feat: add backend constructor

libraries/droplet/Cargo.lock

@@ -158,7 +158,7 @@ dependencies = [
 
 [[package]]
 name = "droplet-rs"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "anyhow",
  "dyn-clone",

libraries/droplet/Cargo.toml

@@ -2,7 +2,7 @@
 edition = "2021"
 authors = ["Drop-OSS"]
 name = "droplet-rs"
-version = "0.8.0"
+version = "0.8.1"
 license = "AGPL-3.0-only"
 description = "Droplet is a `napi.rs` Rust/Node.js package full of high-performance and low-level utils for Drop"
 

libraries/droplet/src/versions/mod.rs

@@ -1,2 +1,54 @@
+use std::path::Path;
+
+use anyhow::Result;
+
+use crate::versions::{
+    backends::{
+        PathVersionBackend, ZipVersionBackend, SEVEN_ZIP_INSTALLED, SUPPORTED_FILE_EXTENSIONS,
+    },
+    types::VersionBackend,
+};
+
+pub mod backends;
 pub mod types;
-pub mod backends;
+pub fn create_backend_constructor<'a>(
+    path: &Path,
+) -> Option<Box<dyn FnOnce() -> Result<Box<dyn VersionBackend + Send + 'a>>>> {
+    if !path.exists() {
+        return None;
+    }
+
+    let is_directory = path.is_dir();
+    if is_directory {
+        let base_dir = path.to_path_buf();
+        return Some(Box::new(move || {
+            Ok(Box::new(PathVersionBackend { base_dir }))
+        }));
+    };
+
+    if *SEVEN_ZIP_INSTALLED {
+        /*
+        Slow 7zip integrity test
+        let mut test = Command::new("7z");
+        test.args(vec!["t", path.to_str().expect("invalid utf path")]);
+        let status = test.status().ok()?;
+        if status.code().unwrap_or(1) == 0 {
+          let buf = path.to_path_buf();
+          return Some(Box::new(move || Ok(Box::new(ZipVersionBackend::new(buf)?))));
+        }
+         */
+        // Fast filename-based test
+        if let Some(extension) = path.extension().and_then(|v| v.to_str()) {
+            let supported = SUPPORTED_FILE_EXTENSIONS
+                .iter()
+                .find(|v| ***v == *extension)
+                .is_some();
+            if supported {
+                let buf = path.to_path_buf();
+                return Some(Box::new(move || Ok(Box::new(ZipVersionBackend::new(buf)?))));
+            }
+        }
+    }
+
+    None
+}