Merge branch 'development' of https://github.com/0xProject/0x-monorepo into feature/instant/dropdown-ui

14 files changed, 226 insertions, 102 deletions

diff --git a/packages/instant/src/components/animations/position_animation.tsx b/packages/instant/src/components/animations/position_animation.tsx
index 4bb21befb..576d29c07 100644
--- a/packages/instant/src/components/animations/position_animation.tsx
+++ b/packages/instant/src/components/animations/position_animation.tsx
@@ -1,5 +1,6 @@
-import { Keyframes } from 'styled-components';
+import { InterpolationValue } from 'styled-components';
 
+import { media, OptionallyScreenSpecific, stylesForMedia } from '../../style/media';
 import { css, keyframes, styled } from '../../style/theme';
 
 export interface TransitionInfo {
@@ -51,30 +52,57 @@ export interface PositionAnimationSettings {
     right?: TransitionInfo;
     timingFunction: string;
     duration?: string;
+    position?: string;
 }
 
-export interface PositionAnimationProps extends PositionAnimationSettings {
-    position: string;
+const generatePositionAnimationCss = (positionSettings: PositionAnimationSettings) => {
+    return css`
+        animation-name: ${slideKeyframeGenerator(
+            positionSettings.position || 'relative',
+            positionSettings.top,
+            positionSettings.bottom,
+            positionSettings.left,
+            positionSettings.right,
+        )};
+        animation-duration: ${positionSettings.duration || '0.3s'};
+        animation-timing-function: ${positionSettings.timingFunction};
+        animation-delay: 0s;
+        animation-iteration-count: 1;
+        animation-fill-mode: forwards;
+        position: ${positionSettings.position || 'relative'};
+        width: 100%;
+    `;
+};
+
+export interface PositionAnimationProps {
+    positionSettings: OptionallyScreenSpecific<PositionAnimationSettings>;
+    zIndex?: OptionallyScreenSpecific<number>;
 }
 
+const defaultAnimation = (positionSettings: OptionallyScreenSpecific<PositionAnimationSettings>) => {
+    const bestDefault = 'default' in positionSettings ? positionSettings.default : positionSettings;
+    return generatePositionAnimationCss(bestDefault);
+};
+const animationForSize = (
+    positionSettings: OptionallyScreenSpecific<PositionAnimationSettings>,
+    sizeKey: 'sm' | 'md' | 'lg',
+    mediaFn: (...args: any[]) => InterpolationValue[],
+) => {
+    // checking default makes sure we have a PositionAnimationSettings object
+    // and then we check to see if we have a setting for the specific `sizeKey`
+    const animationSettingsForSize = 'default' in positionSettings && positionSettings[sizeKey];
+    return animationSettingsForSize && mediaFn`${generatePositionAnimationCss(animationSettingsForSize)}`;
+};
+
 export const PositionAnimation =
     styled.div <
     PositionAnimationProps >
     `
-    animation-name: ${props =>
-        css`
-            ${slideKeyframeGenerator(props.position, props.top, props.bottom, props.left, props.right)};
-        `};
-    animation-duration: ${props => props.duration || '0.3s'};
-    animation-timing-function: ${props => props.timingFunction};
-    animation-delay: 0s;
-    animation-iteration-count: 1;
-    animation-fill-mode: forwards;
-    position: ${props => props.position};
-    height: 100%;
-    width: 100%;
+    && {
+        ${props => props.zIndex && stylesForMedia<number>('z-index', props.zIndex)}
+        ${props => defaultAnimation(props.positionSettings)}
+        ${props => animationForSize(props.positionSettings, 'sm', media.small)}
+        ${props => animationForSize(props.positionSettings, 'md', media.medium)}
+        ${props => animationForSize(props.positionSettings, 'lg', media.large)}
+    }
 `;
-
-PositionAnimation.defaultProps = {
-    position: 'relative',
-};
diff --git a/packages/instant/src/components/animations/slide_animation.tsx b/packages/instant/src/components/animations/slide_animation.tsx
index 66a314c7f..122229dee 100644
--- a/packages/instant/src/components/animations/slide_animation.tsx
+++ b/packages/instant/src/components/animations/slide_animation.tsx
@@ -1,22 +1,24 @@
 import * as React from 'react';
 
+import { OptionallyScreenSpecific } from '../../style/media';
+
 import { PositionAnimation, PositionAnimationSettings } from './position_animation';
 
 export type SlideAnimationState = 'slidIn' | 'slidOut' | 'none';
 export interface SlideAnimationProps {
-    position: string;
     animationState: SlideAnimationState;
-    slideInSettings: PositionAnimationSettings;
-    slideOutSettings: PositionAnimationSettings;
+    slideInSettings: OptionallyScreenSpecific<PositionAnimationSettings>;
+    slideOutSettings: OptionallyScreenSpecific<PositionAnimationSettings>;
+    zIndex?: OptionallyScreenSpecific<number>;
 }
 
 export const SlideAnimation: React.StatelessComponent<SlideAnimationProps> = props => {
     if (props.animationState === 'none') {
         return <React.Fragment>{props.children}</React.Fragment>;
     }
-    const propsToUse = props.animationState === 'slidIn' ? props.slideInSettings : props.slideOutSettings;
+    const positionSettings = props.animationState === 'slidIn' ? props.slideInSettings : props.slideOutSettings;
     return (
-        <PositionAnimation position={props.position} {...propsToUse}>
+        <PositionAnimation positionSettings={positionSettings} zIndex={props.zIndex}>
             {props.children}
         </PositionAnimation>
     );
diff --git a/packages/instant/src/components/sliding_error.tsx b/packages/instant/src/components/sliding_error.tsx
index a923b9932..a8d4e391c 100644
--- a/packages/instant/src/components/sliding_error.tsx
+++ b/packages/instant/src/components/sliding_error.tsx
@@ -1,6 +1,8 @@
 import * as React from 'react';
 
+import { ScreenSpecification } from '../style/media';
 import { ColorOption } from '../style/theme';
+import { zIndex } from '../style/z_index';
 
 import { PositionAnimationSettings } from './animations/position_animation';
 import { SlideAnimation, SlideAnimationState } from './animations/slide_animation';
@@ -21,6 +23,7 @@ export const Error: React.StatelessComponent<ErrorProps> = props => (
         backgroundColor={ColorOption.lightOrange}
         width="100%"
         borderRadius="6px"
+        marginTop="10px"
         marginBottom="10px"
     >
         <Flex justify="flex-start">
@@ -39,25 +42,51 @@ export interface SlidingErrorProps extends ErrorProps {
 }
 export const SlidingError: React.StatelessComponent<SlidingErrorProps> = props => {
     const slideAmount = '120px';
-    const slideUpSettings: PositionAnimationSettings = {
+
+    const desktopSlideIn: PositionAnimationSettings = {
         timingFunction: 'ease-in',
         top: {
             from: slideAmount,
             to: '0px',
         },
+        position: 'relative',
     };
-    const slideDownSettings: PositionAnimationSettings = {
+    const desktopSlideOut: PositionAnimationSettings = {
         timingFunction: 'cubic-bezier(0.25, 0.1, 0.25, 1)',
         top: {
             from: '0px',
             to: slideAmount,
         },
+        position: 'relative',
+    };
+
+    const mobileSlideIn: PositionAnimationSettings = {
+        duration: '0.5s',
+        timingFunction: 'ease-in',
+        top: { from: '-120px', to: '0px' },
+        position: 'fixed',
+    };
+    const moblieSlideOut: PositionAnimationSettings = {
+        duration: '0.5s',
+        timingFunction: 'ease-in',
+        top: { from: '0px', to: '-120px' },
+        position: 'fixed',
+    };
+
+    const slideUpSettings: ScreenSpecification<PositionAnimationSettings> = {
+        default: desktopSlideIn,
+        sm: mobileSlideIn,
     };
+    const slideOutSettings: ScreenSpecification<PositionAnimationSettings> = {
+        default: desktopSlideOut,
+        sm: moblieSlideOut,
+    };
+
     return (
         <SlideAnimation
-            position="relative"
             slideInSettings={slideUpSettings}
-            slideOutSettings={slideDownSettings}
+            slideOutSettings={slideOutSettings}
+            zIndex={{ sm: zIndex.errorPopup, default: zIndex.errorPopBehind }}
             animationState={props.animationState}
         >
             <Error icon={props.icon} message={props.message} />
diff --git a/packages/instant/src/components/sliding_panel.tsx b/packages/instant/src/components/sliding_panel.tsx
index 5e8a73663..99db58e68 100644
--- a/packages/instant/src/components/sliding_panel.tsx
+++ b/packages/instant/src/components/sliding_panel.tsx
@@ -53,6 +53,7 @@ export const SlidingPanel: React.StatelessComponent<SlidingPanelProps> = props =
             from: slideAmount,
             to: '0px',
         },
+        position: 'absolute',
     };
     const slideDownSettings: PositionAnimationSettings = {
         duration: '0.3s',
@@ -61,10 +62,10 @@ export const SlidingPanel: React.StatelessComponent<SlidingPanelProps> = props =
             from: '0px',
             to: slideAmount,
         },
+        position: 'absolute',
     };
     return (
         <SlideAnimation
-            position="absolute"
             slideInSettings={slideUpSettings}
             slideOutSettings={slideDownSettings}
             animationState={animationState}
diff --git a/packages/instant/src/components/ui/container.tsx b/packages/instant/src/components/ui/container.tsx
index 172d384b4..8aa5db9e5 100644
--- a/packages/instant/src/components/ui/container.tsx
+++ b/packages/instant/src/components/ui/container.tsx
@@ -67,9 +67,9 @@ export const Container =
         ${props => cssRuleIfExists(props, 'cursor')}
         ${props => cssRuleIfExists(props, 'overflow')}
         ${props => (props.hasBoxShadow ? `box-shadow: 0px 2px 10px rgba(0, 0, 0, 0.1)` : '')};
-        ${props => props.display && stylesForMedia('display', props.display)}
-        ${props => (props.width ? stylesForMedia('width', props.width) : '')}
-        ${props => (props.height ? stylesForMedia('height', props.height) : '')}
+        ${props => props.display && stylesForMedia<string>('display', props.display)}
+        ${props => props.width && stylesForMedia<string>('width', props.width)}
+        ${props => props.height && stylesForMedia<string>('height', props.height)}
         background-color: ${props => (props.backgroundColor ? props.theme[props.backgroundColor] : 'none')};
         border-color: ${props => (props.borderColor ? props.theme[props.borderColor] : 'none')};
         &:hover {
diff --git a/packages/instant/src/components/zero_ex_instant_container.tsx b/packages/instant/src/components/zero_ex_instant_container.tsx
index 2d3a1f4a8..5748e064e 100644
--- a/packages/instant/src/components/zero_ex_instant_container.tsx
+++ b/packages/instant/src/components/zero_ex_instant_container.tsx
@@ -33,7 +33,7 @@ export class ZeroExInstantContainer extends React.Component<ZeroExInstantContain
                     height={{ default: 'auto', sm: '100%' }}
                     position="relative"
                 >
-                    <Container zIndex={zIndex.errorPopup} position="relative">
+                    <Container position="relative">
                         <LatestError />
                     </Container>
                     <Container
diff --git a/packages/instant/src/components/zero_ex_instant_provider.tsx b/packages/instant/src/components/zero_ex_instant_provider.tsx
index 1fb5cf64f..58e78c522 100644
--- a/packages/instant/src/components/zero_ex_instant_provider.tsx
+++ b/packages/instant/src/components/zero_ex_instant_provider.tsx
@@ -92,12 +92,12 @@ export class ZeroExInstantProvider extends React.Component<ZeroExInstantProvider
             // tslint:disable-next-line:no-floating-promises
             asyncData.fetchAvailableAssetDatasAndDispatchToStore(this._store);
         }
-
+        // tslint:disable-next-line:no-floating-promises
+        asyncData.fetchCurrentBuyQuoteAndDispatchToStore(this._store);
         // warm up the gas price estimator cache just in case we can't
         // grab the gas price estimate when submitting the transaction
         // tslint:disable-next-line:no-floating-promises
         gasPriceEstimator.getGasInfoAsync();
-
         // tslint:disable-next-line:no-floating-promises
         this._flashErrorIfWrongNetwork();
     }
diff --git a/packages/instant/src/containers/selected_erc20_asset_amount_input.ts b/packages/instant/src/containers/selected_erc20_asset_amount_input.ts
index 784eb4bd0..c550aef04 100644
--- a/packages/instant/src/containers/selected_erc20_asset_amount_input.ts
+++ b/packages/instant/src/containers/selected_erc20_asset_amount_input.ts
@@ -1,20 +1,17 @@
-import { AssetBuyer, AssetBuyerError, BuyQuote } from '@0x/asset-buyer';
+import { AssetBuyer } from '@0x/asset-buyer';
 import { AssetProxyId } from '@0x/types';
 import { BigNumber } from '@0x/utils';
-import { Web3Wrapper } from '@0x/web3-wrapper';
 import * as _ from 'lodash';
 import * as React from 'react';
 import { connect } from 'react-redux';
 import { Dispatch } from 'redux';
-import { oc } from 'ts-optchain';
 
 import { ERC20AssetAmountInput } from '../components/erc20_asset_amount_input';
 import { Action, actions } from '../redux/actions';
 import { State } from '../redux/reducer';
 import { ColorOption } from '../style/theme';
 import { AffiliateInfo, ERC20Asset, OrderProcessState } from '../types';
-import { assetUtils } from '../util/asset';
-import { errorFlasher } from '../util/error_flasher';
+import { buyQuoteUpdater } from '../util/buy_quote_updater';
 
 export interface SelectedERC20AssetAmountInputProps {
     fontColor?: ColorOption;
@@ -70,52 +67,9 @@ const mapStateToProps = (state: State, _ownProps: SelectedERC20AssetAmountInputP
     };
 };
 
-const updateBuyQuoteAsync = async (
-    assetBuyer: AssetBuyer,
-    dispatch: Dispatch<Action>,
-    asset: ERC20Asset,
-    assetAmount: BigNumber,
-    affiliateInfo?: AffiliateInfo,
-): Promise<void> => {
-    // get a new buy quote.
-    const baseUnitValue = Web3Wrapper.toBaseUnitAmount(assetAmount, asset.metaData.decimals);
-
-    // mark quote as pending
-    dispatch(actions.setQuoteRequestStatePending());
-
-    const feePercentage = oc(affiliateInfo).feePercentage();
-    let newBuyQuote: BuyQuote | undefined;
-    try {
-        newBuyQuote = await assetBuyer.getBuyQuoteAsync(asset.assetData, baseUnitValue, { feePercentage });
-    } catch (error) {
-        dispatch(actions.setQuoteRequestStateFailure());
-        let errorMessage;
-        if (error.message === AssetBuyerError.InsufficientAssetLiquidity) {
-            const assetName = assetUtils.bestNameForAsset(asset, 'of this asset');
-            errorMessage = `Not enough ${assetName} available`;
-        } else if (error.message === AssetBuyerError.InsufficientZrxLiquidity) {
-            errorMessage = 'Not enough ZRX available';
-        } else if (
-            error.message === AssetBuyerError.StandardRelayerApiError ||
-            error.message.startsWith(AssetBuyerError.AssetUnavailable)
-        ) {
-            const assetName = assetUtils.bestNameForAsset(asset, 'This asset');
-            errorMessage = `${assetName} is currently unavailable`;
-        }
-        if (!_.isUndefined(errorMessage)) {
-            errorFlasher.flashNewErrorMessage(dispatch, errorMessage);
-        } else {
-            throw error;
-        }
-        return;
-    }
-    // We have a successful new buy quote
-    errorFlasher.clearError(dispatch);
-    // invalidate the last buy quote.
-    dispatch(actions.updateLatestBuyQuote(newBuyQuote));
-};
-
-const debouncedUpdateBuyQuoteAsync = _.debounce(updateBuyQuoteAsync, 200, { trailing: true });
+const debouncedUpdateBuyQuoteAsync = _.debounce(buyQuoteUpdater.updateBuyQuoteAsync.bind(buyQuoteUpdater), 200, {
+    trailing: true,
+});
 
 const mapDispatchToProps = (
     dispatch: Dispatch<Action>,
diff --git a/packages/instant/src/redux/async_data.ts b/packages/instant/src/redux/async_data.ts
index c3d190af2..839a90778 100644
--- a/packages/instant/src/redux/async_data.ts
+++ b/packages/instant/src/redux/async_data.ts
@@ -1,7 +1,10 @@
+import { AssetProxyId } from '@0x/types';
 import * as _ from 'lodash';
 
 import { BIG_NUMBER_ZERO } from '../constants';
+import { ERC20Asset } from '../types';
 import { assetUtils } from '../util/asset';
+import { buyQuoteUpdater } from '../util/buy_quote_updater';
 import { coinbaseApi } from '../util/coinbase_api';
 import { errorFlasher } from '../util/error_flasher';
 
@@ -33,4 +36,21 @@ export const asyncData = {
             store.dispatch(actions.setAvailableAssets([]));
         }
     },
+    fetchCurrentBuyQuoteAndDispatchToStore: async (store: Store) => {
+        const { providerState, selectedAsset, selectedAssetAmount, affiliateInfo } = store.getState();
+        const assetBuyer = providerState.assetBuyer;
+        if (
+            !_.isUndefined(selectedAssetAmount) &&
+            !_.isUndefined(selectedAsset) &&
+            selectedAsset.metaData.assetProxyId === AssetProxyId.ERC20
+        ) {
+            await buyQuoteUpdater.updateBuyQuoteAsync(
+                assetBuyer,
+                store.dispatch,
+                selectedAsset as ERC20Asset,
+                selectedAssetAmount,
+                affiliateInfo,
+            );
+        }
+    },
 };
diff --git a/packages/instant/src/style/media.ts b/packages/instant/src/style/media.ts
index beabbac46..5e7aaba37 100644
--- a/packages/instant/src/style/media.ts
+++ b/packages/instant/src/style/media.ts
@@ -14,30 +14,38 @@ const generateMediaWrapper = (screenWidth: ScreenWidths) => (...args: any[]) =>
     }
 `;
 
-const media = {
+export const media = {
     small: generateMediaWrapper(ScreenWidths.Sm),
     medium: generateMediaWrapper(ScreenWidths.Md),
     large: generateMediaWrapper(ScreenWidths.Lg),
 };
 
-export interface ScreenSpecifications {
-    default: string;
-    sm?: string;
-    md?: string;
-    lg?: string;
+export interface ScreenSpecification<T> {
+    default: T;
+    sm?: T;
+    md?: T;
+    lg?: T;
 }
-export type MediaChoice = string | ScreenSpecifications;
-export const stylesForMedia = (cssPropertyName: string, choice: MediaChoice): InterpolationValue[] => {
-    if (typeof choice === 'string') {
+export type OptionallyScreenSpecific<T> = T | ScreenSpecification<T>;
+export type MediaChoice = OptionallyScreenSpecific<string>;
+/**
+ * Given a css property name and a OptionallyScreenSpecific value,
+ * generates css properties with screen-specific viewport styling
+ */
+export function stylesForMedia<T extends string | number>(
+    cssPropertyName: string,
+    choice: OptionallyScreenSpecific<T>,
+): InterpolationValue[] {
+    if (typeof choice === 'object') {
         return css`
-            ${cssPropertyName}: ${choice};
-        `;
-    }
-
-    return css`
         ${cssPropertyName}: ${choice.default};
         ${choice.lg && media.large`${cssPropertyName}: ${choice.lg}`}
         ${choice.md && media.medium`${cssPropertyName}: ${choice.md}`}
         ${choice.sm && media.small`${cssPropertyName}: ${choice.sm}`}
     `;
-};
+    } else {
+        return css`
+            ${cssPropertyName}: ${choice};
+        `;
+    }
+}
diff --git a/packages/instant/src/style/z_index.ts b/packages/instant/src/style/z_index.ts
index 0eedcaf29..bd034182e 100644
--- a/packages/instant/src/style/z_index.ts
+++ b/packages/instant/src/style/z_index.ts
@@ -1,7 +1,8 @@
 export const zIndex = {
-    errorPopup: 10,
+    errorPopBehind: 10,
     mainContainer: 20,
     dropdownItems: 30,
     panel: 40,
+    errorPopup: 50,
     overlayDefault: 100,
 };
diff --git a/packages/instant/src/util/buy_quote_updater.ts b/packages/instant/src/util/buy_quote_updater.ts
new file mode 100644
index 000000000..e697d3ef7
--- /dev/null
+++ b/packages/instant/src/util/buy_quote_updater.ts
@@ -0,0 +1,56 @@
+import { AssetBuyer, AssetBuyerError, BuyQuote } from '@0x/asset-buyer';
+import { BigNumber } from '@0x/utils';
+import { Web3Wrapper } from '@0x/web3-wrapper';
+import * as _ from 'lodash';
+import { Dispatch } from 'redux';
+import { oc } from 'ts-optchain';
+
+import { Action, actions } from '../redux/actions';
+import { AffiliateInfo, ERC20Asset } from '../types';
+import { assetUtils } from '../util/asset';
+import { errorFlasher } from '../util/error_flasher';
+
+export const buyQuoteUpdater = {
+    updateBuyQuoteAsync: async (
+        assetBuyer: AssetBuyer,
+        dispatch: Dispatch<Action>,
+        asset: ERC20Asset,
+        assetAmount: BigNumber,
+        affiliateInfo?: AffiliateInfo,
+    ): Promise<void> => {
+        // get a new buy quote.
+        const baseUnitValue = Web3Wrapper.toBaseUnitAmount(assetAmount, asset.metaData.decimals);
+        // mark quote as pending
+        dispatch(actions.setQuoteRequestStatePending());
+        const feePercentage = oc(affiliateInfo).feePercentage();
+        let newBuyQuote: BuyQuote | undefined;
+        try {
+            newBuyQuote = await assetBuyer.getBuyQuoteAsync(asset.assetData, baseUnitValue, { feePercentage });
+        } catch (error) {
+            dispatch(actions.setQuoteRequestStateFailure());
+            let errorMessage;
+            if (error.message === AssetBuyerError.InsufficientAssetLiquidity) {
+                const assetName = assetUtils.bestNameForAsset(asset, 'of this asset');
+                errorMessage = `Not enough ${assetName} available`;
+            } else if (error.message === AssetBuyerError.InsufficientZrxLiquidity) {
+                errorMessage = 'Not enough ZRX available';
+            } else if (
+                error.message === AssetBuyerError.StandardRelayerApiError ||
+                error.message.startsWith(AssetBuyerError.AssetUnavailable)
+            ) {
+                const assetName = assetUtils.bestNameForAsset(asset, 'This asset');
+                errorMessage = `${assetName} is currently unavailable`;
+            }
+            if (!_.isUndefined(errorMessage)) {
+                errorFlasher.flashNewErrorMessage(dispatch, errorMessage);
+            } else {
+                throw error;
+            }
+            return;
+        }
+        // We have a successful new buy quote
+        errorFlasher.clearError(dispatch);
+        // invalidate the last buy quote.
+        dispatch(actions.updateLatestBuyQuote(newBuyQuote));
+    },
+};
diff --git a/packages/sra-spec/src/json-schemas.ts b/packages/sra-spec/src/json-schemas.ts
index 9eb32de59..f9342ca9e 100644
--- a/packages/sra-spec/src/json-schemas.ts
+++ b/packages/sra-spec/src/json-schemas.ts
@@ -2,6 +2,7 @@ import { schemas as jsonSchemas } from '@0x/json-schemas';
 
 // Only include schemas we actually need
 const {
+    wholeNumberSchema,
     numberSchema,
     addressSchema,
     hexSchema,
@@ -28,6 +29,7 @@ const {
 } = jsonSchemas;
 
 const usedSchemas = {
+    wholeNumberSchema,
     numberSchema,
     addressSchema,
     hexSchema,
diff --git a/packages/utils/src/configured_bignumber.ts b/packages/utils/src/configured_bignumber.ts
index 2b22b6938..34b57d303 100644
--- a/packages/utils/src/configured_bignumber.ts
+++ b/packages/utils/src/configured_bignumber.ts
@@ -11,4 +11,27 @@ BigNumber.config({
     DECIMAL_PLACES: 78,
 });
 
+// Set a debug print function for NodeJS
+// Upstream issue: https://github.com/MikeMcl/bignumber.js/issues/188
+import isNode = require('detect-node');
+if (isNode) {
+    // Dynamically load a NodeJS specific module.
+    // Typescript requires all imports to be global, so we need to use
+    // `const` here and disable the tslint warning.
+    // tslint:disable-next-line: no-var-requires
+    const util = require('util');
+
+    // Set a custom util.inspect function
+    // HACK: We add a function to the BigNumber class by assigning to the
+    //       prototype. The function name is a symbol provided by Node.
+    (BigNumber.prototype as any)[util.inspect.custom] = function(): string {
+        // HACK: When executed, `this` will refer to the BigNumber instance.
+        //       This is also why we need a function expression instead of an
+        //       arrow function, as the latter does not have a `this`.
+        // Return the readable string representation
+        // tslint:disable-next-line: no-invalid-this
+        return this.toString();
+    };
+}
+
 export { BigNumber };