From 75cdbebf08abda460b2172e85b54efc63d107dba Mon Sep 17 00:00:00 2001
From: Mike Bryant <mike@mikebryant.me.uk>
Date: Tue, 31 Mar 2020 18:49:20 +0100
Subject: [PATCH] Fix calculation bug where we weren't lenient enough and
 predicted slightly too high minimum prices

---
 js/scripts.js | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/js/scripts.js b/js/scripts.js
index 2976321..555b6e7 100644
--- a/js/scripts.js
+++ b/js/scripts.js
@@ -1,3 +1,11 @@
+function minimum_rate_from_given_and_base(given_price, buy_price) {
+  return (given_price - 0.5) / buy_price;
+}
+
+function maximum_rate_from_given_and_base(given_price, buy_price) {
+  return (given_price + 0.5) / buy_price;
+}
+
 function* generate_pattern_0_with_lengths(given_prices, high_phase_1_len, dec_phase_1_len, high_phase_2_len, dec_phase_2_len, high_phase_3_len) {
     /*
       // PATTERN 0: high, decreasing, high, decreasing, high
@@ -87,8 +95,8 @@ function* generate_pattern_0_with_lengths(given_prices, high_phase_1_len, dec_ph
       }
       min_pred = given_prices[i];
       max_pred = given_prices[i];
-      min_rate = given_prices[i] / buy_price;
-      max_rate = given_prices[i] / buy_price;
+      min_rate = minimum_rate_from_given_and_base(given_prices[i], buy_price);
+      max_rate = maximum_rate_from_given_and_base(given_prices[i], buy_price);
     }
 
     predicted_prices.push({
@@ -134,8 +142,8 @@ function* generate_pattern_0_with_lengths(given_prices, high_phase_1_len, dec_ph
       }
       min_pred = given_prices[i];
       max_pred = given_prices[i];
-      min_rate = given_prices[i] / buy_price;
-      max_rate = given_prices[i] / buy_price;
+      min_rate = minimum_rate_from_given_and_base(given_prices[i], buy_price);
+      max_rate = maximum_rate_from_given_and_base(given_prices[i], buy_price);
     }
 
     predicted_prices.push({
@@ -238,8 +246,8 @@ function* generate_pattern_1_with_peak(given_prices, peak_start) {
       }
       min_pred = given_prices[i];
       max_pred = given_prices[i];
-      min_rate = given_prices[i] / buy_price;
-      max_rate = given_prices[i] / buy_price;
+      min_rate = minimum_rate_from_given_and_base(given_prices[i], buy_price);
+      max_rate = maximum_rate_from_given_and_base(given_prices[i], buy_price);
     }
 
     predicted_prices.push({
@@ -322,8 +330,8 @@ function* generate_pattern_2(given_prices) {
       }
       min_pred = given_prices[i];
       max_pred = given_prices[i];
-      min_rate = given_prices[i] / buy_price;
-      max_rate = given_prices[i] / buy_price;
+      min_rate = minimum_rate_from_given_and_base(given_prices[i], buy_price);
+      max_rate = maximum_rate_from_given_and_base(given_prices[i], buy_price);
     }
 
     predicted_prices.push({
@@ -399,8 +407,8 @@ function* generate_pattern_3_with_peak(given_prices, peak_start) {
       }
       min_pred = given_prices[i];
       max_pred = given_prices[i];
-      min_rate = given_prices[i] / buy_price;
-      max_rate = given_prices[i] / buy_price;
+      min_rate = minimum_rate_from_given_and_base(given_prices[i], buy_price);
+      max_rate = maximum_rate_from_given_and_base(given_prices[i], buy_price);
     }
 
     predicted_prices.push({
@@ -467,8 +475,8 @@ function* generate_pattern_3_with_peak(given_prices, peak_start) {
         }
         min_pred = given_prices[i];
         max_pred = given_prices[i];
-        min_rate = given_prices[i] / buy_price;
-        max_rate = given_prices[i] / buy_price;
+        min_rate = minimum_rate_from_given_and_base(given_prices[i], buy_price);
+        max_rate = maximum_rate_from_given_and_base(given_prices[i], buy_price);
       }
 
       predicted_prices.push({