Fixes prices calculation

src/RaidGeld.sol

@@ -107,9 +107,6 @@ contract RaidGeld is ERC20, Ownable {
     function addUnit(uint8 unit, uint16 n_units) external onlyPlayer {
         require(unit <= 3, "Unknown unit");
 
-        // First trigger a raid so player receives what he is due at to this moment
-        performRaid(msg.sender);
-
         Army storage army = armies[msg.sender];
         uint16 currentLevel = 0;
         if (unit == 0) {
@@ -128,6 +125,13 @@ contract RaidGeld is ERC20, Ownable {
 
         uint256 cost = RaidGeldUtils.calculateUnitPrice(unit, currentLevel, n_units) * 10 ** decimals();
         require(balanceOf(msg.sender) > cost, "Not enough GELD to add this much");
+        
+        // TODO: Since we are first minting then burning the token, this could be simplified
+        // by first calculating the difference and then minting / burning in just one operation
+
+        // First trigger a raid so player receives what he is due at to this moment
+        performRaid(msg.sender);
+        // then burn the cost of the new army 
         _burn(msg.sender, cost);
 
         // Increase level

src/RaidGeldUtils.sol

@@ -6,14 +6,14 @@ import {Army} from "../src/RaidGeld.sol";
 library RaidGeldUtils {
     function calculateUnitPrice(uint8 unit, uint16 currentLevel, uint16 units) internal pure returns (uint256) {
         require(unit <= 3, "No matching unit found");
-        uint256 rollingPriceCalculation = uint256(unit) * 38;
-        uint256 price = 0;
+        uint256 rollingPriceCalculation = uint256(unit + 1) * 38;
+        uint256 price = rollingPriceCalculation;
 
         // Each level costs 15% more than previous
         uint256 PERCENT_INCREASE = 115;
         for (uint256 i = 1; i < currentLevel + units; i++) {
             rollingPriceCalculation = rollingPriceCalculation * PERCENT_INCREASE / 100;
-            if (i > currentLevel) {
+            if (i >= currentLevel) {
                 price += rollingPriceCalculation;
             }
         }

test/RaidGeld.t.sol

@@ -3,6 +3,7 @@ pragma solidity ^0.8.13;
 
 import {Test, console} from "forge-std/Test.sol";
 import {RaidGeld, Army, Player} from "../src/RaidGeld.sol";
+import  "../src/RaidGeldUtils.sol";
 
 contract raid_geldTest is Test {
     RaidGeld public raid_geld;
@@ -113,23 +114,26 @@ contract raid_geldTest is Test {
         vm.expectRevert();
         raid_geld.addUnit(1, 100);
 
-        // Add 2 units
         Army memory army = raid_geld.getArmy(player1);
         uint256 unit_level = army.moloch_denier.level;
         uint256 balance = raid_geld.balanceOf(player1);
         uint256 income_per_sec = army.profit_per_second;
-        raid_geld.addUnit(0, 2);
         
-        // TODO: maybe try to test against exact values we want here
+        // Add 1 unit
+        raid_geld.addUnit(0, 1);
+        uint256 unitPrice = RaidGeldUtils.calculateUnitPrice(0, 0, 1) * 10 ** 4;
 
         // Check that those tokens were burnt
+        // WARN: In addUnit will mint additional tokens but they are not calculated
+        // into this because the test doesnt move the blockchain so no extra tokens 
+        // are minted to the user
         uint256 newBalance = raid_geld.balanceOf(player1);
-        assertGt(newBalance, balance - 2 * 10 ** 4);
+        assertEq(newBalance, balance - unitPrice);
         army = raid_geld.getArmy(player1);
 
         // Check that unit level increased
         uint256 new_unit_level = army.moloch_denier.level;
-        assertEq(new_unit_level, unit_level + 2);
+        assertEq(new_unit_level, unit_level + 1);
 
         // Check that user income per second increased
         uint256 new_income_per_sec = army.profit_per_second;
@@ -143,7 +147,9 @@ contract raid_geldTest is Test {
         // Register player 1
         vm.startPrank(player1);
         registerPlayer();
-        raid_geld.addUnit(1, 2);
+
+        // bought 1 moloch_denier
+        raid_geld.addUnit(0, 1);
 
         uint256 balance = raid_geld.balanceOf(player1);
 

test/RaidGeldUtils.t.sol

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.13;
+
+import {Test, console} from "forge-std/Test.sol";
+import {Army, Raider} from "../src/RaidGeld.sol";
+import  "../src/RaidGeldUtils.sol";
+
+contract raid_geldTest is Test {
+    function test_0_unit_price() public {
+        // buying 1 unit of moloch_denier
+        uint256 basePriceMolochDenier = RaidGeldUtils.calculateUnitPrice(0, 0, 1);
+        assertEq(basePriceMolochDenier, 38);
+   
+        // buying 3 units
+        // has to be a bit more than 3 * 38 = 114
+        uint256 price = RaidGeldUtils.calculateUnitPrice(0, 0, 3);
+        assertGt(price, 3 * basePriceMolochDenier);
+
+        uint256 basePriceChamp = RaidGeldUtils.calculateUnitPrice(0, 0, 3);
+        // buying 3 units of champions
+        // has to be a bit more than 4 * 38 * 3 = 114
+        price = RaidGeldUtils.calculateUnitPrice(3, 0, 3);
+        assertGt(price, 3 * basePriceChamp);
+
+        // buying 12 units of champions when u already have 10
+        price = RaidGeldUtils.calculateUnitPrice(3, 10, 12);
+        // price should scale up
+        assertGt(price, basePriceChamp * 12);
+    }
+
+    function test_1_profits_per_second() public {
+        Army memory army = Army({
+            moloch_denier: Raider({ level: 1}),
+            apprentice: Raider({ level: 0}),
+            anointed: Raider({ level: 0}),
+            champion: Raider({ level: 0}),
+            profit_per_second: 0 // irrelevant for this test
+        });
+        uint256 profits_per_second = RaidGeldUtils.calculateProfitsPerSecond(army);
+        assertEq(profits_per_second, 1);
+
+        army = Army({
+            moloch_denier: Raider({ level: 2}),
+            apprentice: Raider({ level: 0}),
+            anointed: Raider({ level: 10}),
+            champion: Raider({ level: 1}),
+            profit_per_second: 0 // irrelevant for this test
+        });
+        profits_per_second = RaidGeldUtils.calculateProfitsPerSecond(army);
+        assertEq(profits_per_second, 640);
+    }
+}