feat: add a channel as a logging channel

Closes #1, fixes #10

src/db/mod.rs

@@ -0,0 +1,62 @@
+use std::env;
+
+use poise::serenity_prelude::{ChannelId, GuildId};
+use sqlx::SqlitePool;
+
+pub type Result<T> = ::std::result::Result<T, sqlx::Error>;
+
+pub struct Database {
+    pool: SqlitePool,
+}
+
+impl Database {
+    pub async fn new() -> Result<Self> {
+        Ok(Self {
+            pool: SqlitePool::connect(
+                &env::var("DATABASE_URL")
+                    .expect("Missing enviroment variable DATABASE_URL"),
+            )
+            .await?,
+        })
+    }
+
+    pub async fn get_logging_channel(
+        &self,
+        guild_id: u64,
+    ) -> Result<Vec<u64>> {
+        let guild_id = guild_id as i64;
+        let channels = sqlx::query!(
+            r#"
+SELECT channel_id
+FROM guild_log_channels
+WHERE guild_id = ?1
+            "#,
+            guild_id
+        )
+        .fetch_all(&self.pool)
+        .await?;
+        Ok(channels.iter().map(|id| id.channel_id as u64).collect())
+    }
+
+    pub async fn set_logging_channel(
+        &self,
+        guild_id: GuildId,
+        channel_id: ChannelId,
+    ) -> Result<()> {
+        let guild_id = guild_id.0 as i64;
+        let channel_id = channel_id.0 as i64;
+        let mut conn = self.pool.acquire().await?;
+
+        sqlx::query!(
+            r#"
+INSERT INTO guild_log_channels (guild_id, channel_id)
+VALUES ( ?1, ?2 )
+            "#,
+            guild_id,
+            channel_id
+        )
+        .execute(&mut *conn)
+        .await
+        .map(|_| ())
+    }
+}