collab: Add GET /billing/usage endpoint (#28832)

This PR adds a `GET /billing/usage` endpoint for retrieving billing
usage to show on the `zed.dev/account` page.

Release Notes:

- N/A

crates/collab/src/api/billing.rs

@@ -54,6 +54,7 @@ pub fn router() -> Router {
             post(manage_billing_subscription),
         )
         .route("/billing/monthly_spend", get(get_monthly_spend))
+        .route("/billing/usage", get(get_current_usage))
 }
 
 #[derive(Debug, Deserialize)]
@@ -947,6 +948,93 @@ async fn get_monthly_spend(
     }))
 }
 
+#[derive(Debug, Deserialize)]
+struct GetCurrentUsageParams {
+    github_user_id: i32,
+}
+
+#[derive(Debug, Serialize)]
+struct UsageCounts {
+    pub used: i32,
+    pub limit: Option<i32>,
+    pub remaining: Option<i32>,
+}
+
+#[derive(Debug, Serialize)]
+struct GetCurrentUsageResponse {
+    pub model_requests: UsageCounts,
+    pub edit_predictions: UsageCounts,
+}
+
+async fn get_current_usage(
+    Extension(app): Extension<Arc<AppState>>,
+    Query(params): Query<GetCurrentUsageParams>,
+) -> Result<Json<GetCurrentUsageResponse>> {
+    let user = app
+        .db
+        .get_user_by_github_user_id(params.github_user_id)
+        .await?
+        .ok_or_else(|| anyhow!("user not found"))?;
+
+    let Some(llm_db) = app.llm_db.clone() else {
+        return Err(Error::http(
+            StatusCode::NOT_IMPLEMENTED,
+            "LLM database not available".into(),
+        ));
+    };
+
+    let empty_usage = GetCurrentUsageResponse {
+        model_requests: UsageCounts {
+            used: 0,
+            limit: Some(0),
+            remaining: Some(0),
+        },
+        edit_predictions: UsageCounts {
+            used: 0,
+            limit: Some(0),
+            remaining: Some(0),
+        },
+    };
+
+    let Some(subscription) = app.db.get_active_billing_subscription(user.id).await? else {
+        return Ok(Json(empty_usage));
+    };
+
+    let subscription_period = maybe!({
+        let period_start_at = subscription.current_period_start_at()?;
+        let period_end_at = subscription.current_period_end_at()?;
+
+        Some((period_start_at, period_end_at))
+    });
+
+    let Some((period_start_at, period_end_at)) = subscription_period else {
+        return Ok(Json(empty_usage));
+    };
+
+    let usage = llm_db
+        .get_subscription_usage_for_period(user.id, period_start_at, period_end_at)
+        .await?;
+    let Some(usage) = usage else {
+        return Ok(Json(empty_usage));
+    };
+
+    let model_requests_limit = Some(500);
+    let edit_prediction_limit = Some(2000);
+
+    Ok(Json(GetCurrentUsageResponse {
+        model_requests: UsageCounts {
+            used: usage.model_requests,
+            limit: model_requests_limit,
+            remaining: model_requests_limit.map(|limit| (limit - usage.model_requests).max(0)),
+        },
+        edit_predictions: UsageCounts {
+            used: usage.edit_predictions,
+            limit: edit_prediction_limit,
+            remaining: edit_prediction_limit.map(|limit| (limit - usage.edit_predictions).max(0)),
+        },
+    }))
+}
+
 impl From<SubscriptionStatus> for StripeSubscriptionStatus {
     fn from(value: SubscriptionStatus) -> Self {
         match value {

crates/collab/src/db/tables/billing_subscription.rs

@@ -19,6 +19,18 @@ pub struct Model {
     pub created_at: DateTime,
 }
 
+impl Model {
+    pub fn current_period_start_at(&self) -> Option<DateTimeUtc> {
+        let period_start = self.stripe_current_period_start?;
+        chrono::DateTime::from_timestamp(period_start, 0)
+    }
+
+    pub fn current_period_end_at(&self) -> Option<DateTimeUtc> {
+        let period_end = self.stripe_current_period_end?;
+        chrono::DateTime::from_timestamp(period_end, 0)
+    }
+}
+
 #[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
 pub enum Relation {
     #[sea_orm(

crates/collab/src/llm/db/queries.rs

@@ -2,4 +2,5 @@ use super::*;
 
 pub mod billing_events;
 pub mod providers;
+pub mod subscription_usages;
 pub mod usages;

crates/collab/src/llm/db/queries/subscription_usages.rs

@@ -0,0 +1,22 @@
+use crate::db::UserId;
+
+use super::*;
+
+impl LlmDatabase {
+    pub async fn get_subscription_usage_for_period(
+        &self,
+        user_id: UserId,
+        period_start_at: DateTimeUtc,
+        period_end_at: DateTimeUtc,
+    ) -> Result<Option<subscription_usage::Model>> {
+        self.transaction(|tx| async move {
+            Ok(subscription_usage::Entity::find()
+                .filter(subscription_usage::Column::UserId.eq(user_id))
+                .filter(subscription_usage::Column::PeriodStartAt.eq(period_start_at))
+                .filter(subscription_usage::Column::PeriodEndAt.eq(period_end_at))
+                .one(&*tx)
+                .await?)
+        })
+        .await
+    }
+}

crates/collab/src/llm/db/tables.rs

@@ -2,5 +2,6 @@ pub mod billing_event;
 pub mod model;
 pub mod monthly_usage;
 pub mod provider;
+pub mod subscription_usage;
 pub mod usage;
 pub mod usage_measure;

crates/collab/src/llm/db/tables/subscription_usage.rs

@@ -0,0 +1,20 @@
+use crate::db::UserId;
+use sea_orm::entity::prelude::*;
+use time::PrimitiveDateTime;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
+#[sea_orm(table_name = "subscription_usages")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: i32,
+    pub user_id: UserId,
+    pub period_start_at: PrimitiveDateTime,
+    pub period_end_at: PrimitiveDateTime,
+    pub model_requests: i32,
+    pub edit_predictions: i32,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {}
+
+impl ActiveModelBehavior for ActiveModel {}

crates/collab/src/llm/token.rs

@@ -3,7 +3,7 @@ use crate::db::{billing_subscription, user};
 use crate::llm::{DEFAULT_MAX_MONTHLY_SPEND, FREE_TIER_MONTHLY_SPENDING_LIMIT};
 use crate::{Config, db::billing_preference};
 use anyhow::{Result, anyhow};
-use chrono::{DateTime, NaiveDateTime, Utc};
+use chrono::{NaiveDateTime, Utc};
 use jsonwebtoken::{DecodingKey, EncodingKey, Header, Validation};
 use serde::{Deserialize, Serialize};
 use std::time::Duration;
@@ -84,13 +84,10 @@ impl LlmTokenClaims {
             plan,
             subscription_period: maybe!({
                 let subscription = subscription?;
-                let period_start = subscription.stripe_current_period_start?;
-                let period_start = DateTime::from_timestamp(period_start, 0)?;
+                let period_start_at = subscription.current_period_start_at()?;
+                let period_end_at = subscription.current_period_end_at()?;
 
-                let period_end = subscription.stripe_current_period_end?;
-                let period_end = DateTime::from_timestamp(period_end, 0)?;
-
-                Some((period_start.naive_utc(), period_end.naive_utc()))
+                Some((period_start_at.naive_utc(), period_end_at.naive_utc()))
             }),
         };