Load files

src/main.rs

@@ -3,6 +3,7 @@ use std::path::PathBuf;
 use structopt::StructOpt;
 
 mod commands;
+mod source;
 
 #[derive(Debug, StructOpt)]
 pub struct Opt {

src/source.rs

@@ -0,0 +1,64 @@
+use std::collections::HashMap;
+use std::ops::Range;
+use std::path::{Path, PathBuf};
+use std::{fs, io};
+
+use codespan_reporting::files::SimpleFiles;
+
+#[derive(Debug, thiserror::Error)]
+pub enum LoadFileError {
+    #[error("file already loaded")]
+    FileAlreadyLoaded,
+    #[error("error loading file: {0}")]
+    IoError(#[from] io::Error),
+}
+
+pub struct SourceFiles {
+    files: SimpleFiles<String, String>,
+    files_by_path: HashMap<PathBuf, usize>,
+}
+
+impl SourceFiles {
+    pub fn new() -> Self {
+        Self {
+            files: SimpleFiles::new(),
+            files_by_path: HashMap::new(),
+        }
+    }
+
+    pub fn load(&mut self, path: &Path) -> Result<SourceFile, LoadFileError> {
+        let canonical_path = path.canonicalize()?;
+        if self.files_by_path.contains_key(&canonical_path) {
+            return Err(LoadFileError::FileAlreadyLoaded);
+        }
+
+        let name = path.as_os_str().to_string_lossy().into_owned();
+        let content = fs::read_to_string(path)?;
+        let file_id = self.files.add(name, content);
+        Ok(SourceFile(file_id))
+    }
+
+    pub fn content_of(&self, file: SourceFile) -> Option<&str> {
+        self.files.get(file.0).ok().map(|sf| sf.source() as &str)
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct SourceFile(usize);
+
+impl SourceFile {
+    pub fn span(&self, range: Range<usize>) -> SourceSpan {
+        SourceSpan {
+            file: self.0,
+            start: range.start,
+            end: range.end,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct SourceSpan {
+    file: usize,
+    start: usize,
+    end: usize,
+}