基于Android实现的文件同步设计方案

/测试/test.txt:ADBF5A778175EE757C34D0EBA4E932BC
/jjsskizs.log:D41D8CD98F00B204E9800998ECF8427E
/Hello.txt:D064F3519426DCD30114B900431FC044
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DIR:DELETE:/测试::false:true
DIR:DELETE:/测试目录::false:true
DIR:DELETE:/新目录::false:true
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/** 笔记上次同步状态 */
@Entity class NoteLastSyncState: Serializable {
    @PrimaryKey(autoGenerate = true) var id: Long? = null
    /** 笔记的路径 */
    var path: String? = null
    /** 文件相对路径，直接父路径，用来根据父路径找子路径 */
    var parent: String? = null
    /** 如果文件时移动过来的话，记录从哪里移动过来的 */
    var movedFrom: String? = null
    /** 服务器返回的上次修改的时间，如果有的话，用来判断远程是否修改过 */
    var serverLastModifiedTime: Date? = null
    /** 上次同步时的 Md5 值，用来判断上次同步完成之后是否又被改动过 */
    var lastSyncMd5: String? = null
    /** 备注信息，冗余字段，用 json 存储 */
    var remark: String? = null
    /** 上次同步的时间 */
    var lastSyncTime: Date? = null
}

@Query("SELECT * FROM NoteLastSyncState WHERE path LIKE :parent || '%' ")
fun getUnderParent(parent: String): List<NoteLastSyncState>

/** Check is file changed remotely by last modified time. */
private fun isFileChangedRemotely(
    syncState: NoteLastSyncState,
    remoteFile: CloudResource
): Boolean = syncState.serverLastModifiedTime != null
        && remoteFile.lastUpdate != null
        && remoteFile.lastUpdate.after(syncState.serverLastModifiedTime)

/** Check is file not changed remotely by last modified time. */
private fun isFileNotChangedRemotely(
    syncState: NoteLastSyncState,
    remoteFile: CloudResource
): Boolean = syncState.serverLastModifiedTime != null
        && remoteFile.lastUpdate != null
        && !remoteFile.lastUpdate.after(syncState.serverLastModifiedTime)

runBackground(onFinished, onInterrupted) { failures ->
    val visitors = mutableListOf(File(path))
    val count = AtomicInteger(0)
    while (visitors.isNotEmpty() && !interrupted) {
        try {
            val directory = visitors.removeAt(0)
            val dirRelativePath = sm.relativePathOf(directory.path)

            // Read contents of directory from cloud.
            val listResult = server.list(dirRelativePath)
            val remoteFiles: MutableMap<String, CloudResource> = if (listResult.isFailed) {
                log { "failed to read contents of directory [$dirRelativePath] from cloud, code [${listResult.code}], msg [${listResult.message}] ." }
                val synced = syncDirectoryWhenFailedReadRemotely(directory, failures)
                if (synced) {
                    continue
                }
                mutableMapOf()
            } else {
                insertDirectoryLastSyncState(directory)
                listResult.data.toMutableMap()
            }

            // Read last sync records from local database.
            val syncRecords = mutableMapOf<String, NoteLastSyncState>()
            DB.get().noteLastSyncStateDao().getByParent(dirRelativePath).forEach {
                syncRecords[it.path ?: ""] = it
            }

            // Travel under directory and handle files.
            directory.listFiles()?.forEach { file ->
                if (interrupted) {
                    return@forEach
                }

                val fileRelativePath = sm.relativePathOf(file.path)

                // Files should be ignored.
                if (fileRelativePath == "/$SETTING_FOLDER_NAME/$SETTING_IMAGE_MODEL_DATA") {
                    return@forEach
                }

                val syncRecord = syncRecords[fileRelativePath]

                if (file.isDirectory) {
                    visitors.add(file)

                    // The directory exists in cloud: remove from remote files.
                    if (remoteFiles.containsKey(fileRelativePath)) {
                        remoteFiles.remove(fileRelativePath)
                    }
                } else if (file.isFile) {
                    Thread.sleep(timeDelayMillis.toLong())
                    val remoteFile = remoteFiles[fileRelativePath]

                    // Sync a single file.
                    syncFile(file, syncRecord, remoteFile, failures)

                    if (remoteFile != null) {
                        remoteFiles.remove(fileRelativePath)
                    }
                    notifyProgressChanged(count.addAndGet(1), onProgress)
                }
            }

            // Handle left remote resources.
            syncRemoteResourcesNotFoundLocally(remoteFiles, failures, count, onProgress)
        } catch (t: Throwable) {
            t.printStackTrace()
            log { "failed to sync folder with exception: $t" }
        }
    }
}

/** 云同步服务器接口封装 */
interface ICloudServer {

    /** 读取文件内容 */
    fun readText(rp: String): Resources<String>

    /** Write text to given file with relative path [rp]. */
    fun writeText(text: String, rp: String): Resources<Boolean>

    /** Read bytes of a cloud file. */
    fun readBytes(rp: String): Resources<ByteArray>

    // .....
}

interface ICloudSyncWorker {

    /**
     * Sync a file.
     *
     * @param file the file to sync
     * @param syncRecord note last sync state, might be null
     * @param remoteFile the file info in cloud server
     * @param failures the failures to report, failures will be added to this list.
     */
    fun syncFile(
        file: File,
        syncRecord: NoteLastSyncState?,
        remoteFile: CloudResource?,
        failures: MutableList<ISyncManager.SyncFailure>
    )

    // ...
}