From 8cd859b7905d77a6ebf0cf00257ac0d06bf5e574 Mon Sep 17 00:00:00 2001
From: Rebecca Turner <rbt@sent.as>
Date: Fri, 14 Jun 2024 17:01:12 -0700
Subject: [PATCH] Add `transform_till` and `recognize_till` parsers

Upstream: https://github.com/winnow-rs/winnow/pull/541
---
 src/ghci/parse/mod.rs            |  3 ++
 src/ghci/parse/transform_till.rs | 81 ++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 src/ghci/parse/transform_till.rs

diff --git a/src/ghci/parse/mod.rs b/src/ghci/parse/mod.rs
index ae4a31a..b067cd6 100644
--- a/src/ghci/parse/mod.rs
+++ b/src/ghci/parse/mod.rs
@@ -9,6 +9,7 @@ mod module_set;
 mod show_paths;
 mod show_targets;
 mod target_kind;
+mod transform_till;
 
 use haskell_grammar::module_name;
 use lines::rest_of_line;
@@ -28,3 +29,5 @@ pub use show_paths::parse_show_paths;
 pub use show_paths::ShowPaths;
 pub use show_targets::parse_show_targets;
 pub use target_kind::TargetKind;
+pub use transform_till::recognize_till;
+pub use transform_till::transform_till;
diff --git a/src/ghci/parse/transform_till.rs b/src/ghci/parse/transform_till.rs
new file mode 100644
index 0000000..f7e6e32
--- /dev/null
+++ b/src/ghci/parse/transform_till.rs
@@ -0,0 +1,81 @@
+use winnow::combinator::eof;
+use winnow::combinator::terminated;
+use winnow::error::ErrMode;
+use winnow::error::ErrorKind;
+use winnow::error::ParserError;
+use winnow::stream::Offset;
+use winnow::stream::Stream;
+use winnow::stream::StreamIsPartial;
+use winnow::Parser;
+
+/// Call the `repeat` parser until the `end` parser produces a result.
+///
+/// Then, return the input consumed until the `end` parser was called, and the result of the `end`
+/// parser.
+///
+/// See: <https://github.com/winnow-rs/winnow/pull/541>
+pub fn recognize_till<I, Discard, O, E>(
+    mut repeat: impl Parser<I, Discard, E>,
+    mut end: impl Parser<I, O, E>,
+) -> impl Parser<I, (<I as Stream>::Slice, O), E>
+where
+    I: Stream,
+    E: ParserError<I>,
+{
+    move |input: &mut I| {
+        let start = input.checkpoint();
+
+        loop {
+            let before_end = input.checkpoint();
+            match end.parse_next(input) {
+                Ok(end_parsed) => {
+                    let after_end = input.checkpoint();
+
+                    let offset_to_before_end = before_end.offset_from(&start);
+                    input.reset(start);
+                    let input_until_end = input.next_slice(offset_to_before_end);
+                    input.reset(after_end);
+
+                    return Ok((input_until_end, end_parsed));
+                }
+                Err(ErrMode::Backtrack(_)) => {
+                    input.reset(before_end);
+                    match repeat.parse_next(input) {
+                        Ok(_) => {}
+                        Err(e) => return Err(e.append(input, ErrorKind::Many)),
+                    }
+                }
+                Err(e) => return Err(e),
+            }
+        }
+    }
+}
+
+/// Like [`recognize_till`], but it also applies a `transform` parser to the recognized input.
+pub fn transform_till<I, O1, O2, Discard, E>(
+    mut repeat: impl Parser<I, Discard, E>,
+    mut transform: impl Parser<<I as Stream>::Slice, O1, E>,
+    mut end: impl Parser<I, O2, E>,
+) -> impl Parser<I, (O1, O2), E>
+where
+    I: Stream,
+    E: ParserError<I>,
+    E: ParserError<<I as Stream>::Slice>,
+    <I as Stream>::Slice: Stream + StreamIsPartial,
+{
+    move |input: &mut I| {
+        let (mut until_end, end_parsed) =
+            recognize_till(repeat.by_ref(), end.by_ref()).parse_next(input)?;
+
+        let inner_parsed = terminated(transform.by_ref(), eof)
+            .parse_next(&mut until_end)
+            .map_err(|err_mode| match err_mode {
+                ErrMode::Incomplete(_) => {
+                    panic!("complete parsers should not report `ErrMode::Incomplete(_)`")
+                }
+                ErrMode::Backtrack(inner) | ErrMode::Cut(inner) => ErrMode::Cut(inner),
+            })?;
+
+        Ok((inner_parsed, end_parsed))
+    }
+}