Implement EditorBuffer::save_file()

Needs more tests though.

core/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2024"
 [dev-dependencies]
 ntest = "0.9.3"
 rand = {version="0.9.2", features=["small_rng", "alloc"]}
+tempfile = "3.23.0"

core/src/editor_buffer/io.rs

@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 
 use super::{CommandResponse, EditorBuffer};
-use crate::{Point, TextBuffer, TextBufferWriter};
+use crate::{Point, TextBuffer, TextBufferReader, TextBufferWriter};
 
 impl EditorBuffer {
     pub fn open_file(&mut self, filepath: PathBuf) -> CommandResponse {
@@ -35,16 +35,31 @@ impl EditorBuffer {
         }
     }
 
-    pub fn save_file(&mut self, _filepath: Option<PathBuf>) -> CommandResponse {
-        todo!()
+    pub fn save_file(&mut self, filepath: Option<PathBuf>) -> CommandResponse {
+        if let Some(filepath) = filepath.as_ref().or(self.filepath.as_ref()) {
+            match std::fs::File::create(filepath) {
+                Ok(mut file) => {
+                    match std::io::copy(&mut TextBufferReader::new(&self.buffer), &mut file) {
+                        Ok(bytes_read) => CommandResponse::Success(format!(
+                            "Read {bytes_read} bytes to \"{}\"",
+                            filepath.to_string_lossy()
+                        )),
+                        Err(err) => CommandResponse::Failure(format!("{}", err)),
+                    }
+                }
+                Err(err) => CommandResponse::Failure(format!("{}", err)),
+            }
+        } else {
+            CommandResponse::Failure("Attempting to same file with no name.".into())
+        }
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::{Command, CommandResponse, TextBufferReader, EditorBuffer};
-    use std::io::Read;
-    use std::path::PathBuf;
+    use crate::{Command, CommandResponse, EditorBuffer, TextBufferReader};
+    use std::{io::Read, path::PathBuf};
+    use tempfile::tempdir;
 
     #[test]
     fn load_file_loads_expected_contents() {
@@ -81,4 +96,26 @@ mod tests {
             _ => panic!(),
         }
     }
+
+    #[test]
+    fn save_file_saves_file_with_expected_contents() {
+        let test_file_path: PathBuf = [
+            env!("CARGO_MANIFEST_DIR"),
+            r"test_data/Les_Trois_Mousquetaires.txt",
+        ]
+        .iter()
+        .collect();
+        let mut target = EditorBuffer::new();
+        target.execute(Command::OpenFile(test_file_path.clone()));
+        let temp_dir = tempdir().unwrap();
+        let tmp_file_path = temp_dir.path().join(r"Les_Trois_Mousquetaires.txt");
+        assert!(matches!(
+            dbg!(target.execute(Command::SaveAs(tmp_file_path.clone()))),
+            CommandResponse::Success(_)
+        ));
+
+        let read_text = std::fs::read_to_string(&tmp_file_path).unwrap();
+        let expected_text = std::fs::read_to_string(&test_file_path).unwrap();
+        assert_eq!(&expected_text, &read_text);
+    }
 }