Transforms and Utilities

/**
 * Returns an interpolator between two CSS 2D transform strings.
 * Decomposes transforms into translate, rotate, skew, and scale components.
 * @param a - Starting CSS transform string
 * @param b - Ending CSS transform string
 * @returns Interpolator function returning CSS transform string
 */
function interpolateTransformCss(a: string, b: string): (t: number) => string;

import { interpolateTransformCss } from "d3-interpolate";

// Basic translation
const translateInterp = interpolateTransformCss(
  "translate(0px, 0px)",
  "translate(100px, 50px)"
);
console.log(translateInterp(0.5)); // "translate(50px, 25px)"

// Rotation interpolation
const rotateInterp = interpolateTransformCss(
  "rotate(0deg)",
  "rotate(90deg)"
);
console.log(rotateInterp(0.5)); // "rotate(45deg)"

// Complex multi-component transforms
const complexInterp = interpolateTransformCss(
  "translate(0px, 0px) rotate(0deg) scale(1, 1)",
  "translate(100px, 50px) rotate(180deg) scale(2, 1.5)"
);
console.log(complexInterp(0.5));
// "translate(50px, 25px) rotate(90deg) scale(1.5, 1.25)"

// Skew transforms
const skewInterp = interpolateTransformCss(
  "skewX(0deg)",
  "skewX(30deg)"
);
console.log(skewInterp(0.5)); // "skewX(15deg)"

// Mixed transform shorthand
const mixedInterp = interpolateTransformCss(
  "translate(10px, 20px) scale(0.5)",
  "translate(90px, 80px) scale(2) rotate(45deg)"
);
console.log(mixedInterp(0.25));
// Smooth decomposition and recomposition

/**
 * Returns an interpolator between two SVG 2D transform strings.
 * Uses same decomposition as CSS but with SVG syntax.
 * @param a - Starting SVG transform string
 * @param b - Ending SVG transform string
 * @returns Interpolator function returning SVG transform string
 */
function interpolateTransformSvg(a: string, b: string): (t: number) => string;

import { interpolateTransformSvg } from "d3-interpolate";

// SVG translation (no units)
const svgTranslate = interpolateTransformSvg(
  "translate(0, 0)",
  "translate(100, 50)"
);
console.log(svgTranslate(0.5)); // "translate(50, 50)"

// SVG rotation with center point
const svgRotate = interpolateTransformSvg(
  "rotate(0, 50, 50)",
  "rotate(90, 50, 50)"
);
console.log(svgRotate(0.5)); // "rotate(45, 50, 50)"

// Complex SVG transform
const svgComplex = interpolateTransformSvg(
  "translate(0, 0) scale(1)",
  "translate(100, 100) scale(2) rotate(180)"
);
console.log(svgComplex(0.5));
// "translate(50, 50) scale(1.5) rotate(90)"

// Path animation transforms
const pathTransform = interpolateTransformSvg(
  "translate(0) rotate(0) scale(1, 1)",
  "translate(200) rotate(360) scale(0.5, 2)"
);

/**
 * Returns a discrete interpolator that steps through array values.
 * Effectively a quantize scale with domain [0, 1].
 * @param values - Array of discrete values to step through
 * @returns Interpolator function returning discrete values
 */
function interpolateDiscrete(values: any[]): (t: number) => any;

import { interpolateDiscrete } from "d3-interpolate";

// Animation keyframes
const keyframes = interpolateDiscrete([
  "frame1.jpg",
  "frame2.jpg", 
  "frame3.jpg",
  "frame4.jpg"
]);

console.log(keyframes(0.0));   // "frame1.jpg"
console.log(keyframes(0.3));   // "frame2.jpg"
console.log(keyframes(0.6));   // "frame3.jpg"
console.log(keyframes(0.99));  // "frame4.jpg"

// State machine transitions
const states = interpolateDiscrete(["idle", "loading", "success", "error"]);

// Discrete color themes
const themes = interpolateDiscrete(["light", "dark", "auto"]);
console.log(themes(0.33)); // "dark"

/**
 * Returns n uniformly-spaced samples from an interpolator.
 * First sample at t=0, last at t=1.
 * @param interpolator - Function to sample from
 * @param n - Number of samples (integer ≥ 2)
 * @returns Array of n sampled values
 */
function quantize(interpolator: (t: number) => any, n: number): any[];

import { quantize, interpolateRgb, interpolateHsl, piecewise } from "d3-interpolate";

// Generate color ramps for data visualization
const heatmapColors = quantize(
  interpolateRgb("blue", "red"),
  10
);
console.log(heatmapColors); // 10-step blue to red gradient

// Multi-stop gradients
const sunset = quantize(
  piecewise(interpolateHsl, ["#87CEEB", "#FFA500", "#FF4500", "#8B008B"]),
  20
);

// Generate lookup tables
const easingLUT = quantize(
  (t) => t * t * (3 - 2 * t), // Smoothstep function
  256
);

// SVG gradient stops
const gradientStops = quantize(interpolateRgb("#ff0000", "#0000ff"), 5)
  .map((color, i) => `<stop offset="${i * 25}%" stop-color="${color}"/>`)
  .join('\n');

console.log(`<linearGradient>\n${gradientStops}\n</linearGradient>`);

// CSS animation keyframes
const keyframeValues = quantize(interpolateNumber(0, 360), 8);
const cssKeyframes = keyframeValues
  .map((angle, i) => `${i * 100/7}% { transform: rotate(${angle}deg); }`)
  .join('\n');

// Data point interpolation for smooth charts
const dataInterp = quantize(
  piecewise([10, 25, 15, 30, 20]),
  50 // 50 smooth points between 5 data points
);