/**
 * Split Qwen-style thinking blocks from assistant text for UI.
 * Supports complete and in-progress streams.
 *
 * Common tags: <think>…</think>, <think>…</think>, <thinking>…
 */

const TAG = String.raw`think|thinking|redacted[_-]?thinking|redacted[_-]?reasoning`
const THINK_OPEN = new RegExp(`<\\s*(?:${TAG})\\s*>`, 'i')
const THINK_PAIR = new RegExp(
  `<\\s*(?:${TAG})\\s*>([\\s\\S]*?)<\\s*/\\s*(?:${TAG})\\s*>`,
  'gi'
)

/**
 * @param {string} text
 * @returns {{ thinking: string, answer: string, thinkingOpen: boolean }}
 */
export function partitionThink(text) {
  const full = String(text || '')
  /** @type {string[]} */
  const blocks = []
  let answer = full.replace(THINK_PAIR, (_, body) => {
    const t = String(body || '').trim()
    if (t) blocks.push(t)
    return ''
  })

  // Incomplete open block at end of stream
  let thinkingOpen = false
  const openMatch = answer.match(THINK_OPEN)
  if (openMatch && openMatch.index != null) {
    thinkingOpen = true
    const openIdx = openMatch.index
    const after = answer.slice(openIdx + openMatch[0].length)
    if (after.trim()) blocks.push(after.trim())
    answer = answer.slice(0, openIdx)
  }

  return {
    thinking: blocks.join('\n\n').trim(),
    answer: answer.replace(/^\s+/, '').replace(/\s+$/, ''),
    thinkingOpen,
  }
}

/**
 * Render assistant body HTML: optional collapsible think + answer.
 * @param {string} raw
 * @param {(s: string) => string} formatBody
 * @param {{ openThink?: boolean }} [opts]
 */
export function renderAssistantHtml(raw, formatBody, opts = {}) {
  const { thinking, answer, thinkingOpen } = partitionThink(raw)
  const open = opts.openThink !== false && (thinkingOpen || Boolean(thinking))
  let html = ''
  if (thinking) {
    html += `<details class="qvac-think"${open ? ' open' : ''}>
      <summary class="qvac-think-summary">
        <span class="qvac-think-ico" aria-hidden="true">◐</span>
        <span>Thinking</span>
        ${thinkingOpen ? '<span class="qvac-think-live">live</span>' : ''}
      </summary>
      <div class="qvac-think-body">${formatBody(thinking)}</div>
    </details>`
  }
  const ans = answer || (!thinking ? '…' : '')
  if (ans) {
    html += `<div class="qvac-msg-answer">${formatBody(ans)}</div>`
  } else if (thinkingOpen) {
    html += `<div class="qvac-msg-answer qvac-msg-pending muted">Working…</div>`
  }
  return html || formatBody(raw || '…')
}