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109 lines
3.7 KiB
109 lines
3.7 KiB
/* Currency Conversion Utility
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* This utility function can be used for converting currency related values within metamask.
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* The caller should be able to pass it a value, along with information about the value's
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* numeric base, denomination and currency, and the desired numeric base, denomination and
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* currency. It should return a single value.
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*
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* @param {(number | string | BN)} value The value to convert.
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* @param {Object} [options] Options to specify details of the conversion
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* @param {string} [options.fromCurrency = 'ETH' | 'USD'] The currency of the passed value
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* @param {string} [options.toCurrency = 'ETH' | 'USD'] The desired currency of the result
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* @param {string} [options.fromNumericBase = 'hex' | 'dec' | 'BN'] The numeric basic of the passed value.
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* @param {string} [options.toNumericBase = 'hex' | 'dec' | 'BN'] The desired numeric basic of the result.
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* @param {string} [options.fromDenomination = 'WEI'] The denomination of the passed value
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* @param {number} [options.numberOfDecimals] The desired number of in the result
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* @param {number} [options.conversionRate] The rate to use to make the fromCurrency -> toCurrency conversion
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* @returns {(number | string | BN)}
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*
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* The utility passes value along with the options as a single object to the `converter` function.
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* `converter` uses Ramda.js to apply a composition of conditional setters to the `value` property, depending
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* on the accompanying options. Some of these conditional setters are selected via key-value maps, where
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* the keys are specified in the options parameters and the values are setter functions.
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*/
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const BigNumber = require('bignumber.js')
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const R = require('ramda')
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const { stripHexPrefix } = require('ethereumjs-util')
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BigNumber.config({
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ROUNDING_MODE: BigNumber.ROUND_HALF_DOWN,
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})
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// Big Number Constants
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const BIG_NUMBER_WEI_MULTIPLIER = new BigNumber('1000000000000000000')
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// Individual Setters
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const convert = R.invoker(1, 'times')
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const round = R.invoker(2, 'toFormat')(R.__, BigNumber.ROUND_DOWN)
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// Setter Maps
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const toBigNumber = {
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hex: n => new BigNumber(stripHexPrefix(n), 16),
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dec: n => new BigNumber(n, 10),
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BN: n => new BigNumber(n.toString(16), 16),
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}
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const toNormalizedDenomination = {
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WEI: bigNumber => bigNumber.div(BIG_NUMBER_WEI_MULTIPLIER)
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}
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const baseChange = {
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hex: n => n.toString(16),
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dec: n => n.toString(10),
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BN: n => new BN(n.toString(16)),
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}
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// Predicates
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const fromAndToCurrencyPropsNotEqual = R.compose(
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R.not,
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R.eqBy(R.__, 'fromCurrency', 'toCurrency'),
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R.flip(R.prop)
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)
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// Lens
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const valuePropertyLense = R.over(R.lensProp('value'))
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// conditional 'value' setting wrappers
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const whenPredSetWithPropAndSetter = (pred, prop, setter) => R.when(
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pred,
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R.converge(
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valuePropertyLense,
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[R.pipe(R.prop(prop), setter), R.identity]
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)
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)
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const whenPropApplySetterMap = (prop, setterMap) => whenPredSetWithPropAndSetter(
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R.prop(prop),
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prop,
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R.prop(R.__, setterMap)
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)
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// Conversion utility function
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const converter = R.pipe(
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whenPropApplySetterMap('fromNumericBase', toBigNumber),
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whenPropApplySetterMap('fromDenomination', toNormalizedDenomination),
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whenPredSetWithPropAndSetter(fromAndToCurrencyPropsNotEqual, 'conversionRate', convert),
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whenPredSetWithPropAndSetter(R.prop('numberOfDecimals'), 'numberOfDecimals', round),
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whenPropApplySetterMap('toNumericBase', baseChange),
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R.view(R.lensProp('value'))
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);
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const conversionUtil = (value, {
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fromCurrency = null,
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toCurrency = fromCurrency,
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fromNumericBase,
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toNumericBase,
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fromDenomination,
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numberOfDecimals,
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conversionRate,
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}) => converter({
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fromCurrency,
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toCurrency,
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fromNumericBase,
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toNumericBase,
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fromDenomination,
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numberOfDecimals,
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conversionRate,
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value,
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});
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module.exports = {
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conversionUtil,
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} |