From 56bf0e6be1977d8da6d3fbc4d451cf847e823aee Mon Sep 17 00:00:00 2001
From: Arman Ozak <arman@armanozak.com>
Date: Wed, 19 Aug 2020 03:27:36 +0300
Subject: [PATCH] feat: add a tree structure for generic types

---
 .../packages/schematics/src/utils/index.ts    |  1 +
 .../packages/schematics/src/utils/tree.ts     | 71 +++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 npm/ng-packs/packages/schematics/src/utils/tree.ts

diff --git a/npm/ng-packs/packages/schematics/src/utils/index.ts b/npm/ng-packs/packages/schematics/src/utils/index.ts
index cc9b0052fa..5a56c6d2eb 100644
--- a/npm/ng-packs/packages/schematics/src/utils/index.ts
+++ b/npm/ng-packs/packages/schematics/src/utils/index.ts
@@ -7,4 +7,5 @@ export * from './rule';
 export * from './service';
 export * from './source';
 export * from './text';
+export * from './tree';
 export * from './workspace';
diff --git a/npm/ng-packs/packages/schematics/src/utils/tree.ts b/npm/ng-packs/packages/schematics/src/utils/tree.ts
new file mode 100644
index 0000000000..d142032255
--- /dev/null
+++ b/npm/ng-packs/packages/schematics/src/utils/tree.ts
@@ -0,0 +1,71 @@
+export class TypeNode {
+  children: TypeNode[] = [];
+
+  index = 0;
+
+  constructor(
+    public data: string,
+    public parent: TypeNode | null,
+    public mapperFn = (node: TypeNode) => node.data,
+  ) {}
+
+  toGenerics(): string[] {
+    const generics = this.children.length ? `<${this.children.map(n => `T${n.index}`)}>` : '';
+    return [this.data + generics].concat(
+      this.children.reduce((acc: string[], node) => acc.concat(node.toGenerics()), []),
+    );
+  }
+
+  toString() {
+    const self = this.mapperFn(this);
+
+    if (!self) return '';
+
+    const representation = self + this.children.filter(String || Boolean).join(', ');
+
+    if (!this.parent) return representation;
+
+    const siblings = this.parent.children;
+
+    return (
+      (siblings[0] === this ? '<' : '') +
+      representation +
+      (siblings[siblings.length - 1] === this ? '>' : '')
+    );
+  }
+
+  valueOf() {
+    return this.toString();
+  }
+}
+
+export function parseGenerics(type: string, mapperFn?: TypeNodeMapperFn) {
+  const [rootType, ...types] = type.split('<');
+  const root = new TypeNode(rootType, null, mapperFn);
+
+  types.reduce((parent, t) => {
+    const [left, right] = t.split(/>+,?\s*/);
+
+    const leftNode = new TypeNode(left, parent, mapperFn);
+    leftNode.index = parent.children.length;
+    parent.children.push(leftNode);
+    parent = leftNode;
+
+    let { length } = t.match(/>/g) || [];
+    while (length--) parent = parent.parent!;
+
+    if (right) {
+      parent = parent.parent!;
+      const rightNode = new TypeNode(right, parent, mapperFn);
+      rightNode.index = parent.children.length;
+      parent.children.push(rightNode);
+      parent = rightNode;
+    }
+
+    return parent;
+  }, root);
+
+  return root;
+}
+
+export type TypeNodeMapperFn = (node: TypeNode) => string;