watt: turn into a library

watt/fs.rs

@@ -0,0 +1,80 @@
+use std::{
+  error,
+  fs,
+  io,
+  path::Path,
+  str,
+};
+
+use anyhow::Context;
+
+pub fn exists(path: impl AsRef<Path>) -> bool {
+  let path = path.as_ref();
+
+  path.exists()
+}
+
+pub fn read_dir(path: impl AsRef<Path>) -> anyhow::Result<Option<fs::ReadDir>> {
+  let path = path.as_ref();
+
+  match fs::read_dir(path) {
+    Ok(entries) => Ok(Some(entries)),
+
+    Err(error) if error.kind() == io::ErrorKind::NotFound => Ok(None),
+
+    Err(error) => {
+      Err(error).context(format!(
+        "failed to read directory '{path}'",
+        path = path.display()
+      ))
+    },
+  }
+}
+
+pub fn read(path: impl AsRef<Path>) -> anyhow::Result<Option<String>> {
+  let path = path.as_ref();
+
+  match fs::read_to_string(path) {
+    Ok(string) => Ok(Some(string.trim().to_owned())),
+
+    Err(error) if error.kind() == io::ErrorKind::NotFound => Ok(None),
+
+    Err(error) => {
+      Err(error)
+        .context(format!("failed to read '{path}", path = path.display()))
+    },
+  }
+}
+
+pub fn read_n<N: str::FromStr>(
+  path: impl AsRef<Path>,
+) -> anyhow::Result<Option<N>>
+where
+  N::Err: error::Error + Send + Sync + 'static,
+{
+  let path = path.as_ref();
+
+  match read(path)? {
+    Some(content) => {
+      Ok(Some(content.trim().parse().with_context(|| {
+        format!(
+          "failed to parse contents of '{path}' as a unsigned number",
+          path = path.display(),
+        )
+      })?))
+    },
+
+    None => Ok(None),
+  }
+}
+
+pub fn write(path: impl AsRef<Path>, value: &str) -> anyhow::Result<()> {
+  let path = path.as_ref();
+
+  fs::write(path, value).with_context(|| {
+    format!(
+      "failed to write '{value}' to '{path}'",
+      path = path.display(),
+    )
+  })
+}