From 20674aa65148558fb849eb1bb9c8a5e4a0cf483d Mon Sep 17 00:00:00 2001
From: tslil <tslil@posteo.de>
Date: Wed, 22 Oct 2025 21:02:01 +0100
Subject: Implement two basic selection functions

---
 rprt-engine/src/selection_function.rs | 77 +++++++++++++++++++++++++++++++----
 1 file changed, 69 insertions(+), 8 deletions(-)

(limited to 'rprt-engine/src/selection_function.rs')

diff --git a/rprt-engine/src/selection_function.rs b/rprt-engine/src/selection_function.rs
index 6f05650..3da61c9 100644
--- a/rprt-engine/src/selection_function.rs
+++ b/rprt-engine/src/selection_function.rs
@@ -4,12 +4,15 @@ use crate::state::EditorState;
 use thiserror::Error;
 
 #[derive(Error, Debug)]
-pub enum SFError {}
+pub enum SFError {
+    #[error("Could not find buffer {0}")]
+    BufferNotFound(BufferID),
+}
 
 struct SFComponents {
     niladic: Box<dyn Fn(&EditorState) -> Result<Selection, SFError>>,
-    monadic_rank0: Box<dyn Fn(&EditorState, &BufferID, usize) -> Result<Selection, SFError>>,
-    monadic_rank1: Box<dyn Fn(&EditorState, &BufferID, &Interval) -> Result<Selection, SFError>>,
+    monadic_rank0: Box<dyn Fn(&EditorState, BufferID, usize) -> Result<Selection, SFError>>,
+    monadic_rank1: Box<dyn Fn(&EditorState, BufferID, &Interval) -> Result<Selection, SFError>>,
     dyadic: Option<Box<dyn Fn(&EditorState, &Selection, &Selection) -> Result<Selection, SFError>>>,
 }
 
@@ -31,13 +34,71 @@ impl From<SFComponents> for SelectionFunction<VectoriseError<SFError>> {
             } else {
                 None
             };
-
+        let niladic = Box::new(move |editor_state: &EditorState| {
+            (sfc.niladic)(editor_state).map_err(VectoriseError::ProcessingError)
+        });
+        let monadic = Box::new(Selection::vectorise(sfc.monadic_rank0, sfc.monadic_rank1));
         Self {
-            niladic: Box::new(move |editor_state: &EditorState| {
-                (sfc.niladic)(editor_state).map_err(VectoriseError::ProcessingError)
+            niladic,
+            monadic,
+            dyadic,
+        }
+    }
+}
+
+impl SelectionFunction<VectoriseError<SFError>> {
+    pub fn empty() -> Self {
+        SFComponents {
+            niladic: Box::new(|_| Ok(Selection::empty())),
+            monadic_rank0: Box::new(|_, _, _| Ok(Selection::empty())),
+            monadic_rank1: Box::new(|_, _, _| Ok(Selection::empty())),
+            dyadic: None,
+        }
+        .into()
+    }
+
+    pub fn end_sequential() -> Self {
+        fn get_end_position(es: &EditorState, buffer_id: BufferID) -> Result<Selection, SFError> {
+            if let Some(buf) = es.get_buffer(buffer_id) {
+                Ok(Selection::Position {
+                    buffer_id: buffer_id,
+                    pos: buf.max_pos(),
+                })
+            } else {
+                Err(SFError::BufferNotFound(buffer_id))
+            }
+        }
+
+        SFComponents {
+            niladic: Box::new(|es| get_end_position(es, es.current_buffer_id)),
+            monadic_rank0: Box::new(|es, buffer_id, _| get_end_position(es, buffer_id)),
+            monadic_rank1: Box::new(|es, buffer_id, _| get_end_position(es, buffer_id)),
+            dyadic: None,
+        }
+        .into()
+    }
+
+    pub fn end_structural() -> Self {
+        SFComponents {
+            niladic: Box::new(|es| {
+                if let Some(buf) = es.current_buffer() {
+                    Ok(Selection::Position {
+                        buffer_id: es.current_buffer_id,
+                        pos: buf.max_pos(),
+                    })
+                } else {
+                    Err(SFError::BufferNotFound(es.current_buffer_id))
+                }
+            }),
+            monadic_rank0: Box::new(|_, buffer_id, pos| Ok(Selection::Position { buffer_id, pos })),
+            monadic_rank1: Box::new(|_, buffer_id, int| {
+                Ok(Selection::Position {
+                    buffer_id,
+                    pos: int.end,
+                })
             }),
-            monadic: Box::new(Selection::vectorise(sfc.monadic_rank0, sfc.monadic_rank1)),
-            dyadic: dyadic,
+            dyadic: None,
         }
+        .into()
     }
 }
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