From 8754ef3a95e1cb93581d6d49dd589b4d2cfe2c4b Mon Sep 17 00:00:00 2001
From: Arman Ozak <arman@armanozak.com>
Date: Tue, 8 Dec 2020 17:28:07 +0300
Subject: [PATCH] feat: add utilities for generics

---
 .../packages/schematics/src/utils/generics.ts | 100 ++++++++++++++++++
 .../packages/schematics/src/utils/index.ts    |   1 +
 2 files changed, 101 insertions(+)
 create mode 100644 npm/ng-packs/packages/schematics/src/utils/generics.ts

diff --git a/npm/ng-packs/packages/schematics/src/utils/generics.ts b/npm/ng-packs/packages/schematics/src/utils/generics.ts
new file mode 100644
index 0000000000..8dc7fb2629
--- /dev/null
+++ b/npm/ng-packs/packages/schematics/src/utils/generics.ts
@@ -0,0 +1,100 @@
+import { Generic } from '../models';
+
+export class GenericsCollector {
+  private _generics: Generic[] = [];
+  get generics() {
+    return this._generics;
+  }
+
+  apply = (value: string, index: number) => {
+    const generic = this.get(index);
+    if (generic) {
+      if (!generic.type) generic.setType(value);
+      return value + generic.default;
+    }
+
+    return value;
+  };
+
+  constructor(private getTypeIdentifier = (type: string) => type) {}
+
+  private createGeneric(type: string, ref: string, defaultValue: string) {
+    const _default = this.getTypeIdentifier(defaultValue);
+    const refs = [generateRefWithPlaceholders(ref)];
+    const generic = new Generic({ type, default: _default, refs });
+    return generic;
+  }
+
+  private register(index: number, generic: Generic) {
+    const existing = this.get(index);
+    if (existing) {
+      existing.setDefault(generic.default);
+      existing.setType(generic.type);
+    } else this.set(index, generic);
+  }
+
+  collect(generics: string[], genericArguments: string[]) {
+    generics.forEach((ref, i) => {
+      const generic = this.createGeneric(
+        genericArguments[i],
+        ref,
+        genericArguments.includes(ref) ? '' : ref,
+      );
+      this.register(i, generic);
+    });
+  }
+
+  get(index: number) {
+    return this.generics[index];
+  }
+
+  set(index: number, value: Generic) {
+    this.generics[index] = value;
+  }
+
+  reset() {
+    this._generics = [];
+  }
+}
+
+export function generateRefWithPlaceholders(sourceType: string) {
+  let { identifier, generics } = extractGenerics(sourceType);
+
+  identifier = identifier;
+  generics = generics.map((_, i) => `T${i}`);
+
+  return generics.length ? `${identifier}<${generics}>` : identifier;
+}
+
+export function extractSimpleGenerics(sourceType: string) {
+  const { identifier, generics } = extractGenerics(sourceType);
+
+  return {
+    identifier: getLastSegment(identifier),
+    generics: generics.map(getLastSegment),
+  };
+}
+
+export function extractGenerics(sourceType: string) {
+  const regex = /(?<identifier>[^<]+)(<(?<generics>.+)>)?/g;
+  const { identifier = '', generics = '' } = regex.exec(sourceType)?.groups ?? {};
+
+  return {
+    identifier,
+    generics: generics.split(/,\s*/).filter(Boolean),
+  };
+}
+
+function getLastSegment(str: string) {
+  return str.split('.').pop()!;
+}
+
+export function replacePlaceholdersWithGenerics(
+  type: string,
+  generics: string[],
+  genericsCollector: GenericsCollector,
+) {
+  return generics
+    .map(genericsCollector.apply)
+    .reduce((acc, v, i) => acc.replace(new RegExp(`([<, ])T${i}([,>])`, 'g'), `$1${v}$2`), type);
+}
diff --git a/npm/ng-packs/packages/schematics/src/utils/index.ts b/npm/ng-packs/packages/schematics/src/utils/index.ts
index 178920dccc..e6df05b2e2 100644
--- a/npm/ng-packs/packages/schematics/src/utils/index.ts
+++ b/npm/ng-packs/packages/schematics/src/utils/index.ts
@@ -5,6 +5,7 @@ export * from './barrel';
 export * from './common';
 export * from './enum';
 export * from './file';
+export * from './generics';
 export * from './import';
 export * from './model';
 export * from './namespace';