From c1d4b0a43046b8aa4bad6ebf6ca3f74aba1bb54f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Yaroslav=20de=20la=20Pe=C3=B1a=20Smirnov?=
 <yps@yaroslavps.com>
Date: Fri, 9 Oct 2020 23:51:37 +0300
Subject: take into account shared expenses

---
 budget/src/lib.rs      | 24 ++++++++++++++++++++----
 budget/tests/budget.rs | 14 ++++++++++++--
 budget/tests/test.toml |  3 ++-
 src/main.rs            | 16 ++++++++++++++++
 4 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/budget/src/lib.rs b/budget/src/lib.rs
index 7d7c390..7d194c0 100644
--- a/budget/src/lib.rs
+++ b/budget/src/lib.rs
@@ -49,6 +49,7 @@ pub struct Calculated {
     pub categories_subtotal: HashMap<String, f64>,
     pub total: f64,
     pub balance: f64,
+    pub total_owed: HashMap<u32, f64>,
     pub days_left: f64,
     pub days_left_essential: f64,
     pub last_day: NaiveDate,
@@ -69,9 +70,6 @@ fn recurring_default() -> bool {
 }
 
 // Parse the dates from toml's Datetime to Chrono's NaiveDate
-// Probably unnecessary for now, but since I am planning on using the dates in
-// the future to more easily count the days, it would be better to have them in
-// a proper format
 fn deserialize_date<'de, D>(deserializer: D) -> Result<NaiveDate, D::Error>
 where D: Deserializer<'de> {
     toml::value::Datetime::deserialize(deserializer)
@@ -98,7 +96,7 @@ pub fn parse_account(path: &str) -> Result<Account, ParseError> {
 }
 
 pub fn calculate(account: &Account) -> Option<Calculated> {
-    if account.days.len() < 1 {
+    if account.days.is_empty() {
         return None;
     }
 
@@ -110,6 +108,7 @@ pub fn calculate(account: &Account) -> Option<Calculated> {
         categories_subtotal: HashMap::<String, f64>::new(),
         total: 0.0,
         balance: 0.0,
+        total_owed: HashMap::<u32, f64>::new(),
         days_left: 0.0,
         days_left_essential: 0.0,
         last_day: account.days.last().unwrap().date,
@@ -137,6 +136,23 @@ pub fn calculate(account: &Account) -> Option<Calculated> {
                 if account.essential_categories.contains(category) {
                     calculated.essential_subtotal += expense.price;
                 }
+
+                if expense.shared > 1 {
+                    let owed = 
+                        expense.price * 
+                        (expense.shared as f64 - 1.0) / 
+                        expense.shared as f64;
+
+                    if let Some(total_owed_by) = 
+                    calculated.total_owed.get_mut(&expense.shared) {
+                        *total_owed_by += owed;
+                    } else {
+                        calculated.total_owed.insert(
+                            expense.shared,
+                            owed,
+                        );
+                    }
+                }
             }
         }
     }
diff --git a/budget/tests/budget.rs b/budget/tests/budget.rs
index feae240..6a9214d 100644
--- a/budget/tests/budget.rs
+++ b/budget/tests/budget.rs
@@ -31,7 +31,7 @@ fn can_parse_account() -> Result<(), ParseError>{
                         name: String::from("Bacon"),
                         price: 3.33,
                         qty: 1,
-                        shared: 2,
+                        shared: 3,
                         recurring: false,
                         category: Some(String::from("products")),
                     },
@@ -39,7 +39,7 @@ fn can_parse_account() -> Result<(), ParseError>{
                         name: String::from("Yoghurt"),
                         price: 1.24,
                         qty: 2,
-                        shared: 1,
+                        shared: 2,
                         recurring: false,
                         category: Some(String::from("products")),
                     },
@@ -106,6 +106,7 @@ fn can_calculate() -> Result<(), ParseError> {
         categories_subtotal: HashMap::<String, f64>::new(),
         total: 22.71,
         balance: 397.29,
+        total_owed: HashMap::<u32, f64>::new(),
         days_left: 69.9762219286658,
         days_left_essential: 84.08253968253969,
         last_day: NaiveDate::from_ymd(2020, 10, 04),
@@ -145,6 +146,15 @@ fn can_calculate() -> Result<(), ParseError> {
         5.0,
     );
 
+    should_be.total_owed.insert(
+        2,
+        1.7599999999999998,
+    );
+    should_be.total_owed.insert(
+        3,
+        2.22,
+    );
+
     let account = budget::parse_account("tests/test.toml")?;
     let actually_is = budget::calculate(&account).unwrap();
 
diff --git a/budget/tests/test.toml b/budget/tests/test.toml
index a29467e..ca2c1e5 100644
--- a/budget/tests/test.toml
+++ b/budget/tests/test.toml
@@ -19,13 +19,14 @@ date = 2020-10-01
   name = "Bacon"
   price = 3.33
   category = "products"
-  shared = 2
+  shared = 3
 
   [[days.expenses]]
   name = "Yoghurt"
   price = 1.24
   category = "products"
   qty = 2
+  shared = 2
 
   [[days.expenses]]
   name = "Onion"
diff --git a/src/main.rs b/src/main.rs
index 5c64959..cd401e2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -181,6 +181,20 @@ fn output(account: Account, maybe_calculated: Option<Calculated>) {
 
     println!();
 
+    for (n, owed) in calculated.total_owed.iter() {
+        println!(
+            "{} person(s) owe you in shared expenses: {:.2}",
+            n - 1,
+            owed,
+        );
+
+        if *n > 2 {
+            println!("Each owes you: {}", *owed / (*n as f64 - 1.0));
+        }
+
+        println!();
+    }
+
     println!("Days until balance runs out:");
 
     let days_left_output = format!(
@@ -192,6 +206,8 @@ fn output(account: Account, maybe_calculated: Option<Calculated>) {
         calculated.days_left_essential,
     );
 
+    // TODO: also show much money would be left by the end of the period
+
     let mut all_are_healthy = true;
     let mut essential_are_healthy = true;
 
-- 
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