import { logger } from "@coder/logger"
import { promises as fs } from "fs"

/**
 * Provides a heartbeat using a local file to indicate activity.
 */
export class Heart {
 private heartbeatTimer?: NodeJS.Timeout
 private heartbeatInterval = 60000
 public lastHeartbeat = 0

 public constructor(private readonly heartbeatPath: string, private readonly isActive: () => Promise<boolean>) {}

 public alive(): boolean {
 const now = Date.now()
 return now - this.lastHeartbeat < this.heartbeatInterval
 }
 /**
 * Write to the heartbeat file if we haven't already done so within the
 * timeout and start or reset a timer that keeps running as long as there is
 * activity. Failures are logged as warnings.
 */
 public beat(): void {
 if (this.alive()) {
 return
 }

 logger.trace("heartbeat")
 fs.writeFile(this.heartbeatPath, "").catch((error) => {
 logger.warn(error.message)
 })
 this.lastHeartbeat = Date.now()
 if (typeof this.heartbeatTimer !== "undefined") {
 clearTimeout(this.heartbeatTimer)
 }
 this.heartbeatTimer = setTimeout(() => {
 this.isActive()
 .then((active) => {
 if (active) {
 this.beat()
 }
 })
 .catch((error) => {
 logger.warn(error.message)
 })
 }, this.heartbeatInterval)
 }
}