import { TextSelection } from 'prosemirror-state'
import { Editor, Command } from '../Editor'
import { createExtension } from '../Extension'
import minMax from '../utils/minMax'

type Position = 'start' | 'end' | number | boolean | null

interface ResolvedSelection {
  from: number,
  to: number,
}

function resolveSelection(editor: Editor, position: Position = null): ResolvedSelection {
  if (position === null) {
    return editor.selection
  }

  if (position === 'start' || position === true) {
    return {
      from: 0,
      to: 0,
    }
  }

  if (position === 'end') {
    const { size } = editor.state.doc.content

    return {
      from: size,
      to: size - 1, // TODO: -1 only for nodes with content
    }
  }

  return {
    from: position as number,
    to: position as number,
  }
}

export const Focus = createExtension({
  addCommands() {
    return {
      focus: (position: Position = null): Command => ({
        editor, view, tr, dispatch,
      }) => {
        if ((view.hasFocus() && position === null) || position === false) {
          return true
        }

        const { from, to } = resolveSelection(editor, position)
        const { doc } = tr
        const resolvedFrom = minMax(from, 0, doc.content.size)
        const resolvedEnd = minMax(to, 0, doc.content.size)
        const selection = TextSelection.create(doc, resolvedFrom, resolvedEnd)

        if (dispatch) {
          tr.setSelection(selection)
        }

        view.focus()

        return true
      },
    }
  },
})

declare module '../Editor' {
  interface AllExtensions {
    Focus: typeof Focus,
  }
}