add DiscordGuildCache

- add DiscordGuildCache
- GET /discord endpoint, return guild information.

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/routes/ApiDiscordRoutes.kt

@@ -15,6 +15,7 @@ import space.mori.chzzk_bot.common.events.DiscordRegisterEvent
 import space.mori.chzzk_bot.common.services.UserService
 import space.mori.chzzk_bot.common.utils.getRandomString
 import space.mori.chzzk_bot.webserver.UserSession
+import space.mori.chzzk_bot.webserver.utils.DiscordGuildCache
 
 fun Route.apiDiscordRoutes() {
     val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
@@ -63,7 +64,8 @@ fun Route.apiDiscordRoutes() {
                 call.respond(HttpStatusCode.BadRequest, "User does not exist")
                 return@get
             }
-            call.respond(HttpStatusCode.OK, session.discordGuildList)
+
+            call.respond(HttpStatusCode.OK, DiscordGuildCache.getCachedGuilds(session.discordGuildList))
             return@get
         }
     }

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/utils/DiscordGuildCache.kt

@@ -0,0 +1,75 @@
+package space.mori.chzzk_bot.webserver.utils
+
+import applicationHttpClient
+import io.ktor.client.call.*
+import io.ktor.client.request.*
+import io.ktor.http.*
+import kotlinx.serialization.Serializable
+import space.mori.chzzk_bot.webserver.DiscordGuildListAPI
+import space.mori.chzzk_bot.webserver.dotenv
+import java.time.Instant
+import java.util.concurrent.ConcurrentHashMap
+
+object DiscordGuildCache {
+    private val cache = ConcurrentHashMap<String, CachedGuilds>()
+    private const val EXP_SECONDS = 600L
+
+    suspend fun getCachedGuilds(guildId: String): Guild? {
+        val now = Instant.now()
+
+        return if(cache.isNotEmpty() && cache[guildId]?.timestamp?.plusSeconds(EXP_SECONDS)?.isAfter(now) == true) {
+            cache[guildId]?.guild
+        } else {
+            fetchAllGuilds()
+            cache[guildId]?.guild
+        }
+    }
+
+    suspend fun getCachedGuilds(guildId: List<String>): List<Guild> {
+        return guildId.mapNotNull { getCachedGuilds(it) }
+    }
+
+    private suspend fun fetchGuilds(beforeGuildId: String? = null, limit: Int = 100): List<DiscordGuildListAPI> {
+        val result = applicationHttpClient.get("https://discord.com/api/users/@me/guilds") {
+            headers {
+                append(HttpHeaders.Authorization, "Bot ${dotenv["DISCORD_TOKEN"]}")
+            }
+            parameter("limit", limit)
+            if (beforeGuildId != null) {
+                parameter("before", beforeGuildId)
+            }
+        }
+
+        return result.body<List<DiscordGuildListAPI>>()
+    }
+
+    private suspend fun fetchAllGuilds() {
+        var lastGuildId: String? = null
+        while (true) {
+            val guilds = fetchGuilds(lastGuildId)
+            if (guilds.isEmpty()) {
+                break
+            }
+
+            guilds.forEach {
+                cache[it.id] = CachedGuilds(
+                    Guild(it.id, it.name, it.icon, it.banner)
+                )
+            }
+            lastGuildId = guilds.last().id
+        }
+    }
+}
+
+data class CachedGuilds(
+    val guild: Guild,
+    val timestamp: Instant = Instant.now()
+)
+
+@Serializable
+data class Guild(
+    val id: String,
+    val name: String,
+    val icon: String?,
+    val banner: String?,
+)