chore: moving Swift files to a dedicated folder.

Author: ShikiSuen

Package.swift

@@ -33,13 +33,13 @@ let package = Package(
     .plugin(
       name: "CargoBuild",
       capability: .buildTool(),
-      path: "tools/CargoBuildPlugin"
+      path: "swift/tools/CargoBuildPlugin"
     ),
-    // Swift test target in `tests_swift` to validate C API accessibility from Swift
+    // Swift test target in `swift/unit_tests` to validate C API accessibility from Swift
     .testTarget(
       name: "ChewingTests",
       dependencies: ["CChewing"],
-      path: "tests_swift"
+      path: "swift/unit_tests"
     ),
   ]
 )

scripts/build-cargo.sh swift/scripts/build-cargo.shscripts/build-cargo.sh renamed to swift/scripts/build-cargo.sh

@@ -0,0 +1,69 @@
+import Foundation
+import PackagePlugin
+
+@main
+struct CargoBuildPlugin: BuildToolPlugin {
+  func createBuildCommands(context: PluginContext, target: Target) throws -> [Command] {
+    // Paths
+    let packageDir = context.package.directoryURL
+    let capiDir = packageDir.appendingPathComponent("capi")
+    // Use the plugin's work directory (sandboxed) to avoid macOS permission issues
+    let scratchTarget = context.pluginWorkDirectoryURL.appendingPathComponent("cargo-target")
+
+    // Auto-build is enabled by default. To disable automatic Cargo build, set `LIBCHEWING_AUTO_BUILD_CARGO=0`.
+    if ProcessInfo.processInfo.environment["LIBCHEWING_AUTO_BUILD_CARGO"] == "0" {
+      return []
+    }
+
+    // Prefer common cargo install locations; if not found, abort with a clear error
+    let fm = FileManager.default
+    let home = fm.homeDirectoryForCurrentUser.path
+    let candidates: [URL] = [
+      URL(fileURLWithPath: "/usr/bin/cargo"),
+      URL(fileURLWithPath: "/usr/local/bin/cargo"),
+      URL(fileURLWithPath: "/opt/homebrew/bin/cargo"),
+      URL(fileURLWithPath: "\(home)/.cargo/bin/cargo"),
+    ]
+
+    var cargoURL: URL? = nil
+    for url in candidates {
+      if fm.fileExists(atPath: url.path) {
+        cargoURL = url
+        break
+      }
+    }
+
+    guard let cargo = cargoURL else {
+      struct UserError: Error, CustomStringConvertible {
+        let description: String
+        init(_ s: String) { description = s }
+      }
+      throw UserError(
+        "`cargo` not found on the system. Please install Rust (https://rustup.rs/) to enable automatic builds, or disable automatic Cargo build by setting `LIBCHEWING_AUTO_BUILD_CARGO=0` and run `swift/scripts/build-cargo.sh` manually to produce the library before running `swift build`."
+      )
+    }
+
+    let manifestPath = capiDir.appendingPathComponent("Cargo.toml").path
+    let targetDir = scratchTarget.path
+
+    // Arguments: build the chewing_capi crate in release mode into the plugin workdir target
+    let args = [
+      "build",
+      "--release",
+      "--manifest-path",
+      manifestPath,
+      "--target-dir",
+      targetDir,
+    ]
+
+    return [
+      .prebuildCommand(
+        displayName: "Building chewing_capi via cargo",
+        executable: cargo,
+        arguments: args,
+        environment: [:],
+        outputFilesDirectory: scratchTarget
+      )
+    ]
+  }
+}