start core info module; move version to info

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/info/mod.rs

@@ -0,0 +1,4 @@
+//! Information about the project. This module contains version, build, system,
+//! etc information which can be queried by admins or used by developers.
+
+pub mod version;

src/core/info/version.rs

@@ -0,0 +1,38 @@
+//! one true function for returning the conduwuit version with the necessary
+//! CONDUWUIT_VERSION_EXTRA env variables used if specified
+//!
+//! Set the environment variable `CONDUWUIT_VERSION_EXTRA` to any UTF-8 string
+//! to include it in parenthesis after the SemVer version. A common value are
+//! git commit hashes.
+
+use std::sync::OnceLock;
+
+static BRANDING: &str = "Conduwuit";
+static SEMANTIC: &str = env!("CARGO_PKG_VERSION");
+
+static VERSION: OnceLock<String> = OnceLock::new();
+static USER_AGENT: OnceLock<String> = OnceLock::new();
+
+#[inline]
+#[must_use]
+pub fn name() -> &'static str { BRANDING }
+
+#[inline]
+pub fn version() -> &'static str { VERSION.get_or_init(init_version) }
+
+#[inline]
+pub fn user_agent() -> &'static str { USER_AGENT.get_or_init(init_user_agent) }
+
+fn init_user_agent() -> String { format!("{}/{}", name(), version()) }
+
+fn init_version() -> String {
+	option_env!("CONDUWUIT_VERSION_EXTRA")
+		.or(option_env!("CONDUIT_VERSION_EXTRA"))
+		.map_or(SEMANTIC.to_owned(), |extra| {
+			if extra.is_empty() {
+				SEMANTIC.to_owned()
+			} else {
+				format!("{SEMANTIC} ({extra})")
+			}
+		})
+}