phase 2

CLAUDE.md

@@ -74,6 +74,22 @@ Certain things should cause the function to return `Err`:
 - Passing any flags but `-f` or `-i`
 - Not passing `-i` when the `$DRAWER_KEY` environment variable is undefined
 
+### Phase 2
+
+Phase 2 is about error handling. We want to add some variants to `DrawerError` and a `validate` method to `DrawerOperation`
+that will catch various problems and ensure that we can do the operation correctly. Here are some error cases in no particular order:
+
+- If the command is `Open` and the drawer file does not exist.
+- If the command is `Close` and the target path either does not exist, is not a directory, or is not readable.
+- If the `key` is `EnvVar` but the `$DRAWER_KEY` environment variable is not set, or is not set to a path that exists and is readable.
+- If the `key` is `Path()` but the path does not exist or is not readable.
+- If the command is `Open` and the target is a non-empty directory that exists, and the `force` flag is false
+- If the command is `Close` and the target contains the drawer file (at any level; the target is any parent of the drawer file's path)
+
+The `validate` method should take `&self` and return `Result<(), DrawerError>`. Let's have `main`, which is currently
+creating a `DrawerOperation` and not using it, also call `validate` and print out the error if there is one. This means
+we also need to `impl Display` on `DrawerError`.
+
 ## Commands
 
 ```bash