implement mob combat

include/globals.h

@@ -93,6 +93,9 @@ typedef struct {
   short x;
   uint8_t y;
   short z;
+  // Lower 5 bits: health
+  // Upper 3 bits: reserved (?)
+  uint8_t data;
 } MobData;
 
 #pragma pack(pop)

include/packets.h

@@ -1,6 +1,7 @@
 #ifndef H_PACKETS
 #define H_PACKETS
 
+// Serverbound packets
 int cs_handshake (int client_fd);
 int cs_loginStart (int client_fd, uint8_t *uuid, char *name);
 int cs_clientInformation (int client_fd);
@@ -17,6 +18,7 @@ int cs_closeContainer (int client_fd);
 int cs_clientStatus (int client_fd);
 int cs_chat(int client_fd);
 
+// Clientbound packets
 int sc_loginSuccess (int client_fd, uint8_t *uuid, char *name);
 int sc_knownPacks (int client_fd);
 int sc_finishConfiguration (int client_fd);
@@ -44,6 +46,9 @@ int sc_damageEvent (int client_fd, int id, int type);
 int sc_setHealth (int client_fd, uint8_t health, uint8_t food);
 int sc_respawn (int client_fd);
 int sc_systemChat (int client_fd, char* message, uint16_t len);
+int cs_interact (int client_fd);
+int sc_entityEvent (int client_fd, int entity_id, uint8_t status);
+int sc_removeEntity (int client_fd, int entity_id);
 int sc_registries (int client_fd);
 
 #endif

include/procedures.h

@@ -31,7 +31,8 @@ uint16_t getMiningResult (uint16_t held_item, uint8_t block);
 void bumpToolDurability (PlayerData *player);
 void handlePlayerAction (PlayerData *player, int action, short x, short y, short z);
 
-void spawnMob (uint8_t type, short x, uint8_t y, short z);
+void spawnMob (uint8_t type, short x, uint8_t y, short z, uint8_t health);
+void hurtEntity (int entity_id, int attacker_id, uint8_t damage_type, uint8_t damage);
 void handleServerTick (int64_t time_since_last_tick);
 
 #endif

src/main.c

@@ -158,14 +158,20 @@ void handlePacket (int client_fd, int length, int packet_id) {
       }
       break;
 
-    case 0x1B: {
+    case 0x1B:
       if (state == STATE_PLAY) {
         // Serverbound keep-alive (ignored)
         recv_all(client_fd, recv_buffer, 8, false);
         return;
       }
       break;
-    }
+
+    case 0x19:
+      if (state == STATE_PLAY) {
+        if (cs_interact(client_fd)) break;
+        return;
+      }
+      break;
 
     case 0x1D:
     case 0x1E:
@@ -190,10 +196,7 @@ void handlePacket (int client_fd, int length, int packet_id) {
         if (on_ground) {
           int8_t damage = player->grounded_y - player->y - 3;
           if (damage > 0 && getBlockAt(player->x, player->y, player->z) != B_water) {
-            if (damage >= player->health) player->health = 0;
+            hurtEntity(client_fd, -1, D_fall, damage);
-            else player->health -= damage;
-            sc_damageEvent(client_fd, client_fd, D_fall);
-            sc_setHealth(client_fd, player->health, player->hunger);
           }
           player->grounded_y = player->y;
         }
@@ -295,14 +298,14 @@ void handlePacket (int client_fd, int length, int packet_id) {
             getBlockAt(mob_x, mob_y + 1, mob_z) == B_air
           ) {
             // Spawn passive mobs during the day, hostiles during the night
-            if (world_time < 12000) {
+            if (world_time < 13000) {
               uint32_t mob_choice = (r >> 12) & 3;
-              if (mob_choice == 0) spawnMob(25, mob_x, mob_y, mob_z); // Chicken
+              if (mob_choice == 0) spawnMob(25, mob_x, mob_y, mob_z, 20); // Chicken
-              else if (mob_choice == 1) spawnMob(28, mob_x, mob_y, mob_z); // Cow
+              else if (mob_choice == 1) spawnMob(28, mob_x, mob_y, mob_z, 20); // Cow
-              else if (mob_choice == 2) spawnMob(95, mob_x, mob_y, mob_z); // Pig
+              else if (mob_choice == 2) spawnMob(95, mob_x, mob_y, mob_z, 20); // Pig
-              else if (mob_choice == 3) spawnMob(106, mob_x, mob_y, mob_z); // Sheep
+              else if (mob_choice == 3) spawnMob(106, mob_x, mob_y, mob_z, 20); // Sheep
             } else {
-              spawnMob(145, mob_x, mob_y, mob_z); // Zombie
+              spawnMob(145, mob_x, mob_y, mob_z, 20); // Zombie
             }
           }
         }

src/packets.c

@@ -973,6 +973,52 @@ int cs_chat (int client_fd) {
   return 0;
 }
 
+// C->S Interact
+int cs_interact (int client_fd) {
+
+  int entity_id = readVarInt(client_fd);
+  uint8_t type = readByte(client_fd);
+
+  if (type == 2) {
+    // Ignore target coordinates
+    recv_all(client_fd, recv_buffer, 12, false);
+  }
+  if (type != 1) {
+    // Ignore hand
+    recv_all(client_fd, recv_buffer, 1, false);
+  }
+
+  // Ignore sneaking flag
+  recv_all(client_fd, recv_buffer, 1, false);
+
+  hurtEntity(entity_id, client_fd, D_generic, 1);
+
+  return 0;
+}
+
+// S->C Entity Event
+int sc_entityEvent (int client_fd, int entity_id, uint8_t status) {
+
+  writeVarInt(client_fd, 6);
+  writeByte(client_fd, 0x1E);
+
+  writeUint32(client_fd, entity_id);
+  writeByte(client_fd, status);
+
+  return 0;
+}
+
+// S->C Remove Entities, but for only one entity per packet
+int sc_removeEntity (int client_fd, int entity_id) {
+
+  writeVarInt(client_fd, 2 + sizeVarInt(entity_id));
+  writeByte(client_fd, 0x46);
+
+  writeByte(client_fd, 1);
+  writeVarInt(client_fd, entity_id);
+
+}
+
 // S->C Registry Data (multiple packets) and Update Tags (configuration, multiple packets)
 int sc_registries (int client_fd) {
 

src/procedures.c

@@ -485,7 +485,7 @@ void handlePlayerAction (PlayerData *player, int action, short x, short y, short
 
 }
 
-void spawnMob (uint8_t type, short x, uint8_t y, short z) {
+void spawnMob (uint8_t type, short x, uint8_t y, short z, uint8_t health) {
 
   for (int i = 0; i < MAX_MOBS; i ++) {
     // Look for type 0 (unallocated)
@@ -496,6 +496,7 @@ void spawnMob (uint8_t type, short x, uint8_t y, short z) {
     mob_data[i].x = x;
     mob_data[i].y = y;
     mob_data[i].z = z;
+    mob_data[i].data = health & 31;
 
     // Broadcast entity creation to all players
     for (int j = 0; j < MAX_PLAYERS; j ++) {
@@ -515,6 +516,56 @@ void spawnMob (uint8_t type, short x, uint8_t y, short z) {
 
 }
 
+void hurtEntity (int entity_id, int attacker_id, uint8_t damage_type, uint8_t damage) {
+
+  // Retrieve player data if applicable
+  PlayerData *player;
+  if (attacker_id < 65536 && attacker_id != -1) {
+    if (getPlayerData(attacker_id, &player)) return;
+  } else if (entity_id < 65536) {
+    if (getPlayerData(entity_id, &player)) return;
+  }
+
+  if (attacker_id < 65536 && attacker_id != -1) { // Attacker is a player
+    // Scale damage based on held item
+    uint16_t held_item = player->inventory_items[player->hotbar];
+    if (held_item == I_wooden_sword) damage *= 4;
+    else if (held_item == I_golden_sword) damage *= 4;
+    else if (held_item == I_stone_sword) damage *= 5;
+    else if (held_item == I_iron_sword) damage *= 6;
+    else if (held_item == I_diamond_sword) damage *= 7;
+    else if (held_item == I_netherite_sword) damage *= 8;
+  }
+
+  // Whether this attack caused the target entity to die
+  uint8_t entity_died = false;
+
+  if (entity_id < 65536) { // The attacked entity is a player
+    if (player->health <= damage) {
+      player->health = 0;
+      entity_died = true;
+    } else player->health -= damage;
+    // Update health on the client
+    sc_setHealth(player->client_fd, player->health, player->hunger);
+  } else { // The attacked entity is a mob
+    MobData *mob = &mob_data[entity_id - 65536];
+    uint8_t mob_health = mob->data & 31;
+    if (mob_health <= damage) {
+      mob->data -= mob_health;
+      entity_died = true;
+    } else mob->data -= damage;
+  }
+
+  // Broadcast damage event to all players
+  for (int i = 0; i < MAX_PLAYERS; i ++) {
+    int client_fd = player_data[i].client_fd;
+    if (client_fd == -1) continue;
+    sc_damageEvent(client_fd, entity_id, damage_type);
+    if (entity_died) sc_entityEvent(client_fd, entity_id, 3);
+  }
+
+}
+
 // Simulates events scheduled for regular intervals
 // Takes the time since the last tick in microseconds as the only arguemnt
 void handleServerTick (int64_t time_since_last_tick) {
@@ -540,6 +591,19 @@ void handleServerTick (int64_t time_since_last_tick) {
   for (int i = 0; i < MAX_MOBS; i ++) {
     if (mob_data[i].type == 0) continue;
 
+    // Mob has died, deallocate it
+    if ((mob_data[i].data & 31) == 0) {
+      mob_data[i].type = 0;
+      for (int j = 0; j < MAX_PLAYERS; j ++) {
+        if (player_data[j].client_fd == -1) continue;
+        // Spawn death smoke particles
+        sc_entityEvent(player_data[j].client_fd, 65536 + i, 60);
+        // Remove the entity from the client
+        sc_removeEntity(player_data[j].client_fd, 65536 + i);
+      }
+      continue;
+    }
+
     uint8_t passive = (
       mob_data[i].type == 25 || // Chicken
       mob_data[i].type == 28 || // Cow
@@ -554,7 +618,7 @@ void handleServerTick (int64_t time_since_last_tick) {
 
     // Find the player closest to this mob
     PlayerData* closest_player;
-    uint32_t closest_dist = 65535;
+    uint32_t closest_dist = 65536;
     for (int j = 0; j < MAX_PLAYERS; j ++) {
       if (player_data[j].client_fd == -1) continue;
       uint16_t curr_dist = (
@@ -594,10 +658,7 @@ void handleServerTick (int64_t time_since_last_tick) {
 
       // If we're already next to the player, hurt them and skip movement
       if (closest_dist < 3) {
-        if (closest_player->health < 6) closest_player->health = 0;
+        hurtEntity(closest_player->client_fd, 65536 + i, D_generic, 6);
-        else closest_player->health -= 6;
-        sc_damageEvent(closest_player->client_fd, closest_player->client_fd, D_generic);
-        sc_setHealth(closest_player->client_fd, closest_player->health, closest_player->hunger);
         continue;
       }