/**
* Candles data service
* Handles fetching and transforming historical price data
*/
import { fetchCandles } from "../api.js";
import { CandlesOutput, CandleInterval } from "../types.js";
/**
* Cache entry structure
*/
interface CacheEntry {
data: CandlesOutput;
timestamp: number;
}
/**
* In-memory cache for candle data
* Key format: `${asset}_${interval}_${limit}`
*/
const candlesCache = new Map<string, CacheEntry>();
/**
* Cache TTL: 1 minute for all intervals
* Conservative approach prioritizing data correctness over performance
*/
const CACHE_TTL_MS = 60 * 1000; // 1 minute
/**
* Generate cache key from parameters
*/
function getCacheKey(asset: string, interval: CandleInterval, limit: number): string {
return `${asset.toUpperCase()}_${interval}_${limit}`;
}
/**
* Minimum candle limit for all intervals
* Set conservatively to avoid time-dependent API failures with short intervals
* The 5m interval can require 4-5 candles depending on timing
*/
const MIN_CANDLE_LIMIT = 10;
/**
* Get historical candle data for an asset
* Results are cached for 1 minute to optimize multiple indicator calls
* @param asset - Asset symbol (SOL, ETH, BTC)
* @param interval - Candle interval (5m, 15m, 1h, 4h, 1d, 1w)
* @param limit - Number of candles to retrieve (minimum 10, maximum 500)
*/
export async function getCandles(
asset: string,
interval: CandleInterval,
limit: number
): Promise<CandlesOutput> {
// Validate limit range
if (limit < MIN_CANDLE_LIMIT || limit > 500) {
throw new Error(
`Limit must be between ${MIN_CANDLE_LIMIT} and 500 (got ${limit}). ` +
`Minimum of ${MIN_CANDLE_LIMIT} candles required to ensure API compatibility.`
);
}
// Check cache
const cacheKey = getCacheKey(asset, interval, limit);
const cached = candlesCache.get(cacheKey);
if (cached) {
const age = Date.now() - cached.timestamp;
if (age < CACHE_TTL_MS) {
// Cache hit - return cached data
return cached.data;
} else {
// Cache expired - remove from cache
candlesCache.delete(cacheKey);
}
}
// Cache miss or expired - fetch from API
const response = await fetchCandles(asset, interval, limit);
// Transform API response to output format
// Convert timestamps from milliseconds to seconds
const data = response.result.map((candle) => ({
time: Math.floor(candle.time / 1000), // Convert ms to seconds
open: candle.open,
high: candle.high,
low: candle.low,
close: candle.close,
volume: candle.volume,
}));
const result: CandlesOutput = {
asset: asset.toUpperCase(),
interval,
data,
};
// Store in cache
candlesCache.set(cacheKey, {
data: result,
timestamp: Date.now(),
});
return result;
}
