获取代币的 DEX 日线（开高低收与 VWAP）与精确分数

interface DexDailyPrice {
  base_decimals: number | null;
  quote_decimals: number | null;
  // Raw amounts: numerator is quote_amount_raw, denominator is base_amount_raw.
  first_price_numerator: string;
  first_price_denominator: string;
  last_price_numerator: string;
  last_price_denominator: string;
}

// 1. Raw ratios of one pair share the same decimals, so they compare directly.
// a / b > c / d  is equivalent to  a * d > c * b  (denominators must be non-zero)
export function isPriceUp(row: DexDailyPrice): boolean | null {
  const openNum = BigInt(row.first_price_numerator);
  const openDen = BigInt(row.first_price_denominator);
  const closeNum = BigInt(row.last_price_numerator);
  const closeDen = BigInt(row.last_price_denominator);
  if (openDen === 0n || closeDen === 0n) return null;

  return closeNum * openDen > openNum * closeDen;
}

// 2. Raw ratio -> human-readable price (quote tokens per base token):
//    human = numerator / denominator * 10^(baseDecimals - quoteDecimals)
// Returns null when a decimals value is null (0 is valid) or the denominator is 0.
// The result is truncated to displayDigits digits for display only.
export function rawRatioToHumanString(
  numeratorStr: string,
  denominatorStr: string,
  baseDecimals: number | null,
  quoteDecimals: number | null,
  displayDigits = 18
): string | null {
  if (baseDecimals === null || quoteDecimals === null) return null;
  let num = BigInt(numeratorStr);
  let den = BigInt(denominatorStr);
  if (den === 0n) return null;
  const shift = baseDecimals - quoteDecimals;
  if (shift >= 0) {
    num *= 10n ** BigInt(shift);
  } else {
    den *= 10n ** BigInt(-shift);
  }
  const unit = 10n ** BigInt(displayDigits);
  const scaled = (num * unit) / den;
  const intPart = scaled / unit;
  if (displayDigits === 0) return intPart.toString();
  const fracPart = (scaled % unit).toString().padStart(displayDigits, "0");

  return `${intPart}.${fracPart}`;
}

from fractions import Fraction


def raw_ratio(numerator, denominator):
    """Raw ratio: quote atomic units per base atomic unit. None when the denominator is 0."""
    den = int(denominator)
    if den == 0:
        return None
    return Fraction(int(numerator), den)


def human_price(numerator, denominator, base_decimals, quote_decimals):
    """Quote tokens per base token = raw ratio * 10^(base_decimals - quote_decimals).

    Returns None when a decimals value is None (0 is valid) or the denominator is 0.
    """
    if base_decimals is None or quote_decimals is None:
        return None
    raw = raw_ratio(numerator, denominator)
    if raw is None:
        return None
    return raw * Fraction(10) ** (base_decimals - quote_decimals)


def percentage_change(row):
    """Same pair, same decimals: raw ratios compare directly. Exact Fraction, no float."""
    open_raw = raw_ratio(row["first_price_numerator"], row["first_price_denominator"])
    close_raw = raw_ratio(row["last_price_numerator"], row["last_price_denominator"])
    if open_raw is None or close_raw is None or open_raw == 0:
        return None
    return (close_raw - open_raw) / open_raw * 100


def format_fraction(value, digits=18):
    """Display only: round half to even at `digits` places with exact integer arithmetic."""
    quotient, remainder = divmod(abs(value.numerator) * 10**digits, value.denominator)
    twice = remainder * 2
    if twice > value.denominator or (twice == value.denominator and quotient % 2 == 1):
        quotient += 1
    whole, fraction = divmod(quotient, 10**digits)
    text = str(whole) if digits == 0 else f"{whole}.{fraction:0{digits}d}"
    return f"-{text}" if value < 0 and quotient != 0 else text

interface DateSpan {
  from: string;
  to: string;
}

/**
 * 将任意较长日期区间按最大天数（上限 90 天）切分为连续子区间
 */
export function splitDateRange(startDateStr: string, endDateStr: string, maxDays = 90): DateSpan[] {
  const spans: DateSpan[] = [];
  let currentStart = new Date(startDateStr);
  const end = new Date(endDateStr);

  while (currentStart <= end) {
    const chunkEnd = new Date(currentStart);
    chunkEnd.setUTCDate(chunkEnd.getUTCDate() + (maxDays - 1));
    const effectiveEnd = chunkEnd < end ? chunkEnd : end;

    spans.push({
      from: currentStart.toISOString().slice(0, 10),
      to: effectiveEnd.toISOString().slice(0, 10),
    });

    const nextStart = new Date(effectiveEnd);
    nextStart.setUTCDate(nextStart.getUTCDate() + 1);
    currentStart = nextStart;
  }

  return spans;
}

/**
 * 分段回填特定代币的历史日线
 */
export async function backfillTokenDailyPrices(
  chain: string,
  token: string,
  startDate: string,
  endDate: string,
  apiKey: string
) {
  const chunks = splitDateRange(startDate, endDate, 90);
  const allDailyPrices = [];

  for (const chunk of chunks) {
    const url = new URL(`https://api.blockvectra.com/v1/data/${chain}/dex/prices`);
    url.searchParams.set("token", token);
    url.searchParams.set("from", chunk.from);
    url.searchParams.set("to", chunk.to);

    const res = await fetch(url, {
      headers: { "x-api-key": apiKey },
    });

    if (!res.ok) {
      throw new Error(`Failed to fetch span ${chunk.from}..${chunk.to}: HTTP ${res.status}`);
    }

    const json = await res.json();
    allDailyPrices.push(...json.data);
  }

  return allDailyPrices;
}