Package new assets-builder' artefacts using meta tree (#381)

* fix assets-plan index - wrong for dev

* package new assets-artifacts

* fix "Assets artifacts not found" for crates without assets 🤦🏻‍♂️

* clean up

cargo/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cargo-playdate"
-version = "0.5.0-beta.4"
+version = "0.5.0-beta.5"
 readme = "README.md"
 description = "Build tool for neat yellow console."
 keywords = ["playdate", "build", "cargo", "plugin", "cargo-subcommand"]
@@ -43,7 +43,7 @@ toml.workspace = true
 toml_edit = { version = "0.22", features = ["serde"] }
 regex.workspace = true
 byteorder = "1.5"
-zip = { version = "1.1", features = ["time"] }
+zip = { version = "2.1", features = ["time"] }
 walkdir = "2.5"
 
 anyhow = "1.0"

cargo/src/assets/cache.rs

@@ -0,0 +1,60 @@
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use cargo::CargoResult;
+use playdate::assets::plan::BuildPlan;
+
+pub struct PlanCache {
+	pub difference: Difference,
+	pub serialized: Option<String>,
+	pub path: PathBuf,
+}
+
+
+#[derive(Debug, Clone, Copy, serde::Serialize)]
+pub enum Difference {
+	Same,
+	Different,
+	/// There is not cache file.
+	Missing,
+}
+
+impl Difference {
+	pub fn is_same(&self) -> bool { matches!(self, Self::Same) }
+}
+
+
+#[must_use = "Cached plan must be used"]
+pub fn plan_cache(path: PathBuf, plan: &BuildPlan<'_, '_>) -> CargoResult<PlanCache> {
+	let mut serializable = plan.iter_flatten_meta().collect::<Vec<_>>();
+	serializable.sort();
+
+	#[derive(serde::Serialize)]
+	struct SerializablePlan<'t> {
+		items: &'t [(playdate::assets::plan::MappingKind, PathBuf, (PathBuf, Option<std::time::SystemTime>))],
+		env: &'t BTreeMap<String, String>,
+	}
+
+	let serializable = SerializablePlan { items: &serializable,
+	                                      env: plan.used_env_vars() };
+	let json = serde_json::to_string(&serializable)?;
+
+	let difference = if path.try_exists()? {
+		if std::fs::read_to_string(&path)? == json {
+			log::debug!("Cached plan is the same");
+			Difference::Same
+		} else {
+			log::debug!("Cache mismatch, need diff & rebuild");
+			Difference::Different
+		}
+	} else {
+		log::debug!("Cache mismatch, full rebuilding");
+		Difference::Missing
+	};
+
+	let serialized = (!difference.is_same()).then_some(json);
+
+	Ok(PlanCache { path,
+	               difference,
+	               serialized })
+}