refractor: accounting module (#300)

* Refractor components.
* Add resolvers.
* Add relative router links.
* Replace mat-icons by font-awesome icons.
* Add comments.

Fixes: #298

src/app/accounting/chart-of-accounts/gl-account-tree.service.ts

@@ -1,30 +1,50 @@
+/** Angular Imports */
 import { Injectable } from '@angular/core';
 
+/** rxjs Imports */
 import { BehaviorSubject } from 'rxjs';
 
+/** Custom Components */
 import { GLAccountNode } from './gl-account-node.model';
 
+/**
+ * GL Account tree service.
+ */
 @Injectable({
   providedIn: 'root'
 })
 export class GlAccountTreeService {
 
+  /** GL Account data. */
   glAccountData: any;
-
+  /** Chart of accounts tree data behavior subject to represent chart of accounts tree nodes. */
   treeDataChange = new BehaviorSubject<GLAccountNode[]>([]);
 
+  /**
+   * Gets the chart of accounts tree nodes.
+   */
   get treeData(): GLAccountNode[] { return this.treeDataChange.value; }
 
   constructor() {  }
 
+  /**
+   * Builds the chart of accounts tree and emits the value.
+   * @param {any} glAccountData Chart of accounts data.
+   */
   initialize(glAccountData: any) {
-    const data = this.buildGLAccountTree(glAccountData);
-    this.treeDataChange.next(data);
+    const treeData = this.buildGLAccountTree(glAccountData);
+    this.treeDataChange.next(treeData);
   }
 
+  /**
+   * Builds and returns the chart of accounts tree.
+   * @param {any} glAccountData Chart of accounts data.
+   * @returns {GLAccountNode[]} Chart of accounts tree nodes.
+   */
   buildGLAccountTree(glAccountData: any): GLAccountNode[] {
     const glAccountTree: GLAccountNode[] = [];
 
+    // Header nodes
     glAccountTree.push(new GLAccountNode('GL ACCOUNTS'));
     glAccountTree[0].children.push(new GLAccountNode('ASSET'));
     glAccountTree[0].children.push(new GLAccountNode('EQUITY'));
@@ -32,6 +52,7 @@ export class GlAccountTreeService {
     glAccountTree[0].children.push(new GLAccountNode('INCOME'));
     glAccountTree[0].children.push(new GLAccountNode('LIABILITY'));
 
+    // Sort by parent id (so that child nodes can be added properly)
     glAccountData.sort((glAccountOne: any, glAccountTwo: any) => {
       if (!glAccountOne.parentId) {
         glAccountOne.parentId = 0;
@@ -41,11 +62,14 @@ export class GlAccountTreeService {
 
     const glAccounts: GLAccountNode[] = [];
 
+    // Add gl accounts to any array where index for each is denoted by its id
     for (const glAccount of glAccountData) {
       glAccounts[glAccount.id] =
         new GLAccountNode(glAccount.name, glAccount.glCode, glAccount.type.value, glAccount.usage.value, glAccount.manualEntriesAllowed, glAccount.description);
     }
 
+    // Construct gl account tree by adding all nodes belonging to headers (with parent id = 0) by their type,
+    // and rest as children to respective parent nodes.
     for (const glAccount of glAccountData) {
       if (glAccount.parentId === 0) {
         if (glAccount.type.value === 'ASSET') {