autotrader discount

Author: Trolldemorted

src/SUMMARY.md

@@ -50,6 +50,7 @@
             - [Range](./ships/sea-battles/projectiles/range.md)
             - [Impact](./ships/sea-battles/projectiles/impact.md)
         - [Reefs](./ships/sea-battles/reefs.md)
+- [Auto Traders](./auto-traders.md)
 - [Letters](./letters.md)
     - [Charge](./letters/0a-charge.md)
     - [Indictment](./letters/19-indictment.md)

src/auto-traders.md

@@ -0,0 +1,18 @@
+# Auto Traders
+Both captains and administrators are represented by the same struct.
+The following fields have been identified:
+```c
+struct auto_trader
+{
+  unsigned __int16 field_0_next_auto_trader_index;
+  signed __int16 field_2;
+  int field_4_timestamp;
+  unsigned __int8 field_8;
+  unsigned __int8 field_9_navigation_skill;
+  unsigned __int8 field_A_trade_skill;
+  unsigned __int8 field_B_combat_skill;
+  __int16 field_C_daily_wage;
+  char field_E;
+  unsigned __int8 field_F_merchant_index;
+};
+```

src/towns/ware-prices/buying-price-autotrader-discount.png

@@ -0,0 +1,22 @@
+import logging
+from matplotlib import pyplot as plt
+
+
+def calculate_discount(xp: int):
+    return 100 - (2 * (50 - xp // 43))
+
+
+LOGGER = logging.getLogger()
+plt.clf()
+plt.title("Auto Trader Discount")
+plt.xlabel("Experience")
+plt.ylabel("Discount (Percent)")
+
+x_data = []
+y_data = []
+for i in range(0, 251):
+    x_data.append(i)
+    y_data.append(calculate_discount(i))
+
+plt.plot(x_data, y_data)
+plt.savefig("buying-price-autotrader-discount.png", dpi=200)

src/towns/ware-prices/buying-price-autotrader-discount.py

@@ -1,4 +1,4 @@
-# Buy Price
+# Buying Price
 The `get_buy_price` function at `0x0052E430` takes a ware, town, and buy amount and returns the transaction price.
 
 ## Formula
@@ -29,7 +29,7 @@ where \\(w\_i\\) is the amount being bought from \\(i\\) and \\(f\\) is defined
 
 where \\(w\_{relative\\_stock}\\) and \\(w\_{relative\\_remain}\\) are the stock's and remainder's offsets in the interval and \\(m\_i\\) and \\(v\_i\\) are defined as:
 
-|Bracket|\\(m\_i\\)|\\(v\_i\\)|
+|Interval|\\(m\_i\\)|\\(v\_i\\)|
 |-|-|-|
 |0|4|2.5|
 |1|1.5|0.5|
@@ -48,3 +48,16 @@ Let's assume we buy pig iron from a town with the following thresholds:
 
 If we buy one bundle (2000), the resulting prices at different stock levels would be:
 ![image](buying-price-pigiron.png)
+
+## Auto Trader Discount
+Auto traders (captains and administrators) get a discount depending on their trade skill.
+The discount is calculated as follows:
+```python
+100 - (2 * (50 - xp // 43))
+```
+![image](buying-price-autotrader-discount.png)
+
+The calculation can be observed at `0x004D5347` for captains and at `0x004FF7E8` for administrators.
+Since a new discount is unlocked every 43 experience, auto traders reach the maximum discount at 215 experience, way before they reach level 5 at 250 experience.
+
+The discount is applied after the transaction's amount has been determined.