From 969a81fabe19b097af748e1fe522e9f98d28c934 Mon Sep 17 00:00:00 2001
From: Mykola Bilochub <nbelochub@gmail.com>
Date: Mon, 17 Dec 2018 21:43:30 +0200
Subject: [PATCH] Implement identification primitives

Refs: https://github.com/metarhia/globalstorage/issues/8
Refs: https://github.com/metarhia/Metarhia/issues/21
---
 lib/identification.js | 122 ++++++++++++++++++++++++++++++++++++++++++
 lib/provider.js       |   7 +--
 2 files changed, 123 insertions(+), 6 deletions(-)
 create mode 100644 lib/identification.js

diff --git a/lib/identification.js b/lib/identification.js
new file mode 100644
index 00000000..900c8d8a
--- /dev/null
+++ b/lib/identification.js
@@ -0,0 +1,122 @@
+'use strict';
+
+const { Uint64, sequence } = require('@metarhia/common');
+const { StorageProvider } = require('./provider');
+
+class RemoteServer extends StorageProvider {
+  constructor({
+    host,
+    ports,
+  }, providerOptions) {
+    super(providerOptions);
+    this.host = host;
+    this.ports = ports;
+    if (this.ports.length > 1) {
+      this.ports = sequence(this.ports, 0);
+    }
+    this.pool = [];
+  }
+}
+
+const getTreeDepth = (node, depth = 0) => {
+  if (node[0] && node[1]) {
+    return Math.max(
+      getTreeDepth(node[0], depth + 1),
+      getTreeDepth(node[1], depth + 1)
+    );
+  }
+  return depth;
+};
+
+const arrayifyTree = node => {
+  if (node[0] && node[1]) {
+    return [arrayifyTree(node[0]), arrayifyTree(node[1])];
+  } else {
+    return node;
+  }
+};
+
+const buildIndex = (tree, depth, serverIds) => {
+  const result = new Array(Math.pow(2, depth));
+
+  const parseTree = (index, depth, node) => {
+    const isLeaf = !node[0] || !node[1];
+    if (isLeaf) {
+      const serverSuffix = new Uint64(index)
+        .shiftLeft(SYSTEM_BITMASK_SIZE)
+        .or(serverIds.systemSuffix);
+      const serverBitmask = new Uint64(1)
+        .shiftLeft(depth)
+        .dec()
+        .shiftLeft(SYSTEM_BITMASK_SIZE)
+        .or(SYSTEM_BITMASK);
+
+      result[index] = new RemoteServer(node, Object.assign({}, serverIds, {
+        serverSuffix,
+        serverBitmask,
+      }));
+      for (let i = 1 << depth; i < result.length; i <<= 1) {
+        result[index | i] = result[index];
+      }
+      return;
+    }
+    parseTree(index, depth + 1, node[0]);
+    parseTree(index + (1 << depth), depth + 1, node[1]);
+  };
+  parseTree(0, 0, tree);
+
+  return result;
+};
+
+const SYSTEM_BITMASK_SIZE = 24;
+const SYSTEM_BITMASK = new Uint64(1).shiftLeft(SYSTEM_BITMASK_SIZE).dec();
+
+class ServerTree {
+  constructor(tree, systemId) {
+    this.tree = arrayifyTree(tree);
+    this.depth = getTreeDepth(this.tree);
+    this.serverBitmask = new Uint64(1).shiftLeft(this.depth).dec();
+    this.treeIndex = buildIndex(this.tree, this.depth, {
+      systemSuffix: new Uint64(systemId),
+      systemBitmask: new Uint64(SYSTEM_BITMASK),
+    });
+  }
+
+  findServer(id) {
+    return this.treeIndex[
+      Uint64.shiftRight(id, SYSTEM_BITMASK_SIZE)
+        .and(this.serverBitmask).toUint32()
+    ];
+  }
+
+  toJSON() {
+    return this.tree;
+  }
+}
+
+class SystemList {
+  constructor(systems) {
+    this.systems = {};
+    for (const id in systems) {
+      this.systems[id] = new ServerTree(systems[id], new Uint64(id));
+    }
+  }
+
+  findServer(id) {
+    const serverTree = this.systems[Uint64.and(SYSTEM_BITMASK).toUint32()];
+    if (!serverTree) {
+      return null;
+    }
+    return serverTree.findServer(id);
+  }
+
+  toJSON() {
+    return this.systems;
+  }
+}
+
+module.exports = {
+  RemoteServer,
+  ServerTree,
+  SystemList,
+};
diff --git a/lib/provider.js b/lib/provider.js
index edef7187..b4565b2e 100644
--- a/lib/provider.js
+++ b/lib/provider.js
@@ -6,8 +6,6 @@ const { GSError, codes: errorCodes } = require('./errors');
 const { createRemoteProviderJstpApi } =
   require('./remote.provider.jstp.api.js');
 
-const SYSTEM_BITMASK_SIZE = 24;
-
 // Abstract Storage Provider
 class StorageProvider {
   // Create StorageProvider
@@ -225,7 +223,4 @@ class StorageProvider {
   }
 }
 
-module.exports = {
-  StorageProvider,
-  SYSTEM_BITMASK_SIZE,
-};
+module.exports = { StorageProvider };