Change to use theme utils from mattermost-redux (#1531)

* Change to use theme utils from mattermost-redux

* Updated yarn.lock

app/utils/theme.js

@@ -3,74 +3,17 @@
 
 import {StyleSheet} from 'react-native';
 
+import * as ThemeUtils from 'mattermost-redux/utils/theme_utils';
+
 export function makeStyleSheetFromTheme(getStyleFromTheme) {
-    let lastTheme = null;
-    let style = null;
-
-    return (theme) => {
-        if (theme !== lastTheme) {
-            style = StyleSheet.create(getStyleFromTheme(theme));
-            lastTheme = theme;
-        }
-
-        return style;
-    };
+    return ThemeUtils.makeStyleFromTheme((theme) => {
+        return StyleSheet.create(getStyleFromTheme(theme));
+    });
 }
 
-function normalizeColor(oldColor) {
-    let color = oldColor;
-    if (color.length && color[0] === '#') {
-        color = color.slice(1);
-    }
+export const changeOpacity = ThemeUtils.changeOpacity;
 
-    if (color.length === 3) {
-        const tempColor = color;
-        color = '';
-
-        color += tempColor[0] + tempColor[0];
-        color += tempColor[1] + tempColor[1];
-        color += tempColor[2] + tempColor[2];
-    }
-
-    return color;
-}
-
-export function changeOpacity(oldColor, opacity) {
-    const color = normalizeColor(oldColor);
-
-    const r = parseInt(color.substring(0, 2), 16);
-    const g = parseInt(color.substring(2, 4), 16);
-    const b = parseInt(color.substring(4, 6), 16);
-
-    return `rgba(${r},${g},${b},${opacity})`;
-}
-
-function blendComponent(background, foreground, opacity) {
-    return ((1 - opacity) * background) + (opacity * foreground);
-}
-
-export function blendColors(background, foreground, opacity) {
-    const backgroundNormalized = normalizeColor(background);
-    const foregroundNormalized = normalizeColor(foreground);
-
-    const r = blendComponent(
-        parseInt(backgroundNormalized.substring(0, 2), 16),
-        parseInt(foregroundNormalized.substring(0, 2), 16),
-        opacity
-    );
-    const g = blendComponent(
-        parseInt(backgroundNormalized.substring(2, 4), 16),
-        parseInt(foregroundNormalized.substring(2, 4), 16),
-        opacity
-    );
-    const b = blendComponent(
-        parseInt(backgroundNormalized.substring(4, 6), 16),
-        parseInt(foregroundNormalized.substring(4, 6), 16),
-        opacity
-    );
-
-    return `rgb(${r},${g},${b})`;
-}
+export const blendColors = ThemeUtils.blendColors;
 
 export function concatStyles(...styles) {
     return [].concat(styles);