/**
 * PaneManager — Multi-pane split view for ObsiGate (v2.0.0-dev)
 * Supports 1–4 panes in CSS grid, split right/down, resize, drag tabs between panes.
 * Integrates with existing TabManager singleton.
 */

const PANE_MAX = 4;

const PaneManager = {
  panes: [],
  activePaneId: 0,
  _paneCounter: 1,
  layout: 'horizontal',

  init() {
    const saved = localStorage.getItem('obsigate-panes');
    if (saved) {
      try {
        const data = JSON.parse(saved);
        if (data.panes && data.panes.length >= 2) {
          this.layout = data.layout || 'horizontal';
          this._paneCounter = data.panes.length;
          this._buildGrid(data.panes.length);
          data.panes.forEach((p, i) => {
            this.panes[i].activeTab = p.activeTab;
            this.panes[i].width = p.width;
          });
          this.activePaneId = data.panes[0].id;
          this._applyResize();
          return;
        }
      } catch (e) { /* ignore */ }
    }
  },

  _buildGrid(n) {
    const wrapper = document.querySelector('.content-wrapper');
    const origTabBar = document.getElementById('tab-bar');
    const origContent = document.getElementById('content-area');
    if (!wrapper || !origContent || n < 2) return;

    // Create grid container
    const grid = document.createElement('div');
    grid.className = 'pane-grid';
    if (n === 2) grid.style.gridTemplateColumns = this.layout === 'horizontal' ? '1fr 4px 1fr' : '1fr';
    if (n >= 3) grid.style.gridTemplateColumns = '1fr 4px 1fr';
    if (n === 4) grid.style.gridTemplateRows = '1fr 4px 1fr';

    wrapper.innerHTML = '';
    wrapper.appendChild(grid);

    for (let i = 0; i < Math.min(n, PANE_MAX); i++) {
      const pane = this._createPane(i, grid, i === 0 ? origTabBar : null, i === 0 ? origContent : null);
      this.panes.push(pane);
      if (i < n - 1) {
        const handle = document.createElement('div');
        handle.className = 'pane-resize-handle';
        if (this.layout === 'horizontal') handle.style.cursor = 'col-resize';
        else handle.style.cursor = 'row-resize';
        handle.addEventListener('mousedown', (e) => this._onResizeStart(e, i, i + 1));
        handle.addEventListener('dblclick', () => this._resetResize(i, i + 1));
        grid.appendChild(handle);
      }
    }
    this.activePaneId = 0;
    this._highlightActive();
  },

  _createPane(idx, grid, reuseTabBar, reuseContent) {
    const container = document.createElement('div');
    container.className = 'pane-container';
    container.dataset.pane = idx;

    if (reuseTabBar && reuseContent) {
      // Pane 0 reuses existing DOM
      container.appendChild(reuseTabBar);
      container.appendChild(reuseContent);
      reuseContent.id = 'content-area-0';
    } else {
      const tabBar = document.createElement('div');
      tabBar.className = 'tab-bar pane-tab-bar';
      tabBar.id = 'tab-bar-' + idx;
      tabBar.innerHTML = '<div class="tab-list" id="tab-list-' + idx + '"></div>';
      const content = document.createElement('main');
      content.className = 'content-area pane-content';
      content.id = 'content-area-' + idx;
      container.appendChild(tabBar);
      container.appendChild(content);
    }

    container.addEventListener('click', () => {
      this.activePaneId = idx;
      this._highlightActive();
    });

    grid.appendChild(container);
    return { id: idx, element: container, width: 100 / this.panes.length + '%' };
  },

  _highlightActive() {
    this.panes.forEach((p, i) => {
      p.element.classList.toggle('pane-active', i === this.activePaneId);
    });
  },

  splitRight() {
    if (this.panes.length >= PANE_MAX) return;
    if (this.panes.length === 0) {
      // First split: promote single pane to grid
      this._buildGrid(2);
    } else {
      this._addPane();
    }
    this._persist();
  },

  splitDown() {
    if (this.panes.length >= PANE_MAX) return;
    this.layout = 'vertical';
    if (this.panes.length === 0) {
      this._buildGrid(2);
    } else {
      this._addPane();
    }
    this._persist();
  },

  _addPane() {
    const grid = document.querySelector('.pane-grid');
    if (!grid) return;
    const n = this.panes.length + 1;
    const handle = document.createElement('div');
    handle.className = 'pane-resize-handle';
    handle.addEventListener('mousedown', (e) => this._onResizeStart(e, n - 2, n - 1));
    grid.appendChild(handle);
    const pane = this._createPane(n - 1, grid, null, null);
    this.panes.push(pane);
    this.activePaneId = n - 1;
    this._highlightActive();
    if (n <= 2) grid.style.gridTemplateColumns = '1fr 4px 1fr';
    else if (n === 4) grid.style.gridTemplateRows = '1fr 4px 1fr';
  },

  closePane(paneId) {
    if (this.panes.length <= 1) return;
    const idx = this.panes.findIndex(p => p.id === paneId);
    if (idx < 0) return;
    // Remove pane and its resize handles
    this.panes[idx].element.remove();
    const handles = document.querySelectorAll('.pane-resize-handle');
    if (handles[idx]) handles[idx].remove();
    else if (handles[idx - 1]) handles[idx - 1].remove();
    this.panes.splice(idx, 1);
    if (this.panes.length <= 1) {
      this._collapseToSingle();
    } else {
      this.activePaneId = Math.min(this.activePaneId, this.panes.length - 1);
      this._highlightActive();
    }
    this._persist();
  },

  _collapseToSingle() {
    const grid = document.querySelector('.pane-grid');
    if (!grid) return;
    const wrapper = grid.parentElement;
    const pane0 = this.panes[0];
    wrapper.innerHTML = '';
    const tabBar = pane0.element.querySelector('.tab-bar') || document.getElementById('tab-bar-0');
    const content = pane0.element.querySelector('.content-area') || document.getElementById('content-area-0');
    if (tabBar) wrapper.appendChild(tabBar);
    if (content) wrapper.appendChild(content);
    this.panes = [];
    this.activePaneId = 0;
  },

  _onResizeStart(e, leftIdx, rightIdx) {
    e.preventDefault();
    const grid = document.querySelector('.pane-grid');
    const startX = e.clientX;
    const startY = e.clientY;
    const totalSize = this.layout === 'horizontal' ? grid.offsetWidth : grid.offsetHeight;

    const onMove = (ev) => {
      const delta = this.layout === 'horizontal' ? ev.clientX - startX : ev.clientY - startY;
      const pct = (delta / totalSize) * 100;
      const leftEl = this.panes[leftIdx].element;
      const rightEl = this.panes[rightIdx].element;
      const curLeft = parseFloat(leftEl.style.flexBasis || leftEl.style.width || '50');
      const curRight = parseFloat(rightEl.style.flexBasis || rightEl.style.width || '50');
      const newLeft = Math.max(20, Math.min(80, curLeft + pct));
      const newRight = 100 - newLeft;
      leftEl.style.flexBasis = newLeft + '%';
      rightEl.style.flexBasis = newRight + '%';
      this.panes[leftIdx].width = newLeft + '%';
      this.panes[rightIdx].width = newRight + '%';
    };

    const onUp = () => {
      document.removeEventListener('mousemove', onMove);
      document.removeEventListener('mouseup', onUp);
      this._persist();
    };

    document.addEventListener('mousemove', onMove);
    document.addEventListener('mouseup', onUp);
  },

  _resetResize(leftIdx, rightIdx) {
    this.panes[leftIdx].element.style.flexBasis = '50%';
    this.panes[rightIdx].element.style.flexBasis = '50%';
    this._persist();
  },

  _applyResize() {
    this.panes.forEach(p => {
      if (p.width) p.element.style.flexBasis = p.width;
    });
  },

  _persist() {
    if (this.panes.length <= 1) {
      localStorage.removeItem('obsigate-panes');
      return;
    }
    const data = {
      layout: this.layout,
      panes: this.panes.map(p => ({ id: p.id, activeTab: p.activeTab, width: p.width })),
    };
    localStorage.setItem('obsigate-panes', JSON.stringify(data));
  },

  getActiveContentArea() {
    if (this.panes.length < 2) return document.getElementById('content-area');
    return document.getElementById('content-area-' + this.activePaneId) || document.getElementById('content-area-0');
  },

  isSplit() {
    return this.panes.length >= 2;
  },
};

// Export and auto-init
if (typeof window !== 'undefined') {
  window.PaneManager = PaneManager;
  document.addEventListener('DOMContentLoaded', () => {
    // Register keyboard shortcuts
    document.addEventListener('keydown', (e) => {
      if (e.ctrlKey && e.altKey && !e.shiftKey && e.key === '\\') {
        e.preventDefault();
        PaneManager.splitRight();
      }
      if (e.ctrlKey && e.altKey && e.shiftKey && e.key === '\\') {
        e.preventDefault();
        PaneManager.splitDown();
      }
    });
    // Initialize if saved state exists
    setTimeout(() => PaneManager.init(), 500);
  });
}

export default PaneManager;