4 files changed, 117 insertions, 26 deletions

diff --git a/helix-core/src/commands.rs b/helix-core/src/commands.rs
index 70596045..c4e9f092 100644
--- a/helix-core/src/commands.rs
+++ b/helix-core/src/commands.rs
@@ -1,4 +1,7 @@
+use crate::selection::Range;
 use crate::state::{Direction, Granularity, Mode, State};
+use crate::transaction::{ChangeSet, Transaction};
+use crate::Tendril;
 
 /// A command is a function that takes the current state and a count, and does a side-effect on the
 /// state (usually by creating and applying a transaction).
@@ -49,22 +52,48 @@ pub fn move_line_down(state: &mut State, count: usize) {
     );
 }
 
+// avoid select by default by having a visual mode switch that makes movements into selects
+
+// insert mode:
+// first we calculate the correct cursors/selections
+// then we just append at each cursor
+// lastly, if it was append mode we shift cursor by 1?
+
+// inserts at the start of each selection
 pub fn insert_mode(state: &mut State, _count: usize) {
     state.mode = Mode::Insert;
+
+    state.selection = state
+        .selection
+        .clone()
+        .transform(|range| Range::new(range.to(), range.from()))
+}
+
+// inserts at the end of each selection
+pub fn append_mode(state: &mut State, _count: usize) {
+    state.mode = Mode::Insert;
+
+    // TODO: as transaction
+    state.selection = state.selection.clone().transform(|range| {
+        // TODO: to() + next char
+        Range::new(range.from(), range.to())
+    })
 }
 
+// I inserts at the start of each line with a selection
+// A inserts at the end of each line with a selection
+// o inserts a new line before each line with a selection
+// O inserts a new line after each line with a selection
+
 pub fn normal_mode(state: &mut State, _count: usize) {
     state.mode = Mode::Normal;
 }
 
 // TODO: insert means add text just before cursor, on exit we should be on the last letter.
-pub fn insert(state: &mut State, c: char) {
-    // TODO: needs to work with multiple cursors
-    use crate::transaction::ChangeSet;
+pub fn insert_char(state: &mut State, c: char) {
+    let c = Tendril::from_char(c);
+    let transaction = Transaction::insert(&state, c);
 
-    let pos = state.selection.primary().head;
-    let changes = ChangeSet::insert(&state.doc, pos, c);
-    // TODO: need to store history
-    changes.apply(&mut state.doc);
-    state.selection = state.selection.clone().map(&changes);
+    transaction.apply(state);
+    // TODO: need to store into history if successful
 }
diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index 1c0b6b74..a196417a 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -113,6 +113,11 @@ impl Selection {
         self.ranges[self.primary_index]
     }
 
+    #[must_use]
+    pub fn cursor(&self) -> usize {
+        self.primary().head
+    }
+
     /// Ensure selection containing only the primary selection.
     pub fn into_single(self) -> Self {
         if self.ranges.len() == 1 {
@@ -144,6 +149,10 @@ impl Selection {
         )
     }
 
+    pub fn ranges(&self) -> &[Range] {
+        &self.ranges
+    }
+
     #[must_use]
     /// Constructs a selection holding a single range.
     pub fn single(anchor: usize, head: usize) -> Self {
@@ -200,6 +209,14 @@ impl Selection {
         // TODO: only normalize if needed (any ranges out of order)
         normalize(ranges, primary_index)
     }
+
+    /// Takes a closure and maps each selection over the closure.
+    pub fn transform<F>(self, f: F) -> Self
+    where
+        F: Fn(Range) -> Range,
+    {
+        Self::new(self.ranges.into_iter().map(f).collect(), self.primary_index)
+    }
 }
 
 // TODO: checkSelection -> check if valid for doc length
diff --git a/helix-core/src/transaction.rs b/helix-core/src/transaction.rs
index d078679c..2f40be76 100644
--- a/helix-core/src/transaction.rs
+++ b/helix-core/src/transaction.rs
@@ -1,4 +1,4 @@
-use crate::{Rope, Selection, Tendril};
+use crate::{Rope, Selection, SelectionRange, State, Tendril};
 
 // TODO: divided into three different operations, I sort of like having just
 // Splice { extent, Option<text>, distance } better.
@@ -47,18 +47,6 @@ impl ChangeSet {
         }
     }
 
-    pub fn insert(doc: &Rope, pos: usize, c: char) -> Self {
-        let len = doc.len_chars();
-        Self {
-            changes: vec![
-                Change::Retain(pos),
-                Change::Insert(Tendril::from_char(c)),
-                Change::Retain(len - pos),
-            ],
-            len,
-        }
-    }
-
     // TODO: from iter
 
     /// Combine two changesets together.
@@ -210,8 +198,11 @@ impl ChangeSet {
         unimplemented!()
     }
 
-    pub fn apply(&self, text: &mut Rope) {
-        // TODO: validate text.chars() == self.len
+    /// Returns true if applied successfully.
+    pub fn apply(&self, text: &mut Rope) -> bool {
+        if text.len_chars() != self.len {
+            return false;
+        }
 
         let mut pos = 0;
 
@@ -231,6 +222,7 @@ impl ChangeSet {
                 }
             }
         }
+        true
     }
 
     /// `true` when the set is empty.
@@ -332,7 +324,60 @@ pub struct Transaction {
     // scroll_into_view
 }
 
-impl Transaction {}
+impl Transaction {
+    /// Returns true if applied successfully.
+    pub fn apply(&self, state: &mut State) -> bool {
+        // apply changes to the document
+        if !self.changes.apply(&mut state.doc) {
+            return false;
+        }
+
+        // update the selection: either take the selection specified in the transaction, or map the
+        // current selection through changes.
+        state.selection = self
+            .selection
+            .clone()
+            .unwrap_or_else(|| state.selection.clone().map(&self.changes));
+
+        true
+    }
+
+    pub fn insert(state: &State, text: Tendril) -> Self {
+        let len = state.doc.len_chars();
+        let ranges = state.selection.ranges();
+        let mut changes = Vec::with_capacity(2 * ranges.len() + 1);
+        let mut last = 0;
+
+        for range in state.selection.ranges() {
+            let cur = range.head;
+            changes.push(Change::Retain(cur));
+            changes.push(Change::Insert(text.clone()));
+            last = cur;
+        }
+        changes.push(Change::Retain(len - last));
+
+        Self::from(ChangeSet { changes, len })
+    }
+
+    pub fn change_selection<F>(selection: Selection, f: F) -> Self
+    where
+        F: Fn(SelectionRange) -> ChangeSet,
+    {
+        selection.ranges().iter().map(|range| true);
+        // TODO: most idiomatic would be to return a
+        // Change { from: x, to: y, insert: "str" }
+        unimplemented!()
+    }
+}
+
+impl From<ChangeSet> for Transaction {
+    fn from(changes: ChangeSet) -> Self {
+        Self {
+            changes,
+            selection: None,
+        }
+    }
+}
 
 #[cfg(test)]
 mod test {
diff --git a/helix-term/src/editor.rs b/helix-term/src/editor.rs
index 4abc8477..6c0d5b49 100644
--- a/helix-term/src/editor.rs
+++ b/helix-term/src/editor.rs
@@ -87,7 +87,7 @@ impl Editor {
                 };
 
                 // render the cursor
-                let pos = state.selection.primary().head;
+                let pos = state.selection.cursor();
                 let coords = coords_at_pos(&state.doc.slice(..), pos);
                 execute!(
                     stdout,
@@ -126,7 +126,7 @@ impl Editor {
                                     KeyEvent {
                                         code: KeyCode::Char(c),
                                         ..
-                                    } => helix_core::commands::insert(state, c),
+                                    } => helix_core::commands::insert_char(state, c),
                                     _ => (), // skip
                                 }
                                 self.render();