export type PromptParts = {
  pre: string
  prompt: string
  post: string
}

export function sanitizePromptPart(raw: unknown) {
  return String(raw || '').replace(/\r\n/g, '\n').replace(/\r/g, '')
}

export function composePromptParts(pre: string, prompt: string, post: string) {
  return [pre, prompt, post]
    .map(part => sanitizePromptPart(part).trim())
    .filter(Boolean)
    .join('\n\n')
}

export function applyPromptParts(parts: PromptParts, middle: string) {
  return composePromptParts(parts.pre, middle, parts.post)
}

export function restorePromptParts(saved: string, stored?: Partial<PromptParts> | null, current?: Partial<PromptParts> | null): PromptParts {
  const pre = sanitizePromptPart(stored?.pre ?? '').trim()
  const post = sanitizePromptPart(stored?.post ?? '').trim()
  if (pre || post) {
    return {
      pre,
      prompt: sanitizePromptPart(stored?.prompt ?? saved).trim() || sanitizePromptPart(saved).trim(),
      post
    }
  }
  let mid = sanitizePromptPart(stored?.prompt ?? saved)
  const curPre = sanitizePromptPart(current?.pre || '').trim()
  const curPost = sanitizePromptPart(current?.post || '').trim()
  if (curPre && mid.startsWith(curPre)) mid = mid.slice(curPre.length).replace(/^\n+/, '')
  if (curPost && mid.endsWith(curPost)) mid = mid.slice(0, Math.max(0, mid.length - curPost.length)).replace(/\n+$/, '')
  return {
    pre: current?.pre || '',
    prompt: mid.trim(),
    post: current?.post || ''
  }
}