1 files changed, 106 insertions, 0 deletions
diff --git a/build/syntax_mapping.rs b/build/syntax_mapping.rs
new file mode 100644
index 00000000..850b25b4
--- /dev/null
+++ b/build/syntax_mapping.rs
@@ -0,0 +1,106 @@
+use std::{convert::Infallible, env, fs, path::Path, str::FromStr};
+
+use anyhow::anyhow;
+use indexmap::IndexMap;
+use serde::Deserialize;
+use serde_with::DeserializeFromStr;
+use walkdir::WalkDir;
+
+/// Known mapping targets.
+///
+/// Corresponds to `syntax_mapping::MappingTarget`.
+#[derive(Clone, Debug, Eq, PartialEq, Hash, DeserializeFromStr)]
+pub enum MappingTarget {
+    MapTo(String),
+    MapToUnknown,
+    MapExtensionToUnknown,
+}
+impl FromStr for MappingTarget {
+    type Err = Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "MappingTarget::MapToUnknown" => Ok(Self::MapToUnknown),
+            "MappingTarget::MapExtensionToUnknown" => Ok(Self::MapExtensionToUnknown),
+            syntax => Ok(Self::MapTo(syntax.into())),
+        }
+    }
+}
+impl MappingTarget {
+    fn codegen(&self) -> String {
+        match self {
+            Self::MapTo(syntax) => format!(r###"MappingTarget::MapTo(r#"{syntax}"#)"###),
+            Self::MapToUnknown => "MappingTarget::MapToUnknown".into(),
+            Self::MapExtensionToUnknown => "MappingTarget::MapExtensionToUnknown".into(),
+        }
+    }
+}
+
+/// A struct that models a single .toml file in /src/syntax_mapping/builtins/.
+#[derive(Clone, Debug, Deserialize)]
+struct MappingDefModel {
+    mappings: IndexMap<MappingTarget, Vec<String>>,
+}
+impl MappingDefModel {
+    fn into_mapping_list(self) -> Vec<(String, MappingTarget)> {
+        self.mappings
+            .into_iter()
+            .flat_map(|(target, matcher)| {
+                matcher
+                    .into_iter()
+                    .map(|rule| (rule, target.clone()))
+                    .collect::<Vec<_>>()
+            })
+            .collect()
+    }
+}
+
+#[derive(Clone, Debug)]
+struct MappingList(Vec<(String, MappingTarget)>);
+impl MappingList {
+    fn codegen(&self) -> String {
+        let array_items: Vec<_> = self
+            .0
+            .iter()
+            .map(|(matcher, target)| format!(r###"(r#"{matcher}"#, {t})"###, t = target.codegen()))
+            .collect();
+        let len = array_items.len();
+
+        format!(
+            "static STATIC_RULES: [(&'static str, &'static str); {len}] = [\n{items}\n];",
+            items = array_items.join(",\n")
+        )
+    }
+}
+
+fn read_all_mappings() -> anyhow::Result<MappingList> {
+    let mut all_mappings = vec![];
+
+    for entry in WalkDir::new("src/syntax_mapping/builtins")
+        .into_iter()
+        .map(|entry| entry.unwrap_or_else(|err| panic!("failed to visit a file: {err}")))
+        .filter(|entry| {
+            let path = entry.path();
+            path.is_file() && path.extension().map(|ext| ext == "toml").unwrap_or(false)
+        })
+    {
+        let toml_string = fs::read_to_string(entry.path())?;
+        let mappings = toml::from_str::<MappingDefModel>(&toml_string)?.into_mapping_list();
+        all_mappings.extend(mappings);
+    }
+
+    Ok(MappingList(all_mappings))
+}
+
+/// Build the static syntax mappings defined in /src/syntax_mapping/builtins/
+/// into a .rs source file, which is to be inserted with `include!`.
+pub fn build_static_mappings() -> anyhow::Result<()> {
+    let mappings = read_all_mappings()?;
+
+    let codegen_path = Path::new(&env::var_os("OUT_DIR").ok_or(anyhow!("OUT_DIR is unset"))?)
+        .join("codegen_static_syntax_mappings.rs");
+
+    fs::write(codegen_path, mappings.codegen())?;
+
+    Ok(())
+}