package dev.openfga.sdk.api.auth;

import static dev.openfga.sdk.util.StringUtil.isNullOrWhitespace;

import dev.openfga.sdk.constants.FgaConstants;

import java.time.Instant;

import java.time.temporal.ChronoUnit;

import java.util.Random;

class AccessToken {

private static final int TOKEN_EXPIRY_BUFFER_THRESHOLD_IN_SEC = FgaConstants.TOKEN_EXPIRY_THRESHOLD_BUFFER_IN_SEC;

// We add some jitter so that token refreshes are less likely to collide

private static final int TOKEN_EXPIRY_JITTER_IN_SEC = FgaConstants.TOKEN_EXPIRY_JITTER_IN_SEC;

private Instant expiresAt;

private final Random random = new Random();

private String token;

public boolean isValid() {

if (isNullOrWhitespace(token)) {

return false;

}

// Is expiry is null then the token will not expire so should be considered always valid

if (expiresAt == null) {

return true;

}

// A token should be considered valid until 5 minutes before the expiry with some jitter

// to account for multiple calls to `isValid` at the same time and prevent multiple refresh calls

Instant expiresWithLeeway = expiresAt

.minusSeconds(TOKEN_EXPIRY_BUFFER_THRESHOLD_IN_SEC)

.minusSeconds(random.nextInt(TOKEN_EXPIRY_JITTER_IN_SEC))

.truncatedTo(ChronoUnit.SECONDS);

return Instant.now().truncatedTo(ChronoUnit.SECONDS).isBefore(expiresWithLeeway);

}

public String getToken() {

return token;

}

public void setExpiresAt(Instant expiresAt) {

if (expiresAt != null) {

// Truncate to seconds to zero out the milliseconds to keep comparison simpler

this.expiresAt = expiresAt.truncatedTo(ChronoUnit.SECONDS);

}

}

public void setToken(String token) {

this.token = token;

}

}