From afc7d9df8eac79daa2abe9dd75be31ab0dc1288d Mon Sep 17 00:00:00 2001
From: Abdelilah El Aissaoui <aeab13@gmail.com>
Date: Fri, 25 Feb 2022 00:40:11 +0100
Subject: [PATCH] Improved performance when multiple FS changes occur in a
 fraction of a second

Between update there is a minimum of 0.5s even if there have been multiple file updates
---
 src/main/kotlin/app/git/DiffManager.kt        |  2 +-
 src/main/kotlin/app/git/FileChangesWatcher.kt | 46 ++++++++++++++++---
 .../kotlin/app/viewmodels/TabViewModel.kt     | 20 ++++----
 3 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/src/main/kotlin/app/git/DiffManager.kt b/src/main/kotlin/app/git/DiffManager.kt
index 3d69b83..ca20c53 100644
--- a/src/main/kotlin/app/git/DiffManager.kt
+++ b/src/main/kotlin/app/git/DiffManager.kt
@@ -87,7 +87,7 @@ class DiffManager @Inject constructor(
     }
 }
 
-fun prepareTreeParser(repository: Repository, commit: RevCommit): AbstractTreeIterator? {
+fun prepareTreeParser(repository: Repository, commit: RevCommit): AbstractTreeIterator {
     // from the commit we can build the tree which allows us to construct the TreeParser
     RevWalk(repository).use { walk ->
         val tree: RevTree = walk.parseTree(commit.tree.id)
diff --git a/src/main/kotlin/app/git/FileChangesWatcher.kt b/src/main/kotlin/app/git/FileChangesWatcher.kt
index f5db720..400968c 100644
--- a/src/main/kotlin/app/git/FileChangesWatcher.kt
+++ b/src/main/kotlin/app/git/FileChangesWatcher.kt
@@ -1,17 +1,26 @@
 package app.git
 
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.flow.flow
-import kotlinx.coroutines.flow.flowOn
+import kotlinx.coroutines.*
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.SharedFlow
 import java.io.IOException
 import java.nio.file.*
 import java.nio.file.StandardWatchEventKinds.*
 import java.nio.file.attribute.BasicFileAttributes
 import javax.inject.Inject
 
+private const val MIN_TIME_IN_MS_BETWEEN_REFRESHES = 500L
 
 class FileChangesWatcher @Inject constructor() {
-    suspend fun watchDirectoryPath(pathStr: String, ignoredDirsPath: List<String>) = flow {
+    private var lastNotify = 0L
+    private var asyncJob: Job? = null
+
+    private val _changesNotifier = MutableSharedFlow<Long>()
+    val changesNotifier: SharedFlow<Long> = _changesNotifier
+
+    suspend fun watchDirectoryPath(pathStr: String, ignoredDirsPath: List<String>) = withContext(Dispatchers.IO) {
+        println(ignoredDirsPath)
+
         val watchService = FileSystems.getDefault().newWatchService()
 
         val path = Paths.get(pathStr)
@@ -40,10 +49,33 @@ class FileChangesWatcher @Inject constructor() {
 
         var key: WatchKey
         while (watchService.take().also { key = it } != null) {
-            this.emit(Unit)
             key.pollEvents()
+
+            println("Polled events")
+
+            asyncJob?.cancel()
+
+            // Sometimes external apps can run filesystem multiple operations in a fraction of a second.
+            // To prevent excessive updates, we add a slight delay between updates emission to prevent slowing down
+            // the app by constantly running "git status".
+            val currentTimeMillis = System.currentTimeMillis()
+            val diffTime = currentTimeMillis - lastNotify
+
+            if (diffTime > MIN_TIME_IN_MS_BETWEEN_REFRESHES) {
+                _changesNotifier.emit(currentTimeMillis)
+                println("Sync emit with diff time $diffTime")
+            } else {
+                asyncJob = async {
+                    delay(MIN_TIME_IN_MS_BETWEEN_REFRESHES)
+                    println("Async emit")
+                    if (isActive)
+                        _changesNotifier.emit(currentTimeMillis)
+                }
+            }
+
+            lastNotify = currentTimeMillis
+
             key.reset()
         }
-    }.flowOn(Dispatchers.IO)
-
+    }
 }
\ No newline at end of file
diff --git a/src/main/kotlin/app/viewmodels/TabViewModel.kt b/src/main/kotlin/app/viewmodels/TabViewModel.kt
index 50d11bf..33869a7 100644
--- a/src/main/kotlin/app/viewmodels/TabViewModel.kt
+++ b/src/main/kotlin/app/viewmodels/TabViewModel.kt
@@ -7,13 +7,10 @@ import app.credentials.CredentialsStateManager
 import app.git.*
 import app.newErrorNow
 import app.ui.SelectedItem
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.cancel
+import kotlinx.coroutines.*
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.collect
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
 import org.eclipse.jgit.api.Git
 import org.eclipse.jgit.lib.ObjectId
 import org.eclipse.jgit.lib.Repository
@@ -148,15 +145,18 @@ class TabViewModel @Inject constructor(
     private suspend fun watchRepositoryChanges(git: Git) = tabState.managerScope.launch(Dispatchers.IO) {
         val ignored = git.status().call().ignoredNotInIndex.toList()
 
+        launch {
+            fileChangesWatcher.changesNotifier.collect {
+                if (!tabState.operationRunning) { // Only update if there isn't any process running
+                    println("Changes detected, loading status")
+                    checkUncommitedChanges()
+                }
+            }
+        }
         fileChangesWatcher.watchDirectoryPath(
             pathStr = git.repository.directory.parent,
             ignoredDirsPath = ignored,
-        ).collect {
-            if (!tabState.operationRunning) { // Only update if there isn't any process running
-                println("Changes detected, loading status")
-                checkUncommitedChanges()
-            }
-        }
+        )
     }
 
     private suspend fun checkUncommitedChanges(fullUpdateLog: Boolean = false) = tabState.runOperation(