Start reorganizing code by creating files module

src/files.rs

@@ -0,0 +1,59 @@
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+use std::{fs, io, result};
+
+use chrono_tz::Tz;
+
+use crate::commands::File;
+use crate::parse;
+
+#[derive(Debug)]
+pub struct Files {
+    files: HashMap<PathBuf, File>,
+    timezone: Option<Tz>,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("{0}")]
+    IoError(#[from] io::Error),
+    #[error("{0}")]
+    ParseError(#[from] parse::Error),
+}
+
+pub type Result<T> = result::Result<T, Error>;
+
+impl Files {
+    pub fn load(path: &Path) -> Result<Self> {
+        let mut new = Self {
+            files: HashMap::new(),
+            timezone: None,
+        };
+
+        new.load_file(path)?;
+        new.determine_timezone()?;
+
+        Ok(new)
+    }
+
+    fn load_file(&mut self, path: &Path) -> Result<()> {
+        let canon_path = path.canonicalize()?;
+        if self.files.contains_key(&canon_path) {
+            // We've already loaded this exact file.
+            return Ok(());
+        }
+
+        let content = fs::read_to_string(path)?;
+        let file = parse::parse(path, &content)?;
+        self.files.insert(canon_path, file);
+
+        // TODO Also load all imported files
+
+        Ok(())
+    }
+
+    fn determine_timezone(&mut self) -> Result<()> {
+        // TODO Implement once files can specify time zones
+        Ok(())
+    }
+}