Complete the new crate, but...

Cargo.toml

@@ -17,15 +17,13 @@ rustdoc-args = ["--document-private-items", "--cfg", "docsrs"]
 
 
 [features]
-default = ["single_envvars", "single_envfiles", "multi", "handle", "macros"]
-single_envvars = []
-single_envfiles = []
-multi = ["single_envvars", "single_envfiles"]
-handle = ["multi"]
-macros = ["lazy_static", "handle"]
+default = ["envvars", "envfiles", "envdot"]
+envvars = []
+envfiles = []
+envdot = ["regex"]
 testing = ["tempfile"]
 
-
 [dependencies]
-lazy_static = { version = "1.4.0", optional = true }
-tempfile = { version = "3.5.0", optional = true }
+tempfile = { version = "3.9.0", optional = true }
+regex = { version = "1.10.2", optional = true }
+

src/cache.rs

@@ -0,0 +1,22 @@
+use std::fmt::Debug;
+use std::path::Path;
+
+
+#[derive(Clone, Default, Debug)]
+pub struct MicronfigCache {
+	#[cfg(feature = "envdot")]
+	pub dotenvs: Vec<crate::sources::envdot::DotEnv>
+}
+
+impl MicronfigCache {
+	#[cfg(feature = "envdot")]
+	pub fn add_envdot<P>(&mut self, path: P)
+		where P: AsRef<Path> + Debug
+	{
+		self.dotenvs.push(
+			crate::sources::envdot::DotEnv::from(
+				path
+			)
+		);
+	}
+}

src/lib.rs

@@ -0,0 +1,143 @@
+use std::fmt::Debug;
+
+pub mod sources;
+pub mod cache;
+
+#[macro_export]
+macro_rules! __micronfig_last {
+	[ $head:ty, $( $tail:ty, )+ ] => {
+		$crate::__micronfig_last![ $( $tail, )+ ]
+	};
+	[ $head:ty, ] => {
+		$head
+	}
+}
+
+/// # Examples
+///
+/// ## Get a string directly
+///
+/// ```
+/// micronfig::config! {
+/// 	MY_STRING_A: String,
+/// 	MY_STRING_B: String
+/// }
+/// ```
+///
+/// ## Parse envvar as a number
+///
+/// ```
+/// micronfig::config! {
+/// 	MY_UNSIGNED_NUMBER: u32,
+/// 	MY_SIGNED_NUMBER: i32
+/// }
+/// ```
+///
+/// ## Parse string as an IpAddr
+///
+/// ```
+/// use std::net::IpAddr;
+///
+/// micronfig::config! {
+/// 	MY_IP_ADDR: IpAddr
+/// }
+/// ```
+///
+/// ## Parse string as a number, then convert it into an Ipv4Addr
+///
+/// ```
+/// use std::net::Ipv4Addr;
+///
+/// micronfig::config! {
+/// 	MY_NUMERIC_IP_ADDR: Ipv4Addr
+/// }
+/// ```
+///
+/// ## Parse string with custom logic resulting into a number
+///
+/// ```
+/// struct CustomConverter(u8);
+///
+/// impl From<String> for CustomConverter {
+/// 	fn from(value: String) -> Self {
+///         Self(123)
+///     }
+/// }
+///
+/// impl Into<u8> for CustomConverter {
+/// 	fn into(self) -> u8 {
+///         self.0
+///     }
+/// }
+///
+/// micronfig::config! {
+/// 	MY_ONETWOTHREE: CustomConverter => u8,
+/// 	MY_ONETWOTHREE_BUT_EXPLICIT: String => CustomConverter => u8
+/// }
+/// ```
+///
+#[macro_export]
+macro_rules! config {
+	{ $( $identifier:ident: $( $conversion:ty )=>* ),+ } => {
+		static __micronfig_cache: std::sync::OnceLock<$crate::cache::MicronfigCache> = std::sync::OnceLock::new();
+
+		fn __micronfig_init_cache() -> $crate::cache::MicronfigCache {
+			let mut this = $crate::cache::MicronfigCache::default();
+
+			if cfg!(feature = "envdot") {
+				this.add_envdot("./.env");
+				this.add_envdot("./.env.local");
+			}
+
+			this
+		}
+
+		fn __micronfig_get(key: &str) -> Option<String> {
+			let mut value: Option<String> = None;
+
+			if cfg!(feature = "envfiles") && value.is_none() {
+				value = $crate::sources::envfiles::get(format!("{key}_FILE"));
+			}
+
+			if cfg!(feature = "envvars") && value.is_none() {
+				value = $crate::sources::envvars::get(&key);
+			}
+
+			if cfg!(feature = "envdot") && value.is_none() {
+				let cache = __micronfig_cache.get_or_init(__micronfig_init_cache);
+
+				for dotenv in cache.dotenvs.iter() {
+					value = $crate::sources::envdot::get(dotenv, &key);
+					if value.is_some() {
+						break;
+					}
+				}
+			}
+
+			value
+		}
+
+		$(
+			pub(self) mod $identifier {
+				pub static lock: std::sync::OnceLock<Option< $crate::__micronfig_last![ $( $conversion, )+ ] >> = std::sync::OnceLock::new();
+			}
+
+			pub(crate) fn $identifier () -> &'static Option< $crate::__micronfig_last![ $( $conversion, )+ ] > {
+				$identifier::lock.get_or_init(|| {
+					let key = stringify!($identifier);
+					let value = __micronfig_get(key);
+
+					$(
+						let value: Option<$conversion> = value.map(Into::into);
+					)+
+
+					value
+				})
+			}
+		)+
+	}
+}
+
+config! {
+	SOMETHING: String
+}

src/sources/envdot.rs

@@ -0,0 +1,50 @@
+//! Variables defined in specific dotenv files.
+
+use std::collections::HashMap;
+use std::fmt::Debug;
+use std::fs::File;
+use std::io::Read;
+use std::path::Path;
+use regex::Regex;
+
+#[derive(Clone, Default, PartialEq, Eq, Debug)]
+pub struct DotEnv(
+	HashMap<String, String>
+);
+
+impl DotEnv {
+	pub fn var(&self, key: &str) -> Option<&String> {
+		self.0.get(key)
+	}
+}
+
+impl<P> From<P> for DotEnv
+	where P: AsRef<Path> + Debug
+{
+	fn from(value: P) -> Self {
+		let mut file = File::open(&value)
+			.expect(&*format!("to be able to open {value:?}"));
+
+		let mut contents: String = String::new();
+		file.read_to_string(&mut contents)
+			.expect(&*format!("to be able to read {value:?}"));
+
+		let mut keys: HashMap<String, String> = HashMap::new();
+
+		let re = Regex::new(r#"^(?:export\s+)?([^=]+)\s*=\s*(.+)$"#)
+			.expect("Regex to be valid");
+
+		let _ = contents.split("\n")
+			.filter_map(|line| re.captures(line))
+			.map(|capture| (capture[0].to_owned(), capture[1].to_owned()))
+			.map(|(key, value)| keys.insert(key, value));
+
+		Self(keys)
+	}
+}
+
+/// Get the contents of the file at the path specified by the given environment variable.
+pub fn get(dotenv: &DotEnv, key: &str) -> Option<String>
+{
+	dotenv.var(key).map(|v| v.to_owned())
+}

src/sources/envfiles.rs

@@ -0,0 +1,21 @@
+//! Contents of files at paths defined by environment variables.
+
+/// Get the contents of the file at the path specified by the given environment variable.
+pub fn get<Key>(key: Key) -> Option<String>
+	where Key: AsRef<std::ffi::OsStr>,
+{
+	let path = std::env::var(key).ok()?;
+
+	let path = std::ffi::OsString::from(path);
+	let path = std::path::PathBuf::from(path);
+
+	let mut file = std::fs::File::open(&path)
+		.expect(&*format!("to be able to open file at {path:?}"));
+
+	use std::io::Read;
+	let mut data = String::new();
+	file.read_to_string(&mut data)
+		.expect(&*format!("to be able to read from file at {path:?}"));
+
+	Some(data)
+}

src/sources/envvars.rs

@@ -0,0 +1,8 @@
+//! Environment variables.
+
+/// Get the specified environment variable.
+pub fn get<Key>(key: Key) -> Option<String>
+	where Key: AsRef<std::ffi::OsStr>,
+{
+	std::env::var(key).ok()
+}

src/sources/mod.rs

@@ -0,0 +1,8 @@
+#[cfg(feature = "envvars")]
+pub mod envvars;
+
+#[cfg(feature = "envfiles")]
+pub mod envfiles;
+
+#[cfg(feature = "envdot")]
+pub mod envdot;