try package.swift in root of repo

Package.swift

@@ -0,0 +1,110 @@
+// swift-tools-version: 5.9
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+// Copyright 2024, the Chromium project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import Foundation
+import PackageDescription
+
+enum ConfigurationError: Error {
+  case fileNotFound(String)
+  case parsingError(String)
+  case invalidFormat(String)
+}
+
+let iosRootDirectory = String(URL(string: #file)!.deletingLastPathComponent().absoluteString
+  .dropLast())
+
+func loadPubspecVersion() throws -> String {
+  let pubspecPath = NSString.path(withComponents: [iosRootDirectory, "..", "..", "pubspec.yaml"])
+  do {
+    let yamlString = try String(contentsOfFile: pubspecPath, encoding: .utf8)
+    if let versionLine = yamlString.split(separator: "\n")
+      .first(where: { $0.starts(with: "version:") }) {
+      let version = versionLine.split(separator: ":")[1].trimmingCharacters(in: .whitespaces)
+      return version.replacingOccurrences(of: "+", with: "-")
+    } else {
+      throw ConfigurationError.invalidFormat("No version line found in pubspec.yaml")
+    }
+  } catch {
+    throw ConfigurationError.fileNotFound("Error loading or parsing pubspec.yaml: \(error)")
+  }
+}
+
+func loadFirebaseSDKVersion() throws -> String {
+  let firebaseCoreScriptPath = NSString.path(withComponents: [
+    iosRootDirectory,
+    "..",
+    "..",
+    "..",
+    "firebase_core",
+    "ios",
+    "firebase_sdk_version.rb",
+  ])
+  do {
+    let content = try String(contentsOfFile: firebaseCoreScriptPath, encoding: .utf8)
+    let pattern = #"def firebase_sdk_version!\(\)\n\s+'([^']+)'\nend"#
+    if let regex = try? NSRegularExpression(pattern: pattern, options: []),
+       let match = regex.firstMatch(
+         in: content,
+         range: NSRange(content.startIndex..., in: content)
+       ) {
+      if let versionRange = Range(match.range(at: 1), in: content) {
+        return String(content[versionRange])
+      } else {
+        throw ConfigurationError.invalidFormat("Invalid format in firebase_sdk_version.rb")
+      }
+    } else {
+      throw ConfigurationError.parsingError("No match found in firebase_sdk_version.rb")
+    }
+  } catch {
+    throw ConfigurationError
+      .fileNotFound("Error loading or parsing firebase_sdk_version.rb: \(error)")
+  }
+}
+
+let library_version: String
+let firebase_sdk_version_string: String
+
+do {
+  library_version = try loadPubspecVersion()
+  firebase_sdk_version_string = try loadFirebaseSDKVersion()
+} catch {
+  fatalError("Failed to load configuration: \(error)")
+}
+
+guard let firebase_sdk_version = Version(firebase_sdk_version_string) else {
+  fatalError("Invalid Firebase SDK version: \(firebase_sdk_version_string)")
+}
+
+let package = Package(
+  name: "firebase_core",
+  platforms: [
+    .iOS("13.0"),
+  ],
+  products: [
+    .library(name: "firebase-core", targets: ["firebase_core"]),
+  ],
+  dependencies: [
+    .package(url: "https://github.com/firebase/firebase-ios-sdk", from: firebase_sdk_version),
+  ],
+  targets: [
+    .target(
+      name: "firebase_core",
+      dependencies: [
+        // No product for firebase-core so we pull in the smallest one
+        .product(name: "FirebaseInstallations", package: "firebase-ios-sdk"),
+      ],
+      resources: [
+        .process("Resources"),
+      ],
+      cSettings: [
+        .headerSearchPath("packages/firebase_core/firebase_core/ios/firebase_core/include"),
+        .define("LIBRARY_VERSION", to: "\"\(library_version)\""),
+        .define("LIBRARY_NAME", to: "\"flutter-fire-core\""),
+      ]
+    ),
+  ]
+)