feat(editor): allow opening files passed through argv

src/document.rs

@@ -1,4 +1,5 @@
 use crate::Row;
+use std::fs;
 
 #[derive(Default)]
 pub struct Document {
@@ -13,4 +14,13 @@ impl Document {
     pub fn is_empty(&self) -> bool {
         self.rows.is_empty()
     }
+
+    pub fn open(filename: &str) -> Result<Self, std::io::Error> {
+        let contents = fs::read_to_string(filename)?;
+        let mut rows = vec![];
+        for line in contents.lines() {
+            rows.push(Row::from(line));
+        }
+        Ok(Self { rows })
+    }
 }

src/editor.rs

@@ -1,5 +1,5 @@
 use crate::{Document, Row, Terminal};
-use std::io;
+use std::{io, env};
 use std::result::Result;
 use termion::event::Key;
 
@@ -21,10 +21,17 @@ pub struct Position {
 
 impl Default for Editor {
     fn default() -> Self {
+        let args: Vec<String> = env::args().collect();
+        let document = if args.len() > 1 {
+            let file_name = &args[1];
+            Document::open(file_name).unwrap_or_default()
+        } else {
+            Document::default()
+        };
         Self {
             should_quit: false,
             terminal: Terminal::default().expect("Failed to initialize terminal"),
-            document: Document::default(),
+            document,
             cursor_position: Position::default(),
         }
     }