From 5494cc38911b878556e70f18631e17a8f3ccc95b Mon Sep 17 00:00:00 2001
From: Dani Palou <dani@moodle.com>
Date: Thu, 2 Aug 2018 09:04:48 +0200
Subject: [PATCH] MOBILE-2538 splitview: Handle ionViewCanLeave in details
 pages

---
 src/components/split-view/split-view.ts | 67 +++++++++++++++++++++++--
 1 file changed, 64 insertions(+), 3 deletions(-)

diff --git a/src/components/split-view/split-view.ts b/src/components/split-view/split-view.ts
index eb866c36a..86eae75ce 100644
--- a/src/components/split-view/split-view.ts
+++ b/src/components/split-view/split-view.ts
@@ -14,8 +14,9 @@
 
 // Code based on https://github.com/martinpritchardelevate/ionic-split-pane-demo
 
-import { Component, ViewChild, Input, ElementRef, OnInit, Optional } from '@angular/core';
-import { NavController, Nav } from 'ionic-angular';
+import { Component, ViewChild, Input, ElementRef, OnInit, Optional, OnDestroy } from '@angular/core';
+import { NavController, Nav, ViewController } from 'ionic-angular';
+import { Subscription } from 'rxjs';
 
 /**
  * Directive to create a split view layout.
@@ -40,7 +41,7 @@ import { NavController, Nav } from 'ionic-angular';
     selector: 'core-split-view',
     templateUrl: 'core-split-view.html'
 })
-export class CoreSplitViewComponent implements OnInit {
+export class CoreSplitViewComponent implements OnInit, OnDestroy {
 
     @ViewChild('detailNav') detailNav: Nav;
     @Input() when?: string | boolean = 'md';
@@ -49,6 +50,9 @@ export class CoreSplitViewComponent implements OnInit {
     protected masterPageIndex = 0;
     protected loadDetailPage: any = false;
     protected element: HTMLElement; // Current element.
+    protected detailsDidEnterSubscription: Subscription;
+    protected masterCanLeaveOverridden = false;
+    protected originalMasterCanLeave: Function;
 
     // Empty placeholder for the 'detail' page.
     detailPage: any = null;
@@ -65,6 +69,8 @@ export class CoreSplitViewComponent implements OnInit {
         this.masterPageName = this.masterNav.getActive().component.name;
         this.masterPageIndex = this.masterNav.indexOf(this.masterNav.getActive());
         this.emptyDetails();
+
+        this.handleCanLeave();
     }
 
     /**
@@ -89,6 +95,54 @@ export class CoreSplitViewComponent implements OnInit {
         return this.masterNav;
     }
 
+    /**
+     * Handle ionViewCanLeave functions in details page. By default, this function isn't captured by Ionic when
+     * clicking the back button, it only uses the one in the master page.
+     */
+    handleCanLeave(): void {
+        // Listen for the didEnter event on the details nav to detect everytime a page is loaded.
+        this.detailsDidEnterSubscription = this.detailNav.viewDidEnter.subscribe((detailsViewController: ViewController) => {
+            const masterViewController = this.masterNav.getActive();
+
+            if (this.masterCanLeaveOverridden) {
+                // We've overridden the can leave of the master page for a previous details page. Restore it.
+                masterViewController.instance.ionViewCanLeave = this.originalMasterCanLeave;
+                this.originalMasterCanLeave = undefined;
+                this.masterCanLeaveOverridden = false;
+            }
+
+            if (detailsViewController && detailsViewController.instance && detailsViewController.instance.ionViewCanLeave) {
+                // The details page defines a canLeave function. Check if the master page also defines one.
+                if (masterViewController.instance.ionViewCanLeave) {
+                    // Master page also defines a canLeave function, store it because it will be overridden.
+                    this.originalMasterCanLeave = masterViewController.instance.ionViewCanLeave;
+                }
+
+                // Override the master canLeave function so it also calls the details canLeave.
+                this.masterCanLeaveOverridden = true;
+
+                masterViewController.instance.ionViewCanLeave = (): Promise<any> => {
+                    // Always return a Promise.
+                    return Promise.resolve().then(() => {
+                        if (this.originalMasterCanLeave) {
+                            // First call the master canLeave.
+                            const result = this.originalMasterCanLeave();
+                            if (typeof result == 'boolean' && !result) {
+                                // User cannot leave, return a rejected promise so the details canLeave isn't executed.
+                                return Promise.reject(null);
+                            } else {
+                                return result;
+                            }
+                        }
+                    }).then(() => {
+                        // User can leave the master page. Check if he can also leave the details page.
+                        return detailsViewController.instance.ionViewCanLeave();
+                    });
+                };
+            }
+        });
+    }
+
     /**
      * Check if both panels are shown. It depends on screen width.
      *
@@ -168,4 +222,11 @@ export class CoreSplitViewComponent implements OnInit {
             this.masterNav.insert(this.masterPageIndex + 1, detailView.component, detailView.data);
         }
     }
+
+    /**
+     * Component being destroyed.
+     */
+    ngOnDestroy(): void {
+        this.detailsDidEnterSubscription && this.detailsDidEnterSubscription.unsubscribe();
+    }
 }