Added platform trait and specific platforms implementations plust HostPlatform to provide common api

fj-host/src/lib.rs

@@ -5,6 +5,8 @@
 
 #![deny(missing_docs)]
 
+mod platform;
+
 use std::{
     collections::{HashMap, HashSet},
     ffi::OsStr,
@@ -18,6 +20,8 @@ use std::{
 use notify::Watcher as _;
 use thiserror::Error;
 
+use self::platform::HostPlatform;
+
 /// Represents a Fornjot model
 pub struct Model {
     src_path: PathBuf,
@@ -47,15 +51,7 @@ impl Model {
         let src_path = path.join("src");
 
         let lib_path = {
-            let file = if cfg!(windows) {
-                format!("{}.dll", name)
-            } else if cfg!(target_os = "macos") {
-                format!("lib{}.dylib", name)
-            } else {
-                //Unix
-                format!("lib{}.so", name)
-            };
-
+            let file = HostPlatform::host_file_name(&name);
             let target_dir = target_dir.unwrap_or_else(|| path.join("target"));
             target_dir.join("debug").join(file)
         };

fj-host/src/platform.rs

@@ -0,0 +1,45 @@
+// Represents platform trait
+trait Platform {
+    fn file_name(name: &str) -> String;
+}
+
+// Represents all platforms supported
+
+// Mac OS
+struct Macos;
+// Windows
+struct Windows;
+// Linux
+struct Unix;
+
+impl Platform for Windows {
+    fn file_name(name: &str) -> String {
+        format!("{}.dll", name)
+    }
+}
+impl Platform for Macos {
+    fn file_name(name: &str) -> String {
+        format!("lib{}.dylib", name)
+    }
+}
+impl Platform for Unix {
+    fn file_name(name: &str) -> String {
+        format!("lib{}.so", name)
+    }
+}
+
+// Represents common apis availiable independent of hosts
+pub struct HostPlatform;
+
+impl HostPlatform {
+    pub fn host_file_name(name: &str) -> String {
+        if cfg!(windows) {
+            Windows::file_name(name)
+        } else if cfg!(target_os = "macos") {
+            Macos::file_name(name)
+        } else {
+            //Unix
+            Unix::file_name(name)
+        }
+    }
+}