Merge pull request 'feat: compute total price for bill' (#108) from billing into master

Reviewed-on: #108

.sqlx/query-538d43c832702b03da4a51e0b0794785adfb14b4b8ff0ed7c4a7079e711b8ce7.json

@@ -0,0 +1,94 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "SELECT \n                product_name,\n                product_id,\n                line_item_id,\n                quantity_minor_unit,\n                quantity_minor_number,\n                quantity_major_unit,\n                quantity_major_number,\n                created_time,\n                bill_id,\n                price_per_unit_minor,\n                price_per_unit_major,\n                price_per_unit_currency,\n                deleted\n            FROM cqrs_billing_line_item_query\n            WHERE\n                bill_id = $1;",
+  "describe": {
+    "columns": [
+      {
+        "ordinal": 0,
+        "name": "product_name",
+        "type_info": "Text"
+      },
+      {
+        "ordinal": 1,
+        "name": "product_id",
+        "type_info": "Uuid"
+      },
+      {
+        "ordinal": 2,
+        "name": "line_item_id",
+        "type_info": "Uuid"
+      },
+      {
+        "ordinal": 3,
+        "name": "quantity_minor_unit",
+        "type_info": "Text"
+      },
+      {
+        "ordinal": 4,
+        "name": "quantity_minor_number",
+        "type_info": "Int4"
+      },
+      {
+        "ordinal": 5,
+        "name": "quantity_major_unit",
+        "type_info": "Text"
+      },
+      {
+        "ordinal": 6,
+        "name": "quantity_major_number",
+        "type_info": "Int4"
+      },
+      {
+        "ordinal": 7,
+        "name": "created_time",
+        "type_info": "Timestamptz"
+      },
+      {
+        "ordinal": 8,
+        "name": "bill_id",
+        "type_info": "Uuid"
+      },
+      {
+        "ordinal": 9,
+        "name": "price_per_unit_minor",
+        "type_info": "Int4"
+      },
+      {
+        "ordinal": 10,
+        "name": "price_per_unit_major",
+        "type_info": "Int4"
+      },
+      {
+        "ordinal": 11,
+        "name": "price_per_unit_currency",
+        "type_info": "Text"
+      },
+      {
+        "ordinal": 12,
+        "name": "deleted",
+        "type_info": "Bool"
+      }
+    ],
+    "parameters": {
+      "Left": [
+        "Uuid"
+      ]
+    },
+    "nullable": [
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false,
+      false
+    ]
+  },
+  "hash": "538d43c832702b03da4a51e0b0794785adfb14b4b8ff0ed7c4a7079e711b8ce7"
+}

src/billing/adapters/output/db/postgres/get_line_items_for_bill_id.rs

@@ -0,0 +1,144 @@
+// SPDX-FileCopyrightText: 2024 Aravinth Manivannan <realaravinth@batsense.net>
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use uuid::Uuid;
+
+use super::BillingDBPostgresAdapter;
+use crate::billing::{
+    application::port::output::db::{errors::*, get_line_items_for_bill_id::*},
+    domain::line_item_aggregate::LineItem,
+};
+
+#[async_trait::async_trait]
+impl GetLineItemsForBillIDDBPort for BillingDBPostgresAdapter {
+    async fn get_line_items_for_bill_id(&self, bill_id: Uuid) -> BillingDBResult<Vec<LineItem>> {
+        let mut res = sqlx::query_as!(
+            super::line_item_view::LineItemView,
+            "SELECT 
+                product_name,
+                product_id,
+                line_item_id,
+                quantity_minor_unit,
+                quantity_minor_number,
+                quantity_major_unit,
+                quantity_major_number,
+                created_time,
+                bill_id,
+                price_per_unit_minor,
+                price_per_unit_major,
+                price_per_unit_currency,
+                deleted
+            FROM cqrs_billing_line_item_query
+            WHERE
+                bill_id = $1;",
+            bill_id
+        )
+        .fetch_all(&self.pool)
+        .await?;
+        println!("Got len: {}", res.len());
+        let mut output = Vec::with_capacity(res.len());
+        res.drain(0..).for_each(|r| output.push(r.into()));
+        Ok(output)
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+
+    use super::*;
+    //    use crate::billing::domain::add_product_command::tests::get_customizations;
+    use crate::{
+        billing::{
+            adapters::output::db::postgres::line_item_view::LineItemView, domain::bill_aggregate::*,
+        },
+        types::currency::*,
+        types::quantity::*,
+        utils::uuid::{tests::*, *},
+    };
+
+    async fn create_dummy_line_item(
+        db: &BillingDBPostgresAdapter,
+        bill_id: Uuid,
+        line_item_id: Uuid,
+    ) {
+        let view = LineItemView::default();
+        let version = 0;
+        sqlx::query!(
+            "INSERT INTO cqrs_billing_line_item_query (
+                        version,
+                        product_name,
+                        product_id,
+                        line_item_id,
+                        quantity_minor_unit,
+                        quantity_minor_number,
+                        quantity_major_unit,
+                        quantity_major_number,
+                        created_time,
+                        bill_id,
+                        price_per_unit_minor,
+                        price_per_unit_major,
+                        price_per_unit_currency,
+                        deleted
+                    ) VALUES (
+                        $1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14
+                    );",
+            version,
+            view.product_name,
+            view.product_id,
+            line_item_id,
+            QuantityUnit::DiscreteNumber.to_string(),
+            view.quantity_minor_number,
+            QuantityUnit::DiscreteNumber.to_string(),
+            view.quantity_major_number,
+            view.created_time,
+            bill_id,
+            view.price_per_unit_minor,
+            view.price_per_unit_major,
+            Currency::INR.to_string(),
+            view.deleted,
+        )
+        .execute(&db.pool)
+        .await
+        .unwrap();
+    }
+
+    #[actix_rt::test]
+    async fn test_postgres_get_line_items_for_bill_id() {
+        let settings = crate::settings::tests::get_settings().await;
+        settings.create_db().await;
+        let db = super::BillingDBPostgresAdapter::new(
+            sqlx::postgres::PgPool::connect(&settings.database.url)
+                .await
+                .unwrap(),
+        );
+
+        let bill_id = UUID;
+
+        // state doesn't exist
+        assert!(db
+            .get_line_items_for_bill_id(bill_id)
+            .await
+            .unwrap()
+            .is_empty());
+
+        let u = GenerateUUID;
+        let li_id_1 = u.get_uuid();
+        let li_id_2 = u.get_uuid();
+        create_dummy_line_item(&db, bill_id, li_id_1).await;
+        create_dummy_line_item(&db, bill_id, li_id_2).await;
+
+        // state exists
+        let res = db.get_line_items_for_bill_id(bill_id).await.unwrap();
+
+        assert_eq!(res.len(), 2);
+        assert!(res
+            .iter()
+            .any(|li| *li.bill_id() == bill_id && *li.line_item_id() == li_id_1));
+        assert!(res
+            .iter()
+            .any(|li| *li.bill_id() == bill_id && *li.line_item_id() == li_id_2));
+
+        settings.drop_db().await;
+    }
+}

src/billing/adapters/output/db/postgres/line_item_view.rs

@@ -25,23 +25,23 @@ pub const NEW_LINE_ITEM_NON_UUID: &str = "new_line_item_non_uuid-asdfa-billing";
 // be designed to reflect the response dto that will be returned to a user.
 #[derive(Debug, Serialize, Deserialize)]
 pub struct LineItemView {
-    product_name: String,
-    product_id: Uuid,
-    bill_id: Uuid,
-    created_time: OffsetDateTime,
+    pub product_name: String,
+    pub product_id: Uuid,
+    pub bill_id: Uuid,
+    pub created_time: OffsetDateTime,
 
-    line_item_id: Uuid,
+    pub line_item_id: Uuid,
 
-    quantity_major_number: i32,
-    quantity_minor_number: i32,
-    quantity_major_unit: String,
-    quantity_minor_unit: String,
+    pub quantity_major_number: i32,
+    pub quantity_minor_number: i32,
+    pub quantity_major_unit: String,
+    pub quantity_minor_unit: String,
 
-    price_per_unit_major: i32,
-    price_per_unit_minor: i32,
-    price_per_unit_currency: String,
+    pub price_per_unit_major: i32,
+    pub price_per_unit_minor: i32,
+    pub price_per_unit_currency: String,
 
-    deleted: bool,
+    pub deleted: bool,
 }
 
 impl Default for LineItemView {

src/billing/adapters/output/db/postgres/mod.rs

@@ -10,6 +10,7 @@ use crate::db::{migrate::RunMigrations, sqlx_postgres::Postgres};
 mod bill_id_exists;
 mod bill_view;
 mod errors;
+mod get_line_items_for_bill_id;
 mod line_item_id_exists;
 mod line_item_view;
 mod next_token_id;

src/billing/application/port/output/db/get_line_items_for_bill_id.rs

@@ -0,0 +1,61 @@
+// SPDX-FileCopyrightText: 2024 Aravinth Manivannan <realaravinth@batsense.net>
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use mockall::predicate::*;
+use mockall::*;
+use uuid::Uuid;
+
+use crate::billing::domain::line_item_aggregate::LineItem;
+
+use super::errors::*;
+#[cfg(test)]
+#[allow(unused_imports)]
+pub use tests::*;
+
+#[automock]
+#[async_trait::async_trait]
+pub trait GetLineItemsForBillIDDBPort: Send + Sync {
+    async fn get_line_items_for_bill_id(&self, bill_id: Uuid) -> BillingDBResult<Vec<LineItem>>;
+}
+
+pub type GetLineItemsForBillIDDBPortObj = std::sync::Arc<dyn GetLineItemsForBillIDDBPort>;
+
+#[cfg(test)]
+pub mod tests {
+    use super::*;
+
+    use std::sync::Arc;
+
+    pub fn mock_get_line_items_for_bill_id_db_port_no_line_items(
+        times: Option<usize>,
+    ) -> GetLineItemsForBillIDDBPortObj {
+        let mut m = MockGetLineItemsForBillIDDBPort::new();
+        if let Some(times) = times {
+            m.expect_get_line_items_for_bill_id()
+                .times(times)
+                .returning(|_| Ok(Vec::default()));
+        } else {
+            m.expect_get_line_items_for_bill_id()
+                .returning(|_| Ok(Vec::default()));
+        }
+
+        Arc::new(m)
+    }
+
+    pub fn mock_get_line_items_for_bill_id_db_port_true(
+        times: Option<usize>,
+    ) -> GetLineItemsForBillIDDBPortObj {
+        let mut m = MockGetLineItemsForBillIDDBPort::new();
+        if let Some(times) = times {
+            m.expect_get_line_items_for_bill_id()
+                .times(times)
+                .returning(|_| Ok(vec![LineItem::default()]));
+        } else {
+            m.expect_get_line_items_for_bill_id()
+                .returning(|_| Ok(vec![LineItem::default()]));
+        }
+
+        Arc::new(m)
+    }
+}

src/billing/application/port/output/db/mod.rs

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 pub mod bill_id_exists;
 pub mod errors;
+pub mod get_line_items_for_bill_id;
 pub mod line_item_id_exists;
 pub mod next_token_id;
 pub mod store_id_exists;

src/billing/application/services/compute_bill_total_price_service.rs

@@ -0,0 +1,210 @@
+// SPDX-FileCopyrightText: 2024 Aravinth Manivannan <realaravinth@batsense.net>
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use std::sync::Arc;
+
+use derive_builder::Builder;
+use mockall::predicate::*;
+use mockall::*;
+
+use super::errors::*;
+use crate::{
+    billing::{
+        application::port::output::db::bill_id_exists::*,
+        application::port::output::db::get_line_items_for_bill_id::*,
+        domain::{
+            bill_aggregate::*, bill_total_price_computed_event::*,
+            compute_bill_total_price_command::*,
+        },
+    },
+    types::currency::*,
+};
+
+#[automock]
+#[async_trait::async_trait]
+pub trait ComputeBillTotalPriceBillUseCase: Send + Sync {
+    async fn compute_total_price_for_bill(
+        &self,
+        cmd: ComputeBillTotalPriceBillCommand,
+    ) -> BillingResult<BillTotalPriceComputedEvent>;
+}
+
+pub type ComputeBillTotalPriceBillServiceObj = Arc<dyn ComputeBillTotalPriceBillUseCase>;
+
+#[derive(Clone, Builder)]
+pub struct ComputeBillTotalPriceBillService {
+    db_bill_id_exists: BillIDExistsDBPortObj,
+    db_get_line_items_for_bill_id: GetLineItemsForBillIDDBPortObj,
+}
+
+#[async_trait::async_trait]
+impl ComputeBillTotalPriceBillUseCase for ComputeBillTotalPriceBillService {
+    async fn compute_total_price_for_bill(
+        &self,
+        cmd: ComputeBillTotalPriceBillCommand,
+    ) -> BillingResult<BillTotalPriceComputedEvent> {
+        if !self.db_bill_id_exists.bill_id_exists(cmd.bill_id()).await? {
+            return Err(BillingError::BillIDNotFound);
+        }
+
+        let line_items = self
+            .db_get_line_items_for_bill_id
+            .get_line_items_for_bill_id(*cmd.bill_id())
+            .await?;
+        if line_items.is_empty() {
+            todo!("Can't compute bill");
+        }
+
+        let mut total_price = PriceBuilder::default()
+            .major(0)
+            .minor(0)
+            .currency(Currency::INR)
+            .build()
+            .unwrap();
+
+        for li in line_items.iter() {
+            total_price = total_price.clone() + li.total_price();
+        }
+        // TODO: 3. Tax?
+
+        Ok(BillTotalPriceComputedEventBuilder::default()
+            .added_by_user(*cmd.adding_by())
+            .bill_id(*cmd.bill_id())
+            .total_price(total_price)
+            .build()
+            .unwrap())
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use time::macros::datetime;
+
+    use super::*;
+
+    use crate::billing::domain::bill_total_price_computed_event::tests::get_bill_total_computed_event_from_command;
+    use crate::billing::domain::line_item_aggregate::LineItemBuilder;
+    use crate::tests::bdd::*;
+    use crate::types::quantity::*;
+    use crate::utils::uuid::tests::*;
+
+    pub fn mock_compute_bill_total_price_service(
+        times: Option<usize>,
+        cmd: ComputeBillTotalPriceBillCommand,
+    ) -> ComputeBillTotalPriceBillServiceObj {
+        let mut m = MockComputeBillTotalPriceBillUseCase::new();
+
+        let res = get_bill_total_computed_event_from_command(&cmd);
+
+        if let Some(times) = times {
+            m.expect_compute_total_price_for_bill()
+                .times(times)
+                .returning(move |_| Ok(res.clone()));
+        } else {
+            m.expect_compute_total_price_for_bill()
+                .returning(move |_| Ok(res.clone()));
+        }
+
+        Arc::new(m)
+    }
+
+    #[actix_rt::test]
+    async fn test_service() {
+        let cmd = ComputeBillTotalPriceBillCommand::get_cmd();
+
+        let s = ComputeBillTotalPriceBillServiceBuilder::default()
+            .db_bill_id_exists(mock_bill_id_exists_db_port_true(IS_CALLED_ONLY_ONCE))
+            .db_get_line_items_for_bill_id(mock_get_line_items_for_bill_id_db_port_true(
+                IS_CALLED_ONLY_ONCE,
+            ))
+            .build()
+            .unwrap();
+
+        let res = s.compute_total_price_for_bill(cmd.clone()).await.unwrap();
+        assert_eq!(res.total_price().clone(), Price::default());
+        assert_eq!(res.bill_id(), cmd.bill_id());
+        assert_eq!(res.added_by_user(), cmd.adding_by());
+    }
+
+    #[actix_rt::test]
+    async fn test_service_sum() {
+        let cmd = ComputeBillTotalPriceBillCommand::get_cmd();
+
+        let li = LineItemBuilder::default()
+            .created_time(datetime!(1970-01-01 0:00 UTC))
+            .product_name("test_product".into())
+            .product_id(UUID)
+            .quantity(
+                QuantityBuilder::default()
+                    .major(
+                        QuantityPartBuilder::default()
+                            .number(2)
+                            .unit(QuantityUnit::DiscreteNumber)
+                            .build()
+                            .unwrap(),
+                    )
+                    .minor(
+                        QuantityPartBuilder::default()
+                            .number(1)
+                            .unit(QuantityUnit::DiscreteNumber)
+                            .build()
+                            .unwrap(),
+                    )
+                    .build()
+                    .unwrap(),
+            )
+            .bill_id(UUID)
+            .price_per_unit(
+                PriceBuilder::default()
+                    .major(100)
+                    .minor(20)
+                    .currency(Currency::INR)
+                    .build()
+                    .unwrap(),
+            )
+            .line_item_id(UUID)
+            .build()
+            .unwrap();
+
+        let mut m = MockGetLineItemsForBillIDDBPort::new();
+        m.expect_get_line_items_for_bill_id()
+            .times(IS_CALLED_ONLY_ONCE.unwrap())
+            .returning(move |_| Ok(vec![li.clone(), li.clone()]));
+
+        let s = ComputeBillTotalPriceBillServiceBuilder::default()
+            .db_bill_id_exists(mock_bill_id_exists_db_port_true(IS_CALLED_ONLY_ONCE))
+            .db_get_line_items_for_bill_id(std::sync::Arc::new(m))
+            .build()
+            .unwrap();
+
+        let res = s.compute_total_price_for_bill(cmd.clone()).await.unwrap();
+        assert_eq!(
+            res.total_price().clone(),
+            PriceBuilder::default()
+                .major(100 * 2 * 2)
+                .minor(20 * 2 * 2)
+                .currency(Currency::INR)
+                .build()
+                .unwrap()
+        );
+    }
+
+    #[actix_rt::test]
+    async fn test_service_bill_id_doesnt_exist() {
+        let cmd = ComputeBillTotalPriceBillCommand::get_cmd();
+
+        let s = ComputeBillTotalPriceBillServiceBuilder::default()
+            .db_bill_id_exists(mock_bill_id_exists_db_port_false(IS_CALLED_ONLY_ONCE))
+            .db_get_line_items_for_bill_id(mock_get_line_items_for_bill_id_db_port_true(
+                IS_NEVER_CALLED,
+            ))
+            .build()
+            .unwrap();
+
+        assert_eq!(
+            s.compute_total_price_for_bill(cmd.clone()).await,
+            Err(BillingError::BillIDNotFound)
+        );
+    }
+}

src/billing/application/services/mod.rs

@@ -12,11 +12,13 @@ pub mod errors;
 pub mod add_bill_service;
 pub mod add_line_item_service;
 pub mod add_store_service;
+pub mod compute_bill_total_price_service;
 pub mod delete_bill_service;
 pub mod delete_line_item_service;
 pub mod update_bill_service;
 pub mod update_line_item_service;
 pub mod update_store_service;
+// TODO: 2. reset token number for store_id cronjob
 
 #[automock]
 pub trait BillingServicesInterface: Send + Sync {
@@ -28,6 +30,9 @@ pub trait BillingServicesInterface: Send + Sync {
     fn add_line_item(&self) -> add_line_item_service::AddLineItemServiceObj;
     fn update_line_item(&self) -> update_line_item_service::UpdateLineItemServiceObj;
     fn delete_line_item(&self) -> delete_line_item_service::DeleteLineItemServiceObj;
+    fn compute_total_price_for_bill(
+        &self,
+    ) -> compute_bill_total_price_service::ComputeBillTotalPriceBillServiceObj;
 }
 
 #[derive(Clone, Builder)]
@@ -40,6 +45,8 @@ pub struct BillingServices {
     delete_line_item: delete_line_item_service::DeleteLineItemServiceObj,
     update_bill: update_bill_service::UpdateBillServiceObj,
     delete_bill: delete_bill_service::DeleteBillServiceObj,
+    compute_total_price_for_bill:
+        compute_bill_total_price_service::ComputeBillTotalPriceBillServiceObj,
 }
 
 impl BillingServicesInterface for BillingServices {
@@ -68,4 +75,9 @@ impl BillingServicesInterface for BillingServices {
     fn delete_line_item(&self) -> delete_line_item_service::DeleteLineItemServiceObj {
         self.delete_line_item.clone()
     }
+    fn compute_total_price_for_bill(
+        &self,
+    ) -> compute_bill_total_price_service::ComputeBillTotalPriceBillServiceObj {
+        self.compute_total_price_for_bill.clone()
+    }
 }

src/billing/domain/bill_aggregate.rs

@@ -100,6 +100,13 @@ impl Aggregate for Bill {
                 let res = services.delete_bill().delete_bill(cmd).await?;
                 Ok(vec![BillingEvent::BillDeleted(res)])
             }
+            BillingCommand::ComputeBillTotalPriceBill(cmd) => {
+                let res = services
+                    .compute_total_price_for_bill()
+                    .compute_total_price_for_bill(cmd)
+                    .await?;
+                Ok(vec![BillingEvent::BillTotalPriceComputed(res)])
+            }
             _ => Ok(Vec::default()),
         }
     }
@@ -108,6 +115,9 @@ impl Aggregate for Bill {
         match event {
             BillingEvent::BillAdded(e) => *self = e.bill().clone(),
             BillingEvent::BillUpdated(e) => *self = e.new_bill().clone(),
+            BillingEvent::BillTotalPriceComputed(e) => {
+                self.total_price = Some(e.total_price().clone());
+            }
             BillingEvent::BillDeleted(e) => *self = e.bill().clone(),
             _ => (),
         }
@@ -119,6 +129,8 @@ mod aggregate_tests {
     use std::sync::Arc;
 
     use add_bill_service::tests::mock_add_bill_service;
+    use compute_bill_total_price_service::tests::mock_compute_bill_total_price_service;
+    use compute_bill_total_price_service::*;
     use cqrs_es::test::TestFramework;
     use delete_bill_service::tests::mock_delete_bill_service;
     use update_bill_service::tests::mock_update_bill_service;
@@ -126,6 +138,8 @@ mod aggregate_tests {
     use super::*;
 
     use crate::billing::domain::bill_deleted_event::tests::get_deleted_bill_event_from_command;
+    use crate::billing::domain::bill_total_price_computed_event::tests::get_bill_total_computed_event_from_command;
+    use crate::billing::domain::bill_total_price_computed_event::BillTotalPriceComputedEvent;
     use crate::billing::domain::bill_updated_event::tests::get_updated_bill_event_from_command;
     use crate::billing::domain::delete_bill_command::DeleteBillCommand;
     use crate::billing::domain::update_bill_command::UpdateBillCommand;
@@ -133,6 +147,7 @@ mod aggregate_tests {
 
     use crate::billing::domain::{
         add_bill_command::*, bill_added_event::tests::get_added_bill_event_from_command,
+        bill_total_price_computed_event::tests::*, compute_bill_total_price_command::*,
     };
 
     type BillTestFramework = TestFramework<Bill>;
@@ -173,6 +188,27 @@ mod aggregate_tests {
             .then_expect_events(vec![expected]);
     }
 
+    #[test]
+    fn test_bill_total_price_computed() {
+        let cmd = ComputeBillTotalPriceBillCommand::get_cmd();
+        let expected = get_bill_total_computed_event_from_command(&cmd);
+        let expected = BillingEvent::BillTotalPriceComputed(expected);
+
+        let mut services = MockBillingServicesInterface::new();
+        services
+            .expect_compute_total_price_for_bill()
+            .times(IS_CALLED_ONLY_ONCE.unwrap())
+            .return_const(mock_compute_bill_total_price_service(
+                IS_CALLED_ONLY_ONCE,
+                cmd.clone(),
+            ));
+
+        BillTestFramework::with(Arc::new(services))
+            .given_no_previous_events()
+            .when(BillingCommand::ComputeBillTotalPriceBill(cmd))
+            .then_expect_events(vec![expected]);
+    }
+
     #[test]
     fn test_delete_bill() {
         let cmd = DeleteBillCommand::get_cmd();

src/billing/domain/bill_total_price_computed_event.rs

@@ -0,0 +1,44 @@
+// SPDX-FileCopyrightText: 2024 Aravinth Manivannan <realaravinth@batsense.net>
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use derive_builder::Builder;
+use derive_getters::Getters;
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+
+use super::bill_aggregate::*;
+use crate::types::currency::*;
+
+#[derive(
+    Clone, Debug, Builder, Serialize, Deserialize, Getters, Eq, PartialEq, Ord, PartialOrd,
+)]
+pub struct BillTotalPriceComputedEvent {
+    added_by_user: Uuid,
+    bill_id: Uuid,
+
+    total_price: Price,
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::billing::domain::compute_bill_total_price_command::*;
+
+    use super::*;
+
+    pub fn get_bill_total_computed_event_from_command(
+        cmd: &ComputeBillTotalPriceBillCommand,
+    ) -> BillTotalPriceComputedEvent {
+        BillTotalPriceComputedEventBuilder::default()
+            .added_by_user(cmd.adding_by().clone())
+            .bill_id(*cmd.bill_id())
+            .total_price(Price::default())
+            .build()
+            .unwrap()
+    }
+
+    #[test]
+    fn test_event() {
+        get_bill_total_computed_event_from_command(&ComputeBillTotalPriceBillCommand::get_cmd());
+    }
+}

src/billing/domain/commands.rs

@@ -7,9 +7,11 @@ use serde::{Deserialize, Serialize};
 
 use super::{
     add_bill_command::AddBillCommand, add_line_item_command::AddLineItemCommand,
-    add_store_command::AddStoreCommand, delete_bill_command::DeleteBillCommand,
-    delete_line_item_command::DeleteLineItemCommand, update_bill_command::UpdateBillCommand,
-    update_line_item_command::UpdateLineItemCommand, update_store_command::UpdateStoreCommand,
+    add_store_command::AddStoreCommand,
+    compute_bill_total_price_command::ComputeBillTotalPriceBillCommand,
+    delete_bill_command::DeleteBillCommand, delete_line_item_command::DeleteLineItemCommand,
+    update_bill_command::UpdateBillCommand, update_line_item_command::UpdateLineItemCommand,
+    update_store_command::UpdateStoreCommand,
 };
 
 #[derive(Clone, Debug, Serialize, Deserialize, Eq, PartialEq, Ord, PartialOrd)]
@@ -20,6 +22,7 @@ pub enum BillingCommand {
     AddBill(AddBillCommand),
     UpdateBill(UpdateBillCommand),
     DeleteBill(DeleteBillCommand),
+    ComputeBillTotalPriceBill(ComputeBillTotalPriceBillCommand),
     AddStore(AddStoreCommand),
     UpdateStore(UpdateStoreCommand),
 }

src/billing/domain/compute_bill_total_price_command.rs

@@ -0,0 +1,66 @@
+// SPDX-FileCopyrightText: 2024 Aravinth Manivannan <realaravinth@batsense.net>
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+use derive_builder::Builder;
+use derive_getters::Getters;
+use serde::{Deserialize, Serialize};
+use time::OffsetDateTime;
+use uuid::Uuid;
+
+use super::bill_aggregate::Bill;
+use crate::types::currency::*;
+
+#[derive(
+    Clone, Debug, Serialize, Deserialize, Eq, PartialEq, Ord, PartialOrd, Getters, Builder,
+)]
+pub struct ComputeBillTotalPriceBillCommand {
+    adding_by: Uuid,
+
+    #[builder(default = "OffsetDateTime::now_utc()")]
+    created_time: OffsetDateTime,
+
+    bill_id: Uuid,
+}
+
+#[cfg(test)]
+mod tests {
+    use time::macros::datetime;
+
+    use crate::{
+        billing::{self, domain::bill_aggregate::*},
+        utils::uuid::tests::UUID,
+    };
+
+    use super::*;
+
+    impl ComputeBillTotalPriceBillCommand {
+        pub fn get_cmd() -> Self {
+            let bill_id = UUID;
+            let adding_by = UUID;
+
+            ComputeBillTotalPriceBillCommandBuilder::default()
+                .adding_by(adding_by)
+                .bill_id(bill_id)
+                .created_time(datetime!(1970-01-01 0:00 UTC))
+                .build()
+                .unwrap()
+        }
+    }
+
+    #[test]
+    fn test_cmd() {
+        let bill_id = UUID;
+        let adding_by = UUID;
+
+        let cmd = ComputeBillTotalPriceBillCommandBuilder::default()
+            .adding_by(adding_by)
+            .bill_id(bill_id)
+            .created_time(datetime!(1970-01-01 0:00 UTC))
+            .build()
+            .unwrap();
+
+        assert_eq!(*cmd.bill_id(), bill_id);
+        assert_eq!(*cmd.adding_by(), adding_by);
+    }
+}

src/billing/domain/events.rs

@@ -7,6 +7,7 @@ use serde::{Deserialize, Serialize};
 
 use super::{
     bill_added_event::BillAddedEvent, bill_deleted_event::BillDeletedEvent,
+    bill_total_price_computed_event::BillTotalPriceComputedEvent,
     bill_updated_event::BillUpdatedEvent, line_item_added_event::LineItemAddedEvent,
     line_item_deleted_event::LineItemDeletedEvent, line_item_updated_event::LineItemUpdatedEvent,
     store_added_event::StoreAddedEvent, store_updated_event::StoreUpdatedEvent,
@@ -20,6 +21,7 @@ pub enum BillingEvent {
     BillAdded(BillAddedEvent),
     BillUpdated(BillUpdatedEvent),
     BillDeleted(BillDeletedEvent),
+    BillTotalPriceComputed(BillTotalPriceComputedEvent),
     StoreAdded(StoreAddedEvent),
     StoreUpdated(StoreUpdatedEvent),
 }
@@ -34,9 +36,10 @@ impl DomainEvent for BillingEvent {
             BillingEvent::LineItemAdded { .. } => "BillingLineItemAdded",
             BillingEvent::LineItemUpdated { .. } => "BillingLineItemUpdated",
             BillingEvent::LineItemDeleted { .. } => "BillingLineItemDeleted",
-            BillingEvent::BillAdded { .. } => "BillingBilAdded",
-            BillingEvent::BillUpdated { .. } => "BillingBilUpdated",
-            BillingEvent::BillDeleted { .. } => "BillingBilDeleted",
+            BillingEvent::BillAdded { .. } => "BillingBillAdded",
+            BillingEvent::BillUpdated { .. } => "BillingBillUpdated",
+            BillingEvent::BillDeleted { .. } => "BillingBillDeleted",
+            BillingEvent::BillTotalPriceComputed { .. } => "BillingBillTotalPriceComputed",
             BillingEvent::StoreAdded { .. } => "BillingStoreAdded",
             BillingEvent::StoreUpdated { .. } => "BillingStoreUpdated",
         };

src/billing/domain/line_item_aggregate.rs

@@ -49,9 +49,15 @@ impl Default for LineItem {
 
 impl LineItem {
     pub fn total_price(&self) -> Price {
-        let total_price_as_minor = (self.quantity().major_as_minor().unwrap() // TODO: handle err
+        let price_per_unit_as_minor =
+            self.price_per_unit().major_as_minor() + self.price_per_unit().minor();
+        let total_price_as_minor = if self.quantity().major().is_dividable() {
+            (self.quantity().major_as_minor().unwrap() // TODO: handle err
              + self.quantity().minor().number())
-            * (self.price_per_unit().major_as_minor() + self.price_per_unit().minor());
+                * price_per_unit_as_minor
+        } else {
+            self.quantity().major().number() * price_per_unit_as_minor
+        };
 
         Price::from_minor(
             total_price_as_minor,

src/billing/domain/mod.rs

@@ -12,6 +12,7 @@ pub mod add_bill_command;
 pub mod add_line_item_command;
 pub mod add_store_command;
 pub mod commands;
+pub mod compute_bill_total_price_command;
 pub mod delete_bill_command;
 pub mod delete_line_item_command;
 pub mod update_bill_command;
@@ -21,6 +22,7 @@ pub mod update_store_command;
 // events;
 pub mod bill_added_event;
 pub mod bill_deleted_event;
+pub mod bill_total_price_computed_event;
 pub mod bill_updated_event;
 pub mod events;
 pub mod line_item_added_event;

src/billing/domain/update_bill_command.rs

@@ -29,6 +29,8 @@ pub struct UpdateBillCommand {
 
 #[cfg(test)]
 mod tests {
+    use time::macros::datetime;
+
     use crate::{billing::domain::bill_aggregate::*, utils::uuid::tests::UUID};
 
     use super::*;
@@ -39,6 +41,7 @@ mod tests {
             let adding_by = UUID;
 
             UpdateBillCommandBuilder::default()
+                .created_time(datetime!(1970-01-01 0:00 UTC))
                 .adding_by(adding_by)
                 .store_id(store_id)
                 .total_price(None)

src/types/currency.rs

@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
-use std::str::FromStr;
+use std::{ops::Add, str::FromStr};
 
 use async_trait::async_trait;
 use cqrs_es::Aggregate;
@@ -53,7 +53,12 @@ impl Price {
 
     pub fn from_minor(minor_only: usize, currency: Currency) -> Price {
         let minor = minor_only % 100;
-        let major = (minor_only - minor) / 100;
+        let major_only = minor_only - minor;
+        let major = if major_only == 0 {
+            0
+        } else {
+            (minor_only - minor) / 100
+        };
         Price {
             minor,
             major,
@@ -62,6 +67,16 @@ impl Price {
     }
 }
 
+impl Add for Price {
+    type Output = Self;
+    fn add(self, rhs: Self) -> Self::Output {
+        let self_minor = self.major_as_minor() + self.minor;
+        let rhs_minor = rhs.major_as_minor() + rhs.minor;
+
+        Self::from_minor(self_minor + rhs_minor, self.currency)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -110,4 +125,70 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn test_price_add() {
+        let a = Price {
+            minor: 10,
+            major: 100,
+            currency: Currency::INR,
+        };
+
+        let b = Price {
+            minor: 1,
+            major: 200,
+            currency: Currency::INR,
+        };
+
+        assert_eq!(
+            a + b,
+            Price {
+                minor: 11,
+                major: 300,
+                currency: Currency::INR
+            }
+        );
+    }
+
+    #[test]
+    fn test_price_add_zero() {
+        let a = Price {
+            minor: 0,
+            major: 0,
+            currency: Currency::INR,
+        };
+
+        assert_eq!(
+            a.clone() + a,
+            Price {
+                minor: 0,
+                major: 0,
+                currency: Currency::INR
+            }
+        );
+    }
+
+    #[test]
+    fn test_price_add_overflow() {
+        let a = Price {
+            minor: 80,
+            major: 100,
+            currency: Currency::INR,
+        };
+
+        let b = Price {
+            minor: 80,
+            major: 200,
+            currency: Currency::INR,
+        };
+
+        assert_eq!(
+            a + b,
+            Price {
+                minor: 60,
+                major: 301,
+                currency: Currency::INR
+            }
+        );
+    }
 }

src/types/quantity.rs

@@ -46,7 +46,7 @@ impl FromStr for QuantityUnit {
             MILLI_LITER => Ok(Self::MilliLiter),
             LITER => Ok(Self::Liter),
             MILLI_GRAM => Ok(Self::Milligram),
-            _ => Err("Currency unsupported".into()),
+            _ => Err(format!("Quantity unsupported: {s}")),
         }
     }
 }
@@ -74,6 +74,15 @@ impl QuantityPart {
             }
         }
     }
+
+    pub fn is_dividable(&self) -> bool {
+        match self.unit {
+            QuantityUnit::Kilogram | QuantityUnit::Liter | QuantityUnit::Gram => true,
+            QuantityUnit::Milligram | QuantityUnit::MilliLiter | QuantityUnit::DiscreteNumber => {
+                false
+            }
+        }
+    }
 }
 
 #[derive(