2 files changed, 32 insertions, 0 deletions

diff --git a/client/src/app/core/theme/index.ts b/client/src/app/core/theme/index.ts
new file mode 100644
index 000000000..713f4747b
--- /dev/null
+++ b/client/src/app/core/theme/index.ts
@@ -0,0 +1 @@
+export * from './theme.service'
diff --git a/client/src/app/core/theme/theme.service.ts b/client/src/app/core/theme/theme.service.ts
new file mode 100644
index 000000000..d8e02e2e5
--- /dev/null
+++ b/client/src/app/core/theme/theme.service.ts
@@ -0,0 +1,31 @@
+import { Injectable } from '@angular/core'
+
+@Injectable()
+export class ThemeService {
+  private theme = document.querySelector('body')
+  private previousTheme = {}
+
+  constructor () {
+    // initialise the alternative theme with dark theme colors
+    this.previousTheme['mainBackgroundColor'] = '#111111'
+    this.previousTheme['mainForegroundColor'] = '#fff'
+    this.previousTheme['submenuColor'] = 'rgb(32,32,32)'
+    this.previousTheme['inputColor'] = 'gray'
+    this.previousTheme['inputPlaceholderColor'] = '#fff'
+  }
+
+  toggleDarkTheme () {
+    // switch properties
+    this.switchProperty('mainBackgroundColor')
+    this.switchProperty('mainForegroundColor')
+    this.switchProperty('submenuColor')
+    this.switchProperty('inputColor')
+    this.switchProperty('inputPlaceholderColor')
+  }
+
+  private switchProperty (property, newValue?) {
+    const propertyOldvalue = window.getComputedStyle(this.theme).getPropertyValue('--' + property)
+    this.theme.style.setProperty('--' + property, (newValue) ? newValue : this.previousTheme[property])
+    this.previousTheme[property] = propertyOldvalue
+  }
+}