/
Interpolation.js
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/
Interpolation.js
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/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/
/* eslint no-bitwise: 0 */
'use strict';
var normalizeColor = require('normalize-css-color');
var invariant = require('invariant');
type ExtrapolateType = 'extend' | 'identity' | 'clamp';
export type InterpolationConfigType = {
inputRange: Array<number>;
outputRange: (Array<number> | Array<string>);
easing?: ((input: number) => number);
extrapolate?: ExtrapolateType;
extrapolateLeft?: ExtrapolateType;
extrapolateRight?: ExtrapolateType;
};
var linear = (t) => t;
/**
* Very handy helper to map input ranges to output ranges with an easing
* function and custom behavior outside of the ranges.
*/
class Interpolation {
static create(config: InterpolationConfigType): (input: number) => number | string {
if (config.outputRange && typeof config.outputRange[0] === 'string') {
return createInterpolationFromStringOutputRange(config);
}
var outputRange: Array<number> = (config.outputRange: any);
checkInfiniteRange('outputRange', outputRange);
var inputRange = config.inputRange;
checkInfiniteRange('inputRange', inputRange);
checkValidInputRange(inputRange);
invariant(
inputRange.length === outputRange.length,
'inputRange (' + inputRange.length + ') and outputRange (' +
outputRange.length + ') must have the same length'
);
var easing = config.easing || linear;
var extrapolateLeft: ExtrapolateType = 'extend';
if (config.extrapolateLeft !== undefined) {
extrapolateLeft = config.extrapolateLeft;
} else if (config.extrapolate !== undefined) {
extrapolateLeft = config.extrapolate;
}
var extrapolateRight: ExtrapolateType = 'extend';
if (config.extrapolateRight !== undefined) {
extrapolateRight = config.extrapolateRight;
} else if (config.extrapolate !== undefined) {
extrapolateRight = config.extrapolate;
}
return (input) => {
invariant(
typeof input === 'number',
'Cannot interpolation an input which is not a number'
);
var range = findRange(input, inputRange);
return interpolate(
input,
inputRange[range],
inputRange[range + 1],
outputRange[range],
outputRange[range + 1],
easing,
extrapolateLeft,
extrapolateRight,
);
};
}
}
function interpolate(
input: number,
inputMin: number,
inputMax: number,
outputMin: number,
outputMax: number,
easing: ((input: number) => number),
extrapolateLeft: ExtrapolateType,
extrapolateRight: ExtrapolateType,
) {
var result = input;
// Extrapolate
if (result < inputMin) {
if (extrapolateLeft === 'identity') {
return result;
} else if (extrapolateLeft === 'clamp') {
result = inputMin;
} else if (extrapolateLeft === 'extend') {
// noop
}
}
if (result > inputMax) {
if (extrapolateRight === 'identity') {
return result;
} else if (extrapolateRight === 'clamp') {
result = inputMax;
} else if (extrapolateRight === 'extend') {
// noop
}
}
if (outputMin === outputMax) {
return outputMin;
}
if (inputMin === inputMax) {
if (input <= inputMin) {
return outputMin;
}
return outputMax;
}
// Input Range
if (inputMin === -Infinity) {
result = -result;
} else if (inputMax === Infinity) {
result = result - inputMin;
} else {
result = (result - inputMin) / (inputMax - inputMin);
}
// Easing
result = easing(result);
// Output Range
if (outputMin === -Infinity) {
result = -result;
} else if (outputMax === Infinity) {
result = result + outputMin;
} else {
result = result * (outputMax - outputMin) + outputMin;
}
return result;
}
function colorToRgba(input: string): string {
var int32Color = normalizeColor(input);
if (int32Color === null) {
return input;
}
int32Color = int32Color || 0; // $FlowIssue
var r = (int32Color & 0xff000000) >>> 24;
var g = (int32Color & 0x00ff0000) >>> 16;
var b = (int32Color & 0x0000ff00) >>> 8;
var a = (int32Color & 0x000000ff) / 255;
return `rgba(${r}, ${g}, ${b}, ${a})`;
}
var stringShapeRegex = /[0-9\.-]+/g;
/**
* Supports string shapes by extracting numbers so new values can be computed,
* and recombines those values into new strings of the same shape. Supports
* things like:
*
* rgba(123, 42, 99, 0.36) // colors
* -45deg // values with units
*/
function createInterpolationFromStringOutputRange(
config: InterpolationConfigType,
): (input: number) => string {
var outputRange: Array<string> = (config.outputRange: any);
invariant(outputRange.length >= 2, 'Bad output range');
outputRange = outputRange.map(colorToRgba);
checkPattern(outputRange);
// ['rgba(0, 100, 200, 0)', 'rgba(50, 150, 250, 0.5)']
// ->
// [
// [0, 50],
// [100, 150],
// [200, 250],
// [0, 0.5],
// ]
/* $FlowFixMe(>=0.18.0): `outputRange[0].match()` can return `null`. Need to
* guard against this possibility.
*/
var outputRanges = outputRange[0].match(stringShapeRegex).map(() => []);
outputRange.forEach(value => {
/* $FlowFixMe(>=0.18.0): `value.match()` can return `null`. Need to guard
* against this possibility.
*/
value.match(stringShapeRegex).forEach((number, i) => {
outputRanges[i].push(+number);
});
});
/* $FlowFixMe(>=0.18.0): `outputRange[0].match()` can return `null`. Need to
* guard against this possibility.
*/
var interpolations = outputRange[0].match(stringShapeRegex).map((value, i) => {
return Interpolation.create({
...config,
outputRange: outputRanges[i],
});
});
// rgba requires that the r,g,b are integers.... so we want to round them, but we *dont* want to
// round the opacity (4th column).
const shouldRound = (/^rgb/).test(outputRange[0]);
return (input) => {
var i = 0;
// 'rgba(0, 100, 200, 0)'
// ->
// 'rgba(${interpolations[0](input)}, ${interpolations[1](input)}, ...'
return outputRange[0].replace(stringShapeRegex, () => {
const val = interpolations[i++](input);
return String(shouldRound && i < 4 ? Math.round(val) : val);
});
};
}
function checkPattern(arr: Array<string>) {
var pattern = arr[0].replace(stringShapeRegex, '');
for (var i = 1; i < arr.length; ++i) {
invariant(
pattern === arr[i].replace(stringShapeRegex, ''),
'invalid pattern ' + arr[0] + ' and ' + arr[i],
);
}
}
function findRange(input: number, inputRange: Array<number>) {
for (var i = 1; i < inputRange.length - 1; ++i) {
if (inputRange[i] >= input) {
break;
}
}
return i - 1;
}
function checkValidInputRange(arr: Array<number>) {
invariant(arr.length >= 2, 'inputRange must have at least 2 elements');
for (var i = 1; i < arr.length; ++i) {
invariant(
arr[i] >= arr[i - 1],
/* $FlowFixMe(>=0.13.0) - In the addition expression below this comment,
* one or both of the operands may be something that doesn't cleanly
* convert to a string, like undefined, null, and object, etc. If you really
* mean this implicit string conversion, you can do something like
* String(myThing)
*/
'inputRange must be monotonically increasing ' + arr
);
}
}
function checkInfiniteRange(name: string, arr: Array<number>) {
invariant(arr.length >= 2, name + ' must have at least 2 elements');
invariant(
arr.length !== 2 || arr[0] !== -Infinity || arr[1] !== Infinity,
/* $FlowFixMe(>=0.13.0) - In the addition expression below this comment,
* one or both of the operands may be something that doesn't cleanly convert
* to a string, like undefined, null, and object, etc. If you really mean
* this implicit string conversion, you can do something like
* String(myThing)
*/
name + 'cannot be ]-infinity;+infinity[ ' + arr
);
}
module.exports = Interpolation;