From ec2ff5778b9161fe5805dade2c517177bd8f27ef Mon Sep 17 00:00:00 2001
From: Schrottkatze <git@schrottkatze.de>
Date: Sun, 13 Oct 2024 16:44:59 +0200
Subject: [PATCH] pawarser(setup): basic parser stuff and types around it.
 also, a builder.

---
 crates/pawarser/src/lib.rs | 129 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 128 insertions(+), 1 deletion(-)

diff --git a/crates/pawarser/src/lib.rs b/crates/pawarser/src/lib.rs
index f1413cb..16955d1 100644
--- a/crates/pawarser/src/lib.rs
+++ b/crates/pawarser/src/lib.rs
@@ -1,9 +1,15 @@
 #![feature(iter_collect_into)]
 pub mod parser {
+    use std::cell::Cell;
+
+    use enumset::{EnumSet, EnumSetType};
+
+    use self::{error::SyntaxError, event::Event, input::Input};
+
     pub mod input {
         use enumset::{EnumSet, EnumSetType};
 
-        struct Input<'src, 'toks, SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>> {
+        pub struct Input<'src, 'toks, SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>> {
             raw: &'toks Vec<(SyntaxKind, &'src str)>,
             // enumset of meaningless tokens
             semantically_meaningless: EnumSet<SyntaxKind>,
@@ -36,4 +42,125 @@ pub mod parser {
             }
         }
     }
+    mod event {
+        use enumset::EnumSetType;
+
+        use super::error::SyntaxError;
+
+        pub enum Event<SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>, SyntaxErr: SyntaxError> {
+            Start {
+                kind: NodeKind<SyntaxKind, SyntaxErr>,
+                forward_parent: Option<usize>,
+            },
+            Finish,
+            Eat {
+                count: usize,
+            },
+        }
+
+        impl<SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>, SyntaxErr: SyntaxError>
+            Event<SyntaxKind, SyntaxErr>
+        {
+            pub fn tombstone() -> Self {
+                Self::Start {
+                    kind: NodeKind::Tombstone,
+                    forward_parent: None,
+                }
+            }
+        }
+
+        pub enum NodeKind<SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>, SyntaxErr: SyntaxError> {
+            Tombstone,
+            Syntax(SyntaxKind),
+            Error(SyntaxErr),
+        }
+
+        impl<SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>, SyntaxErr: SyntaxError>
+            NodeKind<SyntaxKind, SyntaxErr>
+        {
+            pub fn is_tombstone(&self) -> bool {
+                matches!(self, Self::Tombstone)
+            }
+            pub fn is_syntax(&self) -> bool {
+                matches!(self, Self::Syntax(_))
+            }
+            pub fn is_error(&self) -> bool {
+                matches!(self, Self::Error(_))
+            }
+        }
+    }
+    mod error {
+        /// A marker trait... for now!
+        // TODO: constrain that conversion to `NodeKind::Error` is enforced to be possible
+        pub trait SyntaxError {}
+    }
+
+    pub struct Parser<
+        'src,
+        'toks,
+        SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>,
+        SyntaxErr: SyntaxError,
+    > {
+        input: Input<'src, 'toks, SyntaxKind>,
+        pos: usize,
+        events: Vec<Event<SyntaxKind, SyntaxErr>>,
+        step_limit: u32,
+        steps: Cell<u32>,
+    }
+
+    pub struct ParserBuilder<
+        'src,
+        'toks,
+        SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>,
+        // SyntaxErr: SyntaxError,
+    > {
+        raw_toks: &'toks Vec<(SyntaxKind, &'src str)>,
+        meaningless_token_kinds: EnumSet<SyntaxKind>,
+        step_limit: u32,
+    }
+
+    impl<'src, 'toks, SyntaxKind: EnumSetType + Into<rowan::SyntaxKind>>
+        ParserBuilder<'src, 'toks, SyntaxKind>
+    {
+        pub fn new(raw_toks: &'toks Vec<(SyntaxKind, &'src str)>) -> Self {
+            Self {
+                raw_toks,
+                meaningless_token_kinds: EnumSet::new(),
+                step_limit: 4096,
+            }
+        }
+
+        /// Sets the parser step limit.
+        /// Defaults to 4096
+        pub fn step_limit(mut self, new: u32) -> Self {
+            self.step_limit = new;
+            self
+        }
+
+        pub fn add_meaningless(mut self, kind: SyntaxKind) -> Self {
+            self.meaningless_token_kinds.insert(kind);
+            self
+        }
+
+        pub fn add_meaningless_many(mut self, kind: Vec<SyntaxKind>) -> Self {
+            self.meaningless_token_kinds
+                .insert_all(kind.into_iter().collect());
+            self
+        }
+
+        pub fn build<SyntaxErr: SyntaxError>(self) -> Parser<'src, 'toks, SyntaxKind, SyntaxErr> {
+            let Self {
+                raw_toks,
+                meaningless_token_kinds,
+                step_limit,
+            } = self;
+            Parser {
+                input: Input::new(raw_toks, Some(meaningless_token_kinds)),
+                pos: 0,
+                events: Vec::new(),
+                step_limit,
+                steps: Cell::new(0),
+            }
+        }
+    }
 }