1 files changed, 155 insertions, 0 deletions

diff --git a/src/parser_impl/mod.rs b/src/parser_impl/mod.rs
new file mode 100644
index 000000000..b58094be3
--- /dev/null
+++ b/src/parser_impl/mod.rs
@@ -0,0 +1,155 @@
+mod event;
+mod input;
+
+use {
+    grammar,
+    lexer::Token,
+    parser_api::Parser,
+    parser_impl::{
+        event::{process, Event},
+        input::{InputPosition, ParserInput},
+    },
+    TextUnit,
+};
+
+use SyntaxKind::{self, EOF, TOMBSTONE};
+
+pub(crate) trait Sink {
+    type Tree;
+
+    fn new(text: String) -> Self;
+
+    fn leaf(&mut self, kind: SyntaxKind, len: TextUnit);
+    fn start_internal(&mut self, kind: SyntaxKind);
+    fn finish_internal(&mut self);
+    fn error(&mut self, err: String);
+    fn finish(self) -> Self::Tree;
+}
+
+/// Parse a sequence of tokens into the representative node tree
+pub(crate) fn parse<S: Sink>(text: String, tokens: &[Token]) -> S::Tree {
+    let events = {
+        let input = input::ParserInput::new(&text, tokens);
+        let parser_impl = ParserImpl::new(&input);
+        let mut parser_api = Parser(parser_impl);
+        grammar::file(&mut parser_api);
+        parser_api.0.into_events()
+    };
+    let mut sink = S::new(text);
+    process(&mut sink, tokens, events);
+    sink.finish()
+}
+
+/// Implementation details of `Parser`, extracted
+/// to a separate struct in order not to pollute
+/// the public API of the `Parser`.
+pub(crate) struct ParserImpl<'t> {
+    inp: &'t ParserInput<'t>,
+
+    pos: InputPosition,
+    events: Vec<Event>,
+}
+
+impl<'t> ParserImpl<'t> {
+    pub(crate) fn new(inp: &'t ParserInput<'t>) -> ParserImpl<'t> {
+        ParserImpl {
+            inp,
+
+            pos: InputPosition::new(),
+            events: Vec::new(),
+        }
+    }
+
+    pub(crate) fn into_events(self) -> Vec<Event> {
+        assert_eq!(self.nth(0), EOF);
+        self.events
+    }
+
+    pub(super) fn nth(&self, n: u32) -> SyntaxKind {
+        self.inp.kind(self.pos + n)
+    }
+
+    pub(super) fn at_kw(&self, t: &str) -> bool {
+        self.inp.text(self.pos) == t
+    }
+
+    pub(super) fn start(&mut self) -> u32 {
+        let pos = self.events.len() as u32;
+        self.event(Event::Start {
+            kind: TOMBSTONE,
+            forward_parent: None,
+        });
+        pos
+    }
+
+    pub(super) fn bump(&mut self) {
+        let kind = self.nth(0);
+        if kind == EOF {
+            return;
+        }
+        self.do_bump(kind);
+    }
+
+    pub(super) fn bump_remap(&mut self, kind: SyntaxKind) {
+        if self.nth(0) == EOF {
+            // TODO: panic!?
+            return;
+        }
+        self.do_bump(kind);
+    }
+
+    fn do_bump(&mut self, kind: SyntaxKind) {
+        self.pos += 1;
+        self.event(Event::Token {
+            kind,
+            n_raw_tokens: 1,
+        });
+    }
+
+    pub(super) fn error(&mut self, msg: String) {
+        self.event(Event::Error { msg })
+    }
+
+    pub(super) fn complete(&mut self, pos: u32, kind: SyntaxKind) {
+        match self.events[pos as usize] {
+            Event::Start {
+                kind: ref mut slot, ..
+            } => {
+                *slot = kind;
+            }
+            _ => unreachable!(),
+        }
+        self.event(Event::Finish);
+    }
+
+    pub(super) fn abandon(&mut self, pos: u32) {
+        let idx = pos as usize;
+        if idx == self.events.len() - 1 {
+            match self.events.pop() {
+                Some(Event::Start {
+                    kind: TOMBSTONE,
+                    forward_parent: None,
+                }) => (),
+                _ => unreachable!(),
+            }
+        }
+    }
+
+    pub(super) fn precede(&mut self, pos: u32) -> u32 {
+        let new_pos = self.start();
+        match self.events[pos as usize] {
+            Event::Start {
+                ref mut forward_parent,
+                ..
+            } => {
+                *forward_parent = Some(new_pos - pos);
+            }
+            _ => unreachable!(),
+        }
+        new_pos
+    }
+
+    fn event(&mut self, event: Event) {
+        self.events.push(event)
+    }
+}