/**
 * This module is used to handle user's interaction with the search form.
 */

import { DeclarationDataCenter } from "./declaration-data.js";

// Search form and input in the upper right toolbar
const SEARCH_FORM = document.querySelector("#search_form");
const SEARCH_INPUT = SEARCH_FORM.querySelector("input[name=q]");

// Search form on the /search.html_page.  These may be null.
const SEARCH_PAGE_INPUT = document.querySelector("#search_page_query")
const SEARCH_RESULTS = document.querySelector("#search_results")

// Max results to show for autocomplete or /search.html page.
const AC_MAX_RESULTS = 30
const SEARCH_PAGE_MAX_RESULTS = undefined

// Create an `div#autocomplete_results` to hold all autocomplete results.
let ac_results = document.createElement("div");
ac_results.id = "autocomplete_results";
SEARCH_FORM.appendChild(ac_results);

/**
 * Attach `selected` class to the the selected autocomplete result.
 */
function handleSearchCursorUpDown(down) {
  const sel = ac_results.querySelector(`.selected`);
  if (sel) {
    sel.classList.remove("selected");
    const toSelect = down
      ? sel.nextSibling 
      : sel.previousSibling;
    toSelect && toSelect.classList.add("selected");
  } else {
    const toSelect = down ? ac_results.firstChild : ac_results.lastChild;
    toSelect && toSelect.classList.add("selected");
  }
}

/**
 * Perform search (when enter is pressed).
 */
function handleSearchEnter() {
  const sel = ac_results.querySelector(`.selected .result_link a`) || document.querySelector(`#search_button`);
  sel.click();
}

/**
 * Allow user to navigate autocomplete results with up/down arrow keys, and choose with enter.
 */
SEARCH_INPUT.addEventListener("keydown", (ev) => {
  switch (ev.key) {
    case "Down":
    case "ArrowDown":
      ev.preventDefault();
      handleSearchCursorUpDown(true);
      break;
    case "Up":
    case "ArrowUp":
      ev.preventDefault();
      handleSearchCursorUpDown(false);
      break;
    case "Enter":
      ev.preventDefault();
      handleSearchEnter();
      break;
  }
});

/**
 * Remove all children of a DOM node.
 */
function removeAllChildren(node) {
  while (node.firstChild) {
    node.removeChild(node.lastChild);
  }
}

/**
 * Handle user input and perform search.
 */
function handleSearch(dataCenter, err, ev, sr, maxResults, autocomplete) {
  const text = ev.target.value;

  // If no input clear all.
  if (!text) {
    sr.removeAttribute("state");
    removeAllChildren(sr);
    return;
  }

  // searching
  sr.setAttribute("state", "loading");

  if (dataCenter) {
    var allowedKinds;
    if (!autocomplete) {
      allowedKinds = new Set();
      document.querySelectorAll(".kind_checkbox").forEach((checkbox) =>
        {
          if (checkbox.checked) {
            allowedKinds.add(checkbox.value);
          }
        } 
      );
    }
    const result = dataCenter.search(text, false, allowedKinds, maxResults);

    // in case user has updated the input.
    if (ev.target.value != text) return;
  
    // update autocomplete results
    removeAllChildren(sr);
    for (const { name, kind, docLink } of result) {
      const row = sr.appendChild(document.createElement("div"));
      row.classList.add("search_result")
      const linkdiv = row.appendChild(document.createElement("div"))
      linkdiv.classList.add("result_link")
      const link = linkdiv.appendChild(document.createElement("a"));
      link.innerText = name;
      link.title = name;
      link.href = SITE_ROOT + docLink;
    }
  }
  // handle error
  else {
    removeAllChildren(sr);
    const d = sr.appendChild(document.createElement("a"));
    d.innerText = `Cannot fetch data, please check your network connection.\n${err}`;
  }
  sr.setAttribute("state", "done");
}

// https://www.joshwcomeau.com/snippets/javascript/debounce/
const debounce = (callback, wait) => {
  let timeoutId = null;
  return (...args) => {
    window.clearTimeout(timeoutId);
    timeoutId = window.setTimeout(() => {
      callback.apply(null, args);
    }, wait);
  };
}

DeclarationDataCenter.init()
  .then((dataCenter) => {
    // Search autocompletion.
    SEARCH_INPUT.addEventListener("input", debounce(ev => handleSearch(dataCenter, null, ev, ac_results, AC_MAX_RESULTS, true), 300));
    if(SEARCH_PAGE_INPUT) {
      SEARCH_PAGE_INPUT.addEventListener("input", ev => handleSearch(dataCenter, null, ev, SEARCH_RESULTS, SEARCH_PAGE_MAX_RESULTS, false))
      document.querySelectorAll(".kind_checkbox").forEach((checkbox) =>
        checkbox.addEventListener("input", ev => SEARCH_PAGE_INPUT.dispatchEvent(new Event("input")))
      );
      SEARCH_PAGE_INPUT.dispatchEvent(new Event("input"))
    };
    SEARCH_INPUT.dispatchEvent(new Event("input"))
  })
  .catch(e => {
    SEARCH_INPUT.addEventListener("input", debounce(ev => handleSearch(null, e, ev, ac_results, AC_MAX_RESULTS, true), 300));
    if(SEARCH_PAGE_INPUT) {
      SEARCH_PAGE_INPUT.addEventListener("input", ev => handleSearch(null, e, ev, SEARCH_RESULTS, SEARCH_PAGE_MAX_RESULTS, false));
    }
  });