import type {
RateLimiter,
RateLimitResult,
RateLimitConfig,
RateLimiterState,
} from "../types.js";
/**
* After-N Rate Limiter
*
* Allows the first N requests, then rejects all subsequent requests.
* Useful for testing "exhausted quota" scenarios.
*/
export class AfterNRateLimiter implements RateLimiter {
private totalRequests = 0;
private config: RateLimitConfig;
constructor(config: RateLimitConfig) {
this.config = config;
}
check(): RateLimitResult {
if (!this.config.enabled) {
return { allowed: true, headers: {} };
}
this.totalRequests++;
const headers: Record<string, string> = {
"x-ratelimit-limit-requests": String(this.config.failAfterN),
"x-ratelimit-remaining-requests": String(
Math.max(0, this.config.failAfterN - this.totalRequests),
),
};
if (this.totalRequests > this.config.failAfterN) {
return {
allowed: false,
retryAfter: 60, // Arbitrary - won't actually work until reset
headers: { ...headers, "retry-after": "60", "retry-after-ms": "60000" },
};
}
return { allowed: true, headers };
}
reset(): void {
this.totalRequests = 0;
}
getState(): RateLimiterState {
return {
strategy: "after-n",
currentCount: this.totalRequests,
maxCount: this.config.failAfterN,
};
}
updateConfig(config: Partial<RateLimitConfig>): void {
this.config = { ...this.config, ...config };
}
}
/**
* Random Rate Limiter
*
* Randomly rejects requests with a configured probability.
* Useful for testing retry logic and error handling.
*/
export class RandomRateLimiter implements RateLimiter {
private config: RateLimitConfig;
constructor(config: RateLimitConfig) {
this.config = config;
}
check(): RateLimitResult {
if (!this.config.enabled) {
return { allowed: true, headers: {} };
}
const headers: Record<string, string> = {
"x-ratelimit-probability": String(this.config.failProbability),
};
if (Math.random() < this.config.failProbability) {
return {
allowed: false,
retryAfter: 1,
headers: { ...headers, "retry-after": "1", "retry-after-ms": "1000" },
};
}
return { allowed: true, headers };
}
reset(): void {
// No state to reset
}
getState(): RateLimiterState {
return {
strategy: "random",
};
}
updateConfig(config: Partial<RateLimitConfig>): void {
this.config = { ...this.config, ...config };
}
}
/**
* Always Rate Limiter
*
* Always rejects requests. Useful for testing rate limit error handling.
*/
export class AlwaysRateLimiter implements RateLimiter {
private config: RateLimitConfig;
constructor(config: RateLimitConfig) {
this.config = config;
}
check(): RateLimitResult {
if (!this.config.enabled) {
return { allowed: true, headers: {} };
}
return {
allowed: false,
retryAfter: 60,
headers: {
"x-ratelimit-limit-requests": "0",
"x-ratelimit-remaining-requests": "0",
"retry-after": "60",
"retry-after-ms": "60000",
},
};
}
reset(): void {
// No state to reset
}
getState(): RateLimiterState {
return {
strategy: "always",
};
}
updateConfig(config: Partial<RateLimitConfig>): void {
this.config = { ...this.config, ...config };
}
}
/**
* No-op Rate Limiter
*
* Never rate limits. Used when rate limiting is disabled.
*/
export class NoOpRateLimiter implements RateLimiter {
check(): RateLimitResult {
return { allowed: true, headers: {} };
}
reset(): void {}
getState(): RateLimiterState {
return { strategy: "none" };
}
updateConfig(): void {}
}
