1 files changed, 29 insertions, 20 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 6d95ff4..1637be7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,7 +5,7 @@ use std::ops::AddAssign;
 use serde::Deserialize;
 use serde::Serialize;
 
-#[derive(Clone, Copy, Serialize)]
+#[derive(Clone, Copy, Serialize, Default)]
 pub struct Capital {
     principal: f64,
     interest: f64,
@@ -30,7 +30,8 @@ pub struct Simulation {
     st: SimState,
     updates: SimUpdates,
     history: Vec<Quota>,
-    topay: Capital,
+    payed_noupdates: Capital,
+    payed_noprepays: Capital,
     payed: Capital,
     payed_amortized: f64,
 }
@@ -53,14 +54,12 @@ impl Simulation {
 
         Simulation {
             st,
-            topay: Capital {
+            payed_noupdates: Capital {
                 principal,
                 interest: topay_total - principal,
             },
-            payed: Capital {
-                principal: 0.,
-                interest: 0.,
-            },
+            payed_noprepays: Capital::default(),
+            payed: Capital::default(),
             payed_amortized: 0.,
             history: vec![],
             updates: SimUpdates::default(),
@@ -70,25 +69,35 @@ impl Simulation {
     pub fn run(&mut self, updates: SimUpdates) {
         self.updates = updates;
         let mut st = self.st.clone();
+        // Fist simulation: no prepayments
+        while st.pending_quotas > 0 && st.principal > 0. {
+            let quota = st.step();
+            self.payed_noprepays += quota.payed;
+            self.apply_updates(&mut st, false);
+        }
+        // Second simulation, the good one
+        let mut st = self.st.clone();
         while st.pending_quotas > 0 && st.principal > 0. {
             let quota = st.step();
             self.payed += quota.payed;
             self.history.push(quota);
-            self.apply_updates(&mut st);
+            self.apply_updates(&mut st, true);
         }
     }
 
-    fn apply_updates(&mut self, st: &mut SimState) {
+    fn apply_updates(&mut self, st: &mut SimState, apply_prepays: bool) {
         for update in self.updates.get(st.period) {
             match update {
                 SimUpdate::Amortize(mut principal) => {
-                    if principal > st.principal {
-                        principal = st.principal;
-                    };
-                    st.principal -= principal;
-                    st.calculate_monthly();
-                    self.payed.principal += principal;
-                    self.payed_amortized += principal;
+                    if apply_prepays {
+                        if principal > st.principal {
+                            principal = st.principal;
+                        };
+                        st.principal -= principal;
+                        st.calculate_monthly();
+                        self.payed.principal += principal;
+                        self.payed_amortized += principal;
+                    }
                 }
                 SimUpdate::SetI1(i1) => {
                     st.i12 = i1 / 12.0;
@@ -123,13 +132,13 @@ impl Simulation {
         println!("\n\n# A PRIORI\n");
         println!(
             "== Total a pagar: {:.2} ({:.2} cap + {:.2} int)",
-            self.topay.total(),
-            self.topay.principal,
-            self.topay.interest
+            self.payed_noupdates.total(),
+            self.payed_noupdates.principal,
+            self.payed_noupdates.interest
         );
         println!(
             "== Los intereses suponen un {:.2}% del total",
-            100. * self.topay.interest / self.topay.total()
+            100. * self.payed_noupdates.interest / self.payed_noupdates.total()
         );
 
         println!("\n\n# RESULTADO FINAL\n");