Add Endor source reader before lexing with provenance and URI provider

crates/frontend/src/source.rs

@@ -0,0 +1,79 @@
+use std::error::Error;
+use std::fmt;
+use std::path::PathBuf;
+
+use crate::{Diagnostic, SourceLocation};
+
+/// Source provenance, independent of filesystem layout or VM heap handles.
+/// Endor revisions are opaque labels supplied by the host, not verified hashes.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum SourceOrigin {
+    Text { name: String },
+    Stream { name: String },
+    File { path: PathBuf },
+    Endor { uri: String, revision: String },
+}
+
+impl fmt::Display for SourceOrigin {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Text { name } | Self::Stream { name } => formatter.write_str(name),
+            Self::File { path } => write!(formatter, "{}", path.display()),
+            Self::Endor { uri, revision } => write!(formatter, "{uri} [revision {revision}]"),
+        }
+    }
+}
+
+/// An owned, immutable UTF-8 snapshot. Reader adapters preserve the text exactly
+/// so token byte offsets still refer to the original decoded source.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SourceUnit {
+    origin: SourceOrigin,
+    text: String,
+}
+
+impl SourceUnit {
+    pub(crate) fn new(origin: SourceOrigin, text: String) -> Self {
+        Self { origin, text }
+    }
+
+    pub fn origin(&self) -> &SourceOrigin {
+        &self.origin
+    }
+
+    pub fn text(&self) -> &str {
+        &self.text
+    }
+
+    /// Bind a diagnostic to this snapshot before discarding its source buffer.
+    pub fn annotate(&self, diagnostic: Diagnostic) -> SourceDiagnostic {
+        SourceDiagnostic {
+            location: diagnostic.location(&self.text),
+            origin: self.origin.clone(),
+            diagnostic: Box::new(diagnostic),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SourceDiagnostic {
+    pub origin: SourceOrigin,
+    pub location: SourceLocation,
+    pub diagnostic: Box<Diagnostic>,
+}
+
+impl fmt::Display for SourceDiagnostic {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            formatter,
+            "{}:{}:{}: {}",
+            self.origin, self.location.line, self.location.column, self.diagnostic.message
+        )
+    }
+}
+
+impl Error for SourceDiagnostic {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        Some(self.diagnostic.as_ref())
+    }
+}