function defaultParsed(rawText = '') {
  const text = String(rawText || '');
  return {
    rawText: text,
    prefixText: '',
    visibleText: text,
    displayText: text,
    blocks: [],
    replyRef: null,
    callSummary: null,
  };
}

function hasTechPrefix(text = '', offset = 0) {
  return String(text || '').startsWith('<SHiNE:', offset) || String(text || '').startsWith('<S:', offset);
}

function getTechPrefixLength(text = '', offset = 0) {
  if (String(text || '').startsWith('<SHiNE:', offset)) return 7;
  if (String(text || '').startsWith('<S:', offset)) return 3;
  return 0;
}

function parseReplyId(value = '') {
  const parts = String(value || '').split('|');
  if (parts.length !== 4) return null;
  const fromLogin = String(parts[0] || '').trim();
  const toLogin = String(parts[1] || '').trim();
  const timeMs = Number(parts[2] || 0);
  const nonce = Number(parts[3] || 0);
  if (!fromLogin || !toLogin || !Number.isFinite(timeMs) || timeMs <= 0 || !Number.isFinite(nonce) || nonce < 0) {
    return null;
  }
  return {
    fromLogin,
    toLogin,
    timeMs,
    nonce,
    baseKey: `${fromLogin}|${toLogin}|${timeMs}|${nonce}`,
  };
}

function formatCallDuration(totalSeconds) {
  const total = Math.max(0, Math.floor(Number(totalSeconds || 0)));
  const hours = Math.floor(total / 3600);
  const minutes = Math.floor((total % 3600) / 60);
  const seconds = total % 60;
  if (hours > 0) {
    return `${hours}:${String(minutes).padStart(2, '0')}:${String(seconds).padStart(2, '0')}`;
  }
  return `${minutes}:${String(seconds).padStart(2, '0')}`;
}

function buildCallDisplayText(callSummary) {
  if (!callSummary) return '';
  if (callSummary.status === 'completed') {
    return `Звонок: ${formatCallDuration(callSummary.durationSec)}`;
  }
  const reason = String(callSummary.reason || '').trim().toLowerCase();
  if (reason === 'offline') return 'Абонент не в сети';
  if (reason === 'no_answer') return 'Нет ответа';
  if (reason === 'connect_failed') return 'Не удалось установить соединение';
  if (reason === 'busy') return 'Абонент занят';
  if (reason === 'declined') return 'Звонок отклонён';
  return 'Звонок не завершён';
}

export function sanitizeUserDmTextForSend(rawText = '') {
  const text = String(rawText || '');
  if (text.startsWith('<SHiNE:')) return `< SHiNE:${text.slice(7)}`;
  if (text.startsWith('<S:')) return `< S:${text.slice(3)}`;
  return text;
}

export function buildDmCallTechBlock({ status = '', durationSec = 0, reason = '' } = {}) {
  const cleanStatus = String(status || '').trim().toLowerCase();
  if (cleanStatus === 'completed') {
    return `<S:call;v=1;status=completed;duration=${Math.max(0, Math.floor(Number(durationSec || 0)))}>`;
  }
  const cleanReason = String(reason || '').trim().toLowerCase();
  return `<S:call;v=1;status=failed;reason=${cleanReason || 'connect_failed'}>`;
}

export function buildDmReplyTechBlock({ baseKey = '' } = {}) {
  const cleanBaseKey = String(baseKey || '').trim();
  if (!cleanBaseKey) return '';
  return `<S:reply;v=1;id=${cleanBaseKey}>`;
}

export function parseDmTechBlocks(rawText = '') {
  const text = String(rawText || '');
  if (!hasTechPrefix(text)) return defaultParsed(text);

  const blocks = [];
  let cursor = 0;
  let replyRef = null;
  let callSummary = null;

  while (hasTechPrefix(text, cursor)) {
    const end = text.indexOf('>', cursor);
    if (end < 0) {
      if (!blocks.length) return defaultParsed(text);
      break;
    }

    const prefixLength = getTechPrefixLength(text, cursor);
    if (!prefixLength) break;
    const inner = text.slice(cursor + prefixLength, end);
    const segments = inner.split(';').map((part) => String(part || '').trim()).filter(Boolean);
    if (!segments.length) {
      if (!blocks.length) return defaultParsed(text);
      break;
    }

    const kind = String(segments[0] || '').trim().toLowerCase();
    const fields = {};
    for (let i = 1; i < segments.length; i += 1) {
      const part = segments[i];
      const eq = part.indexOf('=');
      if (eq <= 0) continue;
      const key = part.slice(0, eq).trim().toLowerCase();
      const value = part.slice(eq + 1).trim();
      if (key) fields[key] = value;
    }

    const block = { kind, version: Number(fields.v || 0), fields };
    blocks.push(block);

    if (kind === 'reply' && !replyRef) {
      replyRef = parseReplyId(fields.id || '');
    } else if (kind === 'call' && !callSummary) {
      const status = String(fields.status || '').trim().toLowerCase();
      if (status === 'completed') {
        const durationSec = Math.max(0, Math.floor(Number(fields.duration || 0)));
        callSummary = {
          status: 'completed',
          durationSec,
        };
      } else {
        callSummary = {
          status: 'failed',
          reason: String(fields.reason || '').trim().toLowerCase(),
        };
      }
    }

    cursor = end + 1;
  }

  const visibleText = text.slice(cursor);
  const displayText = callSummary ? buildCallDisplayText(callSummary) : visibleText;
  return {
    rawText: text,
    prefixText: text.slice(0, cursor),
    visibleText,
    displayText,
    blocks,
    replyRef,
    callSummary,
  };
}