/**

 * @relation(SDOC-SRS-155, scope=file)

 * @relation(SDOC-SRS-156, scope=file)

 *

 * Required DOM contract:

 * - #search

 * - #userinput

 * - #search_results

 * - #results_count

 * - #suggestions

 * - #results_navigation with #start, #previous, #next, #end

 * - meta[name="strictdoc-document-level"]

 * - meta[name="strictdoc-project-hash"]

 * - meta[name="strictdoc-search-index-timestamp"]

 * - meta[name="strictdoc-search-index-path"]

 */

(function() {

  const strictDocSearch = window.StrictDoc?.search;

  if (!strictDocSearch) {

    throw new Error(

      "static_html_search.js requires app_core.js to initialize StrictDoc.search."

    );

  }

  // =========================================================================

  // DOM and meta discovery

  // =========================================================================

  // Collect the DOM nodes that the static search UI depends on.

  function collectRequiredDom() {

    const selectorByRefKey = {

      searchBox: "#search",

      userinput: "#userinput",

      searchResults: "#search_results",

      resultsCount: "#results_count",

      suggestions: "#suggestions",

      navigationStart: "#results_navigation #start",

      navigationPrevious: "#results_navigation #previous",

      navigationNext: "#results_navigation #next",

      navigationEnd: "#results_navigation #end",

    };

    const dom = Object.fromEntries(

      Object.entries(selectorByRefKey).map(([key, selector]) => {

        if (selector.startsWith("#") && !selector.includes(" ")) {

          return [key, document.getElementById(selector.slice(1))];

        }

        return [key, document.querySelector(selector)];

      })

    );

    const missingSelectors = Object.entries(dom)

      .filter(([, element]) => !element)

      .map(([key]) => selectorByRefKey[key]);

    return {

      dom,

      missingSelectors

    };

  }

  // Collect the meta tags that configure search rendering and index loading.

  function collectRequiredMeta() {

    const selectorByMetaKey = {

      documentLevel: 'meta[name="strictdoc-document-level"]',

      projectHash: 'meta[name="strictdoc-project-hash"]',

      searchIndexTimestamp: 'meta[name="strictdoc-search-index-timestamp"]',

      searchIndexPath: 'meta[name="strictdoc-search-index-path"]',

    };

    const meta = Object.fromEntries(

      Object.entries(selectorByMetaKey).map(([key, selector]) => {

        return [key, document.querySelector(selector)?.content];

      })

    );

    const missingSelectors = Object.entries(meta)

      .filter(([, content]) => !content)

      .map(([key]) => selectorByMetaKey[key]);

    return {

      meta,

      missingSelectors,

    };

  }

  // =========================================================================

  // Query parsing and result shaping

  // =========================================================================

  function escapeRegExp(text) {

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

  }

  // Highlight matched terms in result text before rendering the suggestion entry.

  function highlightWord(text, word) {

    let newStr = text.replace(new RegExp(escapeRegExp(word), "gi"), (match) => "<mark>" +

      match + "</mark>");

    return newStr;

  }

  // Intersect per-token result sets for AND-style queries.

  function intersectSets(sets) {

    if (sets.length === 0) return new Set();

    let intersection = new Set(sets[0]);

    for (const s of sets.slice(1)) {

      intersection = new Set([...intersection].filter(x => s.has(x)));

    }

    return intersection;

  }

  // Parse the raw search text into a minimal query model used by the live search UI.

  function parseSearchQuery(searchQuery) {

    const regex = /"([^"]+)"|(\S+)/g;

    const tokens = [];

    let hasQuoted = false;

    const matches = [...searchQuery.matchAll(regex)];

    for (const match of matches) {

      if (match[1]) {

        // Quoted phrase → split into words

        hasQuoted = true;

        tokens.push(match[1].trim().split(/\s+/));

      } else if (match[2]) {

        // Single word

        tokens.push([match[2]]);

      }

    }

    if (hasQuoted) {

      return {

        mode: "AND",

        terms: tokens.flat(),

      };

    }

    return {

      mode: "OR",

      terms: tokens.flat(),

    };

  }

  // Execute a token query by unioning all indexed token matches.

  function executeOrQuery(parsedQuery, searchIndex) {

    let uniqueResults = new Set();

    for (const token of parsedQuery.terms) {

      const tokenResults = searchIndex[token];

      if (tokenResults) {

        uniqueResults = new Set([...uniqueResults, ...tokenResults]);

      }

    }

    return Array.from(uniqueResults);

  }

  // Execute a phrase query by intersecting the per-token index matches first.

  function executeAndQuery(parsedQuery, searchIndex) {

    const firstTerm = parsedQuery.terms[0];

    const firstTermResults = searchIndex[firstTerm];

    if (!firstTermResults || firstTermResults.length === 0) {

      return [];

    }

    let uniqueResults = new Set(firstTermResults);

    for (let i = 1; i < parsedQuery.terms.length; i++) {

      const termResults = searchIndex[parsedQuery.terms[i]];

      const termUniqueResults = new Set(termResults);

      uniqueResults = intersectSets([uniqueResults, termUniqueResults]);

      if (uniqueResults.size === 0) {

        break;

      }

    }

    return Array.from(uniqueResults);

  }

  // Refine AND-style results by verifying the combined phrase against node fields.

  function refineAndQueryResults(results, parsedQuery, nodesByMid) {

    const finalAndResults = [];

    const finalUniqueResults = new Set();

    const andQuery = parsedQuery.terms.join(" ");

    for (const result of results) {

      const node = nodesByMid[parseInt(result, 10)];

      console.assert(!!node, "node must be defined for result: " + result);

      Object.entries(node).forEach(([_, value]) => {

        if (value === "") {

          return;

        }

        if (!finalUniqueResults.has(result) && value.toLowerCase().includes(andQuery)) {

          finalUniqueResults.add(result);

          finalAndResults.push(result);

        }

      });

    }

    return {

      results: finalAndResults,

      highlightElements: [andQuery],

    };

  }

  // Build the data needed by the results view: result ids plus highlight terms.

  function buildSearchViewModel(parsedQuery, searchQuery, searchIndex, nodesByMid) {

    // Keep the existing live-input behavior for search text that still contains

    // a quote character but has not been parsed as a quoted phrase query.

    if (parsedQuery.mode === "OR" && searchQuery.includes('"')) {

      return {

        results: [],

        highlightElements: parsedQuery.terms,

      };

    }

    // ** "AND"

    // Quoted phrase queries first intersect token matches, then verify

    // that the full phrase exists in the matched node fields.

    if (parsedQuery.mode === "AND") {

      const results = executeAndQuery(parsedQuery, searchIndex);

      return refineAndQueryResults(results, parsedQuery, nodesByMid);

    }

    // ** "OR"

    // Unquoted queries use the default token-based OR search path.

    const results = executeOrQuery(parsedQuery, searchIndex);

    return {

      results,

      highlightElements: parsedQuery.terms,

    };

  }

  // =========================================================================

  // Live search UI

  // =========================================================================

  // Render and paginate the live search result list.

  class SearchResultsView {

    static PAGE_SIZE = 5;

    constructor(dom, { userinput, searchData, documentLevel }) {

      this.userinput = userinput;

      this.searchData = searchData;

      this.documentLevel = documentLevel;

      console.assert(

        !isNaN(this.documentLevel),

        "SearchResultsView: documentLevel must be a valid number."

      );

      this.searchBox = dom.searchBox;

      this.searchResults = dom.searchResults;

      this.resultsCount = dom.resultsCount;

      this.suggestions = dom.suggestions;

      this.navigationStart = dom.navigationStart;

      this.navigationPrevious = dom.navigationPrevious;

      this.navigationNext = dom.navigationNext;

      this.navigationEnd = dom.navigationEnd;

      this.navigationStart.addEventListener("click", () => this.displayPage(

        1), true);

      this.navigationPrevious.addEventListener("click", () => this

        .displayPage(this.currentPage - 1), true);

      this.navigationNext.addEventListener("click", () => this.displayPage(

        this.currentPage + 1), true);

      this.navigationEnd.addEventListener("click", () => this.displayPage(

          Math.ceil(this.results.length / SearchResultsView.PAGE_SIZE)),

        true);

      this.selectedIndex = 0;

      this.results = null;

      this.highlightElements = null;

      this.currentPage = 1;

      this.suggestions.addEventListener("click", this.acceptSuggestion, true);

      document.addEventListener("keydown", (event) => this.handleEscape(

        event), true);

    }

    handleEscape(event) {

      if (event.key === "Escape") {

        this.hideResults();

        // On Esc, remove focus from the input field.

        // Otherwise the field remains focused and a subsequent click won't fire a 'focus' event,

        // so the search won't restart. Blurring ensures the next refocus re‑triggers search with

        // the existing text.

        if (document.activeElement === this.userinput) {

          this.userinput.blur();

        }

      }

    }

    hideResults() {

      this.searchBox.removeAttribute("active");

      this.resultsCount.innerHTML = "";

      this.suggestions.replaceChildren();

      this.selectedIndex = 0;

    }

    populateResults(results, highlightElements) {

      const resultsLength = results.length;

      if (resultsLength == 0) {

        this.suggestions.replaceChildren();

        this.resultsCount.innerHTML = `No results.`;

        return;

      }

      this.results = results;

      this.highlightElements = highlightElements;

      this.displayPage(1);

      this.searchBox.setAttribute("active", "");

    }

    displayPage(page) {

      // Ignore requests that point outside the available pagination range.

      if (page < 1 || page > Math.ceil(this.results.length /

          SearchResultsView.PAGE_SIZE)) {

        return;

      }

      // Slice the full result list down to the subset rendered on this page.

      const pageResults = this.results.slice(

        (page - 1) * SearchResultsView.PAGE_SIZE,

        page * SearchResultsView.PAGE_SIZE

      );

      // Persist the current page so the navigation buttons can move relative to it.

      this.currentPage = page;

      // Reuse already rendered result containers where possible.

      const children = this.suggestions.childNodes;

      // Render each result entry for the requested page.

      for (let i = 0; i < pageResults.length; i++) {

        let nodeId = pageResults[i];

        let resultElement = children[i];

        // Create a result container only when the current page needs more rows

        // than were already rendered for the previous page.

        if (!resultElement) {

          resultElement = document.createElement("div");

          this.suggestions.appendChild(resultElement);

        }

        this.renderResultElement(resultElement, nodeId);

      }

      // Remove leftover DOM rows when the new page has fewer results than the previous one.

      while (children.length > pageResults.length) {

        this.suggestions.removeChild(this.suggestions.lastChild);

      }

      // Update pagination controls based on the current page position.

      this.updatePaginationState(page);

      // Refresh the result counter text for the currently visible range.

      this.updateResultsCount(page);

      // Reset keyboard selection to the first visible result on each page change.

      this._selectResult(0);

    }

    updatePaginationState(page) {

      if (this.results.length > SearchResultsView.PAGE_SIZE) {

        if (page < 2) {

          this.navigationStart.setAttribute("disabled", "");

          this.navigationPrevious.setAttribute("disabled", "");

        } else {

          this.navigationStart.removeAttribute("disabled");

          this.navigationPrevious.removeAttribute("disabled");

        }

        if (page >= Math.ceil(this.results.length / SearchResultsView

            .PAGE_SIZE)) {

          this.navigationNext.setAttribute("disabled", "");

          this.navigationEnd.setAttribute("disabled", "");

        } else {

          this.navigationNext.removeAttribute("disabled");

          this.navigationEnd.removeAttribute("disabled");

        }

      } else {

        this.navigationStart.setAttribute("disabled", "");

        this.navigationPrevious.setAttribute("disabled", "");

        this.navigationNext.setAttribute("disabled", "");

        this.navigationEnd.setAttribute("disabled", "");

      }

    }

    updateResultsCount(page) {

      // Compute the human-readable result range shown above the list.

      const rangeStart = (page - 1) * SearchResultsView.PAGE_SIZE + 1;

      const rangeEnd = Math.min(page * SearchResultsView.PAGE_SIZE, this

        .results.length);

      this.resultsCount.innerHTML = `\

  Results: <b>${rangeStart}–${rangeEnd}</b> from ${this.results.length}

  `;

    }

    renderResultElement(resultElement, nodeId) {

      // Resolve the indexed node data behind the current search result id.

      const node = this.searchData.nodesByMid[parseInt(nodeId, 10)];

      console.assert(!!node, "node must be defined for result: " +

        nodeId);

      // Build the HTML fragment with node fields, applying term highlighting

      // to every visible field except the navigation link field.

      let nodeFieldsHtml = "";

      Object.entries(node).forEach(([key, value]) => {

        if (value === "" || key === "_LINK") {

          return;

        }

        for (let i = 0; i < this.highlightElements.length; i++) {

          const highlightElement = this.highlightElements[i];

          value = highlightWord(value, highlightElement);

        }

        nodeFieldsHtml = nodeFieldsHtml +

          `<div class="static_search-result-node-field"><span class="static_search-result-node-field-key">${key}:</span> ${value}</div>`;

      });

      const pathPrefix = (this.documentLevel === 0) ? "" : "../".repeat(

        this.documentLevel);

      // Render the visible result entry together with the deep link to the node.

      const nodeLink = node["_LINK"];

      resultElement.innerHTML = `<div class="static_search-result-node">

      ${nodeFieldsHtml}

      <div class="static_search-result-node-link">

          <a href="${pathPrefix}index.html?a=${nodeLink}">Go to node →</a>

      </div>

      </div>

      `;

    }

    selectNextResult() {

      if (this.selectedIndex < (this.suggestions.childNodes.length - 1)) {

        this._selectResult(this.selectedIndex + 1);

      }

    }

    selectPreviousResult() {

      if (this.selectedIndex > 0) {

        this._selectResult(this.selectedIndex - 1);

      }

    }

    acceptSuggestion(event) {

      // Nothing for now.

    }

    _selectResult(index) {

      let node = this.suggestions.childNodes[this.selectedIndex];

      node && (node.style.backgroundColor = "");

      this.selectedIndex = index;

      node = this.suggestions.childNodes[index];

      node && (node.style.backgroundColor = "rgba(0, 0, 255, 0.1)");

    }

  }

  // Orchestrate user input events and translate them into search updates.

  class SearchInputController {

    constructor({ userinput, searchData, searchResultsView }) {

      this.userinput = userinput;

      this.searchData = searchData;

      this.searchResultsView = searchResultsView;

      this.previousInputValue = "";

    }

    attachEventListeners() {

      this.userinput.addEventListener("input", () => this.handleInput(), true);

      this.userinput.addEventListener("keyup", (event) => this.handleKeyUp(

        event), true);

      this.userinput.addEventListener("keydown", (event) => this.handleKeyDown(

        event), true);

      this.userinput.addEventListener("focus", (event) => this.handleFocus(

        event), true);

    }

    handleInput() {

      // Wait until the search index and node lookup map are loaded.

      // TODO: Replace this per-input guard with an explicit "search index ready"

      // state and a visible UI signal for the user when live search is not ready yet.

      if (!this.searchData.index || !this.searchData.nodesByMid) {

        console.log(

          "Search: Cannot perform search: Search index is not available yet.")

        return;

      }

      // Reset the live search UI when the input becomes empty.

      if (this.userinput.value === "") {

        this.previousInputValue = "";

        this.searchResultsView.hideResults();

        return;

      }

      // Preserve the current live-input behavior for quote editing.

      // FIXME

      // If the previous input step already auto-inserted "" and the user has

      // edited the field back down to a single quote, treat that as deleting

      // the auto-completed quote pair and clear the field completely.

      if (this.previousInputValue === '""' && this.userinput.value === '"') {

        this.userinput.value = ""

      // If the user has typed a single quote into an otherwise empty field,

      // auto-insert the matching closing quote.

      } else if (this.userinput.value === '"') {

        const quote = this.userinput.value;

        this.userinput.value = quote + quote;

        // Place the cursor between the two quotes

        // so the next typed characters become the quoted phrase.

        this.userinput.setSelectionRange(1, 1);

      }

      // Persist the latest input value for the next edit step.

      this.previousInputValue = this.userinput.value;

      // Build the normalized search query from the current input.

      const searchQuery = this.userinput.value.toLowerCase();

      // Parse the query and build the view model shown in the live results list.

      const parsedQuery = parseSearchQuery(searchQuery);

      const searchViewModel = buildSearchViewModel(

        parsedQuery,

        searchQuery,

        this.searchData.index,

        this.searchData.nodesByMid

      );

      this.searchResultsView.populateResults(

        searchViewModel.results,

        searchViewModel.highlightElements

      );

    }

    handleKeyDown(event) {

      if (event && event.key === "Enter") {

        event.preventDefault && event.preventDefault();

        const searchQuery = this.userinput.value || "";

        const encodedQuery = encodeURIComponent(searchQuery);

        window.location.assign(`/search?q=${encodedQuery}`);

      }

    }

    handleFocus(event) {

      // FIXME: Nothing for now.

    }

    handleKeyUp(event) {

      if (event) {

        const key = event.key;

        if (key === "ArrowUp") {

          this.searchResultsView.selectPreviousResult();

          event.preventDefault && event.preventDefault();

          return;

        }

        if (key === "ArrowDown") {

          this.searchResultsView.selectNextResult();

          event.preventDefault && event.preventDefault();

          return;

        }

      }

    }

  }

  // =========================================================================

  // Search index initialization

  // =========================================================================

  // Open the IndexedDB database that caches the generated search index.

  function openSearchIndexDB(name, version = 1) {

    return new Promise((resolve, reject) => {

      const request = indexedDB.open(name, version);

      request.onupgradeneeded = (e) => {

        const db = e.target.result;

        db.createObjectStore("indexes", {

          keyPath: "name"

        });

      };

      request.onsuccess = () => resolve(request.result);

      request.onerror = () => reject(request.error);

    });

  }

  // Drop the cached search index when it becomes stale.

  function deleteSearchIndexDB(name) {

    return new Promise((resolve, reject) => {

      const delReq = indexedDB.deleteDatabase(name);

      delReq.onsuccess = () => resolve();

      delReq.onerror = () => reject(delReq.error);

    });

  }

  // Read a cached value from the search index store.

  function getFromSearchIndexStore(db, storeName, key) {

    return new Promise((resolve, reject) => {

      const tx = db.transaction(storeName, "readonly");

      const store = tx.objectStore(storeName);

      const req = store.get(key);

      req.onsuccess = () => resolve(req.result);

      req.onerror = () => reject(req.error);

    });

  }

  // Persist the current search index payload to the cache store.

  function saveToSearchIndexStore(db, storeName, items) {

    return new Promise((resolve, reject) => {

      const tx = db.transaction(storeName, "readwrite");

      const store = tx.objectStore(storeName);

      items.forEach((item) => store.put(item));

      tx.oncomplete = () => resolve();

      tx.onerror = () => reject(tx.error);

    });

  }

  // Load the generated search index JavaScript file into the page.

  function loadScript(url) {

    return new Promise((resolve, reject) => {

      const script = document.createElement("script");

      script.src = url;

      script.onload = () => {

        script.remove();

        resolve();

      };

      script.onerror = () => reject(new Error(

        `Failed to load script ${url}`));

      document.head.appendChild(script);

    });

  }

  // Load the generated search index, optionally bypassing the browser cache.

  async function loadSearchIndexFromScript(pathToSearchIndex, cacheBusting) {

    const searchIndexURL = new URL(pathToSearchIndex, window.location.href);

    if (cacheBusting) {

      searchIndexURL.searchParams.set("_refresh", Date.now().toString());

    }

    console.time("Search: LOAD_JS_INDEX");

    await loadScript(searchIndexURL.href);

    console.timeEnd("Search: LOAD_JS_INDEX");

    console.log("Search: JS search index loaded successfully.");

  }

  // Save the in-memory search index into IndexedDB for faster reloads.

  async function saveCurrentSearchIndexToDB({

    dbName,

    dbVersion,

    timestampMeta,

    searchData,

  }) {

    console.time("Search: SAVE_DB_INDEX");

    const db = await openSearchIndexDB(dbName, dbVersion);

    await saveToSearchIndexStore(db, "indexes", [{

      name: "STRICTDOC_SEARCH_INDEX",

      value: searchData.index

    }, {

      name: "STRICTDOC_SEARCH_NODES_BY_MID",

      value: searchData.nodesByMid

    }, {

      name: "TIMESTAMP",

      value: timestampMeta

    }, ]);

    db.close();

    console.timeEnd("Search: SAVE_DB_INDEX");