import type { Editor } from "@tiptap/react"
import { readPageFlowMetrics } from "@/lib/drive/extensions/docs-page-flow-decoration"

/** Focus editor at viewport coords; clamp to prose bounds when click is on padding. */
export function focusEditorAtPointer(
  editor: Editor,
  clientX: number,
  clientY: number
): void {
  if (editor.isDestroyed || !editor.isInitialized) return

  const direct = editor.view.posAtCoords({ left: clientX, top: clientY })
  if (direct) {
    editor.chain().focus().setTextSelection(direct.pos).run()
    return
  }

  const prose = editor.view.dom
  const rect = prose.getBoundingClientRect()
  if (rect.width <= 0 || rect.height <= 0) {
    editor.chain().focus("end").run()
    return
  }

  const clampedLeft = Math.min(Math.max(clientX, rect.left + 1), rect.right - 1)
  const clampedTop = Math.min(Math.max(clientY, rect.top + 1), rect.bottom - 1)
  const clamped = editor.view.posAtCoords({ left: clampedLeft, top: clampedTop })
  if (clamped) {
    editor.chain().focus().setTextSelection(clamped.pos).run()
    return
  }

  const metrics = readPageFlowMetrics(prose)
  if (metrics) {
    const localY = clientY - rect.top
    if (localY >= metrics.bodyAreaH) {
      editor.chain().focus("end").run()
      return
    }
  }

  editor.chain().focus(clientY < rect.top + rect.height / 2 ? "start" : "end").run()
}