From 8907130570df1a67d30a0266c2ba17c27975d713 Mon Sep 17 00:00:00 2001
From: Guillermo Ramos
Date: Tue, 4 Feb 2025 00:09:04 +0100
Subject: Mortgage updates

---
 src/lib.rs  | 100 ++++++++++++++++++++++++++++++++++++++++++++----------------
 src/main.rs |  12 ++++++--
 2 files changed, 84 insertions(+), 28 deletions(-)

(limited to 'src')

diff --git a/src/lib.rs b/src/lib.rs
index fc75ebd..7f8a58a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,9 +1,10 @@
+use std::collections::HashMap;
 use std::fmt;
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Mortgage {
     period: u32,
-    capital: f64,
+    principal: f64,
     i12: f64,
     quota: f64,
     quotas: u32,
@@ -13,65 +14,112 @@ impl fmt::Display for Mortgage {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(
             f,
-            "{:5} | {:4.2}\t{:.2}\t{:.2}\t{:.2}",
+            "{:3} | {:5} | {:4.2}\t{:.2}\t{:.2}\t{:.2}",
+            if self.period % 12 == 0 {
+                format!("Y{}", (self.period / 12) + 1)
+            } else {
+                "".to_string()
+            },
             self.period,
             self.quota,
-            self.interests(),
-            self.amortized(),
-            self.capital
+            self.quota_interest(),
+            self.quota_principal(),
+            self.principal
         )
     }
 }
 
 impl Mortgage {
-    pub fn new(capital: f64, i1: f64, years: u32) -> Self {
+    pub fn new(principal: f64, i1: f64, years: u32) -> Self {
         let quotas = years * 12;
         let i12 = i1 / 12.0;
         Mortgage {
             period: 0,
-            capital,
+            principal,
             i12,
-            quota: Self::quota(capital, i12, quotas),
+            quota: Self::quota(principal, i12, quotas),
             quotas,
         }
     }
 
-    pub fn run(&mut self) {
-        let to_pay = self.quota * self.quotas as f64;
-        let capital = self.capital;
-        let interest = to_pay - capital;
+    pub fn run(&mut self, updates: HashMap<u32, MortgageUpdate>) {
+        let principal = self.principal;
 
-        println!("Cuota | c\tIn\tAn\tCn");
-        while self.quotas > 0 {
+        let topay_total = self.quota * self.quotas as f64;
+        let topay_interest = topay_total - principal;
+
+        let mut payed_total = 0.;
+        let mut payed_principal = 0.;
+        let mut payed_interest = 0.;
+        let mut payed_amortized = 0.;
+
+        println!("Año | Cuota | c\t\tIn\tAn\tCn");
+        while self.quotas > 0 && self.principal > 0. {
             println!("{self}");
+            if let Some(update) = updates.get(&self.period) {
+                payed_amortized += self.update(update);
+            }
+            payed_total += self.quota;
+            payed_principal += self.quota_principal();
+            payed_interest += self.quota_interest();
             self.step();
         }
+
+        payed_total += payed_amortized;
+
+        println!("\n# A PRIORI");
+        println!(
+            "== Total a pagar: {:.2} ({} cap + {topay_interest:.2} int)",
+            topay_total, principal
+        );
+        println!(
+            "== Los intereses suponen un {:.2}% del total",
+            100. * topay_interest / topay_total
+        );
+
+        println!("\n# A POSTERIORI");
         println!(
-            "\n== Total a pagar: {:.2} ({} cap + {interest:.2} int)",
-            to_pay, capital
+            "== Total pagado: {:.2} ({:.2} cap + {:.2} int + {:.2} amortizado)",
+            payed_total, payed_principal, payed_interest, payed_amortized
         );
         println!(
-            "== Los intereses suponen un {:.2}% del capital",
-            100. * interest / capital
+            "== Los intereses suponen un {:.2}% del total",
+            100. * payed_interest / payed_total
         );
         println!("\n");
     }
 
-    fn quota(capital: f64, i12: f64, quotas: u32) -> f64 {
-        capital * i12 / (1.0 - (1.0 + i12).powi(-(quotas as i32)))
+    fn update(&mut self, update: &MortgageUpdate) -> f64 {
+        print!("  [MORTGAGE UPDATE: ");
+        match update {
+            MortgageUpdate::Amortize(principal) => {
+                println!("{principal:.2} amortized to reduce quotas]");
+                self.principal -= principal;
+                self.quota = Self::quota(self.principal, self.i12, self.quotas);
+                *principal
+            }
+        }
+    }
+
+    fn quota(principal: f64, i12: f64, quotas: u32) -> f64 {
+        principal * i12 / (1.0 - (1.0 + i12).powi(-(quotas as i32)))
     }
 
     fn step(&mut self) {
         self.period += 1;
         self.quotas -= 1;
-        self.capital = (1.0 + self.i12) * self.capital - self.quota;
+        self.principal = (1.0 + self.i12) * self.principal - self.quota;
     }
 
-    fn interests(&self) -> f64 {
-        self.i12 * self.capital
+    fn quota_interest(&self) -> f64 {
+        self.i12 * self.principal
     }
 
-    fn amortized(&self) -> f64 {
-        self.quota - self.interests()
+    fn quota_principal(&self) -> f64 {
+        self.quota - self.quota_interest()
     }
 }
+
+pub enum MortgageUpdate {
+    Amortize(f64),
+}
diff --git a/src/main.rs b/src/main.rs
index 76c7913..bbe01af 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,12 @@
+use hiccup::Mortgage;
+use hiccup::MortgageUpdate::{self, *};
+use std::collections::HashMap;
+
 fn main() {
-    let mut m = hiccup::Mortgage::new(390_000., 0.028, 30);
-    m.run();
+    let mut updates: HashMap<u32, MortgageUpdate> =
+        HashMap::from_iter((1..29).map(|y| (y * 12, Amortize(24_000.))));
+    updates.insert(0, Amortize(15_000.));
+    let m = Mortgage::new(390_000., 0.028, 30);
+    m.clone().run(updates);
+    // m.clone().run(HashMap::new());
 }
-- 
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