71 lines
1.9 KiB
JavaScript
71 lines
1.9 KiB
JavaScript
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// @ts-check
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import { GifNodeType } from "./constants.js";
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import crel, { fragment } from "../common/crel.js";
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import getOwn from "../common/getOwn.js";
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import { areBytesEqual } from "../common/bytes.js";
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/** @typedef {import("../../types/gif.d.ts").GifNode} GifNode */
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const textEncoder = new TextEncoder();
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const VERSION_87 = textEncoder.encode("87a");
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const VERSION_89 = textEncoder.encode("89a");
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/**
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* @param {(string | Node)[]} children
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*/
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const p = (...children) => crel("p", {}, ...children);
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/**
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* @typedef {object} NodeUi
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* @prop {string} title
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* @prop {HTMLElement | DocumentFragment} description
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*/
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/** @type {Record<string, (node: GifNode) => NodeUi>} */
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const NODE_UI_FNS = {
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[GifNodeType.root]: () => ({
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title: "GIF file",
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description: fragment(),
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}),
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// Header
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[GifNodeType.header]: () => ({
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title: "GIF header",
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description: fragment(
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p('GIFs start with a 6-byte header. This is typically the string "GIF87a" or "GIF89a", encoded as ASCII.'),
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),
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}),
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[GifNodeType.headerSignature]: () => ({
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title: "GIF signature",
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description: p('GIFs start with the string "GIF", encoded as ASCII.'),
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}),
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[GifNodeType.headerVersion]: ({ bytes }) => {
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/** @type {string} */ let end;
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if (areBytesEqual(bytes, VERSION_87)) {
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end = "87a";
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} else if (areBytesEqual(bytes, VERSION_89)) {
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end = "89a";
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} else {
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end = "something unexpected! This might not be a valid GIF file";
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}
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return {
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title: "GIF version",
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description: p(
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`The version of the GIF format. This is typically "87a" or "89a". In this case, the version is ${end}.`,
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),
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};
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},
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};
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/**
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* @param {GifNode} node
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* @returns {NodeUi}
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*/
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export default (node) => {
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const uiFn = getOwn(NODE_UI_FNS, node.type);
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if (!uiFn) throw new Error("Found a node with no matching UI function");
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return uiFn(node);
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};
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