// Directory tree for the sidebar file-explorer pane.
// Lazy-loads children when a node is expanded. Tracks one selected path.
// Row click = select + always expand.  Chevron click = toggle collapse/expand.

let _onSelect = null;
let _selectedPath = null;

const ICON_CLOSED = `<svg width="14" height="14" viewBox="0 0 14 14" fill="none" xmlns="http://www.w3.org/2000/svg"><path d="M1 3.5C1 2.67 1.67 2 2.5 2H5.38l1.5 1.5H11.5C12.33 3.5 13 4.17 13 5v5.5C13 11.33 12.33 12 11.5 12h-9C1.67 12 1 11.33 1 10.5V3.5Z" fill="#7c6af7" fill-opacity=".75"/><path d="M1 5.5h12v5C13 11.33 12.33 12 11.5 12h-9C1.67 12 1 11.33 1 10.5V5.5Z" fill="#9180ff" fill-opacity=".9"/></svg>`;
const ICON_OPEN   = `<svg width="14" height="14" viewBox="0 0 14 14" fill="none" xmlns="http://www.w3.org/2000/svg"><path d="M1 3.5C1 2.67 1.67 2 2.5 2H5.38l1.5 1.5H11.5C12.33 3.5 13 4.17 13 5v5.5C13 11.33 12.33 12 11.5 12h-9C1.67 12 1 11.33 1 10.5V3.5Z" fill="#c9b8ff" fill-opacity=".7"/><path d="M1 5.5h12v5C13 11.33 12.33 12 11.5 12h-9C1.67 12 1 11.33 1 10.5V5.5Z" fill="#e0d5ff" fill-opacity=".85"/></svg>`;
const ICON_HOME   = `<svg width="14" height="14" viewBox="0 0 14 14" fill="none" xmlns="http://www.w3.org/2000/svg"><path d="M7 1.5L1 6.5V12.5H5.5V9H8.5V12.5H13V6.5L7 1.5Z" fill="#6ac8f7" fill-opacity=".9"/></svg>`;

export function init(container, onSelect) {
  _onSelect = onSelect;
  container.innerHTML = '';
  container.classList.add('tree-root');
}

export async function loadTree(rootPath, selectedPath) {
  _selectedPath = selectedPath;
  const container = document.querySelector('.file-explorer');
  if (!container) return;
  container.innerHTML = '';

  const rootNode = createNode({
    name: rootPath.split('/').pop() || rootPath,
    path: rootPath,
    hasChildren: true,
    isRoot: true,
  });
  container.appendChild(rootNode);
  await expandNode(rootNode, selectedPath);
}

function createNode({ name, path: nodePath, hasChildren, isRoot = false }) {
  const wrap = document.createElement('div');
  wrap.className = 'tree-node';
  wrap.dataset.path = nodePath;
  wrap.dataset.expanded = 'false';
  wrap.dataset.hasChildren = hasChildren ? 'true' : 'false';
  wrap.dataset.isRoot = isRoot ? 'true' : 'false';

  const row = document.createElement('div');
  row.className = 'tree-row';

  const chevron = document.createElement('span');
  chevron.className = 'tree-chevron';
  if (hasChildren) {
    chevron.innerHTML = `<svg width="10" height="10" viewBox="0 0 10 10"><path d="M3 2l4 3-4 3" stroke="currentColor" stroke-width="1.5" fill="none" stroke-linecap="round" stroke-linejoin="round"/></svg>`;
  }

  const icon = document.createElement('span');
  icon.className = 'tree-icon';
  icon.innerHTML = isRoot ? ICON_HOME : ICON_CLOSED;

  const label = document.createElement('span');
  label.className = 'tree-label';
  label.textContent = name;
  label.title = nodePath;

  row.appendChild(chevron);
  row.appendChild(icon);
  row.appendChild(label);
  wrap.appendChild(row);

  if (hasChildren) {
    const children = document.createElement('div');
    children.className = 'tree-children';
    wrap.appendChild(children);
  }

  // Chevron click: toggle collapse/expand without changing selection
  chevron.addEventListener('click', (e) => {
    e.stopPropagation();
    if (!hasChildren) return;
    if (wrap.dataset.expanded === 'true') {
      collapseNode(wrap);
    } else {
      expandNode(wrap, null);
    }
  });

  // Row click: select + always expand (never collapse)
  row.addEventListener('click', () => {
    selectNode(wrap);
    if (hasChildren && wrap.dataset.expanded !== 'true') {
      expandNode(wrap, null);
    }
  });

  return wrap;
}

function nodeIcon(nodeEl) {
  return nodeEl.dataset.isRoot === 'true' ? ICON_HOME : ICON_OPEN;
}

function selectNode(nodeEl) {
  const path = nodeEl.dataset.path;
  document.querySelectorAll('.tree-row.active').forEach(r => r.classList.remove('active'));
  nodeEl.querySelector(':scope > .tree-row').classList.add('active');
  _selectedPath = path;
  if (_onSelect) _onSelect(path);
}

function collapseNode(nodeEl) {
  nodeEl.dataset.expanded = 'false';
  const row = nodeEl.querySelector(':scope > .tree-row');
  row.querySelector('.tree-chevron').classList.remove('open');
  row.querySelector('.tree-icon').innerHTML = nodeEl.dataset.isRoot === 'true' ? ICON_HOME : ICON_CLOSED;
  const children = nodeEl.querySelector(':scope > .tree-children');
  if (children) children.style.display = 'none';
}

async function expandNode(nodeEl, autoExpandPath) {
  nodeEl.dataset.expanded = 'true';
  const row = nodeEl.querySelector(':scope > .tree-row');
  row.querySelector('.tree-chevron').classList.add('open');
  row.querySelector('.tree-icon').innerHTML = nodeIcon(nodeEl);

  const childrenEl = nodeEl.querySelector(':scope > .tree-children');
  if (!childrenEl) return;
  childrenEl.style.display = '';

  // Lazy-load children on first expansion
  if (!childrenEl.dataset.loaded) {
    childrenEl.dataset.loaded = 'true';
    const dirs = await window.api.listDirectories(nodeEl.dataset.path);
    if (dirs === null) {
      const err = document.createElement('div');
      err.className = 'tree-access-error';
      err.textContent = '접근 불가';
      childrenEl.appendChild(err);
    } else {
      dirs.forEach(dir => childrenEl.appendChild(createNode(dir)));
    }
  }

  // Auto-expand toward the target path
  if (autoExpandPath && autoExpandPath !== nodeEl.dataset.path) {
    const childNodes = childrenEl.querySelectorAll(':scope > .tree-node');
    for (const child of childNodes) {
      const cp = child.dataset.path;
      if (autoExpandPath === cp || autoExpandPath.startsWith(cp + '/')) {
        await expandNode(child, autoExpandPath);
        break;
      }
    }
  }

  // Reached the target — select it
  if (autoExpandPath === nodeEl.dataset.path) {
    selectNode(nodeEl);
  }
}

// Mark a path as selected and ensure the node is expanded to show its children.
// Called from renderer when a folder is loaded externally (e.g. "폴더 열기" dialog).
export async function setSelectedPath(folderPath) {
  _selectedPath = folderPath;
  document.querySelectorAll('.tree-row.active').forEach(r => r.classList.remove('active'));
  const node = document.querySelector(`.tree-node[data-path="${CSS.escape(folderPath)}"]`);
  if (!node) return;
  node.querySelector(':scope > .tree-row').classList.add('active');
  if (node.dataset.hasChildren === 'true' && node.dataset.expanded !== 'true') {
    await expandNode(node, null);
  }
}