interface MarkdownLinkRange {
  start: number
  end: number
  text: string
  url: string
}

const MARKDOWN_LINK_PATTERN = /\[([^\]\n]*)\]\(([^)\n]*)\)/g

export function findMarkdownLinkRange(
  markdown: string,
  from: number,
  to: number
): MarkdownLinkRange | null {
  MARKDOWN_LINK_PATTERN.lastIndex = 0

  for (const match of markdown.matchAll(MARKDOWN_LINK_PATTERN)) {
    const start = match.index
    if (start > 0 && markdown[start - 1] === '!') continue

    const fullMatch = match[0]
    const text = match[1]
    const url = match[2]
    const textStart = start + 1
    const textEnd = textStart + text.length
    const urlStart = textEnd + 2
    const urlEnd = urlStart + url.length
    const end = start + fullMatch.length
    const cursorInside = from === to && from >= start && from <= end
    const selectionInsideText = from >= textStart && to <= textEnd
    const selectionInsideUrl = from >= urlStart && to <= urlEnd
    const selectionCoversLink = from <= start && to >= end

    if (cursorInside || selectionInsideText || selectionInsideUrl || selectionCoversLink) {
      return { start, end, text, url }
    }
  }

  return null
}