4 files changed, 35 insertions, 0 deletions

diff --git a/client/src/app/core/core.module.ts b/client/src/app/core/core.module.ts
index 30ac10119..d4917f902 100644
--- a/client/src/app/core/core.module.ts
+++ b/client/src/app/core/core.module.ts
@@ -14,6 +14,7 @@ import { ConfirmComponent, ConfirmService } from './confirm'
 import { throwIfAlreadyLoaded } from './module-import-guard'
 import { LoginGuard, RedirectService, UserRightGuard } from './routing'
 import { ServerService } from './server'
+import { ThemeService } from './theme'
 
 @NgModule({
   imports: [
@@ -45,6 +46,7 @@ import { ServerService } from './server'
     AuthService,
     ConfirmService,
     ServerService,
+    ThemeService,
     LoginGuard,
     UserRightGuard,
     RedirectService
diff --git a/client/src/app/core/index.ts b/client/src/app/core/index.ts
index 3c01e05aa..521afc29c 100644
--- a/client/src/app/core/index.ts
+++ b/client/src/app/core/index.ts
@@ -2,4 +2,5 @@ export * from './auth'
 export * from './server'
 export * from './confirm'
 export * from './routing'
+export * from './theme'
 export * from './core.module'
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
+  }
+}