From fae2d8199dbb364e57d28e0e4f1df313f54528e1 Mon Sep 17 00:00:00 2001
From: "Lin, Hung-Shin" <wancat@wancat.cc>
Date: Wed, 15 Nov 2023 14:30:37 +0800
Subject: [PATCH] feat: calculate layer

---
 packages/utils/dag.js      | 30 +++++++++++++++++++++++
 packages/utils/dag.test.js | 50 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 packages/utils/dag.js
 create mode 100644 packages/utils/dag.test.js

diff --git a/packages/utils/dag.js b/packages/utils/dag.js
new file mode 100644
index 0000000..22369b4
--- /dev/null
+++ b/packages/utils/dag.js
@@ -0,0 +1,30 @@
+export default class DAG {
+  constructor(nodes) {
+    this.nodes = new Map(nodes.map((node) => [node._id, node]))
+    this.edges = []
+  }
+
+  setLayer(id) {
+    console.log(`setLayer(${id})`)
+    const node = this.nodes.get(id)
+    if (!node) {
+      throw new Error(`Node ${id} not found`)
+    }
+    if (node.layer !== undefined) {
+      return node.layer
+    }
+    const previousLayer = node.requirements.map((rId) => this.setLayer(rId))
+    node.layer = Math.max(...previousLayer, 0) + 1
+    return node.layer
+  }
+
+  format() {
+    this.nodes.forEach((_, id) => {
+      this.setLayer(id)
+    })
+  }
+
+  get(id) {
+    return this.nodes.get(id)
+  }
+}
diff --git a/packages/utils/dag.test.js b/packages/utils/dag.test.js
new file mode 100644
index 0000000..272eeea
--- /dev/null
+++ b/packages/utils/dag.test.js
@@ -0,0 +1,50 @@
+import DAG from './dag.js'
+
+describe('dag', () => {
+  const data = [
+    {
+      _id: 'helloworld',
+      title: 'Hello, Linux World!',
+      requirements: [],
+    },
+    {
+      _id: 'spell',
+      title: 'Learn to spell',
+      requirements: ['helloworld'],
+    },
+    {
+      _id: 'discover',
+      title: 'Discover the World!',
+      requirements: ['spell'],
+    },
+    {
+      _id: 'read',
+      title: 'Read the File',
+      requirements: ['spell'],
+    },
+    {
+      _id: 'remove',
+      requirements: ['read', 'discover'],
+    },
+    {
+      _id: 'move',
+      requirements: ['helloworld'],
+    },
+    {
+      _id: 'copy',
+      requirements: ['remove', 'move'],
+    },
+  ]
+
+  it('should set layers', () => {
+    const dag = new DAG(data)
+    dag.format()
+    expect(dag.get('helloworld').layer).toBe(1)
+    expect(dag.get('spell').layer).toBe(2)
+    expect(dag.get('move').layer).toBe(2)
+    expect(dag.get('read').layer).toBe(3)
+    expect(dag.get('discover').layer).toBe(3)
+    expect(dag.get('remove').layer).toBe(4)
+    expect(dag.get('copy').layer).toBe(5)
+  })
+})