pawarser: Implement Parser::finish

crates/json-pawarser/src/syntax_error.rs

@@ -1,6 +1,6 @@
 use crate::syntax_kind::SyntaxKind;
 
-#[derive(Clone)]
+#[derive(Clone, PartialEq, Eq)]
 pub enum SyntaxError {
     DisallowedKeyType(SyntaxKind),
     MemberMissingValue,

crates/pawarser/src/parser.rs

@@ -1,6 +1,9 @@
-use std::cell::Cell;
+use std::{cell::Cell, marker::PhantomData, mem};
 
 use enumset::{EnumSet, EnumSetType};
+use rowan::{GreenNode, GreenNodeBuilder};
+
+use crate::parser::event::NodeKind;
 
 use self::{event::Event, input::Input, marker::Marker};
 pub use error::SyntaxError;
@@ -13,7 +16,7 @@ pub mod marker;
 /// this is used to define some required SyntaxKinds like an EOF token or an error token
 pub trait SyntaxElement
 where
-    Self: EnumSetType + Into<rowan::SyntaxKind> + Clone,
+    Self: EnumSetType + Into<rowan::SyntaxKind> + Clone + PartialEq + Eq,
 {
     /// EOF value. This will be used by the rest of the parser library to represent an EOF.
     const EOF: Self;
@@ -93,6 +96,90 @@ impl<'src, 'toks, SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError>
         assert!(steps <= self.step_limit, "the parser seems stuck.");
         self.steps.set(steps + 1);
     }
+
+    pub fn finish(
+        Self {
+            input,
+            pos,
+            mut events,
+            step_limit,
+            steps,
+        }: Self,
+    ) -> ParserOutput<SyntaxKind, SyntaxErr> {
+        let (mut raw_toks, meaningless_tokens) = input.dissolve();
+        let mut builder = GreenNodeBuilder::new();
+        // TODO: document what the hell a forward parent is
+        let mut fw_parents = Vec::new();
+        let mut errors: Vec<SyntaxErr> = Vec::new();
+        raw_toks.reverse();
+
+        for i in 0..events.len() {
+            match mem::replace(&mut events[i], Event::tombstone()) {
+                Event::Start {
+                    kind,
+                    forward_parent,
+                } => {
+                    if kind == NodeKind::Tombstone && forward_parent.is_none() {
+                        continue;
+                    }
+
+                    // resolving forward parents
+                    // temporarily jump around with the parser index and replace them with tombstones
+                    fw_parents.push(kind);
+                    let mut idx = i;
+                    let mut fp = forward_parent;
+                    while let Some(fwd) = fp {
+                        idx += fwd as usize;
+                        fp = match mem::replace(&mut events[idx], Event::tombstone()) {
+                            Event::Start {
+                                kind,
+                                forward_parent,
+                            } => {
+                                fw_parents.push(kind);
+                                forward_parent
+                            }
+                            _ => unreachable!(),
+                        }
+                    }
+
+                    // clear semantically meaningless tokens before the new tree node for aesthetic reasons
+                    while raw_toks
+                        .last()
+                        .is_some_and(|v| meaningless_tokens.contains(v.0))
+                    {
+                        // update first next Eat event
+                        match events.iter_mut().find(|ev| matches!(ev, Event::Eat { .. })) {
+                            Some(Event::Eat { count }) => *count -= 1,
+                            _ => unreachable!(),
+                        }
+
+                        // put whitespace into lst
+                        let (tok, text) = raw_toks.pop().unwrap();
+                        builder.token(tok.into(), text);
+                    }
+
+                    // insert forward parents into the tree in correct order
+                    for kind in fw_parents.drain(..).rev() {
+                        match kind {
+                            NodeKind::Syntax(kind) => builder.start_node(kind.into()),
+                            NodeKind::Error(err) => {
+                                errors.push(err);
+                                builder.start_node(SyntaxKind::ERROR.into())
+                            }
+                            _ => {}
+                        }
+                    }
+                }
+                Event::Finish => builder.finish_node(),
+                Event::Eat { count } => (0..count).for_each(|_| {
+                    let (tok, text) = raw_toks.pop().unwrap();
+                    builder.token(tok.into(), text);
+                }),
+            }
+        }
+
+        todo!()
+    }
 }
 
 pub struct ParserBuilder<

crates/pawarser/src/parser/error.rs

@@ -2,6 +2,6 @@
 // TODO: constrain that conversion to `NodeKind::Error` is enforced to be possible
 pub trait SyntaxError
 where
-    Self: Clone,
+    Self: Clone + PartialEq + Eq,
 {
 }

crates/pawarser/src/parser/event.rs

@@ -22,7 +22,7 @@ impl<SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError> Event<SyntaxKind, Syntax
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, PartialEq, Eq)]
 pub enum NodeKind<SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError> {
     Tombstone,
     Syntax(SyntaxKind),

crates/pawarser/src/parser/input.rs

@@ -55,4 +55,13 @@ impl<'src, SyntaxKind: SyntaxElement> Input<'src, SyntaxKind> {
     pub fn meaningless_tail_len(&self) -> usize {
         self.raw.len() - (self.meaningful_toks.last().unwrap() + 1)
     }
+
+    pub fn dissolve(self) -> (Vec<(SyntaxKind, &'src str)>, EnumSet<SyntaxKind>) {
+        let Self {
+            raw,
+            semantically_meaningless,
+            ..
+        } = self;
+        (raw, semantically_meaningless)
+    }
 }

crates/pawarser/src/parser/marker.rs

@@ -69,6 +69,17 @@ pub struct CompletedMarker<SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError> {
 
 impl<SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError> CompletedMarker<SyntaxKind, SyntaxErr> {
     pub fn precede(self, p: &mut Parser<SyntaxKind, SyntaxErr>, name: &str) -> Marker {
-        todo!()
+        let new_pos = p.start(name);
+
+        match &mut p.events[self.pos] {
+            Event::Start { forward_parent, .. } => {
+                // point forward parent of the node this marker completed to the new node
+                // will later be used to make the new node a parent of the current node.
+                *forward_parent = Some(new_pos.pos - self.pos)
+            }
+            _ => unreachable!(),
+        }
+
+        new_pos
     }
 }