feat(picker): add argument-position mask to tag phase

Pass a mutable mask to tag functions so Pickable implementations can
detect which argument positions have already been claimed by other
Pickables during the same parsing pass

2 files changed, 15 insertions, 3 deletions

diff --git a/mingling_picker/src/pickable.rs b/mingling_picker/src/pickable.rs
index 808830c..3f86745 100644
--- a/mingling_picker/src/pickable.rs
+++ b/mingling_picker/src/pickable.rs
@@ -78,4 +78,10 @@ pub struct TagPhaseContext<'a> {
 
     /// A read-only list of all arguments in the current [`Picker`].
     pub args: &'a PickerArgs<'a>,
+
+    /// Mask indicating which argument positions have already been claimed.
+    ///
+    /// For example, if the mask is `[0, 0, 1, 0]`, then the argument at index `2`
+    /// has already been tagged by another `Pickable`.
+    pub mask: &'a [u8],
 }
diff --git a/mingling_picker/src/picker/parse.rs b/mingling_picker/src/picker/parse.rs
index f9a59d7..ec3c08c 100644
--- a/mingling_picker/src/picker/parse.rs
+++ b/mingling_picker/src/picker/parse.rs
@@ -36,7 +36,7 @@ internal_repeat!(1..=32 => {
                     PickerFlagAttr,
 
                     // Tag Func
-                    Box<dyn FnOnce(&PickerArgs<'a>) -> Vec<usize>>,
+                    Box<dyn FnOnce(&PickerArgs<'a>, &[u8]) -> Vec<usize>>,
 
                     // Pick Func
                     Box<dyn FnOnce(&[&str], &mut Option<Route>)>,
@@ -51,10 +51,11 @@ internal_repeat!(1..=32 => {
                         T$::get_attr(self.flag_$),
 
                         // Tag Func
-                        Box::new(|args| {
+                        Box::new(|args, mask| {
                             let ctx = TagPhaseContext {
                                 arg_info: &arg_infos[$],
                                 args,
+                                mask
                             };
                             T$::tag(ctx)
                         }),
@@ -104,11 +105,16 @@ internal_repeat!(1..=32 => {
             // Parsing
             for (_, tag_func, pick_func, _idx) in bundle {
 
+                // Mask
+                let mut mask: Vec<u8> = vec![0u8; $];
+
                 // Tag phase
-                let tagged = tag_func(&self.args);
+                let tagged = tag_func(&self.args, mask.as_slice());
                 let mut args_to_pick: Vec<&str> = vec![];
 
                 for i in tagged {
+                    mask[i] = 1;
+
                     // Update args to pick
                     args_to_pick.push(self.args.get(i).unwrap_or_default());
                 }