import type { Editor } from '@tiptap/core'
import { getSelectionRanges, NodeRangeSelection } from '@tiptap/extension-node-range'
import type { Node } from '@tiptap/pm/model'
import { type SelectionRange, NodeSelection } from '@tiptap/pm/state'

import type { NormalizedNestedOptions } from '../types/options.js'
import { cloneElement } from './cloneElement.js'
import { findElementNextToCoords } from './findNextElementFromCursor.js'
import { getDraggedBlockDir, getDraggedBlockElement } from './getDraggedBlockDir.js'
import { removeNode } from './removeNode.js'

export interface DragContext {
  node: Node | null
  pos: number
}

export function getDragImageOffset(direction: string, wrapperWidth: number): number {
  return direction === 'rtl' ? wrapperWidth : 0
}

// The drag preview clone resets its margin so it sits flush against the wrapper
// origin. Skip the reset when the user explicitly copies a margin property via
// `dragImageProperties`, otherwise we would discard the value they asked for.
export function shouldResetMargin(dragImageProperties?: string[]): boolean {
  if (!dragImageProperties) {
    return true
  }

  return !dragImageProperties.some(property => {
    const p = property.trim().toLowerCase()
    return p === 'margin' || p.startsWith('margin-')
  })
}

function getDragHandleRanges(
  event: DragEvent,
  editor: Editor,
  nestedOptions?: NormalizedNestedOptions,
  dragContext?: DragContext,
): SelectionRange[] {
  const { doc } = editor.view.state

  // In nested mode with known context, use the pre-calculated position
  // This prevents recalculation issues when mouse position shifts during drag start
  if (nestedOptions?.enabled && dragContext?.node && dragContext.pos >= 0) {
    const nodeStart = dragContext.pos
    const nodeEnd = dragContext.pos + dragContext.node.nodeSize

    return [
      {
        $from: doc.resolve(nodeStart),
        $to: doc.resolve(nodeEnd),
      },
    ]
  }

  // Fallback: recalculate from mouse position (used in non-nested mode)
  const result = findElementNextToCoords({
    editor,
    x: event.clientX,
    y: event.clientY,
    direction: 'right',
    nestedOptions,
  })

  if (!result.resultNode || result.pos === null) {
    return []
  }

  // For non-nested mode, use depth 0 to select the outermost block
  // Atom nodes (e.g. images) have nodeSize=1 with no opening/closing tokens,
  // so we must not subtract 1 or we'll create an empty range.
  const offset = result.resultNode.isText || result.resultNode.isAtom ? 0 : -1
  const $from = doc.resolve(result.pos)
  const $to = doc.resolve(result.pos + result.resultNode.nodeSize + offset)

  return getSelectionRanges($from, $to, 0, { extendOnBoundaryOverlap: false })
}

export function dragHandler(
  event: DragEvent,
  editor: Editor,
  nestedOptions?: NormalizedNestedOptions,
  dragContext?: DragContext,
  dragImageProperties?: string[],
) {
  const { view } = editor

  if (!event.dataTransfer) {
    return
  }

  const { empty, $from, $to } = view.state.selection

  const dragHandleRanges = getDragHandleRanges(event, editor, nestedOptions, dragContext)

  const selectionRanges = getSelectionRanges($from, $to, 0, { extendOnBoundaryOverlap: false })
  const isDragHandleWithinSelection = selectionRanges.some(range => {
    return dragHandleRanges.find(dragHandleRange => {
      return dragHandleRange.$from === range.$from && dragHandleRange.$to === range.$to
    })
  })

  const ranges = empty || !isDragHandleWithinSelection ? dragHandleRanges : selectionRanges

  if (!ranges.length) {
    return
  }

  const { tr } = view.state
  const wrapper = document.createElement('div')

  const from = ranges[0].$from.pos
  const to = ranges[ranges.length - 1].$to.pos
  const direction = getDraggedBlockDir(view, from)

  wrapper.setAttribute('dir', direction)

  // For nested mode, create slice directly to avoid NodeRangeSelection expanding to parent
  const isNestedDrag = nestedOptions?.enabled && dragContext?.node
  const isSingleBlock = ranges.length === 1

  let slice
  let selection

  if (isNestedDrag && isSingleBlock) {
    // Create slice directly from the exact positions
    slice = view.state.doc.slice(from, to)

    // Use NodeSelection for nested mode to select exactly the target node
    // NodeRangeSelection would expand to the parent
    selection = NodeSelection.create(view.state.doc, from)
  } else {
    selection = NodeRangeSelection.create(view.state.doc, from, to)
    slice = selection.content()
  }

  const resetMargin = shouldResetMargin(dragImageProperties)

  ranges.forEach(range => {
    const element = getDraggedBlockElement(view, range.$from.pos) as HTMLElement | null

    if (!element) {
      return
    }

    const clonedElement = cloneElement(element, dragImageProperties)

    if (resetMargin) {
      clonedElement.style.margin = '0'
    }

    wrapper.append(clonedElement)
  })

  wrapper.style.position = 'absolute'
  wrapper.style.top = '-10000px'
  document.body.append(wrapper)

  event.dataTransfer.clearData()
  const wrapperRect = wrapper.getBoundingClientRect()
  const dragImageX = getDragImageOffset(direction, wrapperRect.width)

  event.dataTransfer.setDragImage(wrapper, dragImageX, 0)

  let cleanedUp = false

  const cleanupDragPreview = () => {
    if (cleanedUp) {
      return
    }

    cleanedUp = true
    removeNode(wrapper)
    document.removeEventListener('drop', cleanupDragPreview)
    document.removeEventListener('dragend', cleanupDragPreview)
  }

  // Tell ProseMirror the dragged content.
  // Pass the NodeSelection as `node` so ProseMirror's drop handler can use it
  // to precisely delete the original node via `node.replace(tr)`. Without this,
  // ProseMirror falls back to `tr.deleteSelection()` which relies on the current
  // selection — but the browser may change the selection during drag, causing the
  // original node to not be deleted on drop.
  const nodeSelection = selection instanceof NodeSelection ? selection : undefined

  // The `node` property is used at runtime by ProseMirror's drop handler but is
  // not exposed in the public type declaration for `view.dragging`.
  view.dragging = { slice, move: true, node: nodeSelection } as typeof view.dragging

  tr.setSelection(selection)

  view.dispatch(tr)

  // Clean up the drag preview whether the drag results in a valid drop or not.
  document.addEventListener('drop', cleanupDragPreview)
  document.addEventListener('dragend', cleanupDragPreview)
}