Add a parent to ParametersContext so we can chain parameters contexts for use with the select helper.

src/renderer/parameters_context.rs

@@ -21,6 +21,7 @@ use std::collections::HashMap;
 
 #[derive(Debug)]
 pub struct ParametersContext<'a> {
+    parent: Option<&'a ParametersContext<'a>>,
     params: HashMap<&'a str, (&'a RValue<'a>, Option<BreadcrumbTreeElement<'a>>)>,
 }
 
@@ -29,6 +30,7 @@ impl<'a> ParametersContext<'a> {
         renderer: &DustRenderer,
         breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
         params: &'a Vec<KVPair>,
+        parent: Option<&'a ParametersContext<'a>>,
     ) -> Self {
         // If the parameter is a Path, then we resolve it immediately
         // to a context element because those are resolved using the
@@ -60,12 +62,17 @@ impl<'a> ParametersContext<'a> {
                 .collect();
 
         ParametersContext {
+            parent: parent,
             params: rendered_params,
         }
     }
 
     pub fn contains_key(&self, segment: &str) -> bool {
         self.params.contains_key(segment)
+            || self
+                .parent
+                .map(|p| p.contains_key(segment))
+                .unwrap_or(false)
     }
 }
 
@@ -83,7 +90,11 @@ impl<'a> Walkable for ParametersContext<'a> {
     fn walk(&self, segment: &str) -> Result<&dyn IntoContextElement, WalkError> {
         match self.params.get(segment).map(|(_rvalue, bte)| bte) {
             Some(Some(bte)) => Ok(bte.borrow()),
-            _ => Err(WalkError::CantWalk),
+            Some(None) => Err(WalkError::CantWalk),
+            None => self
+                .parent
+                .map(|p| p.walk(segment))
+                .unwrap_or(Err(WalkError::CantWalk)),
         }
     }
 

src/renderer/renderer.rs

@@ -169,7 +169,8 @@ impl<'a> DustRenderer<'a> {
                 }
             }
             DustTag::DTSection(container) => {
-                let injected_context = ParametersContext::new(self, breadcrumbs, &container.params);
+                let injected_context =
+                    ParametersContext::new(self, breadcrumbs, &container.params, None);
                 let val = walk_path(breadcrumbs, &container.path.keys)
                     .map(|ice| ice.into_context_element(self, breadcrumbs));
                 match val {
@@ -325,7 +326,7 @@ impl<'a> DustRenderer<'a> {
                     return Ok(rendered_content);
                 } else {
                     let injected_context =
-                        ParametersContext::new(self, breadcrumbs, &partial.params);
+                        ParametersContext::new(self, breadcrumbs, &partial.params, None);
                     let new_breadcrumbs = self.new_breadcrumbs_partial(
                         breadcrumbs,
                         breadcrumbs,
@@ -373,7 +374,7 @@ impl<'a> DustRenderer<'a> {
                 );
 
                 let param_map =
-                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params);
+                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params, None);
 
                 let left_side = self.tap(breadcrumbs, &param_map, "key");
                 let right_side = self.tap(breadcrumbs, &param_map, "value");
@@ -425,7 +426,7 @@ impl<'a> DustRenderer<'a> {
                 );
 
                 let param_map =
-                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params);
+                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params, None);
 
                 let left_side = self.tap(breadcrumbs, &param_map, "key");
                 let right_side = self.tap(breadcrumbs, &param_map, "value");
@@ -477,7 +478,7 @@ impl<'a> DustRenderer<'a> {
                 );
 
                 let param_map =
-                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params);
+                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params, None);
 
                 let left_side = self.tap(breadcrumbs, &param_map, "key");
                 let right_side = self.tap(breadcrumbs, &param_map, "value");
@@ -518,7 +519,7 @@ impl<'a> DustRenderer<'a> {
                 );
 
                 let param_map =
-                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params);
+                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params, None);
 
                 let left_side = self.tap(breadcrumbs, &param_map, "key");
                 let right_side = self.tap(breadcrumbs, &param_map, "value");
@@ -559,7 +560,7 @@ impl<'a> DustRenderer<'a> {
                 );
 
                 let param_map =
-                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params);
+                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params, None);
 
                 let left_side = self.tap(breadcrumbs, &param_map, "key");
                 let right_side = self.tap(breadcrumbs, &param_map, "value");
@@ -600,7 +601,7 @@ impl<'a> DustRenderer<'a> {
                 );
 
                 let param_map =
-                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params);
+                    ParametersContext::new(self, breadcrumbs, &parameterized_block.params, None);
 
                 let left_side = self.tap(breadcrumbs, &param_map, "key");
                 let right_side = self.tap(breadcrumbs, &param_map, "value");
@@ -756,7 +757,31 @@ impl<'a> DustRenderer<'a> {
                     }
                 }
             }
-            DustTag::DTHelperSelect(parameterized_block) => todo!(),
+            DustTag::DTHelperSelect(parameterized_block) => {
+                let new_breadcrumbs = self.new_breadcrumbs_partial(
+                    breadcrumbs,
+                    breadcrumbs,
+                    None,
+                    &parameterized_block.explicit_context,
+                );
+                match &parameterized_block.contents {
+                    None => return Ok("".to_owned()),
+                    Some(body) => {
+                        let comparison_helpers = body.elements.iter().filter_map(|te| match te {
+                            TemplateElement::TETag(dt) => match dt {
+                                DustTag::DTHelperEquals(_)
+                                | DustTag::DTHelperNotEquals(_)
+                                | DustTag::DTHelperGreaterThan(_)
+                                | DustTag::DTHelperLessThan(_)
+                                | DustTag::DTHelperGreaterThanOrEquals(_)
+                                | DustTag::DTHelperLessThanOrEquals(_) => Some(dt),
+                                _ => None,
+                            },
+                            _ => None,
+                        });
+                    }
+                }
+            }
             DustTag::DTHelperAny(parameterized_block) => todo!(),
             DustTag::DTHelperNone(parameterized_block) => todo!(),
         }
@@ -944,6 +969,24 @@ impl<'a> DustRenderer<'a> {
             !std::borrow::Borrow::<dyn IntoContextElement + 'b>::borrow(b).is_pseudo_element()
         })
     }
+
+    fn perform_comparison_check(
+        &'a self,
+        tag: &'a DustTag,
+        breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
+        select_parameters: Option<&'a ParametersContext<'a>>,
+    ) -> bool {
+        let param_map = match tag {
+            DustTag::DTHelperEquals(parameterized_block)
+            | DustTag::DTHelperNotEquals(parameterized_block)
+            | DustTag::DTHelperGreaterThan(parameterized_block)
+            | DustTag::DTHelperLessThan(parameterized_block)
+            | DustTag::DTHelperGreaterThanOrEquals(parameterized_block)
+                | DustTag::DTHelperLessThanOrEquals(parameterized_block) => ParametersContext::new(self, breadcrumbs, &parameterized_block.params, select_parameters),
+            _ => panic!("perform_comparison_check only implemented for comparison helpers (eq, ne, gt, gte, lt, lte)")
+        };
+        todo!()
+    }
 }
 
 struct BlockContext<'a> {