Implement caching

.gitignore

@@ -5,3 +5,4 @@
 build
 
 .env
+.aoc_cache

app/src/test/kotlin/util/InputDownloader.kt

@@ -9,10 +9,17 @@ import java.net.CookieHandler
 import java.net.CookieManager
 import java.net.ConnectException
 import java.time.Duration
+import java.io.File
 import io.github.cdimascio.dotenv.dotenv
+import kotlin.text.trim
 
 class InputDownloader {
     fun getInput(day: Int): String {
+        val cache = readCache(day, false)
+        if (cache != null) {
+            return cache.trim()
+        }
+
         val dotenv = dotenv()
         val sessionCookie = HttpCookie("session", dotenv["AOC_TOKEN"]);
         sessionCookie.path = "/"
@@ -39,10 +46,16 @@ class InputDownloader {
             throw ConnectException("Failed to download input for day $day. Is the day open yet?")
         }
 
+        writeCache(day, false, res.body())
         return res.body().trim()
     }
 
     fun getExample(day: Int): String {
+        val cache = readCache(day, true)
+        if (cache != null) {
+            return cache.trim()
+        }
+
         val client = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build()
 
         val req = HttpRequest.newBuilder()
@@ -59,6 +72,27 @@ class InputDownloader {
         val start = bod.indexOf("<pre><code>")
         val stop = bod.indexOf("</code></pre>")
         val sliced = bod.substring(start + 11..<stop)
+        writeCache(day, true, sliced)
         return sliced.trim()
     }
+
+    fun readCache(day: Int, example: Boolean): String? {
+        val cacheFileName = "./.aoc_cache/day_$day/" + if (example) { "example.txt" } else { "solution.txt" }
+        var cacheFile = File(cacheFileName)
+        if (!cacheFile.exists()) {
+            return null
+        }
+
+        val inputStream = cacheFile.inputStream()
+        val cacheString = inputStream.bufferedReader().use { it.readText() }
+        return cacheString
+    }
+
+    fun writeCache(day: Int, example: Boolean, str: String) {
+        val cacheFileName = "./.aoc_cache/day_$day/"
+        File(cacheFileName).mkdirs()
+        var cacheFile = File(cacheFileName + if (example) { "example.txt" } else { "solution.txt" })
+
+        cacheFile.writeText(str)
+    }
 }