fix app price calculation

fix overflow when calculating account escrow
calculates app price per minute based on resource usage

src/db/app.rs

@@ -592,6 +592,17 @@ impl ActiveAppWithNode {
         }
     }
 
+    fn total_units(&self) -> f64 {
+        // TODO: Optimize this based on price of hardware.
+        (self.vcpus as f64 * 5f64)
+            + (self.memory_mib as f64 / 200f64)
+            + (self.disk_size_mib as f64 / 1024f64 / 10f64)
+    }
+
+    pub fn price_per_minute(&self) -> u64 {
+        (self.total_units() * self.price_per_unit as f64) as u64
+    }
+
     pub async fn list_all(db: &Surreal<Client>) -> Result<Vec<Self>, Error> {
         let mut query_response = db.query(format!("SELECT * FROM {ACTIVE_APP} FETCH out;")).await?;
         let active_apps: Vec<Self> = query_response.take(0)?;

src/db/general.rs

@@ -61,7 +61,7 @@ impl Account {
         email: &str,
         escrow: u64,
     ) -> Result<(), Error> {
-        let escrow = escrow * TOKEN_DECIMAL;
+        let escrow = escrow.saturating_mul(TOKEN_DECIMAL);
         let mut op_account = Self::get(db, wallet).await?;
         let op_total_balance = op_account.balance.saturating_add(op_account.escrow);
         if op_total_balance < escrow {

src/grpc/types.rs

@@ -274,6 +274,7 @@ impl From<VmNodeResources> for db::VmNodeResources {
 
 impl From<db::ActiveAppWithNode> for AppContract {
     fn from(value: db::ActiveAppWithNode) -> Self {
+        let nano_per_minute = value.price_per_minute();
         let public_package_mr_enclave =
             Some(hex::decode(value.mr_enclave.clone()).unwrap_or_default());
 
@@ -297,7 +298,7 @@ impl From<db::ActiveAppWithNode> for AppContract {
 
             created_at: value.created_at.to_rfc3339(),
             updated_at: value.created_at.to_rfc3339(),
-            nano_per_minute: value.price_per_unit,
+            nano_per_minute,
             locked_nano: value.locked_nano,
             collected_at: value.collected_at.to_rfc3339(),
             hratls_pubkey: value.hratls_pubkey,