wip: new syntax tree editor

crates/syntax/src/syntax_editor/edit_algo.rs

@@ -0,0 +1,215 @@
+use std::{collections::VecDeque, ops::RangeInclusive};
+
+use rowan::TextRange;
+
+use crate::{
+    syntax_editor::{Change, ChangeKind},
+    ted, SyntaxElement, SyntaxNode, SyntaxNodePtr,
+};
+
+use super::{SyntaxEdit, SyntaxEditor};
+
+pub(super) fn apply_edits(editor: SyntaxEditor) -> SyntaxEdit {
+    // Algorithm overview:
+    //
+    // - Sort changes by (range, type)
+    //   - Ensures that parent edits are before child edits
+    //   - Ensures that inserts will be guaranteed to be inserted at the right range
+    // - Validate changes
+    //   - Checking for invalid changes is easy since the changes will be sorted by range
+    // - Fixup change targets
+    //   - standalone change? map to original syntax tree
+    //   - dependent change?
+    //     - try to map to parent change (either independent or another dependent)
+    //     - note: need to keep track of a parent change stack, since a change can be a parent of multiple changes
+    // - Apply changes
+    //   - find changes to apply to real tree by applying nested changes first
+    //   - changed nodes become part of the changed node set (useful for the formatter to only change those parts)
+    // - Propagate annotations
+
+    let SyntaxEditor { root, mut changes, mappings, annotations } = editor;
+
+    dbg!(("initial: ", &root));
+    dbg!(&changes);
+
+    // Sort changes by range then change kind, so that we can:
+    // - ensure that parent edits are ordered before child edits
+    // - ensure that inserts will be guaranteed to be inserted at the right range
+    // - easily check for disjoint replace ranges
+    changes.sort_by(|a, b| {
+        a.target_range()
+            .start()
+            .cmp(&b.target_range().start())
+            .then(a.change_kind().cmp(&b.change_kind()))
+    });
+
+    let disjoint_replaces_ranges = changes.iter().zip(changes.iter().skip(1)).all(|(l, r)| {
+        l.change_kind() == ChangeKind::Replace
+            && r.change_kind() == ChangeKind::Replace
+            && (l.target_parent() != r.target_parent()
+                || l.target_range().intersect(r.target_range()).is_none())
+    });
+
+    if stdx::never!(
+        !disjoint_replaces_ranges,
+        "some replace change ranges intersect: {:?}",
+        changes
+    ) {
+        return SyntaxEdit { root, annotations: Default::default(), changed_elements: vec![] };
+    }
+
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+    struct DependentChange {
+        parent: u32,
+        child: u32,
+    }
+
+    // Build change tree
+    let mut changed_ancestors: VecDeque<ChangedAncestor> = VecDeque::new();
+    let mut dependent_changes = vec![];
+    let mut independent_changes = vec![];
+
+    for (change_index, change) in changes.iter().enumerate() {
+        // Check if this change is dependent on another change (i.e. it's contained within another range)
+        if let Some(index) = changed_ancestors
+            .iter()
+            .rev()
+            .position(|ancestor| ancestor.affected_range().contains_range(change.target_range()))
+        {
+            // Pop off any ancestors that aren't applicable
+            changed_ancestors.drain((index + 1)..);
+
+            let ancestor = &changed_ancestors[index];
+
+            dependent_changes.push(DependentChange {
+                parent: ancestor.change_index as u32,
+                child: change_index as u32,
+            });
+        } else {
+            // This change is independent of any other change
+
+            // Drain the changed ancestors since we're no longer in a set of dependent changes
+            changed_ancestors.drain(..);
+
+            independent_changes.push(change_index as u32);
+        }
+
+        // Add to changed ancestors, if applicable
+        match change {
+            Change::Replace(target, _) => {
+                changed_ancestors.push_back(ChangedAncestor::single(target, change_index))
+            }
+        }
+    }
+
+    dbg!(("before: ", &changes, &dependent_changes, &independent_changes));
+
+    // Map change targets to the correct syntax nodes
+    let tree_mutator = TreeMutator::new(&root);
+
+    for index in independent_changes {
+        match &mut changes[index as usize] {
+            Change::Replace(target, _) => {
+                *target = tree_mutator.make_element_mut(target);
+            }
+        }
+    }
+
+    for DependentChange { parent, child } in dependent_changes.into_iter() {
+        let (input_ancestor, output_ancestor) = match &changes[parent as usize] {
+            // insert? unreachable
+            Change::Replace(target, Some(new_target)) => {
+                (to_owning_node(target), to_owning_node(new_target))
+            }
+            Change::Replace(_, None) => continue, // silently drop outdated change
+        };
+
+        match &mut changes[child as usize] {
+            Change::Replace(target, _) => {
+                *target = mappings.upmap_child_element(target, &input_ancestor, output_ancestor)
+            }
+        }
+    }
+
+    dbg!(("after: ", &changes));
+
+    // Apply changes
+    for change in changes {
+        match change {
+            Change::Replace(target, None) => ted::remove(target),
+            Change::Replace(target, Some(new_target)) => ted::replace(target, new_target),
+        }
+    }
+
+    dbg!(("modified:", tree_mutator.mutable_clone));
+
+    todo!("draw the rest of the owl")
+}
+
+fn to_owning_node(element: &SyntaxElement) -> SyntaxNode {
+    match element {
+        SyntaxElement::Node(node) => node.clone(),
+        SyntaxElement::Token(token) => token.parent().unwrap().clone(),
+    }
+}
+
+struct ChangedAncestor {
+    kind: ChangedAncestorKind,
+    change_index: usize,
+}
+
+enum ChangedAncestorKind {
+    Single { node: SyntaxNode },
+    Range { changed_nodes: RangeInclusive<SyntaxNode>, in_parent: SyntaxNode },
+}
+
+impl ChangedAncestor {
+    fn single(element: &SyntaxElement, change_index: usize) -> Self {
+        let kind = match element {
+            SyntaxElement::Node(node) => ChangedAncestorKind::Single { node: node.clone() },
+            SyntaxElement::Token(token) => {
+                ChangedAncestorKind::Single { node: token.parent().unwrap() }
+            }
+        };
+
+        Self { kind, change_index }
+    }
+
+    fn affected_range(&self) -> TextRange {
+        match &self.kind {
+            ChangedAncestorKind::Single { node } => node.text_range(),
+            ChangedAncestorKind::Range { changed_nodes, in_parent: _ } => TextRange::new(
+                changed_nodes.start().text_range().start(),
+                changed_nodes.end().text_range().end(),
+            ),
+        }
+    }
+}
+
+struct TreeMutator {
+    immutable: SyntaxNode,
+    mutable_clone: SyntaxNode,
+}
+
+impl TreeMutator {
+    fn new(immutable: &SyntaxNode) -> TreeMutator {
+        let immutable = immutable.clone();
+        let mutable_clone = immutable.clone_for_update();
+        TreeMutator { immutable, mutable_clone }
+    }
+
+    fn make_element_mut(&self, element: &SyntaxElement) -> SyntaxElement {
+        match element {
+            SyntaxElement::Node(node) => SyntaxElement::Node(self.make_syntax_mut(&node)),
+            SyntaxElement::Token(token) => {
+                let parent = self.make_syntax_mut(&token.parent().unwrap());
+                parent.children_with_tokens().nth(token.index()).unwrap()
+            }
+        }
+    }
+
+    fn make_syntax_mut(&self, node: &SyntaxNode) -> SyntaxNode {
+        let ptr = SyntaxNodePtr::new(node);
+        ptr.to_node(&self.mutable_clone)
+    }
+}