[WIP]

migrations/15_create-loans-table.sql

@@ -0,0 +1,10 @@
+CREATE TABLE IF NOT EXISTS Loans (
+    id serial PRIMARY KEY,
+    uid bigint NOT NULL REFERENCES Users(uid),
+    chat_id bigint NOT NULL REFERENCES Chats(id),
+    left_to_pay int NOT NULL CHECK ( left_to_pay >= 0 ),
+    created_at date NOT NULL DEFAULT current_date,
+    repaid_at date
+);
+
+CREATE INDEX IF NOT EXISTS idx_loans_uid ON Loans(uid);

src/repo/loans.rs

@@ -0,0 +1,73 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+use teloxide::types::UserId;
+use tokio::sync::RwLock;
+use crate::config::FeatureToggles;
+use crate::repo;
+use crate::repo::{ChatIdKind, ChatIdPartiality};
+
+#[derive(Clone)]
+pub struct Loans {
+    pool: sqlx::Pool<sqlx::Postgres>,
+    features: FeatureToggles,
+    chat_id_cache: Arc<RwLock<HashMap<ChatIdKind, i64>>>,
+    chats_repo: repo::Chats,
+}
+
+impl Loans {
+    pub fn new(pool: sqlx::Pool<sqlx::Postgres>, features: FeatureToggles) -> Self {
+        Self {
+            chats_repo: repo::Chats::new(pool.clone(), features),
+            pool,
+            features,
+            chat_id_cache: Arc::new(RwLock::new(HashMap::new())),
+        }
+    }
+
+    pub async fn get_active_loan(&self, uid: UserId, chat_id: ChatIdPartiality) -> anyhow::Result<u32> {
+        let internal_chat_id =  match self.get_internal_chat_id(chat_id.kind()).await? {
+            Some(id) => id,
+            None => return Ok(Default::default())
+        };
+        sqlx::query_scalar!("SELECT left_to_pay FROM loans WHERE uid = $1 AND chat_id = $2 AND repaid_at IS NULL",
+                uid.0 as i64, internal_chat_id)
+            .fetch_optional(&self.pool)
+            .await
+            .map(|maybe_loan| maybe_loan.map(|value| value as u32).unwrap_or_default())
+            .map_err(|e| e.into())
+    }
+
+    pub async fn pay(&self, uid: UserId, chat_id: ChatIdPartiality, value: u32) -> anyhow::Result<()> {
+        let internal_chat_id = match self.get_internal_chat_id(chat_id.kind()).await? {
+            Some(id) => id,
+            None => return Ok(())   // TODO: check or logging?
+        };
+        sqlx::query!("UPDATE Loans SET left_to_pay = left_to_pay - $3 WHERE uid = $1 AND chat_id = $2 AND repaid_at IS NULL",
+                uid.0 as i64, internal_chat_id, value as i64)
+            .execute(&self.pool)
+            .await
+            .map(|_| ())
+            .map_err(|e| e.into())
+    }
+
+    async fn get_internal_chat_id(&self, chat_id: ChatIdKind) -> anyhow::Result<Option<i64>> {
+        let maybe_internal_id = self.chat_id_cache
+            .read().await
+            .get(&chat_id).copied();
+        let internal_id = match maybe_internal_id {
+            None => {
+                let maybe_id = self.chats_repo.get_chat(chat_id.clone())
+                    .await?
+                    .map(|chat| chat.internal_id);
+                if let Some(id) = maybe_id {
+                    self.chat_id_cache
+                        .write().await
+                        .insert(chat_id, id);
+                }
+                maybe_id
+            }
+            Some(id) => Some(id)
+        };
+        Ok(internal_id)
+    }
+}

src/repo/mod.rs

@@ -3,6 +3,7 @@ mod dicks;
 mod chats;
 mod import;
 mod promo;
+mod loans;
 
 #[cfg(test)]
 pub(crate) mod test;
@@ -95,7 +96,7 @@ impl ChatIdFull {
     }
 }
 
-#[derive(Debug, derive_more::Display, Clone)]
+#[derive(Debug, derive_more::Display, Clone, Eq, PartialEq, Hash)]
 pub enum ChatIdKind {
     ID(ChatId),
     Instance(String)