function parseStreamJsonLine(line) {
  const text = String(line ?? '').trim();
  if (!text) return null;
  try {
    const parsed = JSON.parse(text);
    return parsed && typeof parsed === 'object' ? parsed : null;
  } catch {
    return null;
  }
}

export function parseCursorAgentStreamJsonEvents(stdout) {
  const events = [];
  for (const line of String(stdout ?? '').split('\n')) {
    const parsed = parseStreamJsonLine(line);
    if (parsed) events.push(parsed);
  }
  return events;
}

export function normalizeCursorAgentUsage(raw) {
  if (!raw || typeof raw !== 'object') return null;
  const inputTokens = Number(raw.inputTokens ?? raw.input_tokens ?? 0);
  const outputTokens = Number(raw.outputTokens ?? raw.output_tokens ?? 0);
  const cacheReadTokens = Number(raw.cacheReadTokens ?? raw.cache_read_tokens ?? 0);
  const cacheWriteTokens = Number(raw.cacheWriteTokens ?? raw.cache_write_tokens ?? 0);
  const billableInput = inputTokens + cacheWriteTokens;
  const billableOutput = outputTokens;
  if (billableInput <= 0 && billableOutput <= 0) return null;
  return {
    inputTokens: billableInput,
    outputTokens: billableOutput,
    cacheReadTokens: cacheReadTokens > 0 ? cacheReadTokens : 0,
    cacheWriteTokens: cacheWriteTokens > 0 ? cacheWriteTokens : 0,
  };
}

export function parseCursorAgentUsage(stdout) {
  const events = parseCursorAgentStreamJsonEvents(stdout);
  for (let index = events.length - 1; index >= 0; index -= 1) {
    const event = events[index];
    if (event?.type !== 'result') continue;
    const usage = normalizeCursorAgentUsage(event.usage);
    if (usage) return usage;
  }
  return null;
}

function extractAssistantText(message) {
  if (!message || typeof message !== 'object') return '';
  const content = message.content ?? message.message?.content;
  if (typeof content === 'string') return content.trim();
  if (!Array.isArray(content)) return '';
  return content
    .map((part) => {
      if (!part || typeof part !== 'object') return '';
      if (part.type === 'text') return String(part.text ?? '').trim();
      return '';
    })
    .filter(Boolean)
    .join('\n')
    .trim();
}

export function extractCursorAgentDisplayText(stdout) {
  const events = parseCursorAgentStreamJsonEvents(stdout);
  for (let index = events.length - 1; index >= 0; index -= 1) {
    const event = events[index];
    if (event?.type === 'result') {
      const resultText = String(event.result ?? '').trim();
      if (resultText) return resultText;
    }
    if (event?.type === 'assistant') {
      const assistantText = extractAssistantText(event.message ?? event);
      if (assistantText) return assistantText;
    }
  }
  return '';
}

export function buildCursorBillingTokenState(usage, priorBillingState = null) {
  const normalized = normalizeCursorAgentUsage(usage);
  if (!normalized) return null;
  const priorIn = Number(priorBillingState?.lastInputTokens ?? 0);
  const priorOut = Number(priorBillingState?.lastOutputTokens ?? 0);
  return {
    accumulatedInputTokens: priorIn + normalized.inputTokens,
    accumulatedOutputTokens: priorOut + normalized.outputTokens,
  };
}