From 49ee38a93637e67bbe017f11d116931ecb29b3d2 Mon Sep 17 00:00:00 2001
From: InsanusMokrassar <ovsyannikov.alexey95@gmail.com>
Date: Thu, 26 Nov 2020 15:03:40 +0600
Subject: [PATCH] FileStandardKeyValueRepo

---
 CHANGELOG.md                                  |   4 +
 .../repos/FileStandardKeyValueRepo.kt         | 168 ++++++++++++++++++
 2 files changed, 172 insertions(+)
 create mode 100644 repos/common/src/jvmMain/kotlin/dev/inmo/micro_utils/repos/FileStandardKeyValueRepo.kt

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9076a6f3a37..f69a5c3bdd6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@
         * `Pagination` got new extension: `Pagination#isFirstPage`
 * `Coroutines`:
     * New extension `FlowCollector#invoke` has been added
+* `Repos`
+    * `Common`
+        * `JVM` (and `Android` since `Android API 26`):
+            * `FileStandardKeyValueRepo` has been added
 
 ## 0.4.5
 
diff --git a/repos/common/src/jvmMain/kotlin/dev/inmo/micro_utils/repos/FileStandardKeyValueRepo.kt b/repos/common/src/jvmMain/kotlin/dev/inmo/micro_utils/repos/FileStandardKeyValueRepo.kt
new file mode 100644
index 00000000000..3e698df4e29
--- /dev/null
+++ b/repos/common/src/jvmMain/kotlin/dev/inmo/micro_utils/repos/FileStandardKeyValueRepo.kt
@@ -0,0 +1,168 @@
+package dev.inmo.micro_utils.repos
+
+import dev.inmo.micro_utils.pagination.*
+import dev.inmo.micro_utils.pagination.utils.reverse
+import kotlinx.coroutines.*
+import kotlinx.coroutines.flow.*
+import java.io.File
+import java.nio.file.FileSystems
+import java.nio.file.Path
+import java.nio.file.StandardWatchEventKinds.*
+
+private inline val String.isAbsolute
+    get() = startsWith(File.separator)
+
+class FileReadStandardKeyValueRepo(
+    private val folder: File
+) : ReadStandardKeyValueRepo<String, File> {
+    init {
+        folder.mkdirs()
+    }
+
+    override suspend fun get(k: String): File? {
+        val file = File(folder, k)
+        if (file.exists()) {
+            return file
+        }
+        return null
+    }
+
+    override suspend fun values(pagination: Pagination, reversed: Boolean): PaginationResult<File> {
+        val count = count()
+        val resultPagination = if (reversed) pagination.reverse(count) else pagination
+        val filesPaths = folder.list() ?.copyOfRange(resultPagination.firstIndex, resultPagination.lastIndex) ?: return emptyPaginationResult()
+        if (reversed) {
+            filesPaths.reverse()
+        }
+        return filesPaths.map { File(folder, it) }.createPaginationResult(
+            resultPagination,
+            count
+        )
+    }
+
+    override suspend fun keys(pagination: Pagination, reversed: Boolean): PaginationResult<String> {
+        val count = count()
+        val resultPagination = if (reversed) pagination.reverse(count) else pagination
+        val filesPaths = folder.list() ?.copyOfRange(resultPagination.firstIndex, resultPagination.lastIndex) ?: return emptyPaginationResult()
+        if (reversed) {
+            filesPaths.reverse()
+        }
+        return filesPaths.toList().createPaginationResult(
+            resultPagination,
+            count
+        )
+    }
+
+    override suspend fun keys(
+        v: File,
+        pagination: Pagination,
+        reversed: Boolean
+    ): PaginationResult<String> {
+        val resultPagination = if (reversed) pagination.reverse(1L) else pagination
+        return if (resultPagination.isFirstPage) {
+            val fileSubpath = v.absolutePath.removePrefix(folder.absolutePath)
+            if (fileSubpath == v.absolutePath) {
+                emptyList()
+            } else {
+                listOf(fileSubpath)
+            }
+        } else {
+            emptyList()
+        }.createPaginationResult(resultPagination, 1L)
+    }
+
+    override suspend fun contains(key: String): Boolean {
+        return File(folder, key).exists()
+    }
+
+    override suspend fun count(): Long = folder.list() ?.size ?.toLong() ?: 0L
+}
+
+/**
+ * Files watching will not correctly works on Android with version of API lower than API 26
+ */
+class FileWriteStandardKeyValueRepo(
+    private val folder: File,
+    filesChangedProcessingScope: CoroutineScope? = null
+) : WriteStandardKeyValueRepo<String, File> {
+    private val _onNewValue = MutableSharedFlow<Pair<String, File>>()
+    override val onNewValue: Flow<Pair<String, File>> = _onNewValue.asSharedFlow()
+    private val _onValueRemoved = MutableSharedFlow<String>()
+    override val onValueRemoved: Flow<String> = _onValueRemoved.asSharedFlow()
+
+    init {
+        folder.mkdirs()
+        filesChangedProcessingScope ?.let {
+            it.launch {
+                try {
+                    val folderPath = folder.toPath()
+                    while (isActive) {
+                        val key = try {
+                            folderPath.register(FileSystems.getDefault().newWatchService(), ENTRY_CREATE, ENTRY_MODIFY, ENTRY_DELETE)
+                        } catch (e: Exception) {
+                            // add verbose way to show that file watching is not working
+                            return@launch
+                        }
+
+                        for (event in key.pollEvents()) {
+                            val relativeFilePath = (event.context() as? Path) ?: continue
+                            val file = relativeFilePath.toFile()
+                            val relativePath = file.toRelativeString(folder)
+
+                            when (event.kind()) {
+                                ENTRY_CREATE, ENTRY_MODIFY -> {
+                                    launch {
+                                        _onNewValue.emit(relativePath to file)
+                                    }
+                                }
+                                ENTRY_DELETE -> {
+                                    launch {
+                                        _onValueRemoved.emit(relativePath)
+                                    }
+                                }
+                            }
+                        }
+
+                        if (key.isValid || folder.exists()) {
+                            continue
+                        }
+                        break
+                    }
+                } catch (e: Throwable) {
+                    // add verbose way to notify that this functionality is disabled
+                }
+            }
+        }
+    }
+
+    override suspend fun set(toSet: Map<String, File>) {
+        supervisorScope {
+            toSet.map { (filename, fileSource) ->
+                launch {
+                    val file = File(folder, filename)
+
+                    file.delete()
+                    fileSource.copyTo(file, overwrite = true)
+                    _onNewValue.emit(filename to file)
+                }
+            }
+        }.joinAll()
+    }
+
+    override suspend fun unset(toUnset: List<String>) {
+        toUnset.forEach {
+            val file = File(folder, it)
+            if (file.exists()) {
+                file.delete()
+                _onValueRemoved.emit(it)
+            }
+        }
+    }
+}
+
+class FileStandardKeyValueRepo(
+    folder: File,
+    filesChangedProcessingScope: CoroutineScope? = null
+) : StandardKeyValueRepo<String, File>,
+    WriteStandardKeyValueRepo<String, File> by FileWriteStandardKeyValueRepo(folder, filesChangedProcessingScope),
+    ReadStandardKeyValueRepo<String, File> by FileReadStandardKeyValueRepo(folder)
\ No newline at end of file