Implement chit_balances

backend/canisters/user_index/api/can.did

@@ -117,6 +117,12 @@ type SearchResponse = variant {
     };
 };
 
+type ChitBalancesArgs = record {
+    users : vec UserId;
+    year : nat16;
+    month : nat8;
+};
+
 type DiamondMembershipFeesResponse = variant {
     Success : vec record {
         token : Cryptocurrency;
@@ -404,6 +410,9 @@ service : {
     // Search for users matching some query
     search : (SearchArgs) -> (SearchResponse) query;
 
+    // Gets the CHIT balances for multiple users for a chosen month
+    chit_balances : (ChitBalancesArgs) -> (ChitBalancesResponse) query;
+
     // Retrieves the current fees to pay for Diamond membership
     diamond_membership_fees : (EmptyArgs) -> (DiamondMembershipFeesResponse) query;
 

backend/canisters/user_index/api/src/main.rs

@@ -3,6 +3,7 @@ use candid_gen::generate_candid_method;
 #[allow(deprecated)]
 fn main() {
     generate_candid_method!(user_index, check_username, query);
+    generate_candid_method!(user_index, chit_balances, query);
     generate_candid_method!(user_index, chit_leaderboard, query);
     generate_candid_method!(user_index, current_user, query);
     generate_candid_method!(user_index, diamond_membership_fees, query);

backend/canisters/user_index/api/src/queries/chit_balances.rs

@@ -0,0 +1,21 @@
+use candid::CandidType;
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use types::UserId;
+
+#[derive(CandidType, Serialize, Deserialize, Debug)]
+pub struct Args {
+    pub users: Vec<UserId>,
+    pub year: u16,
+    pub month: u8,
+}
+
+#[derive(CandidType, Serialize, Deserialize, Debug)]
+pub enum Response {
+    Success(SuccessResult),
+}
+
+#[derive(CandidType, Serialize, Deserialize, Debug)]
+pub struct SuccessResult {
+    pub balances: HashMap<UserId, i32>,
+}

backend/canisters/user_index/api/src/queries/mod.rs

@@ -1,5 +1,6 @@
 pub mod c2c_lookup_user;
 pub mod check_username;
+pub mod chit_balances;
 pub mod chit_leaderboard;
 pub mod current_user;
 pub mod diamond_membership_fees;

backend/canisters/user_index/impl/src/queries/chit_balances.rs

@@ -0,0 +1,23 @@
+use crate::{read_state, RuntimeState};
+use ic_cdk::query;
+use user_index_canister::chit_balances::{Response::*, *};
+use utils::time::MonthKey;
+
+#[query]
+fn chit_balances(args: Args) -> Response {
+    read_state(|state| chit_balances_impl(args, state))
+}
+
+fn chit_balances_impl(args: Args, state: &RuntimeState) -> Response {
+    let month_key = MonthKey::new(args.year as u32, args.month);
+
+    let balances = args
+        .users
+        .iter()
+        .flat_map(|u| state.data.users.get_by_user_id(u))
+        .map(|u| (u.user_id, u.chit_per_month.get(&month_key).copied().unwrap_or_default()))
+        .filter(|(_, c)| *c > 0)
+        .collect();
+
+    Success(SuccessResult { balances })
+}

backend/canisters/user_index/impl/src/queries/mod.rs

@@ -1,5 +1,6 @@
 pub mod c2c_lookup_user;
 pub mod check_username;
+pub mod chit_balances;
 pub mod chit_leaderboard;
 pub mod current_user;
 pub mod diamond_membership_fees;