import type { Msg } from '../types.js'

import { transcriptBodyWidth } from './inputMetrics.js'

const hashText = (text: string) => {
  let h = 5381

  for (let i = 0; i < text.length; i++) {
    h = ((h << 5) + h) ^ text.charCodeAt(i)
  }

  return (h >>> 0).toString(36)
}

export const messageHeightKey = (msg: Msg) => {
  const todoSig = msg.todos?.map(t => `${t.status}:${t.content}`).join('\u0001') ?? ''

  const panelSig =
    msg.panelData?.sections
      .map(s => `${s.title ?? ''}:${s.text?.length ?? 0}:${s.items?.length ?? 0}:${s.rows?.length ?? 0}`)
      .join('\u0001') ?? ''

  const introSig = msg.kind === 'intro' ? (msg.info?.version ?? '') : ''

  return [
    msg.role,
    msg.kind ?? '',
    hashText([msg.text, msg.thinking ?? '', msg.tools?.join('\n') ?? '', todoSig, panelSig, introSig].join('\0'))
  ].join(':')
}

// Hard cap on rows the estimator will count. Each row above this is
// invisible to the estimator (gets clipped to MAX_ESTIMATE_LINES), but
// post-mount Yoga measurement converges to the real height on first
// render. Without this, a long assistant turn (10k+ chars) costs O(text)
// per offset rebuild × every uncached item — cold-mounting a 1000-row
// transcript becomes a multi-million-char wrap walk that blocks the UI.
//
// 800 covers any realistic assistant message (the prior history-clip
// ceiling was 16 lines, then full text — this is the sane middle).
const MAX_ESTIMATE_LINES = 800

export const wrappedLines = (text: string, width: number, maxLines: number = MAX_ESTIMATE_LINES) => {
  const w = Math.max(1, width)
  // Worst case: every cell is its own row at width=1, plus a small
  // slack for the trailing partial line. Walking past this byte budget
  // cannot increase n any further once n is already past maxLines, so
  // bail. Saves O(text) walks on multi-megabyte single-line messages.
  const budget = Math.min(text.length, maxLines * w + maxLines)
  let n = 0
  let start = 0

  for (let i = 0; i <= budget; i++) {
    if (i === text.length || i === budget || text.charCodeAt(i) === 10) {
      const rows = Math.max(1, Math.ceil((i - start) / w))
      n += rows >= maxLines - n ? maxLines - n : rows
      start = i + 1

      if (n >= maxLines) {
        return maxLines
      }
    }
  }

  return n
}

export const estimatedMsgHeight = (
  msg: Msg,
  cols: number,
  {
    compact,
    details,
    userPrompt = '',
    withSeparator = false
  }: {
    compact: boolean
    details: boolean
    userPrompt?: string
    withSeparator?: boolean
  }
) => {
  if (msg.kind === 'intro') {
    return msg.info?.version ? 9 : 5
  }

  if (msg.kind === 'panel') {
    return Math.max(3, (msg.panelData?.sections.length ?? 1) * 2 + 1)
  }

  if (msg.kind === 'trail' && msg.todos?.length) {
    if (msg.todoCollapsedByDefault) {
      return 2
    }

    return Math.max(2, msg.todos.length + 2)
  }

  const bodyWidth = transcriptBodyWidth(cols, msg.role, userPrompt)
  const text = msg.text
  let h = wrappedLines(text || ' ', bodyWidth)

  if (!compact && msg.role === 'assistant') {
    // Paragraph gaps add up to 6 extra rows of breathing room. Slice
    // first so the regex never walks more than the first ~16k chars of
    // a giant assistant message — post-mount Yoga measurement converges
    // to the real height regardless of how the estimate undercounts.
    const scan = text.length > 16_000 ? text.slice(0, 16_000) : text
    h += Math.min(6, (scan.match(/\n\s*\n/g) ?? []).length)
  }

  if (details) {
    h += (msg.tools?.length ?? 0) + wrappedLines(msg.thinking ?? '', bodyWidth)
  }

  if (msg.role === 'user' || msg.kind === 'diff') {
    h += 2
  } else if (msg.kind === 'slash') {
    h++
  }

  // Inter-turn separator above non-first user messages (1 rule row + 1
  // top-margin row). The render-side gate is in appLayout.tsx; we trust
  // the caller to pass `withSeparator` only when it matches that gate.
  if (withSeparator) {
    h += 2
  }

  return Math.max(1, h)
}