From dd88f473111518343129757c1b79f0996e426fad Mon Sep 17 00:00:00 2001
From: paulbrejla <paul@paulbrejla.com>
Date: Fri, 1 Dec 2023 11:18:14 +0100
Subject: [PATCH] Adds global rate limit filter

---
 .../holidays/rest/impl/RateLimitFilter.kt     | 45 +++++++++++++++++++
 src/main/resources/application.yml            |  2 +
 2 files changed, 47 insertions(+)
 create mode 100644 src/main/kotlin/de/paulbrejla/holidays/rest/impl/RateLimitFilter.kt

diff --git a/src/main/kotlin/de/paulbrejla/holidays/rest/impl/RateLimitFilter.kt b/src/main/kotlin/de/paulbrejla/holidays/rest/impl/RateLimitFilter.kt
new file mode 100644
index 0000000..8f5db65
--- /dev/null
+++ b/src/main/kotlin/de/paulbrejla/holidays/rest/impl/RateLimitFilter.kt
@@ -0,0 +1,45 @@
+package de.paulbrejla.holidays.rest.impl
+
+import de.paulbrejla.holidays.application.api.RateLimitService
+import org.springframework.beans.factory.annotation.Value
+import org.springframework.http.HttpStatus
+import org.springframework.stereotype.Component
+import org.springframework.web.server.ResponseStatusException
+import javax.servlet.Filter
+import javax.servlet.FilterChain
+import javax.servlet.ServletException
+import javax.servlet.ServletRequest
+import javax.servlet.ServletResponse
+import javax.servlet.http.HttpServletResponse
+
+@Component
+class RateLimitFilter(val rateLimitService: RateLimitService) : Filter {
+    @Value("\${rateLimit.globalBucket.id}")
+    var globalBucketId: String = ""
+
+    @Value("\${rateLimit.globalBucket.capacity}")
+    var globalBucketCapacity: Long = 0
+
+
+    override fun doFilter(request: ServletRequest?, response: ServletResponse?, chain: FilterChain?) {
+        if (!this.shouldFulfillRequestWithinRateLimit(globalBucketId)) { // Maybe add additional x-rate-limit headers later.
+            (response as HttpServletResponse).apply {
+                this.status = HttpStatus.TOO_MANY_REQUESTS.value()
+                this.addHeader("X-RateLimit-Limit", globalBucketCapacity.toString())
+                this.addHeader("X-RateLimit-Remaining", "0")
+            }
+        } else {
+            chain!!.doFilter(request, response)
+        }
+    }
+
+    private fun shouldFulfillRequestWithinRateLimit(bucketId: String): Boolean {
+        return rateLimitService.resolveBucket(bucketId)
+            .tryConsumeAndReturnRemaining(1).run {
+                if (this.isConsumed)
+                    true
+                else
+                    false
+            }
+    }
+}
\ No newline at end of file
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index 092614e..2c8760f 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -10,6 +10,8 @@ spring:
       path: /h2-console
 server:
   port: ${SERVER_PORT:80}
+  error:
+    include-stacktrace: never
 loader:
   source: ${LOADER_SOURCE}
   remoteURL: ${LOADER_REMOTE_URL}