// ── On-demand library loader ────────────────────────────────────────────────
//
// Fetches procedure definitions from JSON files in the libraries/ directory.
// At startup only the index is loaded; individual libraries are fetched when
// the user clicks their tab for the first time.
//
// Depends on: app.js (addLibTab, deriveNaturalName)
//             blocks-proc.js (WCProcedure)
//             wcprogram.js (BLOCK_REGISTRY)


/** @type {Set<string>} Tracks which libraries have been loaded (prevents re-loading). */
const LOADED_LIBS = new Set();
/** @type {Array<{id:string, name:string, group?:string}>} */
let LIB_INDEX = [];

/**
 * Creates param rows on a procedure block and sets their name/type values.
 * Follows the same pattern as WCProcedure.restoreData().
 * @param {HTMLElement} proc A wc-procedure element
 * @param {Array<[string,string]>} inputs Array of [name, type] pairs
 * @param {Array<[string,string]>} outputs Array of [name, type] pairs
 */
function _addProcParams(proc, inputs, outputs) {
  for (const [name, type] of inputs) {
    proc._addParamRow(proc.querySelector(".proc-inputs"), "in");
    const rows = proc.querySelectorAll(".proc-inputs .proc-param-row");
    const last = rows[rows.length - 1];
    last.querySelector(".proc-param-name").value = name;
    last.querySelector(".proc-param-type").value = type;
  }
  for (const [name, type] of outputs) {
    proc._addParamRow(proc.querySelector(".proc-outputs"), "out");
    const rows = proc.querySelectorAll(".proc-outputs .proc-param-row");
    const last = rows[rows.length - 1];
    last.querySelector(".proc-param-name").value = name;
    last.querySelector(".proc-param-type").value = type;
  }
}

/**
 * Fetches libraries/index.json and returns the library metadata array.
 * Called once at startup.
 * @returns {Promise<Array<{id:string, name:string, group?:string}>>}
 */
async function loadLibraryIndex() {
  try {
    const res = await fetch("libraries/index.json");
    if (!res.ok) throw new Error(`HTTP ${res.status}`);
    LIB_INDEX = await res.json();
  } catch (e) {
    showError("Could not load library index: " + e.message);
    LIB_INDEX = [];
  }
  return LIB_INDEX;
}


/**
 * Loads a single library by its id (e.g. "stdio", "sdl3").
 * Creates the tab if it doesn't exist yet, then populates all procedures.
 * Idempotent — subsequent calls for the same lib are no-ops.
 */
async function loadLibrary(libId) {
  if (LOADED_LIBS.has(libId)) return;
  LOADED_LIBS.add(libId);

  const prog = $id("main-program");
  if (!prog) return;

  let data;
  try {
    const res = await fetch(`libraries/${libId}.json`);
    if (!res.ok) throw new Error(`HTTP ${res.status}`);
    data = await res.json();
  } catch (e) {
    showError(`Could not load library "${libId}": ${e.message}`);
    return;
  }

  const procs = data.procedures;
  if (!procs || !procs.length) return;

  /* Mark this lib as the active tab if it's the first one loaded */
  const isFirst = LOADED_LIBS.size === 1;

  /* Ensure the tab exists — but don't duplicate if already created from index */
  if (!document.querySelector(`.lib-tab[data-lib-name="${libId}"]`)) {
    addLibTab(libId, isFirst);
  }

  for (const pd of procs) {
    const proc = prog.newProcedureNode(libId);
    if (!proc) continue;
    proc.querySelector(".proc-tech-name").textContent = pd.name;
    proc.querySelector(".proc-natural-name").value = pd.naturalName || deriveNaturalName(pd.name);
    if (pd.desc) {
      const db = proc.querySelector(".proc-desc-body");
      if (db) db.textContent = pd.desc;
    }
    proc.dataset.readonly = "true";
    if (pd.returnStyle === "value") proc.dataset.returnStyle = "value";
    if (pd.returnStyle === "error") proc.dataset.returnStyle = "error";
    if (pd.formatString) proc.dataset.formatString = "true";
    _addProcParams(proc, pd.inputs || [], pd.outputs || []);
  }

}


/**
 * Returns the loaded library index (synchronous after loadLibraryIndex).
 * @returns {Array<{id:string, name:string, group?:string}>}
 */
function getLibraryIndex() {
  return LIB_INDEX;
}


/**
 * Checks if a library has been loaded yet.
 * @param {string} libId
 * @returns {boolean}
 */
function isLibraryLoaded(libId) {
  return LOADED_LIBS.has(libId);
}


/**
 * Marks a library as loaded (for user-created libs that don't have JSON files).
 * @param {string} libId
 */
function markLibLoaded(libId) {
  LOADED_LIBS.add(libId);
}