import type { Inline, Segment } from './types'

/** 取 segments 拼起来的文字里 [from, to) 这一段，每个字保留原来的词性。 */
export function sliceSegments(segments: Segment[], from: number, to: number): Segment[] {
  const out: Segment[] = []
  let offset = 0
  for (const segment of segments) {
    const start = Math.max(from, offset)
    const end = Math.min(to, offset + segment.text.length)
    if (start < end)
      out.push({ text: segment.text.slice(start - offset, end - offset), role: segment.role })
    offset += segment.text.length
    if (offset >= to)
      break
  }
  return out
}

/**
 * 给输入框里改过的文字上色：`tokens` 是 `code` 的着色，和 `code` 相同的开头、结尾沿用原来的词性，
 * 中间改动的部分先不着色，等扩展端按新代码着色的文档到了再换成准确的。
 */
export function recolor(tokens: Segment[], code: string, text: string): Segment[] {
  if (text === code)
    return tokens
  const shorter = Math.min(code.length, text.length)
  let head = 0
  while (head < shorter && code[head] === text[head])
    head++
  let tail = 0
  while (tail < shorter - head && code[code.length - 1 - tail] === text[text.length - 1 - tail])
    tail++
  const changed = text.slice(head, text.length - tail)
  return [
    ...sliceSegments(tokens, 0, head),
    ...(changed ? [{ text: changed, role: 'plain' as const }] : []),
    ...sliceSegments(tokens, code.length - tail, code.length),
  ]
}

/** 着色的词拼成的文字（给折叠按钮的说明用）；框写成框头加框里的文字。 */
export function inlineText(pieces: Inline[]): string {
  return pieces.map(piece => 'role' in piece ? piece.text : `${piece.label} ${inlineText(piece.segments)}`).join('')
}

/** 文字里有没有 offset 处的那个名字，框里的也算。 */
export function showsOffset(pieces: Inline[], offset: number): boolean {
  return pieces.some(piece => 'role' in piece ? piece.offset === offset : showsOffset(piece.segments, offset))
}