Harden file_io exercises: remove magic number, dedupe paths

- file_io3: replace the hardcoded expected file size (117) with
  SAMPLE_TEXT.len(), so the check is derived from the actual content
  instead of an unexplained magic number.
- file_io3: use create_dir_all instead of create_dir, and add a
  sample_file_path() helper shared by main/create_required_files/
  file_cleanup to avoid three separate ad-hoc path constructions.
- file_io1/file_io2: hoist the sample text into a SAMPLE_TEXT constant
  used by both the exercise and its solution, removing duplicated
  literals.

No behavioral change: all three solutions were rebuilt and run
locally, producing identical output (file size still 117, permissions
still non-readonly) with no leftover files.

exercises/24_file_io/file_io1.rs

@@ -2,6 +2,8 @@ use std::fs;
 use std::path::Path;
 
 const TEST_FILE_NAME: &str = "SampleTextFile.txt";
+const SAMPLE_TEXT: &str = "This is the file content.";
+
 fn main() -> Result<(), std::io::Error> {
     create_required_files()?;
 
@@ -25,7 +27,7 @@ fn create_required_files() -> Result<(), std::io::Error> {
     let file_path = Path::new(TEST_FILE_NAME);
 
     if !file_path.exists() {
-        fs::write(file_path, "This is the file content.")?;
+        fs::write(file_path, SAMPLE_TEXT)?;
     } else {
         println!("File already exist.");
     }

exercises/24_file_io/file_io2.rs

@@ -4,6 +4,9 @@ use std::path::Path;
 
 const TEST_INPUT_FILE_NAME: &str = "MultiLineTextFile.txt";
 const TEST_OUTPUT_FILE_NAME: &str = "MultiLineOutputFile.txt";
+const SAMPLE_TEXT: &str = "This is the first line of the text.
+        This is the second line.
+        And this is the third and the last line.";
 
 fn main() -> Result<(), std::io::Error> {
     create_required_files()?;
@@ -45,10 +48,7 @@ fn create_required_files() -> Result<(), std::io::Error> {
     let file_path = Path::new(TEST_INPUT_FILE_NAME);
 
     if !file_path.exists() {
-        let text = "This is the first line of the text.
+        fs::write(file_path, SAMPLE_TEXT).inspect_err(|err| {
-        This is the second line.
-        And this is the third and the last line.";
-        fs::write(file_path, text).inspect_err(|err| {
             eprintln!("Couldn't create the test file : {}", err);
         })?;
     }

exercises/24_file_io/file_io3.rs

@@ -2,12 +2,18 @@ use std::fs;
 use std::io::Error;
 use std::path::PathBuf;
 
+const SAMPLE_TEXT: &str = "This is the first line of the text.
+        This is the second line.
+        And this is the third and the last line.";
+
+fn sample_file_path() -> PathBuf {
+    PathBuf::from("SampleFilesFolder/MultiLineTextFile.txt")
+}
+
 fn main() -> Result<(), std::io::Error> {
     create_required_files()?;
-    let mut path_buffer = PathBuf::new();
 
-    path_buffer.push("SampleFilesFolder");
+    let path_buffer = sample_file_path();
-    path_buffer.push("MultiLineTextFile.txt");
 
     // TODO : How to get metadata using path_buffer ?
     let meta_data_result = path_buffer.
@@ -17,7 +23,7 @@ fn main() -> Result<(), std::io::Error> {
             println!("Metadata about the file : {:?}", path_buffer);
             println!("File creation time {:?}", meta_data.created());
             println!("File size {}", meta_data.len());
-            assert_eq!(meta_data.len(), 117);
+            assert_eq!(meta_data.len(), SAMPLE_TEXT.len() as u64);
             println!("File permissions {:?}", meta_data.permissions());
             assert!(!meta_data.permissions().readonly());
         }
@@ -30,24 +36,21 @@ fn main() -> Result<(), std::io::Error> {
 }
 
 fn create_required_files() -> Result<(), std::io::Error> {
-    let file_path = PathBuf::from("SampleFilesFolder/MultiLineTextFile.txt");
+    let file_path = sample_file_path();
 
-    let dir_path = match file_path.parent(){
+    let dir_path = match file_path.parent() {
         Some(parent) => parent,
         None => return Err(Error::other("Could not get parent path")),
     };
 
     if !dir_path.exists() {
-        fs::create_dir(dir_path).inspect_err(|x| {
+        fs::create_dir_all(dir_path).inspect_err(|x| {
             eprintln!("Could not create directory: {:?}", x);
         })?;
     }
 
     if !file_path.exists() {
-        let text = "This is the first line of the text.
+        fs::write(&file_path, SAMPLE_TEXT).inspect_err(|err| {
-        This is the second line.
-        And this is the third and the last line.";
-        fs::write(&file_path, text).inspect_err(|err| {
             eprintln!("Couldn't create test file: {:?}", err);
         })?;
     }
@@ -56,23 +59,21 @@ fn create_required_files() -> Result<(), std::io::Error> {
 }
 
 fn file_cleanup() -> Result<(), std::io::Error> {
-    let mut path_buffer = PathBuf::new();
+    let path_buffer = sample_file_path();
-
-    path_buffer.push("SampleFilesFolder");
-    path_buffer.push("MultiLineTextFile.txt");
 
     if path_buffer.exists() {
         fs::remove_file(&path_buffer).inspect(|_| {
             println!("Test file removed");
         })?;
     }
-    path_buffer.pop();
 
-    if path_buffer.exists() {
+    if let Some(dir_path) = path_buffer.parent() {
-        fs::remove_dir(&path_buffer).inspect(|_| {
+        if dir_path.exists() {
+            fs::remove_dir(dir_path).inspect(|_| {
                 println!("Test dir removed");
             })?;
         }
+    }
 
     Ok(())
 }

solutions/24_file_io/file_io1.rs

@@ -2,6 +2,8 @@ use std::fs;
 use std::path::Path;
 
 const TEST_FILE_NAME: &str = "SampleTextFile.txt";
+const SAMPLE_TEXT: &str = "This is the file content.";
+
 fn main() -> Result<(), std::io::Error> {
     create_required_files()?;
 
@@ -9,7 +11,7 @@ fn main() -> Result<(), std::io::Error> {
 
     match read_str_result {
         Ok(contents) => {
-            assert_eq!("This is the file content.", contents);
+            assert_eq!(SAMPLE_TEXT, contents);
         }
         Err(err) => {
             eprintln!("File read error. {}", err);
@@ -24,7 +26,7 @@ fn create_required_files() -> Result<(), std::io::Error> {
     let file_path = Path::new(TEST_FILE_NAME);
 
     if !file_path.exists() {
-        fs::write(file_path, "This is the file content.")?;
+        fs::write(file_path, SAMPLE_TEXT)?;
     } else {
         println!("File already exist.");
     }

solutions/24_file_io/file_io2.rs

@@ -4,6 +4,9 @@ use std::path::Path;
 
 const TEST_INPUT_FILE_NAME: &str = "MultiLineTextFile.txt";
 const TEST_OUTPUT_FILE_NAME: &str = "MultiLineOutputFile.txt";
+const SAMPLE_TEXT: &str = "This is the first line of the text.
+        This is the second line.
+        And this is the third and the last line.";
 
 fn main() -> Result<(), std::io::Error> {
     create_required_files()?;
@@ -44,10 +47,7 @@ fn create_required_files() -> Result<(), std::io::Error> {
     let file_path = Path::new(TEST_INPUT_FILE_NAME);
 
     if !file_path.exists() {
-        let text = "This is the first line of the text.
+        fs::write(file_path, SAMPLE_TEXT).inspect_err(|err| {
-        This is the second line.
-        And this is the third and the last line.";
-        fs::write(file_path, text).inspect_err(|err| {
             eprintln!("Couldn't create the test file : {}", err);
         })?;
     }

solutions/24_file_io/file_io3.rs

@@ -2,12 +2,18 @@ use std::fs;
 use std::io::Error;
 use std::path::PathBuf;
 
+const SAMPLE_TEXT: &str = "This is the first line of the text.
+        This is the second line.
+        And this is the third and the last line.";
+
+fn sample_file_path() -> PathBuf {
+    PathBuf::from("SampleFilesFolder/MultiLineTextFile.txt")
+}
+
 fn main() -> Result<(), std::io::Error> {
     create_required_files()?;
-    let mut path_buffer = PathBuf::new();
 
-    path_buffer.push("SampleFilesFolder");
+    let path_buffer = sample_file_path();
-    path_buffer.push("MultiLineTextFile.txt");
 
     let meta_data_result = path_buffer.metadata();
 
@@ -16,7 +22,7 @@ fn main() -> Result<(), std::io::Error> {
             println!("Metadata about the file : {:?}", path_buffer);
             println!("File creation time {:?}", meta_data.created());
             println!("File size {}", meta_data.len());
-            assert_eq!(meta_data.len(), 117);
+            assert_eq!(meta_data.len(), SAMPLE_TEXT.len() as u64);
             println!("File permissions {:?}", meta_data.permissions());
             assert!(!meta_data.permissions().readonly());
         }
@@ -29,7 +35,7 @@ fn main() -> Result<(), std::io::Error> {
 }
 
 fn create_required_files() -> Result<(), std::io::Error> {
-    let file_path = PathBuf::from("SampleFilesFolder/MultiLineTextFile.txt");
+    let file_path = sample_file_path();
 
     let dir_path = match file_path.parent() {
         Some(parent) => parent,
@@ -37,16 +43,13 @@ fn create_required_files() -> Result<(), std::io::Error> {
     };
 
     if !dir_path.exists() {
-        fs::create_dir(dir_path).inspect_err(|x| {
+        fs::create_dir_all(dir_path).inspect_err(|x| {
             eprintln!("Could not create directory: {:?}", x);
         })?;
     }
 
     if !file_path.exists() {
-        let text = "This is the first line of the text.
+        fs::write(&file_path, SAMPLE_TEXT).inspect_err(|err| {
-        This is the second line.
-        And this is the third and the last line.";
-        fs::write(&file_path, text).inspect_err(|err| {
             eprintln!("Couldn't create test file: {:?}", err);
         })?;
     }
@@ -55,23 +58,21 @@ fn create_required_files() -> Result<(), std::io::Error> {
 }
 
 fn file_cleanup() -> Result<(), std::io::Error> {
-    let mut path_buffer = PathBuf::new();
+    let path_buffer = sample_file_path();
-
-    path_buffer.push("SampleFilesFolder");
-    path_buffer.push("MultiLineTextFile.txt");
 
     if path_buffer.exists() {
         fs::remove_file(&path_buffer).inspect(|_| {
             println!("Test file removed");
         })?;
     }
-    path_buffer.pop();
 
-    if path_buffer.exists() {
+    if let Some(dir_path) = path_buffer.parent() {
-        fs::remove_dir(&path_buffer).inspect(|_| {
+        if dir_path.exists() {
+            fs::remove_dir(dir_path).inspect(|_| {
                 println!("Test dir removed");
             })?;
         }
+    }
 
     Ok(())
 }