import { createCanvasSurface } from '../core/canvas_surface.js';

const MAX_STATIC_LAYERS = 24;

export function createStaticLayerCanvas(width, height) {
  return createCanvasSurface(width, height)?.canvas || null;
}

export function drawCachedStaticLayer(state, g, layerId, key, rect, build) {
  if (!state || !rect || rect.w <= 0 || rect.h <= 0) return;
  if (!state.staticLayers) state.staticLayers = new Map();
  const fullKey = `${layerId}:${key}:${Math.max(0, rect.w | 0)}x${Math.max(0, rect.h | 0)}`;
  let layer = state.staticLayers.get(fullKey);
  if (layer) {
    // Map-Reihenfolge als kleine LRU-Liste verwenden.
    state.staticLayers.delete(fullKey);
    state.staticLayers.set(fullKey, layer);
  }
  if (!layer) {
    const canvas = createStaticLayerCanvas(rect.w, rect.h);
    if (!canvas) return;
    const ctx = canvas.getContext('2d');
    build(ctx, rect);
    layer = { canvas };
    state.staticLayers.set(fullKey, layer);
    while (state.staticLayers.size > MAX_STATIC_LAYERS) {
      state.staticLayers.delete(state.staticLayers.keys().next().value);
    }
  }
  g.drawImage(layer.canvas, rect.x, rect.y);
}