i18next/react-i18next

import { Fragment, isValidElement, cloneElement, createElement, Children } from 'react';
import HTML from 'html-parse-stringify';
import { isObject, isString, warn, warnOnce } from './utils.js';
import { getDefaults } from './defaults.js';
import { getI18n } from './i18nInstance.js';

const hasChildren = (node, checkLength) => {
  if (!node) return false;
  const base = node.props?.children ?? node.children;
  if (checkLength) return base.length > 0;
  return !!base;
};

const getChildren = (node) => {
  if (!node) return [];
  const children = node.props?.children ?? node.children;
  return node.props?.i18nIsDynamicList ? getAsArray(children) : children;
};

const hasValidReactChildren = (children) =>
  Array.isArray(children) && children.every(isValidElement);

const getAsArray = (data) => (Array.isArray(data) ? data : [data]);

const mergeProps = (source, target) => {
  const newTarget = { ...target };
  // overwrite source.props when target.props already set
  newTarget.props = Object.assign(source.props, target.props);
  return newTarget;
};

export const nodesToString = (children, i18nOptions) => {
  if (!children) return '';
  let stringNode = '';

  // do not use `React.Children.toArray`, will fail at object children
  const childrenArray = getAsArray(children);
  const keepArray = i18nOptions?.transSupportBasicHtmlNodes
    ? (i18nOptions.transKeepBasicHtmlNodesFor ?? [])
    : [];

  // e.g. lorem <br/> ipsum {{ messageCount, format }} dolor <strong>bold</strong> amet
  childrenArray.forEach((child, childIndex) => {
    if (isString(child)) {
      // actual e.g. lorem
      // expected e.g. lorem
      stringNode += `${child}`;
    } else if (isValidElement(child)) {
      const { props, type } = child;
      const childPropsCount = Object.keys(props).length;
      const shouldKeepChild = keepArray.indexOf(type) > -1;
      const childChildren = props.children;

      if (!childChildren && shouldKeepChild && !childPropsCount) {
        // actual e.g. lorem <br/> ipsum
        // expected e.g. lorem <br/> ipsum
        stringNode += `<${type}/>`;
      } else if (
        (!childChildren && (!shouldKeepChild || childPropsCount)) ||
        props.i18nIsDynamicList
      ) {
        // actual e.g. lorem <hr className="test" /> ipsum
        // expected e.g. lorem <0></0> ipsum
        // or
        // we got a dynamic list like
        // e.g. <ul i18nIsDynamicList>{['a', 'b'].map(item => ( <li key={item}>{item}</li> ))}</ul>
        // expected e.g. "<0></0>", not e.g. "<0><0>a</0><1>b</1></0>"
        stringNode += `<${childIndex}></${childIndex}>`;
      } else if (shouldKeepChild && childPropsCount === 1 && isString(childChildren)) {
        // actual e.g. dolor <strong>bold</strong> amet
        // expected e.g. dolor <strong>bold</strong> amet
        stringNode += `<${type}>${childChildren}</${type}>`;
      } else {
        // regular case mapping the inner children
        const content = nodesToString(childChildren, i18nOptions);
        stringNode += `<${childIndex}>${content}</${childIndex}>`;
      }
    } else if (child === null) {
      warn(`Trans: the passed in value is invalid - seems you passed in a null child.`);
    } else if (isObject(child)) {
      // e.g. lorem {{ value, format }} ipsum
      const { format, ...clone } = child;
      const keys = Object.keys(clone);

      if (keys.length === 1) {
        const value = format ? `${keys[0]}, ${format}` : keys[0];
        stringNode += `{{${value}}}`;
      } else {
        // not a valid interpolation object (can only contain one value plus format)
        warn(
          `react-i18next: the passed in object contained more than one variable - the object should look like {{ value, format }} where format is optional.`,
          child,
        );
      }
    } else {
      warn(
        `Trans: the passed in value is invalid - seems you passed in a variable like {number} - please pass in variables for interpolation as full objects like {{number}}.`,
        child,
      );
    }
  });

  return stringNode;
};

const renderNodes = (children, targetString, i18n, i18nOptions, combinedTOpts, shouldUnescape) => {
  if (targetString === '') return [];

  // check if contains tags we need to replace from html string to react nodes
  const keepArray = i18nOptions.transKeepBasicHtmlNodesFor || [];
  const emptyChildrenButNeedsHandling =
    targetString && new RegExp(keepArray.map((keep) => `<${keep}`).join('|')).test(targetString);

  // no need to replace tags in the targetstring
  if (!children && !emptyChildrenButNeedsHandling && !shouldUnescape) return [targetString];

  // v2 -> interpolates upfront no need for "some <0>{{var}}</0>"" -> will be just "some {{var}}" in translation file
  const data = {};

  const getData = (childs) => {
    const childrenArray = getAsArray(childs);

    childrenArray.forEach((child) => {
      if (isString(child)) return;
      if (hasChildren(child)) getData(getChildren(child));
      else if (isObject(child) && !isValidElement(child)) Object.assign(data, child);
    });
  };

  getData(children);

  // parse ast from string with additional wrapper tag
  // -> avoids issues in parser removing prepending text nodes
  const ast = HTML.parse(`<0>${targetString}</0>`);
  const opts = { ...data, ...combinedTOpts };

  const renderInner = (child, node, rootReactNode) => {
    const childs = getChildren(child);
    const mappedChildren = mapAST(childs, node.children, rootReactNode);
    // `mappedChildren` will always be empty if using the `i18nIsDynamicList` prop,
    // but the children might not necessarily be react components
    return (hasValidReactChildren(childs) && mappedChildren.length === 0) ||
      child.props?.i18nIsDynamicList
      ? childs
      : mappedChildren;
  };

  const pushTranslatedJSX = (child, inner, mem, i, isVoid) => {
    if (child.dummy) {
      child.children = inner; // needed on preact!
      mem.push(cloneElement(child, { key: i }, isVoid ? undefined : inner));
    } else {
      mem.push(
        ...Children.map([child], (c) => {
          const props = { ...c.props };
          delete props.i18nIsDynamicList;
          // <c.type {...props} key={i} ref={c.ref} {...(isVoid ? {} : { children: inner })} />;
          return createElement(
            c.type,
            {
              ...props,
              key: i,
              ref: c.ref,
            },
            isVoid ? null : inner,
          );
        }),
      );
    }
  };

  // reactNode (the jsx root element or child)
  // astNode (the translation string as html ast)
  // rootReactNode (the most outer jsx children array or trans components prop)
  const mapAST = (reactNode, astNode, rootReactNode) => {
    const reactNodes = getAsArray(reactNode);
    const astNodes = getAsArray(astNode);

    return astNodes.reduce((mem, node, i) => {
      const translationContent =
        node.children?.[0]?.content &&
        i18n.services.interpolator.interpolate(node.children[0].content, opts, i18n.language);

      if (node.type === 'tag') {
        // regular array (components or children)
        let tmp = reactNodes[parseInt(node.name, 10)];

        // trans components is an object
        if (rootReactNode.length === 1 && !tmp) tmp = rootReactNode[0][node.name];

        // neither
        if (!tmp) tmp = {};

        const child =
          Object.keys(node.attrs).length !== 0 ? mergeProps({ props: node.attrs }, tmp) : tmp;

        const isElement = isValidElement(child);

        const isValidTranslationWithChildren =
          isElement && hasChildren(node, true) && !node.voidElement;

        const isEmptyTransWithHTML =
          emptyChildrenButNeedsHandling && isObject(child) && child.dummy && !isElement;

        const isKnownComponent =
          isObject(children) && Object.hasOwnProperty.call(children, node.name);

        if (isString(child)) {
          const value = i18n.services.interpolator.interpolate(child, opts, i18n.language);
          mem.push(value);
        } else if (
          hasChildren(child) || // the jsx element has children -> loop
          isValidTranslationWithChildren // valid jsx element with no children but the translation has -> loop
        ) {
          const inner = renderInner(child, node, rootReactNode);
          pushTranslatedJSX(child, inner, mem, i);
        } else if (isEmptyTransWithHTML) {
          // we have a empty Trans node (the dummy element) with a targetstring that contains html tags needing
          // conversion to react nodes
          // so we just need to map the inner stuff
          const inner = mapAST(
            reactNodes /* wrong but we need something */,
            node.children,
            rootReactNode,
          );
          pushTranslatedJSX(child, inner, mem, i);
        } else if (Number.isNaN(parseFloat(node.name))) {
          if (isKnownComponent) {
            const inner = renderInner(child, node, rootReactNode);
            pushTranslatedJSX(child, inner, mem, i, node.voidElement);
          } else if (i18nOptions.transSupportBasicHtmlNodes && keepArray.indexOf(node.name) > -1) {
            if (node.voidElement) {
              mem.push(createElement(node.name, { key: `${node.name}-${i}` }));
            } else {
              const inner = mapAST(
                reactNodes /* wrong but we need something */,
                node.children,
                rootReactNode,
              );

              mem.push(createElement(node.name, { key: `${node.name}-${i}` }, inner));
            }
          } else if (node.voidElement) {
            mem.push(`<${node.name} />`);
          } else {
            const inner = mapAST(
              reactNodes /* wrong but we need something */,
              node.children,
              rootReactNode,
            );

            mem.push(`<${node.name}>${inner}</${node.name}>`);
          }
        } else if (isObject(child) && !isElement) {
          const content = node.children[0] ? translationContent : null;

          // v1
          // as interpolation was done already we just have a regular content node
          // in the translation AST while having an object in reactNodes
          // -> push the content no need to interpolate again
          if (content) mem.push(content);
        } else {
          // If component does not have children, but translation - has
          // with this in component could be components={[<span class='make-beautiful'/>]} and in translation - 'some text <0>some highlighted message</0>'
          pushTranslatedJSX(
            child,
            translationContent,
            mem,
            i,
            node.children.length !== 1 || !translationContent,
          );
        }
      } else if (node.type === 'text') {
        const wrapTextNodes = i18nOptions.transWrapTextNodes;
        const content = shouldUnescape
          ? i18nOptions.unescape(
              i18n.services.interpolator.interpolate(node.content, opts, i18n.language),
            )
          : i18n.services.interpolator.interpolate(node.content, opts, i18n.language);
        if (wrapTextNodes) {
          mem.push(createElement(wrapTextNodes, { key: `${node.name}-${i}` }, content));
        } else {
          mem.push(content);
        }
      }
      return mem;
    }, []);
  };

  // call mapAST with having react nodes nested into additional node like
  // we did for the string ast from translation
  // return the children of that extra node to get expected result
  const result = mapAST(
    [{ dummy: true, children: children || [] }],
    ast,
    getAsArray(children || []),
  );
  return getChildren(result[0]);
};

export function Trans({
  children,
  count,
  parent,
  i18nKey,
  context,
  tOptions = {},
  values,
  defaults,
  components,
  ns,
  i18n: i18nFromProps,
  t: tFromProps,
  shouldUnescape,
  ...additionalProps
}) {
  const i18n = i18nFromProps || getI18n();

  if (!i18n) {
    warnOnce('You will need to pass in an i18next instance by using i18nextReactModule');
    return children;
  }

  const t = tFromProps || i18n.t.bind(i18n) || ((k) => k);

  const reactI18nextOptions = { ...getDefaults(), ...i18n.options?.react };

  // prepare having a namespace
  let namespaces = ns || t.ns || i18n.options?.defaultNS;
  namespaces = isString(namespaces) ? [namespaces] : namespaces || ['translation'];

  const nodeAsString = nodesToString(children, reactI18nextOptions);
  const defaultValue =
    defaults || nodeAsString || reactI18nextOptions.transEmptyNodeValue || i18nKey;
  const { hashTransKey } = reactI18nextOptions;
  const key =
    i18nKey ||
    (hashTransKey ? hashTransKey(nodeAsString || defaultValue) : nodeAsString || defaultValue);
  if (i18n.options?.interpolation?.defaultVariables) {
    // eslint-disable-next-line no-param-reassign
    values =
      values && Object.keys(values).length > 0
        ? { ...values, ...i18n.options.interpolation.defaultVariables }
        : { ...i18n.options.interpolation.defaultVariables };
  }
  const interpolationOverride =
    values ||
    (count !== undefined && !i18n.options?.interpolation?.alwaysFormat) || // https://github.com/i18next/react-i18next/issues/1719 + https://github.com/i18next/react-i18next/issues/1801
    !children // if !children gets problems in future, undo that fix: https://github.com/i18next/react-i18next/issues/1729 by removing !children from this condition
      ? tOptions.interpolation
      : { interpolation: { ...tOptions.interpolation, prefix: '#$?', suffix: '?$#' } };
  const combinedTOpts = {
    ...tOptions,
    context: context || tOptions.context, // Add `context` from the props or fallback to the value from `tOptions`
    count,
    ...values,
    ...interpolationOverride,
    defaultValue,
    ns: namespaces,
  };
  const translation = key ? t(key, combinedTOpts) : defaultValue;

  if (components) {
    Object.keys(components).forEach((c) => {
      const componentKey = components[c].key || c;
      const comp = cloneElement(components[c], { key: componentKey });
      if (
        !comp.props ||
        !comp.props.children ||
        (translation.indexOf(`${c}/>`) < 0 && translation.indexOf(`${c} />`) < 0)
      )
        return;

      // eslint-disable-next-line react/no-unstable-nested-components
      function Componentized() {
        // <>{comp}</>
        return createElement(Fragment, null, comp);
      }
      // <Componentized />
      components[c] = createElement(Componentized);
    });
  }

  const content = renderNodes(
    components || children,
    translation,
    i18n,
    reactI18nextOptions,
    combinedTOpts,
    shouldUnescape,
  );

  // allows user to pass `null` to `parent`
  // and override `defaultTransParent` if is present
  const useAsParent = parent ?? reactI18nextOptions.defaultTransParent;

  return useAsParent ? createElement(useAsParent, additionalProps, content) : content;
}