fix(Core): Implement retail-like fishing skill-up functionality (#4809)

src/server/game/Entities/Player/Player.cpp

@@ -6383,6 +6383,24 @@ bool Player::UpdateGatherSkill(uint32 SkillId, uint32 SkillValue, uint32 RedLeve
     return false;
 }
 
+float getProbabilityOfLevelUp(uint32 SkillValue)
+{
+    /* According to El's Extreme Angling page, from 1 to 115 the probability of a skill
+     * level up is 100% since 100/1 = 100. From 115 - 135 should average 2 catches per
+     * skill up so that means 100/2 = 50%.
+     * This returns the probability depending on the player's SkillValue.
+     */
+    if (!SkillValue)
+    {
+        return 0.0f;
+    }
+
+    std::array bounds{ 115, 135, 160, 190, 215, 295, 315, 355, 425, 450 };
+    std::array<float, 11> dens{ 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 9.0f, 10.0f, 11.0f, 12.0f, 1.0f };
+    auto it = std::lower_bound(std::begin(bounds), std::end(bounds), SkillValue);
+    return 100 / dens[std::distance(std::begin(bounds), it)];
+}
+
 bool Player::UpdateFishingSkill()
 {
 #if defined(ENABLE_EXTRAS) && defined(ENABLE_EXTRA_LOGS)
@@ -6391,11 +6409,15 @@ bool Player::UpdateFishingSkill()
 
     uint32 SkillValue = GetPureSkillValue(SKILL_FISHING);
 
-    int32 chance = SkillValue < 75 ? 100 : 2500 / (SkillValue - 50);
+    if (SkillValue >= GetMaxSkillValue(SKILL_FISHING))
+    {
+        return false;
+    }
 
-    uint32 gathering_skill_gain = sWorld->getIntConfig(CONFIG_SKILL_GAIN_GATHERING);
-
-    return UpdateSkillPro(SKILL_FISHING, chance * 10, gathering_skill_gain);
+    /* Whenever the player clicks on the fishing gameobject the
+     * core will decide based on a probability if the skill raises or not.
+     */
+    return UpdateSkillPro(SKILL_FISHING, static_cast<int32>(getProbabilityOfLevelUp(SkillValue)) * 10, sWorld->getIntConfig(CONFIG_SKILL_GAIN_GATHERING));
 }
 
 // levels sync. with spell requirement for skill levels to learn