phaseflow/src/lib/garmin.ts

// ABOUTME: Garmin Connect API client using stored OAuth tokens.
// ABOUTME: Fetches body battery, HRV, and intensity minutes from Garmin.

import { logger } from "@/lib/logger";
import type { GarminTokens, HrvStatus } from "@/types";

// Use connectapi subdomain directly (same as garth library)
const GARMIN_API_URL = "https://connectapi.garmin.com";

// Headers matching garth library's http.py USER_AGENT
function getGarminHeaders(oauth2Token: string): Record<string, string> {
  return {
    Authorization: `Bearer ${oauth2Token}`,
    "User-Agent": "GCM-iOS-5.19.1.2",
  };
}

export interface BodyBatteryData {
  current: number | null;
  yesterdayLow: number | null;
}

export async function fetchGarminData(
  endpoint: string,
  oauth2Token: string,
): Promise<unknown> {
  const response = await fetch(`${GARMIN_API_URL}${endpoint}`, {
    headers: getGarminHeaders(oauth2Token),
  });

  if (!response.ok) {
    throw new Error(`Garmin API error: ${response.status}`);
  }

  return response.json();
}

export function isTokenExpired(tokens: GarminTokens): boolean {
  const expiresAt = new Date(tokens.expires_at);
  return expiresAt <= new Date();
}

/**
 * Calculate days until refresh token expiry.
 * This is what users care about - when they need to re-authenticate.
 * Falls back to access token expiry if refresh token expiry not available.
 */
export function daysUntilExpiry(tokens: GarminTokens): number {
  const expiresAt = tokens.refresh_token_expires_at
    ? new Date(tokens.refresh_token_expires_at)
    : new Date(tokens.expires_at);
  const now = new Date();
  const diffMs = expiresAt.getTime() - now.getTime();
  return Math.floor(diffMs / (1000 * 60 * 60 * 24));
}

export async function fetchHrvStatus(
  date: string,
  oauth2Token: string,
): Promise<HrvStatus> {
  try {
    const response = await fetch(`${GARMIN_API_URL}/hrv-service/hrv/${date}`, {
      headers: getGarminHeaders(oauth2Token),
    });

    if (!response.ok) {
      logger.warn(
        { status: response.status, endpoint: "hrv-service" },
        "Garmin HRV API error",
      );
      return "Unknown";
    }

    const text = await response.text();
    if (!text.startsWith("{") && !text.startsWith("[")) {
      logger.error(
        { endpoint: "hrv-service", responseBody: text.slice(0, 1000) },
        "Garmin returned non-JSON response",
      );
      return "Unknown";
    }
    const data = JSON.parse(text);
    const status = data?.hrvSummary?.status;

    if (status === "BALANCED") {
      logger.info({ status: "BALANCED" }, "Garmin HRV data received");
      return "Balanced";
    }
    if (status === "UNBALANCED") {
      logger.info({ status: "UNBALANCED" }, "Garmin HRV data received");
      return "Unbalanced";
    }
    logger.info(
      { rawStatus: status, hasData: !!data?.hrvSummary },
      "Garmin HRV returned unknown status",
    );
    return "Unknown";
  } catch (error) {
    logger.error(
      { err: error, endpoint: "hrv-service" },
      "Garmin HRV fetch failed",
    );
    return "Unknown";
  }
}

export async function fetchBodyBattery(
  date: string,
  oauth2Token: string,
): Promise<BodyBatteryData> {
  try {
    // Calculate yesterday's date for the API request
    const dateObj = new Date(date);
    dateObj.setDate(dateObj.getDate() - 1);
    const yesterday = dateObj.toISOString().split("T")[0];

    const response = await fetch(
      `${GARMIN_API_URL}/wellness-service/wellness/bodyBattery/reports/daily?startDate=${yesterday}&endDate=${date}`,
      {
        headers: getGarminHeaders(oauth2Token),
      },
    );

    if (!response.ok) {
      logger.warn(
        { status: response.status, endpoint: "bodyBattery" },
        "Garmin body battery API error",
      );
      return { current: null, yesterdayLow: null };
    }

    const text = await response.text();
    if (!text.startsWith("{") && !text.startsWith("[")) {
      logger.error(
        { endpoint: "bodyBattery", responseBody: text.slice(0, 1000) },
        "Garmin returned non-JSON response",
      );
      return { current: null, yesterdayLow: null };
    }
    const data = JSON.parse(text) as Array<{
      date: string;
      bodyBatteryValuesArray?: Array<[number, string, number, number]>;
    }>;

    // Find today's and yesterday's data from the response array
    const todayData = data?.find((d) => d.date === date);
    const yesterdayData = data?.find((d) => d.date === yesterday);

    // Current = last value in today's bodyBatteryValuesArray (index 2 is the level)
    const todayValues = todayData?.bodyBatteryValuesArray ?? [];
    const current =
      todayValues.length > 0 ? todayValues[todayValues.length - 1][2] : null;

    // Yesterday low = minimum level in yesterday's bodyBatteryValuesArray
    const yesterdayValues = yesterdayData?.bodyBatteryValuesArray ?? [];
    const yesterdayLow =
      yesterdayValues.length > 0
        ? Math.min(...yesterdayValues.map((v) => v[2]))
        : null;

    logger.info(
      {
        current,
        yesterdayLow,
        hasCurrentData: todayValues.length > 0,
        hasYesterdayData: yesterdayValues.length > 0,
      },
      "Garmin body battery data received",
    );

    return { current, yesterdayLow };
  } catch (error) {
    logger.error(
      { err: error, endpoint: "bodyBattery" },
      "Garmin body battery fetch failed",
    );
    return { current: null, yesterdayLow: null };
  }
}

export async function fetchIntensityMinutes(
  date: string,
  oauth2Token: string,
): Promise<number> {
  try {
    // Calculate 7 days before the date for weekly range
    const endDate = date;
    const startDateObj = new Date(date);
    startDateObj.setDate(startDateObj.getDate() - 7);
    const startDate = startDateObj.toISOString().split("T")[0];

    const response = await fetch(
      `${GARMIN_API_URL}/usersummary-service/stats/im/weekly?start=${startDate}&end=${endDate}`,
      {
        headers: getGarminHeaders(oauth2Token),
      },
    );

    if (!response.ok) {
      logger.warn(
        { status: response.status, endpoint: "intensityMinutes" },
        "Garmin intensity minutes API error",
      );
      return 0;
    }

    const text = await response.text();
    if (!text.startsWith("{") && !text.startsWith("[")) {
      logger.error(
        { endpoint: "intensityMinutes", responseBody: text.slice(0, 1000) },
        "Garmin returned non-JSON response",
      );
      return 0;
    }
    const data = JSON.parse(text) as Array<{
      calendarDate: string;
      moderateValue?: number;
      vigorousValue?: number;
    }>;

    const entry = data?.[0];
    if (!entry) {
      logger.info(
        { hasData: false },
        "Garmin intensity minutes: no weekly data",
      );
      return 0;
    }

    const moderate = entry.moderateValue ?? 0;
    const vigorous = entry.vigorousValue ?? 0;
    const total = moderate + vigorous;

    logger.info(
      { moderate, vigorous, total },
      "Garmin intensity minutes data received",
    );

    return total;
  } catch (error) {
    logger.error(
      { err: error, endpoint: "intensityMinutes" },
      "Garmin intensity minutes fetch failed",
    );
    return 0;
  }
}