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreDestroy) FileCount() Int { return 0 }
+
+// Size satisfies [KnownSize] with a constant value.
+func (c *CoreDestroy) Size() Word { return SizePrefix + Size(SizeInt) }
+
+// MarshalBinary satisfies [encoding.BinaryMarshaler] via [Marshal].
+func (c *CoreDestroy) MarshalBinary() ([]byte, error) { return Marshal(c) }
+
+// UnmarshalBinary satisfies [encoding.BinaryUnmarshaler] via [Unmarshal].
+func (c *CoreDestroy) UnmarshalBinary(data []byte) error { return Unmarshal(data, c) }
+
+// destroy queues a [CoreDestroy] message for the PipeWire server.
+// This is not safe to use directly, callers should use the exported method
+// on the proxy implementation instead.
+func (core *Core) destroy(id Int) error {
+	return core.ctx.writeMessage(
+		PW_ID_CORE,
+		&CoreDestroy{id},
+	)
+}
+
 // A RegistryGlobal event is emitted to notify a client about a new global object.
 type RegistryGlobal struct {
 	// The global id.
@@ -889,6 +959,8 @@ func (core *Core) consume(opcode byte, files []int, unmarshal func(v any)) error
 			panic(&UnknownProxyIdError[*CoreRemoveId]{Id: coreRemoveId.ID, Event: &coreRemoveId})
 		} else {
 			delete(core.ctx.proxy, coreRemoveId.ID)
+			// not always populated so this is not checked
+			delete(core.ctx.pendingDestruction, coreRemoveId.ID)
 			return proxy.remove()
 		}