lang: add pipelines and rename parser to lst_parser

crates/lang/src/lst_parser.rs

@@ -0,0 +1,149 @@
+use drop_bomb::DropBomb;
+
+use self::{error::SyntaxError, events::Event, input::Input, syntax_kind::SyntaxKind};
+
+pub mod syntax_kind;
+#[cfg(test)]
+mod tests;
+
+pub mod error;
+pub mod events;
+pub mod grammar;
+pub mod input;
+pub mod output;
+
+pub struct Parser<'src, 'toks> {
+    input: Input<'src, 'toks>,
+    pos: usize,
+    events: Vec<Event>,
+    errors: Vec<SyntaxError>,
+}
+
+impl<'src, 'toks> Parser<'src, 'toks> {
+    pub fn new(input: Input<'src, 'toks>) -> Self {
+        Self {
+            input,
+            pos: 0,
+            events: Vec::new(),
+            errors: Vec::new(),
+        }
+    }
+
+    pub fn finish(self) -> (Vec<Event>, Vec<SyntaxError>) {
+        (self.events, self.errors)
+    }
+
+    pub(crate) fn nth(&self, n: usize) -> SyntaxKind {
+        self.input.kind(self.pos + n)
+    }
+
+    pub fn eat_succeeding_ws(&mut self) {
+        self.push_ev(Event::Eat {
+            count: self.input.meaningless_tail_len(),
+        });
+    }
+
+    pub(crate) fn current(&self) -> SyntaxKind {
+        self.input.kind(self.pos)
+    }
+
+    pub(crate) fn start(&mut self, name: &str) -> Marker {
+        let pos = self.events.len();
+        self.push_ev(Event::tombstone());
+        Marker::new(pos, name)
+    }
+
+    pub(crate) fn at(&self, kind: SyntaxKind) -> bool {
+        self.nth_at(0, kind)
+    }
+
+    pub(crate) fn eat(&mut self, kind: SyntaxKind) -> bool {
+        if !self.at(kind) {
+            return false;
+        }
+
+        self.do_bump();
+        true
+    }
+
+    pub(crate) fn nth_at(&self, n: usize, kind: SyntaxKind) -> bool {
+        self.nth(n) == kind
+    }
+
+    fn do_bump(&mut self) {
+        self.push_ev(Event::Eat {
+            count: self.input.preceding_meaningless(self.pos),
+        });
+        self.pos += 1;
+    }
+
+    fn push_ev(&mut self, event: Event) {
+        self.events.push(event)
+    }
+}
+
+pub(crate) struct Marker {
+    pos: usize,
+    bomb: DropBomb,
+}
+
+impl Marker {
+    pub(crate) fn new(pos: usize, name: &str) -> Self {
+        Self {
+            pos,
+            bomb: DropBomb::new(format!("Marker {name} must be completed or abandoned")),
+        }
+    }
+
+    pub(crate) fn complete(mut self, p: &mut Parser<'_, '_>, kind: SyntaxKind) -> CompletedMarker {
+        self.bomb.defuse();
+        match &mut p.events[self.pos] {
+            Event::Start { kind: slot, .. } => *slot = kind,
+            _ => unreachable!(),
+        }
+        p.push_ev(Event::Finish);
+
+        CompletedMarker {
+            pos: self.pos,
+            kind,
+        }
+    }
+
+    pub(crate) fn complete_err(mut self, p: &mut Parser, kind: SyntaxError) -> CompletedMarker {
+        p.errors.push(kind);
+        self.complete(p, SyntaxKind::PARSE_ERR)
+    }
+
+    pub(crate) fn abandon(mut self, p: &mut Parser<'_, '_>) {
+        self.bomb.defuse();
+        if self.pos == p.events.len() - 1 {
+            match p.events.pop() {
+                Some(Event::Start {
+                    kind: SyntaxKind::TOMBSTONE,
+                    forward_parent: None,
+                }) => (),
+                _ => unreachable!(),
+            }
+        }
+    }
+}
+
+pub(crate) struct CompletedMarker {
+    pos: usize,
+    kind: SyntaxKind,
+}
+
+impl CompletedMarker {
+    pub(crate) fn precede(self, p: &mut Parser<'_, '_>, name: &str) -> Marker {
+        let new_pos = p.start(name);
+
+        match &mut p.events[self.pos] {
+            Event::Start { forward_parent, .. } => {
+                *forward_parent = Some(new_pos.pos - self.pos);
+            }
+            _ => unreachable!(),
+        }
+
+        new_pos
+    }
+}