1 files changed, 83 insertions, 0 deletions
diff --git a/packages/instant/src/components/scaling_amount_input.tsx b/packages/instant/src/components/scaling_amount_input.tsx
new file mode 100644
index 000000000..5dc719293
--- /dev/null
+++ b/packages/instant/src/components/scaling_amount_input.tsx
@@ -0,0 +1,83 @@
+import { BigNumber } from '@0x/utils';
+import * as _ from 'lodash';
+import * as React from 'react';
+
+import { Maybe } from '../types';
+
+import { ColorOption } from '../style/theme';
+import { maybeBigNumberUtil } from '../util/maybe_big_number';
+import { util } from '../util/util';
+
+import { ScalingInput } from './scaling_input';
+
+export interface ScalingAmountInputProps {
+    isDisabled: boolean;
+    maxFontSizePx: number;
+    textLengthThreshold: number;
+    fontColor?: ColorOption;
+    value?: BigNumber;
+    onAmountChange: (value?: BigNumber) => void;
+    onFontSizeChange: (fontSizePx: number) => void;
+}
+interface ScalingAmountInputState {
+    stringValue: string;
+}
+
+const { stringToMaybeBigNumber, areMaybeBigNumbersEqual } = maybeBigNumberUtil;
+export class ScalingAmountInput extends React.Component<ScalingAmountInputProps, ScalingAmountInputState> {
+    public static defaultProps = {
+        onAmountChange: util.boundNoop,
+        onFontSizeChange: util.boundNoop,
+        isDisabled: false,
+    };
+    public constructor(props: ScalingAmountInputProps) {
+        super(props);
+        this.state = {
+            stringValue: _.isUndefined(props.value) ? '' : props.value.toString(),
+        };
+    }
+    public componentDidUpdate(): void {
+        const parsedStateValue = stringToMaybeBigNumber(this.state.stringValue);
+        const currentValue = this.props.value;
+
+        if (!areMaybeBigNumbersEqual(parsedStateValue, currentValue)) {
+            // we somehow got into the state in which the value passed in and the string value
+            // in state have differed, reset state
+            // we dont expect to ever get into this state, but let's make sure
+            // we reset if we do since we're dealing with important numbers
+            this.setState({
+                stringValue: _.isUndefined(currentValue) ? '' : currentValue.toString(),
+            });
+        }
+    }
+
+    public render(): React.ReactNode {
+        const { textLengthThreshold, fontColor, maxFontSizePx, onFontSizeChange } = this.props;
+        return (
+            <ScalingInput
+                maxFontSizePx={maxFontSizePx}
+                textLengthThreshold={textLengthThreshold}
+                onFontSizeChange={onFontSizeChange}
+                fontColor={fontColor}
+                onChange={this._handleChange}
+                value={this.state.stringValue}
+                placeholder="0.00"
+                emptyInputWidthCh={3.5}
+                isDisabled={this.props.isDisabled}
+            />
+        );
+    }
+    private readonly _handleChange = (event: React.ChangeEvent<HTMLInputElement>): void => {
+        const sanitizedValue = event.target.value.replace(/[^0-9.]/g, ''); // only allow numbers and "."
+        this.setState({
+            stringValue: sanitizedValue,
+        });
+
+        // Trigger onAmountChange with a valid BigNumber, or undefined if the sanitizedValue is invalid or empty
+        const bigNumberValue: Maybe<BigNumber> = _.isEmpty(sanitizedValue)
+            ? undefined
+            : stringToMaybeBigNumber(sanitizedValue);
+
+        this.props.onAmountChange(bigNumberValue);
+    };
+}