import type { InsertResult } from '@admin/utils/editor/insert-result'
import type { EditorView } from '@codemirror/view'

export function transformSelectedMarkdownLines(
  view: EditorView | null,
  currentValue: string,
  transformLine: (line: string, index: number) => string,
  fallbackLine: string
): InsertResult {
  if (!view) {
    return {
      newValue: `${currentValue}${currentValue ? '\n' : ''}${fallbackLine}`,
      newCursorPos: currentValue.length + fallbackLine.length
    }
  }

  const { from, to } = view.state.selection.main
  const startLine = view.state.doc.lineAt(from)
  const endLine = view.state.doc.lineAt(to)
  const effectiveEndLine =
    to > from && to === endLine.from ? view.state.doc.lineAt(to - 1) : endLine
  const start = startLine.from
  const end = effectiveEndLine.to
  const selected = view.state.doc.sliceString(start, end)
  const selectedLines = selected.length > 0 ? selected.split('\n') : ['']
  const nextLines = selectedLines.map((line, index) => transformLine(line || fallbackLine, index))
  const nextText = nextLines.join('\n')

  view.dispatch({
    changes: { from: start, to: end, insert: nextText },
    selection: { anchor: start + nextText.length }
  })

  return {
    newValue: currentValue.slice(0, start) + nextText + currentValue.slice(end),
    newCursorPos: start + nextText.length
  }
}