'use client'

import type { ExcalidrawElement } from '@excalidraw/excalidraw/element/types'
import type { BinaryFiles } from '@excalidraw/excalidraw/types'

/**
 * Parses canvas JSON from DB — either a bare elements array or { elements, files }.
 * Returns null for PPTX placeholders or invalid JSON.
 */
export function parseExcalidrawSceneFromCanvasData(
  dataStr: string
): { elements: readonly ExcalidrawElement[]; files: BinaryFiles | null } | null {
  if (!dataStr?.trim()) return null
  try {
    const parsed = JSON.parse(dataStr)
    if (parsed && parsed.type === 'pptx') return null
    if (Array.isArray(parsed)) {
      return { elements: parsed as ExcalidrawElement[], files: null }
    }
    if (parsed?.elements && Array.isArray(parsed.elements)) {
      const files =
        parsed.files && typeof parsed.files === 'object' ? (parsed.files as BinaryFiles) : null
      return { elements: parsed.elements as readonly ExcalidrawElement[], files }
    }
  } catch {
    /* ignore */
  }
  return null
}

/**
 * Renders Excali scene to PNG in the browser (uses Excalidraw export helpers).
 */
export async function exportExcalidrawSceneToPngBlob(dataStr: string): Promise<Blob | null> {
  const scene = parseExcalidrawSceneFromCanvasData(dataStr)
  if (!scene || scene.elements.length === 0) return null

  const { exportToBlob, getNonDeletedElements, MIME_TYPES } = await import('@excalidraw/excalidraw')
  const elements = getNonDeletedElements(scene.elements as ExcalidrawElement[])
  if (!elements.length) return null

  try {
    return await exportToBlob({
      elements,
      files: scene.files,
      mimeType: MIME_TYPES.png,
      exportPadding: 24,
      maxWidthOrHeight: 2400,
      appState: {
        exportBackground: true,
        exportWithDarkMode: false,
        viewBackgroundColor: '#ffffff',
      },
    })
  } catch (e) {
    console.error('[excalidraw-export-image] exportToBlob failed:', e)
    return null
  }
}