/*
 * Copyright (C) 2026 Mateusz Gruszczyński @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 *
 * Frontend internationalization. Language files live in /lang at the repository
 * root and are embedded into the Rust binary at build time.
 */

const STORAGE_KEY = "rustpad:language";
const FALLBACK_LANGUAGE = "en";
const TRANSLATABLE_ATTRIBUTES = ["placeholder", "title", "aria-label", "aria-description"];
const SKIP_SELECTOR = [
  "script",
  "style",
  "textarea",
  "#editor",
  "#preview",
  "#chat-messages",
  ".markdown-body",
  ".revision__snippet",
  ".revision__preview",
  ".chat-message",
  ".resource-title-line a",
  ".share-list-identity",
  ".note-card-title h3",
  ".note-table-link",
  "#document-title",
  "#workspace-title",
  "#public-title",
  "#room-users",
  "[data-account-primary]",
  "[data-account-secondary]",
  "[contenteditable='true']",
  "[data-i18n-ignore]",
].join(",");

const textState = new WeakMap();
const attributeState = new WeakMap();
const bundles = new Map();
let catalog = [];
let activeCode = FALLBACK_LANGUAGE;
let activeBundle = null;
let fallbackBundle = null;
let sourceIndex = new Map();
let sourcePatterns = [];
let observer = null;
let initialized = false;
let initialization = null;

function configVersion() {
  return window.__RUSTPAD_CONFIG__?.assetVersion || "dev";
}

function normalizeSource(value) {
  return String(value ?? "").replace(/\s+/g, " ").trim();
}

function escapeRegExp(value) {
  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
}

function compileSourcePattern(source, key) {
  const names = [];
  let cursor = 0;
  let expression = "^";
  const placeholder = /\{([a-zA-Z0-9_]+)\}/g;
  let match;
  while ((match = placeholder.exec(source))) {
    expression += escapeRegExp(source.slice(cursor, match.index));
    expression += "(.+?)";
    names.push(match[1]);
    cursor = match.index + match[0].length;
  }
  expression += escapeRegExp(source.slice(cursor));
  expression += "$";
  try {
    return { key, source, names, regex: new RegExp(expression, "u") };
  } catch {
    return null;
  }
}

function rebuildSourceIndex() {
  sourceIndex = new Map();
  sourcePatterns = [];
  const indexedBundles = new Set();
  const candidates = [fallbackBundle, ...bundles.values()].filter(Boolean);
  for (const bundle of candidates) {
    if (indexedBundles.has(bundle)) continue;
    indexedBundles.add(bundle);
    for (const [key, rawValue] of Object.entries(bundle.translations || {})) {
      if (typeof rawValue !== "string" || !rawValue.trim()) continue;
      const value = normalizeSource(rawValue);
      if (!sourceIndex.has(value)) sourceIndex.set(value, key);
      if (/\{[a-zA-Z0-9_]+\}/.test(value)) {
        const pattern = compileSourcePattern(value, key);
        if (pattern) sourcePatterns.push(pattern);
      }
    }
  }
  sourcePatterns.sort((left, right) => right.source.length - left.source.length);
}

function interpolate(value, params = {}) {
  return String(value ?? "").replace(/\{([a-zA-Z0-9_]+)\}/g, (match, name) =>
    Object.prototype.hasOwnProperty.call(params, name) ? String(params[name]) : match
  );
}

export function t(key, params = {}, fallback = key) {
  const active = activeBundle?.translations?.[key];
  const base = fallbackBundle?.translations?.[key];
  const value = typeof active === "string" ? active : typeof base === "string" ? base : fallback;
  return interpolate(value, params);
}

export function tp(key, count, params = {}, fallback = "") {
  const numericCount = Number(count);
  let category = "other";
  try { category = new Intl.PluralRules(getLocale()).select(numericCount); } catch { /* use other */ }
  const candidates = [`${key}.${category}`, `${key}.other`, `${key}.many`, `${key}.few`, `${key}.one`];
  for (const candidate of candidates) {
    const active = activeBundle?.translations?.[candidate];
    const base = fallbackBundle?.translations?.[candidate];
    const value = typeof active === "string" ? active : typeof base === "string" ? base : null;
    if (value != null) return interpolate(value, { ...params, count: numericCount });
  }
  return interpolate(fallback || String(numericCount), { ...params, count: numericCount });
}

function matchSource(value) {
  const normalized = normalizeSource(value);
  if (!normalized) return null;
  const exactKey = sourceIndex.get(normalized);
  if (exactKey) return { key: exactKey, params: {} };
  for (const pattern of sourcePatterns) {
    const match = normalized.match(pattern.regex);
    if (!match) continue;
    const params = {};
    pattern.names.forEach((name, index) => { params[name] = match[index + 1]; });
    return { key: pattern.key, params };
  }
  return null;
}

export function translateSource(value) {
  const raw = String(value ?? "");
  if (!raw.trim()) return raw;
  const leading = raw.match(/^\s*/u)?.[0] || "";
  const trailing = raw.match(/\s*$/u)?.[0] || "";
  const match = matchSource(raw);
  if (!match) return raw;
  return `${leading}${t(match.key, match.params, normalizeSource(raw))}${trailing}`;
}

export function translateApiMessage(message) {
  return translateSource(message);
}

function isSkipped(element) {
  return element instanceof Element && Boolean(element.closest(SKIP_SELECTOR));
}

function translateTextNode(node, force = false) {
  const parent = node.parentElement;
  if (!parent || isSkipped(parent)) return;
  const current = node.data;
  let state = textState.get(node);
  if (!state || (!force && current !== state.rendered)) {
    state = { original: current, rendered: current };
    textState.set(node, state);
  }
  const rendered = translateSource(state.original);
  state.rendered = rendered;
  if (node.data !== rendered) node.data = rendered;
}

function attributeMap(element) {
  let map = attributeState.get(element);
  if (!map) {
    map = new Map();
    attributeState.set(element, map);
  }
  return map;
}

function translateAttribute(element, name, force = false) {
  if (!element.hasAttribute(name) || isSkipped(element)) return;
  const current = element.getAttribute(name) || "";
  const map = attributeMap(element);
  let state = map.get(name);
  if (!state || (!force && current !== state.rendered)) {
    state = { original: current, rendered: current };
    map.set(name, state);
  }
  const rendered = translateSource(state.original);
  state.rendered = rendered;
  if (current !== rendered) element.setAttribute(name, rendered);
}

function translateExplicit(element) {
  const key = element.dataset.i18n;
  if (key) element.textContent = t(key);
  for (const attribute of TRANSLATABLE_ATTRIBUTES) {
    const attrKey = element.dataset[`i18n${attribute.replace(/(^|-)([a-z])/g, (_, __, char) => char.toUpperCase())}`];
    if (attrKey) element.setAttribute(attribute, t(attrKey));
  }
}

function translateElementAttributes(element, force = false) {
  translateExplicit(element);
  if (isSkipped(element)) return;
  for (const name of TRANSLATABLE_ATTRIBUTES) translateAttribute(element, name, force);
}

function translateTree(root = document, force = false) {
  if (root instanceof Element) translateElementAttributes(root, force);
  const elementRoot = root instanceof Document ? root.documentElement : root;
  if (!elementRoot) return;

  const elementWalker = document.createTreeWalker(elementRoot, NodeFilter.SHOW_ELEMENT);
  let element = elementWalker.currentNode;
  while (element) {
    if (element instanceof Element) translateElementAttributes(element, force);
    element = elementWalker.nextNode();
  }

  const textWalker = document.createTreeWalker(elementRoot, NodeFilter.SHOW_TEXT);
  let textNode = textWalker.nextNode();
  while (textNode) {
    translateTextNode(textNode, force);
    textNode = textWalker.nextNode();
  }
}

function startObserver() {
  observer?.disconnect();
  observer = new MutationObserver(mutations => {
    for (const mutation of mutations) {
      if (mutation.type === "characterData") {
        translateTextNode(mutation.target);
        continue;
      }
      if (mutation.type === "attributes") {
        translateAttribute(mutation.target, mutation.attributeName);
        continue;
      }
      for (const node of mutation.addedNodes) {
        if (node.nodeType === Node.TEXT_NODE) translateTextNode(node);
        else if (node instanceof Element) translateTree(node);
      }
    }
  });
  observer.observe(document.documentElement, {
    subtree: true,
    childList: true,
    characterData: true,
    attributes: true,
    attributeFilter: TRANSLATABLE_ATTRIBUTES,
  });
}

async function fetchJson(path) {
  const separator = path.includes("?") ? "&" : "?";
  const response = await fetch(`${path}${separator}v=${encodeURIComponent(configVersion())}`, {
    credentials: "same-origin",
    headers: { Accept: "application/json" },
  });
  if (!response.ok) throw new Error(t("i18n.loadFailed", { status: response.status }, `Could not load language resource (${response.status})`));
  return response.json();
}

async function loadCatalog() {
  if (catalog.length) return catalog;
  const result = await fetchJson("/lang");
  catalog = Array.isArray(result) ? result.filter(item => item && item.code && item.locale) : [];
  return catalog;
}

async function loadBundle(code) {
  if (bundles.has(code)) return bundles.get(code);
  const bundle = await fetchJson(`/lang/${encodeURIComponent(code)}.json`);
  if (!bundle?.meta?.code || !bundle?.translations) throw new Error(`Invalid language bundle: ${code}`);
  bundles.set(bundle.meta.code, bundle);
  return bundle;
}

function preferredCode() {
  // English is always the default. A cached language is only used while an
  // authenticated profile is expected; the server session remains the source
  // of truth and will re-apply its saved preference after validation.
  let hasAccountSession = false;
  let saved = "";
  try {
    hasAccountSession = localStorage.getItem("rustpad:auth-state") === "1";
    if (hasAccountSession) saved = localStorage.getItem(STORAGE_KEY) || "";
  } catch { /* storage may be blocked */ }
  if (!hasAccountSession) return FALLBACK_LANGUAGE;
  const available = new Set(catalog.map(item => item.code));
  return available.has(saved) ? saved : FALLBACK_LANGUAGE;
}

function applyDocumentLanguage() {
  const meta = activeBundle?.meta || fallbackBundle?.meta;
  if (!meta) return;
  document.documentElement.lang = meta.code;
  document.documentElement.dataset.locale = meta.locale;
}

export async function setLanguage(code, { persist = true } = {}) {
  await initI18n();
  const available = catalog.find(item => item.code === code);
  const target = available ? available.code : FALLBACK_LANGUAGE;
  activeBundle = await loadBundle(target);
  activeCode = activeBundle.meta.code;
  rebuildSourceIndex();
  if (persist) {
    try { localStorage.setItem(STORAGE_KEY, activeCode); } catch { /* storage may be blocked */ }
  }
  applyDocumentLanguage();
  translateTree(document, true);
  document.dispatchEvent(new CustomEvent("rustpad:languagechange", {
    detail: { language: activeCode, locale: activeBundle.meta.locale },
  }));
  return activeCode;
}

export function getLanguage() {
  return activeCode;
}

export function getLocale() {
  return activeBundle?.meta?.locale || fallbackBundle?.meta?.locale || "en-US";
}

export function getAvailableLanguages() {
  return catalog.map(item => ({ ...item }));
}

function languageLabel(language) {
  const nativeName = language.native_name || language.name || language.code;
  const englishName = language.name || nativeName;
  return nativeName === englishName ? nativeName : `${nativeName} · ${englishName}`;
}

function closeLanguagePicker(picker, { focusTrigger = false } = {}) {
  if (!(picker instanceof HTMLElement)) return;
  const menu = picker.querySelector(".profile-language-menu");
  const trigger = picker.querySelector(".profile-language-trigger");
  if (menu instanceof HTMLElement) menu.hidden = true;
  picker.removeAttribute("data-open");
  trigger?.setAttribute("aria-expanded", "false");
  if (focusTrigger) trigger?.focus();
}

function focusLanguageOption(menu, direction = 1) {
  const options = [...menu.querySelectorAll(".profile-language-option")];
  if (!options.length) return;
  const current = document.activeElement;
  const index = options.indexOf(current);
  const next = index < 0
    ? (direction > 0 ? 0 : options.length - 1)
    : (index + direction + options.length) % options.length;
  options[next].focus();
}

function bindLanguagePicker(input, picker) {
  if (picker.dataset.languagePickerBound === "true") return;
  picker.dataset.languagePickerBound = "true";
  const trigger = picker.querySelector(".profile-language-trigger");
  const menu = picker.querySelector(".profile-language-menu");
  if (!(trigger instanceof HTMLButtonElement) || !(menu instanceof HTMLElement)) return;

  const open = (focusSelected = false) => {
    menu.hidden = false;
    picker.dataset.open = "true";
    trigger.setAttribute("aria-expanded", "true");
    if (focusSelected) {
      const selected = menu.querySelector('[aria-selected="true"]') || menu.querySelector(".profile-language-option");
      selected?.focus();
    }
  };

  trigger.addEventListener("click", () => {
    if (menu.hidden) open(false);
    else closeLanguagePicker(picker);
  });
  trigger.addEventListener("keydown", event => {
    if (event.key === "ArrowDown" || event.key === "ArrowUp") {
      event.preventDefault();
      open(true);
    }
  });
  menu.addEventListener("click", event => {
    const option = event.target.closest(".profile-language-option");
    if (!(option instanceof HTMLElement)) return;
    input.value = option.dataset.languageCode || FALLBACK_LANGUAGE;
    populateLanguageSelect(input, input.value);
    closeLanguagePicker(picker, { focusTrigger: true });
    input.dispatchEvent(new Event("change", { bubbles: true }));
  });
  menu.addEventListener("keydown", event => {
    if (event.key === "ArrowDown" || event.key === "ArrowUp") {
      event.preventDefault();
      focusLanguageOption(menu, event.key === "ArrowDown" ? 1 : -1);
    } else if (event.key === "Home" || event.key === "End") {
      event.preventDefault();
      const options = [...menu.querySelectorAll(".profile-language-option")];
      (event.key === "Home" ? options[0] : options.at(-1))?.focus();
    } else if (event.key === "Escape") {
      event.preventDefault();
      closeLanguagePicker(picker, { focusTrigger: true });
    }
  });
  document.addEventListener("pointerdown", event => {
    if (!picker.contains(event.target)) closeLanguagePicker(picker);
  });
  picker.closest("dialog")?.addEventListener("close", () => closeLanguagePicker(picker));
}

export function populateLanguageSelect(input, selectedCode = getLanguage()) {
  const selected = catalog.find(item => item.code === selectedCode)
    || catalog.find(item => item.code === FALLBACK_LANGUAGE)
    || catalog[0];
  if (!selected) return;

  if (input instanceof HTMLSelectElement) {
    input.replaceChildren(...catalog.map(language => {
      const option = document.createElement("option");
      option.value = language.code;
      option.textContent = languageLabel(language);
      option.title = `${language.native_name || language.name || language.code} (${language.locale})`;
      option.lang = language.code;
      return option;
    }));
    input.value = selected.code;
    return;
  }

  if (!(input instanceof HTMLInputElement)) return;
  const picker = input.closest("[data-language-picker]");
  if (!(picker instanceof HTMLElement)) return;
  bindLanguagePicker(input, picker);

  const current = picker.querySelector(".profile-language-current");
  const trigger = picker.querySelector(".profile-language-trigger");
  const menu = picker.querySelector(".profile-language-menu");
  input.value = selected.code;
  if (current instanceof HTMLElement) {
    current.textContent = languageLabel(selected);
    current.lang = selected.code;
  }
  if (trigger instanceof HTMLElement) {
    trigger.title = `${selected.native_name || selected.name || selected.code} (${selected.locale})`;
  }
  if (!(menu instanceof HTMLElement)) return;

  menu.replaceChildren(...catalog.map(language => {
    const option = document.createElement("button");
    const nativeName = language.native_name || language.name || language.code;
    const englishName = language.name || nativeName;
    const isSelected = language.code === selected.code;
    option.type = "button";
    option.className = "profile-language-option";
    option.dataset.languageCode = language.code;
    option.setAttribute("role", "option");
    option.setAttribute("aria-selected", isSelected ? "true" : "false");
    option.lang = language.code;
    option.innerHTML = `<span class="profile-language-option__check" aria-hidden="true">${isSelected ? "✓" : ""}</span><span class="profile-language-option__copy"><strong></strong><small></small></span>`;
    option.querySelector("strong").textContent = nativeName;
    option.querySelector("small").textContent = nativeName === englishName ? language.locale : `${englishName} · ${language.locale}`;
    return option;
  }));
}

export function formatDateTime(value, options) {
  const date = value instanceof Date ? value : new Date(value);
  if (Number.isNaN(date.getTime())) return String(value ?? "");
  return new Intl.DateTimeFormat(getLocale(), options).format(date);
}

export function formatTime(value, options = { hour: "2-digit", minute: "2-digit" }) {
  return formatDateTime(value, options);
}

export function formatNumber(value, options) {
  return new Intl.NumberFormat(getLocale(), options).format(value);
}

function revealDocumentAfterI18n() {
  const root = document.documentElement;
  root.removeAttribute("data-i18n-pending");
  if (root.style.visibility === "hidden") root.style.removeProperty("visibility");
}

export async function initI18n() {
  if (initialized) return;
  if (initialization) return initialization;
  initialization = (async () => {
    try {
      await loadCatalog();
      const code = preferredCode();
      const [fallback, preferred] = await Promise.all([
        loadBundle(FALLBACK_LANGUAGE),
        code === FALLBACK_LANGUAGE ? Promise.resolve(null) : loadBundle(code),
      ]);
      fallbackBundle = fallback;
      activeBundle = preferred || fallbackBundle;
      activeCode = activeBundle.meta.code;
      rebuildSourceIndex();
    } catch (error) {
      console.warn("RustPad i18n initialization failed; using source language.", error);
      catalog = catalog.length ? catalog : [{ code: "en", name: "English", native_name: "English", locale: "en-US" }];
      fallbackBundle = fallbackBundle || { meta: catalog[0], translations: {} };
      activeBundle = fallbackBundle;
      activeCode = FALLBACK_LANGUAGE;
      rebuildSourceIndex();
    }
    applyDocumentLanguage();
    translateTree(document);
    startObserver();
    revealDocumentAfterI18n();
    initialized = true;
  })();
  await initialization;
}