From 756fd8977577d98ecc20babd7dad61324e6b4ecd Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Tue, 29 Jun 2021 20:24:03 -0600
Subject: parse the easy one

---
 src/parse.rs | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 119 insertions(+), 3 deletions(-)

diff --git a/src/parse.rs b/src/parse.rs
index e528f01..b16fc24 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -1,6 +1,122 @@
+enum Context<'a> {
+    HalfIncludeGuard(&'a str),
+    IncludeGuard(&'a str),
+    If(&'a str),
+    Ifndef(&'a str),
+}
+
+impl<'a> Context<'a> {
+    fn modality(&self) -> Option<Modality<'a>> {
+        match self {
+            Context::HalfIncludeGuard(_) => None,
+            Context::IncludeGuard(_) => None,
+            Context::If(x) => Some(Modality::If(x)),
+            Context::Ifndef(x) => Some(Modality::Ifndef(x)),
+        }
+    }
+}
+
+#[derive(Debug)]
+enum Modality<'a> {
+    If(&'a str),
+    Ifndef(&'a str),
+
+    And(Vec<Self>),
+}
+
+impl<'a> Modality<'a> {
+    fn and(a: Option<Self>, b: Option<Self>) -> Option<Self> {
+        match (a, b) {
+            (Some(a), Some(b)) => Some(Self::And(vec![a, b])),
+            (Some(a), None) => Some(a),
+            (None, Some(b)) => Some(b),
+            (None, None) => None,
+        }
+    }
+}
+
+trait VecContextExt<'a> {
+    fn modality(&self) -> Option<Modality<'a>>;
+}
+
+impl<'a> VecContextExt<'a> for Vec<Context<'a>> {
+    fn modality(&self) -> Option<Modality<'a>> {
+        self.iter()
+            .rev()
+            .map(Context::modality)
+            .fold(None, Modality::and)
+    }
+}
+
 #[derive(Debug)]
-pub struct FileItem;
+enum FileItem<'a> {
+    LineComment(&'a str),
+    IncludeLocal(&'a str),
+    IncludeGlobal(&'a str),
+}
+
+#[derive(Debug)]
+pub struct FullFileItem<'a> {
+    data: FileItem<'a>,
+    modality: Option<Modality<'a>>,
+}
 
-pub fn parse(file: &str) -> Vec<FileItem> {
-    todo!()
+pub fn parse(file: &str) -> Vec<FullFileItem> {
+    let mut context: Vec<Context> = vec![];
+    let mut result = vec![];
+    for line in file.lines() {
+        if line.starts_with("//") {
+            result.push(FullFileItem {
+                data: FileItem::LineComment(line.strip_prefix("//").unwrap()),
+                modality: context.modality(),
+            });
+        } else if line.trim().is_empty() {
+            // don't do anything
+        } else if line.starts_with("#ifndef ") && context.is_empty() {
+            // this is probably the include guard
+            context.push(Context::HalfIncludeGuard(
+                line.strip_prefix("#ifndef ").unwrap(),
+            ));
+        } else if line.starts_with("#define ") {
+            match context.last() {
+                Some(Context::HalfIncludeGuard(expected_guard)) => {
+                    // this is the other half of the include guard
+                    let actual_guard = line.strip_prefix("#define ").unwrap();
+                    assert_eq!(
+                        actual_guard, *expected_guard,
+                        "weird other half of include guard"
+                    );
+                    context.pop();
+                    context.push(Context::IncludeGuard(actual_guard));
+                }
+                _ => {
+                    todo!("handle #define in non-include guard contexts: {:?}", line);
+                }
+            }
+        } else if line.trim().starts_with("#include ") {
+            let good_part = line.trim().strip_prefix("#include ").unwrap();
+            let item = if line.ends_with("\"") {
+                FileItem::IncludeLocal(good_part.trim_matches('"'))
+            } else if line.ends_with(">") {
+                FileItem::IncludeGlobal(good_part.trim_start_matches('<').trim_end_matches('>'))
+            } else {
+                todo!("handle weird includes {:?}", line);
+            };
+            result.push(FullFileItem {
+                data: item,
+                modality: context.modality(),
+            });
+        } else if line.starts_with("#if ") {
+            let condition = line.strip_prefix("#if ").unwrap();
+            context.push(Context::If(condition));
+        } else if line.starts_with("#ifndef ") {
+            let condition = line.strip_prefix("#ifndef ").unwrap();
+            context.push(Context::Ifndef(condition));
+        } else if line.starts_with("#endif") {
+            context.pop();
+        } else {
+            todo!("handle line {:?}", line);
+        }
+    }
+    result
 }
-- 
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