1 files changed, 135 insertions, 0 deletions
diff --git a/src/Extensions/FileManagerExtensions.cs b/src/Extensions/FileManagerExtensions.cs
new file mode 100644
index 0000000..6f497e7
--- /dev/null
+++ b/src/Extensions/FileManagerExtensions.cs
@@ -0,0 +1,135 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Text.Json;
+using System.Threading.Tasks;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+using VNLib.Tools.Build.Executor.Model;
+using VNLib.Tools.Build.Executor.Constants;
+using static VNLib.Tools.Build.Executor.Constants.Config;
+
+namespace VNLib.Tools.Build.Executor.Extensions
+{
+
+    internal static class FileManagerExtensions
+    {
+
+        private static readonly ConditionalWeakTable<IProject, object> _projectHashes = new();
+
+        /// <summary>
+        /// Gets all external dependencies for the current module
+        /// </summary>
+        /// <param name="module"></param>
+        /// <returns>An array of project names of all the dependencies outside a given module</returns>
+        public static string[] GetExternalDependencies(this IModuleData module)
+        {
+            /*
+             * We need to get all child project dependencies that rely on projects
+             * outside of the current module.
+             * 
+             * This assumes all projects within this model are properly linked
+             * and assumed to be build together, as is 99% of the case, otherwise
+             * custom build impl will happen at the Task level
+             */
+
+            //Get the project file names contained in the current module
+            string[] selfProjects = module.Projects.Select(static p => p.ProjectFile.Name).ToArray();
+
+            return module.Projects.SelectMany(static p => p.GetDependencies()).Where(dep => !selfProjects.Contains(dep)).ToArray();
+        }
+
+        /// <summary>
+        /// Determines if any source files have changed
+        /// </summary>
+        /// <param name="commit">The most recent commit hash</param>
+        public static async Task CheckSourceChangedAsync(this IModuleFileManager manager, IProject project, BuildConfig config, string commit)
+        {
+            //Compute current sum
+            string sum = await project.GetSourceFileHashAsync(config);
+
+            //Old sum file exists
+            byte[]? sumData = await manager.ReadCheckSumAsync(project);
+
+            //Try to read the old sum file
+            if (sumData != null)
+            {
+                //Parse sum file
+                using JsonDocument sumDoc = JsonDocument.Parse(sumData);
+
+                //Get the sum
+                string? hexSum = sumDoc.RootElement.GetProperty("sum").GetString();
+
+                //Confirm the current sum and the found sum are equal
+                if (sum.Equals(hexSum, StringComparison.OrdinalIgnoreCase))
+                {
+                    Log.Verbose("Project {p} source is {up}", project.ProjectName, "up-to-date");
+
+                    //Project source is up-to-date
+                    project.UpToDate = true;
+
+                    //No changes made
+                    return;
+                }
+            }
+
+            Log.Verbose("Project {p} source is {up}", project.ProjectName, "changed");
+
+            //Store sum change
+            object sumChange = new Dictionary<string, string>()
+            {
+                { "sum", sum },
+                { "commit", commit },
+                { "modified", DateTimeOffset.UtcNow.ToString("s") }
+            };
+
+            //Store sum change for later
+            _projectHashes.Add(project, sumChange);
+
+            project.UpToDate = false;
+        }
+
+        /// <summary>
+        /// Creates the module's output directory
+        /// </summary>
+        /// <param name="manager"></param>
+        public static void CreateOutput(this IModuleFileManager manager)
+        {
+            //Create output directory for solution
+            _ = Directory.CreateDirectory(manager.OutputDir);
+        }
+
+        /// <summary>
+        /// Deletes the output's module directory
+        /// </summary>
+        /// <param name="manager"></param>
+        public static void CleanOutput(this IModuleFileManager manager)
+        {
+            //Delete output directory for solution
+            if (Directory.Exists(manager.OutputDir))
+            {
+                Directory.Delete(manager.OutputDir, true);
+            }
+        }
+       
+
+        /// <summary>
+        /// Writes the source file checksum change to the project's sum file
+        /// </summary>
+        /// <param name="project"></param>
+        /// <param name="project">The project to write the checksum for</param>
+        /// <returns>A task that resolves when the sum file has been updated</returns>
+        public static Task CommitSumChangeAsync(this IModuleFileManager manager, IProject project)
+        {
+            if (!_projectHashes.TryGetValue(project, out object? sumChange))
+            {
+                return Task.CompletedTask;
+            }
+
+            byte[] sumData = JsonSerializer.SerializeToUtf8Bytes(sumChange);
+
+            return manager.WriteChecksumAsync(project, sumData);
+        }
+    }
+}
+\ No newline at end of file