Calendar/src/renderers/GridRenderer.ts

import { CalendarConfig } from '../core/CalendarConfig';
import { CalendarView } from '../types/CalendarTypes';
import { ColumnRenderer, ColumnRenderContext } from './ColumnRenderer';
import { eventBus } from '../core/EventBus';
import { DateService } from '../utils/DateService';
import { CoreEvents } from '../constants/CoreEvents';
import { TimeFormatter } from '../utils/TimeFormatter';

/**
 * GridRenderer - Centralized DOM rendering for calendar grid structure
 *
 * ARCHITECTURE OVERVIEW:
 * =====================
 * GridRenderer is responsible for creating and managing the complete DOM structure
 * of the calendar grid. It follows the Strategy Pattern by delegating specific
 * rendering tasks to specialized renderers (DateHeaderRenderer, ColumnRenderer).
 *
 * RESPONSIBILITY HIERARCHY:
 * ========================
 * GridRenderer (this file)
 * ├─ Creates overall grid skeleton
 * ├─ Manages time axis (hour markers)
 * └─ Delegates to specialized renderers:
 *    ├─ DateHeaderRenderer → Renders date headers
 *    └─ ColumnRenderer → Renders day columns
 *
 * DOM STRUCTURE CREATED:
 * =====================
 * <swp-calendar-container>
 *   <swp-header-spacer />                    ← GridRenderer
 *   <swp-time-axis>                          ← GridRenderer
 *     <swp-hour-marker>00:00</...>           ← GridRenderer (iterates hours)
 *   </swp-time-axis>
 *   <swp-grid-container>                     ← GridRenderer
 *     <swp-calendar-header>                  ← GridRenderer creates container
 *       <swp-day-header />                   ← DateHeaderRenderer (iterates dates)
 *     </swp-calendar-header>
 *     <swp-scrollable-content>               ← GridRenderer
 *       <swp-time-grid>                      ← GridRenderer
 *         <swp-grid-lines />                 ← GridRenderer
 *         <swp-day-columns>                  ← GridRenderer creates container
 *           <swp-day-column />               ← ColumnRenderer (iterates dates)
 *         </swp-day-columns>
 *       </swp-time-grid>
 *     </swp-scrollable-content>
 *   </swp-grid-container>
 * </swp-calendar-container>
 *
 * RENDERING FLOW:
 * ==============
 * 1. renderGrid() - Entry point called by GridManager
 *    ├─ First render: createCompleteGridStructure()
 *    └─ Updates: updateGridContent()
 *
 * 2. createCompleteGridStructure()
 *    ├─ Creates header spacer
 *    ├─ Creates time axis (calls createOptimizedTimeAxis)
 *    └─ Creates grid container (calls createOptimizedGridContainer)
 *
 * 3. createOptimizedGridContainer()
 *    ├─ Creates calendar header container
 *    ├─ Creates scrollable content structure
 *    └─ Creates column container (calls renderColumnContainer)
 *
 * 4. renderColumnContainer()
 *    └─ Delegates to ColumnRenderer.render()
 *       └─ ColumnRenderer iterates dates and creates columns
 *
 * OPTIMIZATION STRATEGY:
 * =====================
 * - Caches DOM references (cachedGridContainer, cachedTimeAxis)
 * - Uses DocumentFragment for batch DOM insertions
 * - Only updates changed content on re-renders
 * - Delegates specialized tasks to strategy renderers
 *
 * USAGE EXAMPLE:
 * =============
 * const gridRenderer = new GridRenderer(columnRenderer, dateService, config);
 * gridRenderer.renderGrid(containerElement, new Date(), 'week');
 */
export class GridRenderer {
  private cachedGridContainer: HTMLElement | null = null;
  private cachedTimeAxis: HTMLElement | null = null;
  private dateService: DateService;
  private columnRenderer: ColumnRenderer;
  private config: CalendarConfig;

  constructor(
    columnRenderer: ColumnRenderer,
    dateService: DateService,
    config: CalendarConfig
  ) {
    this.dateService = dateService;
    this.columnRenderer = columnRenderer;
    this.config = config;
  }

  /**
   * Main entry point for rendering the complete calendar grid
   *
   * This method decides between full render (first time) or optimized update.
   * It caches the grid reference for performance.
   *
   * @param grid - Container element where grid will be rendered
   * @param currentDate - Base date for the current view (e.g., any date in the week)
   * @param view - Calendar view type (day/week/month)
   */
  public renderGrid(
    grid: HTMLElement,
    currentDate: Date,
    view: CalendarView = 'week'
  ): void {

    if (!grid || !currentDate) {
      return;
    }

    // Cache grid reference for performance
    this.cachedGridContainer = grid;

    // Only clear and rebuild if grid is empty (first render)
    if (grid.children.length === 0) {
      this.createCompleteGridStructure(grid, currentDate, view);
    } else {
      // Optimized update - only refresh dynamic content
      this.updateGridContent(grid, currentDate, view);
    }
  }

  /**
   * Creates the complete grid structure from scratch
   *
   * Uses DocumentFragment for optimal performance by minimizing reflows.
   * Creates all child elements in memory first, then appends everything at once.
   *
   * Structure created:
   * 1. Header spacer (placeholder for alignment)
   * 2. Time axis (hour markers 00:00-23:00)
   * 3. Grid container (header + scrollable content)
   *
   * @param grid - Parent container
   * @param currentDate - Current view date
   * @param view - View type
   */
  private createCompleteGridStructure(
    grid: HTMLElement,
    currentDate: Date,
    view: CalendarView
  ): void {
    // Create all elements in memory first for better performance
    const fragment = document.createDocumentFragment();

    // Create header spacer
    const headerSpacer = document.createElement('swp-header-spacer');
    fragment.appendChild(headerSpacer);

    // Create time axis with caching
    const timeAxis = this.createOptimizedTimeAxis();
    this.cachedTimeAxis = timeAxis;
    fragment.appendChild(timeAxis);

    // Create grid container with caching
    const gridContainer = this.createOptimizedGridContainer(currentDate, view);
    this.cachedGridContainer = gridContainer;
    fragment.appendChild(gridContainer);

    // Append all at once to minimize reflows
    grid.appendChild(fragment);
  }

  /**
   * Creates the time axis with hour markers
   *
   * Iterates from dayStartHour to dayEndHour (configured in GridSettings).
   * Each marker shows the hour in the configured time format.
   *
   * @returns Time axis element with all hour markers
   */
  private createOptimizedTimeAxis(): HTMLElement {
    const timeAxis = document.createElement('swp-time-axis');
    const timeAxisContent = document.createElement('swp-time-axis-content');
    const gridSettings = this.config.getGridSettings();
    const startHour = gridSettings.dayStartHour;
    const endHour = gridSettings.dayEndHour;

    const fragment = document.createDocumentFragment();
    for (let hour = startHour; hour < endHour; hour++) {
      const marker = document.createElement('swp-hour-marker');
      const date = new Date(2024, 0, 1, hour, 0);
      marker.textContent = TimeFormatter.formatTime(date);
      fragment.appendChild(marker);
    }

    timeAxisContent.appendChild(fragment);
    timeAxisContent.style.top = '-1px'; 
    timeAxis.appendChild(timeAxisContent);
    return timeAxis;
  }

  /**
   * Creates the main grid container with header and columns
   *
   * This is the scrollable area containing:
   * - Calendar header (dates/resources) - created here, populated by DateHeaderRenderer
   * - Time grid (grid lines + day columns) - structure created here
   * - Column container - created here, populated by ColumnRenderer
   *
   * @param currentDate - Current view date
   * @param view - View type
   * @returns Complete grid container element
   */
  private createOptimizedGridContainer(
    currentDate: Date,
    view: CalendarView
  ): HTMLElement {
    const gridContainer = document.createElement('swp-grid-container');

    // Create calendar header as first child - always exists now!
    const calendarHeader = document.createElement('swp-calendar-header');
    gridContainer.appendChild(calendarHeader);

    // Create scrollable content structure
    const scrollableContent = document.createElement('swp-scrollable-content');
    const timeGrid = document.createElement('swp-time-grid');

    // Add grid lines
    const gridLines = document.createElement('swp-grid-lines');
    timeGrid.appendChild(gridLines);

    // Create column container
    const columnContainer = document.createElement('swp-day-columns');
    this.renderColumnContainer(columnContainer, currentDate, view);
    timeGrid.appendChild(columnContainer);

    scrollableContent.appendChild(timeGrid);
    gridContainer.appendChild(scrollableContent);

    return gridContainer;
  }


  /**
   * Delegates column rendering to the injected ColumnRenderer strategy
   *
   * This is where the Strategy Pattern is applied:
   * - DateColumnRenderer iterates dates and creates day columns
   * - Could be swapped with other implementations (e.g., ResourceColumnRenderer)
   *
   * @param columnContainer - Empty container to populate
   * @param currentDate - Current view date
   * @param view - View type
   */
  private renderColumnContainer(
    columnContainer: HTMLElement,
    currentDate: Date,
    view: CalendarView
  ): void {
    const context: ColumnRenderContext = {
      currentWeek: currentDate, // ColumnRenderer expects currentWeek property
      config: this.config
    };

    this.columnRenderer.render(columnContainer, context);
  }

  /**
   * Optimized update of grid content without full rebuild
   *
   * Only updates the column container content, leaving the structure intact.
   * This is much faster than recreating the entire grid.
   *
   * @param grid - Existing grid element
   * @param currentDate - New view date
   * @param view - View type
   */
  private updateGridContent(
    grid: HTMLElement,
    currentDate: Date,
    view: CalendarView
  ): void {
    // Update column container if needed
    const columnContainer = grid.querySelector('swp-day-columns');
    if (columnContainer) {
      columnContainer.innerHTML = '';
      this.renderColumnContainer(columnContainer as HTMLElement, currentDate, view);
    }
  }
  /**
   * Creates a new grid for slide animations during navigation
   *
   * Used by NavigationManager for smooth week-to-week transitions.
   * Creates a complete grid positioned absolutely for animation.
   *
   * Note: Positioning is handled by Animation API, not here.
   *
   * @param parentContainer - Container for the new grid
   * @param weekStart - Start date of the new week
   * @returns New grid element ready for animation
   */
  public createNavigationGrid(parentContainer: HTMLElement, weekStart: Date): HTMLElement {
    // Use SAME method as initial load - respects workweek settings
    const newGrid = this.createOptimizedGridContainer(weekStart, 'week');

    // Position new grid for animation - NO transform here, let Animation API handle it
    newGrid.style.position = 'absolute';
    newGrid.style.top = '0';
    newGrid.style.left = '0';
    newGrid.style.width = '100%';
    newGrid.style.height = '100%';

    // Add to parent container
    parentContainer.appendChild(newGrid);

    return newGrid;
  }
}