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import { h, t } from "./lustre/element.mjs";
import { fold } from "../gleam_stdlib/gleam/list.mjs";
const Element = h("").constructor;
const Text = t("").constructor;
export function morph(prev, curr) {
if (curr instanceof Element) {
return prev?.nodeType === 1 && prev.nodeName === curr[0].toUpperCase()
? morphElement(prev, curr)
: createElement(prev, curr);
}
if (curr instanceof Text) {
return prev?.nodeType === 3
? morphText(prev, curr)
: createText(prev, curr);
}
return document.createComment(
[
"[internal lustre error] I couldn't work out how to render this element. This",
"function should only be called internally by lustre's runtime: if you think",
"this is an error, please open an issue at",
"https://github.come/hayleigh-dot-dev/lustre/issues/new.",
].join(" ")
);
}
// ELEMENTS --------------------------------------------------------------------
function createElement(prev, curr) {
const el = document.createElement(curr[0]);
let attr = curr[1];
while (attr.head) {
morphAttr(el, attr.head[0], attr.head[1]);
attr = attr.tail;
}
let child = curr[2];
while (child.head) {
el.appendChild(morph(null, child.head));
child = child.tail;
}
if (prev) prev.replaceWith(el);
return el;
}
function morphElement(prev, curr) {
const prevAttrs = prev.attributes;
const currAttrs = new Map();
let currAttr = curr[1];
while (currAttr.head) {
currAttrs.set(currAttr.head[0], currAttr.head[1]);
currAttr = currAttr.tail;
}
for (const { name, value: prevValue } of prevAttrs) {
if (!currAttrs.has(name)) prev.removeAttribute(name);
const value = currAttrs.get(name);
if (value !== prevValue) {
morphAttr(prev, name, value);
currAttrs.delete(name);
}
}
for (const [name, value] of currAttrs) {
morphAttr(prev, name, value);
}
let prevChild = prev.firstChild;
let currChild = curr[2];
while (prevChild) {
if (currChild.head) {
morph(prevChild, currChild.head);
currChild = currChild.tail;
}
prevChild = prevChild.nextSibling;
}
while (currChild.head) {
prev.appendChild(morph(null, currChild.head));
currChild = currChild.tail;
}
return prev;
}
// ATTRIBUTES ------------------------------------------------------------------
function morphAttr(el, name, value) {
switch (typeof value) {
case "string":
el.setAttribute(name, value);
break;
// Boolean attributes work a bit differently in HTML. Their presence always
// implies true: to set an attribute to false you need to remove it entirely.
case "boolean":
value ? el.setAttribute(name, name) : el.removeAttribute(name);
break;
// For properties, we're leaning on reference equality to avoid unnecessary
// updates.
default:
if (el[name] !== value) el[name] = value;
}
}
// TEXT ------------------------------------------------------------------------
function createText(prev, curr) {
const el = document.createTextNode(curr[0]);
if (prev) prev.replaceWith(el);
return el;
}
function morphText(prev, curr) {
const prevValue = prev.nodeValue;
const currValue = curr[0];
if (prevValue !== currValue) prev.nodeValue = currValue;
return prev;
}
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