1 files changed, 119 insertions, 6 deletions

diff --git a/src/dev/check.rs b/src/dev/check.rs
index 9002eaf..ac2c603 100644
--- a/src/dev/check.rs
+++ b/src/dev/check.rs
@@ -1,11 +1,128 @@
 use anyhow::{bail, Context, Result};
-use std::{cmp::Ordering, fs};
+use std::{
+    cmp::Ordering,
+    fs::{self, read_dir},
+    path::PathBuf,
+};
 
 use crate::{
     info_file::{ExerciseInfo, InfoFile},
     CURRENT_FORMAT_VERSION, DEVELOPING_OFFICIAL_RUSTLINGS,
 };
 
+fn forbidden_char(input: &str) -> Option<char> {
+    input.chars().find(|c| *c != '_' && !c.is_alphanumeric())
+}
+
+fn check_info_file_exercises(info_file: &InfoFile) -> Result<hashbrown::HashSet<PathBuf>> {
+    let mut names = hashbrown::HashSet::with_capacity(info_file.exercises.len());
+    let mut paths = hashbrown::HashSet::with_capacity(info_file.exercises.len());
+    for exercise_info in &info_file.exercises {
+        if let Some(c) = forbidden_char(&exercise_info.name) {
+            bail!(
+                "Char `{c}` in the exercise name `{}` is not allowed",
+                exercise_info.name,
+            );
+        }
+
+        if let Some(dir) = &exercise_info.dir {
+            if let Some(c) = forbidden_char(dir) {
+                bail!("Char `{c}` in the exercise dir `{dir}` is not allowed");
+            }
+        }
+
+        if !names.insert(exercise_info.name.as_str()) {
+            bail!(
+                "The exercise name {} is duplicated. Exercise names must all be unique",
+                exercise_info.name,
+            );
+        }
+
+        paths.insert(PathBuf::from(exercise_info.path()));
+    }
+
+    Ok(paths)
+}
+
+fn check_exercise_dir_files(
+    info_file: &InfoFile,
+    info_file_paths: hashbrown::HashSet<PathBuf>,
+) -> Result<hashbrown::HashSet<String>> {
+    let mut names = hashbrown::HashSet::with_capacity(info_file.exercises.len());
+    for entry in read_dir("exercises").context("Failed to open the `exercises` directory")? {
+        let entry = entry.context("Failed to read the `exercises` directory")?;
+
+        if entry.file_type().unwrap().is_file() {
+            let path = entry.path();
+            let file_name = path.file_name().unwrap();
+            if file_name == "README.md" {
+                continue;
+            }
+
+            if !info_file_paths.contains(&path) {
+                bail!("`{}` is expected to be an exercise file corresponding to some exercise in `info.toml`", path.display());
+            }
+
+            let file_name = file_name.to_string_lossy();
+            names.insert(file_name[..file_name.len() - 3].to_string());
+            continue;
+        }
+
+        let dir_path = entry.path();
+        for entry in read_dir(&dir_path)
+            .with_context(|| format!("Failed to open the directory {}", dir_path.display()))?
+        {
+            let entry = entry
+                .with_context(|| format!("Failed to read the directory {}", dir_path.display()))?;
+            let path = entry.path();
+
+            if !entry.file_type().unwrap().is_file() {
+                bail!("Found {} but expected only files", path.display());
+            }
+
+            let file_name = path.file_name().unwrap();
+            if file_name == "README.md" {
+                continue;
+            }
+
+            if !info_file_paths.contains(&path) {
+                bail!("`{}` is expected to be an exercise file corresponding to some exercise in `info.toml`", path.display());
+            }
+
+            let file_name = file_name.to_string_lossy();
+            names.insert(file_name[..file_name.len() - 3].to_string());
+        }
+    }
+
+    Ok(names)
+}
+
+fn check_info_file(info_file: &InfoFile) -> Result<()> {
+    match info_file.format_version.cmp(&CURRENT_FORMAT_VERSION) {
+        Ordering::Less => bail!("`format_version` < {CURRENT_FORMAT_VERSION} (supported version)\nPlease migrate to the latest format version"),
+        Ordering::Greater => bail!("`format_version` > {CURRENT_FORMAT_VERSION} (supported version)\nTry updating the Rustlings program"),
+        Ordering::Equal => (),
+    }
+
+    let info_file_paths = check_info_file_exercises(info_file)?;
+    let names_in_exercises_dir = check_exercise_dir_files(info_file, info_file_paths)?;
+
+    // Now, we know that every file has an exercise in `info.toml`.
+    // But we need to check that every exercise in `info.toml` has a file.
+    if names_in_exercises_dir.len() != info_file.exercises.len() {
+        for exercise_info in &info_file.exercises {
+            if !names_in_exercises_dir.contains(&exercise_info.name) {
+                bail!(
+                    "No exercise file found for the exercise `{}`",
+                    exercise_info.name,
+                );
+            }
+        }
+    }
+
+    Ok(())
+}
+
 pub fn bins_start_end_ind(cargo_toml: &str) -> Result<(usize, usize)> {
     let start_ind = cargo_toml
         .find("bin = [")
@@ -62,11 +179,7 @@ fn check_cargo_toml(
 pub fn check() -> Result<()> {
     let info_file = InfoFile::parse()?;
 
-    match info_file.format_version.cmp(&CURRENT_FORMAT_VERSION) {
-        Ordering::Less => bail!("`format_version` < {CURRENT_FORMAT_VERSION} (supported version)\nPlease migrate to the latest format version"),
-        Ordering::Greater => bail!("`format_version` > {CURRENT_FORMAT_VERSION} (supported version)\nTry updating the Rustlings program"),
-        Ordering::Equal => (),
-    }
+    check_info_file(&info_file)?;
 
     if DEVELOPING_OFFICIAL_RUSTLINGS {
         check_cargo_toml(