Added support for trading.

8 files changed, 489 insertions, 74 deletions

diff --git a/src/game-server/character.cpp b/src/game-server/character.cpp
index 4ab26c96..1fb9b2fe 100644
--- a/src/game-server/character.cpp
+++ b/src/game-server/character.cpp
@@ -32,10 +32,9 @@
 
 Character::Character(MessageIn & msg):
     Being(OBJECT_CHARACTER, 65535),
-    mClient(NULL),
-    mAttributesChanged(true),
-    mDatabaseID(-1), mName(), mGender(0), mHairStyle(0), mHairColor(0),
-    mLevel(0), mMoney(0)
+    mClient(NULL), mTrading(NULL), mDatabaseID(-1),
+    mMoney(0), mGender(0), mHairStyle(0), mHairColor(0), mLevel(0),
+    mAttributesChanged(true)
 {
     // prepare attributes vector
     mAttributes.resize(NB_ATTRIBUTES_CHAR, 1);
diff --git a/src/game-server/character.hpp b/src/game-server/character.hpp
index 15c72a3d..efb93e1e 100644
--- a/src/game-server/character.hpp
+++ b/src/game-server/character.hpp
@@ -33,6 +33,7 @@ class GameClient;
 class MessageIn;
 class MessageOut;
 class Point;
+class Trade;
 
 /**
  * The representation of a player's character in the game world.
@@ -76,6 +77,17 @@ class Character : public Being
         Possessions &getPossessions()
         { return mPossessions; }
 
+        /**
+         * Gets the trade object the character is involved in.
+         */
+        Trade *getTrading() const
+        { return mTrading; }
+
+        /**
+         * Sets the trade object the character is involved in.
+         */
+        void setTrading(Trade *t)
+        { mTrading = t; }
 
         /*
          * Character data:
@@ -105,7 +117,7 @@ class Character : public Being
         /** Gets the gender of the character (male or female). */
         int
         getGender() const
-        { return mGender;}
+        { return mGender; }
 
         /** Sets the gender of the character (male or female). */
         void
@@ -200,25 +212,26 @@ class Character : public Being
         Character &operator=(Character const &);
 
         GameClient *mClient;   /**< Client computer. */
+        Trade *mTrading;       /**< Trade object the character is involved in. */
 
         /** Atributes as the client should currently know them. */
         std::vector<unsigned short> mOldAttributes;
 
-        /**
-         * true when one or more attributes might have changed since the
-         * client has been updated about them.
-         */
-        bool mAttributesChanged;
+        Possessions mPossessions;    /**< Possesssions of the character. */
 
-        int mDatabaseID;             /**< Character's database ID. */
         std::string mName;           /**< Name of the character. */
+        int mDatabaseID;             /**< Character's database ID. */
+        unsigned short mMoney;       /**< Wealth of the character. */
         unsigned char mGender;       /**< Gender of the character. */
         unsigned char mHairStyle;    /**< Hair Style of the character. */
         unsigned char mHairColor;    /**< Hair Color of the character. */
         unsigned char mLevel;        /**< Level of the character. */
-        unsigned int mMoney;         /**< Wealth of the being. */
 
-        Possessions mPossessions;    /**< Possesssions of the character. */
+        /**
+         * true when one or more attributes might have changed since the
+         * client has been updated about them.
+         */
+        bool mAttributesChanged;
 };
 
 #endif // _TMWSERV_CHARACTER_HPP_
diff --git a/src/game-server/gamehandler.cpp b/src/game-server/gamehandler.cpp
index 8010374b..34988edc 100644
--- a/src/game-server/gamehandler.cpp
+++ b/src/game-server/gamehandler.cpp
@@ -34,6 +34,7 @@
 #include "game-server/mapcomposite.hpp"
 #include "game-server/npc.hpp"
 #include "game-server/state.hpp"
+#include "game-server/trade.hpp"
 #include "net/messagein.hpp"
 #include "net/messageout.hpp"
 #include "net/netcomputer.hpp"
@@ -116,6 +117,34 @@ void GameHandler::process()
     ConnectionHandler::process();
 }
 
+static MovingObject *findBeingNear(Object *p, int id)
+{
+    MapComposite *map = p->getMap();
+    Point const &ppos = p->getPosition();
+    // TODO: use a less arbitrary value.
+    for (MovingObjectIterator i(map->getAroundPointIterator(ppos, 48)); i; ++i)
+    {
+        MovingObject *o = *i;
+        if (o->getPublicID() != id) continue;
+        return ppos.inRangeOf(o->getPosition(), 48) ? o : NULL;
+    }
+    return NULL;
+}
+
+static Character *findCharacterNear(Object *p, int id)
+{
+    MapComposite *map = p->getMap();
+    Point const &ppos = p->getPosition();
+    // TODO: use a less arbitrary value.
+    for (CharacterIterator i(map->getAroundPointIterator(ppos, 48)); i; ++i)
+    {
+        Character *o = *i;
+        if (o->getPublicID() != id) continue;
+        return ppos.inRangeOf(o->getPosition(), 48) ? o : NULL;
+    }
+    return NULL;
+}
+
 void GameHandler::processMessage(NetComputer *comp, MessageIn &message)
 {
     GameClient &computer = *static_cast< GameClient * >(comp);
@@ -148,18 +177,7 @@ void GameHandler::processMessage(NetComputer *comp, MessageIn &message)
         case PGMSG_NPC_SELECT:
         {
             int id = message.readShort();
-            MapComposite *map = computer.character->getMap();
-            MovingObject *o = NULL;
-            Point ppos = computer.character->getPosition();
-            // TODO: use a less arbitrary value.
-            for (MovingObjectIterator i(map->getAroundPointIterator(ppos, 48)); i; ++i)
-            {
-                if ((*i)->getPublicID() == id)
-                {
-                    o = *i;
-                    break;
-                }
-            }
+            MovingObject *o = findBeingNear(computer.character, id);
             if (!o || o->getType() != OBJECT_NPC) break;
 
             NPC *q = static_cast< NPC * >(o);
@@ -290,6 +308,48 @@ void GameHandler::processMessage(NetComputer *comp, MessageIn &message)
             computer.status = CLIENT_LOGIN;
         } break;
 
+        case PGMSG_TRADE_REQUEST:
+        {
+            int id = message.readShort();
+
+            if (Trade *t = computer.character->getTrading())
+            {
+                if (t->request(computer.character, id)) break;
+            }
+
+            Character *q = findCharacterNear(computer.character, id);
+            if (!q || q->getTrading())
+            {
+                result.writeShort(GPMSG_TRADE_CANCEL);
+                break;
+            }
+
+            new Trade(computer.character, q);
+        } break;
+
+        case PGMSG_TRADE_CANCEL:
+        case PGMSG_TRADE_ACCEPT:
+        case PGMSG_TRADE_ADD_ITEM:
+        {
+            Trade *t = computer.character->getTrading();
+            if (!t) break;
+
+            switch (message.getId())
+            {
+                case PGMSG_TRADE_CANCEL:
+                    t->cancel(computer.character);
+                    break;
+                case PGMSG_TRADE_ACCEPT :
+                    t->accept(computer.character);
+                    break;
+                case PGMSG_TRADE_ADD_ITEM:
+                    int slot = message.readByte();
+                    t->addItem(computer.character, slot, message.readByte());
+                    break;
+            }
+        } break;
+
+
 
 // The following messages should be handled by the chat server, not the game server.
 #if 0
diff --git a/src/game-server/inventory.cpp b/src/game-server/inventory.cpp
index 7cefd72b..2d3a66c6 100644
--- a/src/game-server/inventory.cpp
+++ b/src/game-server/inventory.cpp
@@ -31,15 +31,62 @@
 #include "game-server/itemmanager.hpp"
 #include "net/messageout.hpp"
 
-Inventory::Inventory(Character *p)
-  : poss(p->getPossessions()), msg(GPMSG_INVENTORY), client(p)
-{}
+Inventory::Inventory(Character *p, bool d):
+    mPoss(&p->getPossessions()), msg(GPMSG_INVENTORY), mClient(p), mDelayed(d)
+{
+}
 
 Inventory::~Inventory()
 {
     if (msg.getLength() > 2)
     {
-        gameHandler->sendTo(client, msg);
+        if (mDelayed)
+        {
+            Possessions &poss = mClient->getPossessions();
+            if (mPoss != &poss)
+            {
+                poss = *mPoss;
+                delete mPoss;
+            }
+        }
+        gameHandler->sendTo(mClient, msg);
+    }
+}
+
+void Inventory::cancel()
+{
+    msg.clear();
+    msg.writeShort(GPMSG_INVENTORY);
+    mPoss = &mClient->getPossessions();
+}
+
+void Inventory::commit()
+{
+    if (msg.getLength() > 2)
+    {
+        if (mDelayed)
+        {
+            Possessions &poss = mClient->getPossessions();
+            if (mPoss != &poss)
+            {
+                poss = *mPoss;
+                delete mPoss;
+                mPoss = &poss;
+            }
+        }
+        gameHandler->sendTo(mClient, msg);
+        msg.clear();
+        msg.writeShort(GPMSG_INVENTORY);
+    }
+}
+
+void Inventory::prepare()
+{
+    if (!mDelayed) return;
+    Possessions &poss = mClient->getPossessions();
+    if (mPoss == &poss)
+    {
+        mPoss = new Possessions(poss);
     }
 }
 
@@ -49,7 +96,7 @@ void Inventory::sendFull() const
 
     for (int i = 0; i < EQUIPMENT_SLOTS; ++i)
     {
-        if (int id = poss.equipment[i])
+        if (int id = mPoss->equipment[i])
         {
             m.writeByte(i);
             m.writeShort(id);
@@ -57,8 +104,8 @@ void Inventory::sendFull() const
     }
 
     int slot = EQUIP_CLIENT_INVENTORY;
-    for (std::vector< InventoryItem >::iterator i = poss.inventory.begin(),
-         i_end = poss.inventory.end(); i != i_end; ++i)
+    for (std::vector< InventoryItem >::const_iterator i = mPoss->inventory.begin(),
+         i_end = mPoss->inventory.end(); i != i_end; ++i)
     {
         if (i->itemId)
         {
@@ -73,13 +120,13 @@ void Inventory::sendFull() const
         }
     }
 
-    gameHandler->sendTo(client, m);
+    gameHandler->sendTo(mClient, m);
 }
 
 int Inventory::getItem(int slot) const
 {
-    for (std::vector< InventoryItem >::iterator i = poss.inventory.begin(),
-         i_end = poss.inventory.end(); i != i_end; ++i)
+    for (std::vector< InventoryItem >::const_iterator i = mPoss->inventory.begin(),
+         i_end = mPoss->inventory.end(); i != i_end; ++i)
     {
         if (slot == 0)
         {
@@ -99,8 +146,8 @@ int Inventory::getItem(int slot) const
 int Inventory::getIndex(int slot) const
 {
     int index = 0;
-    for (std::vector< InventoryItem >::iterator i = poss.inventory.begin(),
-         i_end = poss.inventory.end(); i != i_end; ++i, ++index)
+    for (std::vector< InventoryItem >::const_iterator i = mPoss->inventory.begin(),
+         i_end = mPoss->inventory.end(); i != i_end; ++i, ++index)
     {
         if (slot == 0)
         {
@@ -120,8 +167,8 @@ int Inventory::getIndex(int slot) const
 int Inventory::getSlot(int index) const
 {
     int slot = 0;
-    for (std::vector< InventoryItem >::iterator i = poss.inventory.begin(),
-         i_end = poss.inventory.begin() + index; i != i_end; ++i)
+    for (std::vector< InventoryItem >::const_iterator i = mPoss->inventory.begin(),
+         i_end = mPoss->inventory.begin() + index; i != i_end; ++i)
     {
         slot += i->itemId ? 1 : i->amount;
     }
@@ -131,9 +178,9 @@ int Inventory::getSlot(int index) const
 int Inventory::fillFreeSlot(int itemId, int amount, int maxPerSlot)
 {
     int slot = 0;
-    for (int i = 0, i_end = poss.inventory.size(); i < i_end; ++i)
+    for (int i = 0, i_end = mPoss->inventory.size(); i < i_end; ++i)
     {
-        InventoryItem &it = poss.inventory[i];
+        InventoryItem &it = mPoss->inventory[i];
         if (it.itemId == 0)
         {
             int nb = std::min(amount, maxPerSlot);
@@ -146,7 +193,7 @@ int Inventory::fillFreeSlot(int itemId, int amount, int maxPerSlot)
             {
                 --it.amount;
                 InventoryItem iu = { itemId, nb };
-                poss.inventory.insert(poss.inventory.begin() + i, iu);
+                mPoss->inventory.insert(mPoss->inventory.begin() + i, iu);
                 ++i_end;
             }
 
@@ -168,7 +215,7 @@ int Inventory::fillFreeSlot(int itemId, int amount, int maxPerSlot)
         int nb = std::min(amount, maxPerSlot);
         amount -= nb;
         InventoryItem it = { itemId, nb };
-        poss.inventory.push_back(it);
+        mPoss->inventory.push_back(it);
 
         msg.writeByte(slot + EQUIP_CLIENT_INVENTORY);
         msg.writeShort(itemId);
@@ -181,11 +228,13 @@ int Inventory::fillFreeSlot(int itemId, int amount, int maxPerSlot)
 
 int Inventory::insert(int itemId, int amount)
 {
+    prepare();
+
     int slot = 0;
     int maxPerSlot = ItemManager::getItem(itemId)->getMaxPerSlot();
 
-    for (std::vector< InventoryItem >::iterator i = poss.inventory.begin(),
-         i_end = poss.inventory.end(); i != i_end; ++i)
+    for (std::vector< InventoryItem >::iterator i = mPoss->inventory.begin(),
+         i_end = mPoss->inventory.end(); i != i_end; ++i)
     {
         if (i->itemId == itemId)
         {
@@ -216,8 +265,8 @@ int Inventory::count(int itemId) const
 {
     int nb = 0;
 
-    for (std::vector< InventoryItem >::iterator i = poss.inventory.begin(),
-         i_end = poss.inventory.end(); i != i_end; ++i)
+    for (std::vector< InventoryItem >::const_iterator i = mPoss->inventory.begin(),
+         i_end = mPoss->inventory.end(); i != i_end; ++i)
     {
         if (i->itemId == itemId)
         {
@@ -230,17 +279,17 @@ int Inventory::count(int itemId) const
 
 void Inventory::freeIndex(int i)
 {
-    InventoryItem &it = poss.inventory[i];
+    InventoryItem &it = mPoss->inventory[i];
 
-    if (i == (int)poss.inventory.size() - 1)
+    if (i == (int)mPoss->inventory.size() - 1)
     {
-        poss.inventory.pop_back();
+        mPoss->inventory.pop_back();
     }
-    else if (poss.inventory[i + 1].itemId == 0)
+    else if (mPoss->inventory[i + 1].itemId == 0)
     {
         it.itemId = 0;
-        it.amount = poss.inventory[i + 1].amount + 1;
-        poss.inventory.erase(poss.inventory.begin() + i + 1);
+        it.amount = mPoss->inventory[i + 1].amount + 1;
+        mPoss->inventory.erase(mPoss->inventory.begin() + i + 1);
     }
     else
     {
@@ -248,19 +297,21 @@ void Inventory::freeIndex(int i)
         it.amount = 1;
     }
 
-    if (i > 0 && poss.inventory[i - 1].itemId == 0)
+    if (i > 0 && mPoss->inventory[i - 1].itemId == 0)
     {
         // Note: "it" is no longer a valid iterator.
-        poss.inventory[i - 1].amount += poss.inventory[i].amount;
-        poss.inventory.erase(poss.inventory.begin() + i);
+        mPoss->inventory[i - 1].amount += mPoss->inventory[i].amount;
+        mPoss->inventory.erase(mPoss->inventory.begin() + i);
     }
 }
 
 int Inventory::remove(int itemId, int amount)
 {
-    for (int i = poss.inventory.size() - 1; i >= 0; --i)
+    prepare();
+
+    for (int i = mPoss->inventory.size() - 1; i >= 0; --i)
     {
-        InventoryItem &it = poss.inventory[i];
+        InventoryItem &it = mPoss->inventory[i];
         if (it.itemId == itemId)
         {
             int nb = std::min((int)it.amount, amount);
@@ -290,13 +341,14 @@ int Inventory::remove(int itemId, int amount)
 int Inventory::removeFromSlot(int slot, int amount)
 {
     int i = getIndex(slot);
-
     if (i < 0)
     {
         return amount;
     }
 
-    InventoryItem &it = poss.inventory[i];
+    prepare();
+
+    InventoryItem &it = mPoss->inventory[i];
     int nb = std::min((int)it.amount, amount);
     it.amount -= nb;
     amount -= nb;
@@ -322,6 +374,8 @@ bool Inventory::equip(int slot)
         return false;
     }
 
+    prepare();
+
     int availableSlots = 0, firstSlot = 0, secondSlot = 0;
 
     switch (ItemManager::getItem(itemId)->getType())
@@ -330,13 +384,13 @@ bool Inventory::equip(int slot)
         {
             // Special case 1, the two one-handed weapons are to be placed back
             // in the inventory, if there are any.
-            int id = poss.equipment[EQUIP_FIGHT1_SLOT];
+            int id = mPoss->equipment[EQUIP_FIGHT1_SLOT];
             if (id && !insert(id, 1))
             {
                 return false;
             }
 
-            id = poss.equipment[EQUIP_FIGHT2_SLOT];
+            id = mPoss->equipment[EQUIP_FIGHT2_SLOT];
             if (id && !insert(id, 1))
             {
                 return false;
@@ -346,8 +400,8 @@ bool Inventory::equip(int slot)
             msg.writeShort(itemId);
             msg.writeByte(EQUIP_FIGHT2_SLOT);
             msg.writeShort(0);
-            poss.equipment[EQUIP_FIGHT1_SLOT] = itemId;
-            poss.equipment[EQUIP_FIGHT2_SLOT] = 0;
+            mPoss->equipment[EQUIP_FIGHT1_SLOT] = itemId;
+            mPoss->equipment[EQUIP_FIGHT2_SLOT] = 0;
             removeFromSlot(slot, 1);
             return true;
         }
@@ -355,7 +409,7 @@ bool Inventory::equip(int slot)
         case ITEM_EQUIPMENT_PROJECTILE:
             msg.writeByte(EQUIP_PROJECTILE_SLOT);
             msg.writeShort(itemId);
-            poss.equipment[EQUIP_PROJECTILE_SLOT] = itemId;
+            mPoss->equipment[EQUIP_PROJECTILE_SLOT] = itemId;
             return true;
 
         case ITEM_EQUIPMENT_ONE_HAND_WEAPON:
@@ -400,19 +454,19 @@ bool Inventory::equip(int slot)
             return false;
     }
 
-    int id = poss.equipment[firstSlot];
+    int id = mPoss->equipment[firstSlot];
 
     switch (availableSlots)
     {
     case 2:
-        if (id && !poss.equipment[secondSlot] &&
+        if (id && !mPoss->equipment[secondSlot] &&
             ItemManager::getItem(id)->getType() !=
                 ITEM_EQUIPMENT_TWO_HANDS_WEAPON)
         {
             // The first slot is full and the second slot is empty.
             msg.writeByte(secondSlot);
             msg.writeShort(itemId);
-            poss.equipment[secondSlot] = itemId;
+            mPoss->equipment[secondSlot] = itemId;
             removeFromSlot(slot, 1);
             return true;
         }
@@ -425,7 +479,7 @@ bool Inventory::equip(int slot)
         }
         msg.writeByte(firstSlot);
         msg.writeShort(itemId);
-        poss.equipment[firstSlot] = itemId;
+        mPoss->equipment[firstSlot] = itemId;
         removeFromSlot(slot, 1);
         return true;
 
diff --git a/src/game-server/inventory.hpp b/src/game-server/inventory.hpp
index 1ae3cbb5..a05f166b 100644
--- a/src/game-server/inventory.hpp
+++ b/src/game-server/inventory.hpp
@@ -65,19 +65,31 @@ class GameClient;
  */
 class Inventory
 {
-        Possessions &poss;
-        MessageOut msg;
-        Character *client;
-
     public:
-        Inventory(Character *);
 
         /**
+         * Creates a view on the possessions of a character.
+         * @param delayed true if changes have to be cancelable.
+         */
+        Inventory(Character *, bool delayed = false);
+
+        /**
+         * Commits delayed changes.
          * Sends the update message to the client.
          */
         ~Inventory();
 
         /**
+         * Commits delayed changes.
+         */
+        void commit();
+
+        /**
+         * Cancels delayed changes.
+         */
+        void cancel();
+
+        /**
          * Sends a complete inventory update to the client.
          */
         void sendFull() const;
@@ -122,6 +134,12 @@ class Inventory
         int getItem(int slot) const;
 
     private:
+
+        /**
+         * Ensures we are working on a copy in delayed mode.
+         */
+        void prepare();
+
         /**
          * Fills some slots with items.
          * @return number of items not inserted.
@@ -142,6 +160,11 @@ class Inventory
          * Gets the slot number of an inventory index.
          */
         int getSlot(int index) const;
+
+        Possessions *mPoss; /**< Pointer to the modified possessions. */
+        MessageOut msg;     /**< Update message containing all the changes. */
+        Character *mClient; /**< Character to notify. */
+        bool mDelayed;      /**< Delayed changes. */
 };
 
 
diff --git a/src/game-server/state.cpp b/src/game-server/state.cpp
index fa51972c..19c3ea60 100644
--- a/src/game-server/state.cpp
+++ b/src/game-server/state.cpp
@@ -37,6 +37,7 @@
 #include "game-server/mapmanager.hpp"
 #include "game-server/monster.hpp"
 #include "game-server/npc.hpp"
+#include "game-server/trade.hpp"
 #include "net/messageout.hpp"
 #include "utils/logger.h"
 
@@ -499,6 +500,12 @@ void GameState::remove(Thing *ptr)
 
     if (ptr->canMove())
     {
+        if (ptr->getType() == OBJECT_CHARACTER)
+        {
+            Character *ch = static_cast< Character * >(ptr);
+            if (Trade *t = ch->getTrading()) t->cancel(ch);
+        }
+
         MovingObject *obj = static_cast< MovingObject * >(ptr);
         MessageOut msg(GPMSG_BEING_LEAVE);
         msg.writeShort(obj->getPublicID());
diff --git a/src/game-server/trade.cpp b/src/game-server/trade.cpp
new file mode 100644
index 00000000..c6cd8425
--- /dev/null
+++ b/src/game-server/trade.cpp
@@ -0,0 +1,169 @@
+/*
+ *  The Mana World Server
+ *  Copyright 2007 The Mana World Development Team
+ *
+ *  This file is part of The Mana World.
+ *
+ *  The Mana World is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  any later version.
+ *
+ *  The Mana World is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with The Mana World; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *  $Id$
+ */
+
+#include <algorithm>
+#include <cassert>
+
+#include "game-server/trade.hpp"
+
+#include "defines.h"
+#include "game-server/character.hpp"
+#include "game-server/gamehandler.hpp"
+#include "game-server/inventory.hpp"
+#include "net/messageout.hpp"
+
+Trade::Trade(Character *c1, Character *c2):
+    mChar1(c1), mChar2(c2), mState(TRADE_INIT)
+{
+    MessageOut msg(GPMSG_TRADE_REQUEST);
+    msg.writeShort(c1->getPublicID());
+    c2->getClient()->send(msg);
+    c1->setTrading(this);
+    c2->setTrading(this);
+}
+
+Trade::~Trade()
+{
+    mChar1->setTrading(NULL);
+    mChar2->setTrading(NULL);
+}
+
+void Trade::cancel(Character *c)
+{
+    MessageOut msg(GPMSG_TRADE_CANCEL);
+    if (c != mChar1) mChar1->getClient()->send(msg);
+    if (c != mChar2) mChar2->getClient()->send(msg);
+    delete this;
+}
+
+bool Trade::request(Character *c, int id)
+{
+    if (mState != TRADE_INIT || c != mChar2 || mChar1->getPublicID() != id)
+    {
+        /* This is not an ack for the current transaction. So assume
+           a new one is about to start and cancel the current one. */
+        cancel(c);
+        return false;
+    }
+
+    // Starts trading.
+    mState = TRADE_RUN;
+    MessageOut msg(GPMSG_TRADE_START);
+    mChar1->getClient()->send(msg);
+    mChar2->getClient()->send(msg);
+    return true;
+}
+
+static bool performTrade(TradedItems items, Inventory &inv1, Inventory &inv2)
+{
+    for (TradedItems::const_iterator i = items.begin(),
+         i_end = items.end(); i != i_end; ++i)
+    {
+        if (i->id != inv1.getItem(i->slot) ||
+            inv1.removeFromSlot(i->slot, i->amount) != 0 ||
+            inv2.insert(i->id, i->amount) != 0)
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+void Trade::accept(Character *c)
+{
+    if (mState == TRADE_RUN)
+    {
+        if (c == mChar2)
+        {
+            std::swap(mChar1, mChar2);
+            std::swap(mItems1, mItems2);
+        }
+        assert(c == mChar1);
+        // First player agrees.
+        mState = TRADE_EXIT;
+        MessageOut msg(GPMSG_TRADE_ACCEPT);
+        mChar2->getClient()->send(msg);
+        return;
+    }
+
+    if (mState != TRADE_EXIT || c != mChar2)
+    {
+        // First player has already agreed. We only care about the second one.
+        return;
+    }
+
+    Inventory v1(mChar1, true), v2(mChar2, true);
+    if (!performTrade(mItems1, v1, v2) || !performTrade(mItems2, v2, v1))
+    {
+        v1.cancel();
+        v2.cancel();
+        cancel(NULL);
+        return;
+    }
+
+    MessageOut msg(GPMSG_TRADE_COMPLETE);
+    mChar1->getClient()->send(msg);
+    mChar2->getClient()->send(msg);
+    delete this;
+}
+
+void Trade::addItem(Character *c, int slot, int amount)
+{
+    if (mState == TRADE_INIT) return;
+
+    Character *other;
+    TradedItems *items;
+    if (c == mChar1)
+    {
+        other = mChar2;
+        items = &mItems1;
+    }
+    else
+    {
+        assert(c == mChar2);
+        other = mChar1;
+        items = &mItems2;
+    }
+
+    // Arbitrary limit to prevent a client from DOSing the server.
+    if (items->size() >= 50) return;
+
+    Inventory inv(c, true);
+    int id = inv.getItem(slot);
+    if (id == 0) return;
+
+    /* Checking now if there is enough items is useless as it can change
+       later on. At worst, the transaction will be cancelled at the end if
+       the client lied. */
+
+    TradedItem ti = { id, slot, amount };
+    items->push_back(ti);
+
+    MessageOut msg(GPMSG_TRADE_ADD_ITEM);
+    msg.writeShort(id);
+    msg.writeByte(amount);
+    other->getClient()->send(msg);
+
+    // Go back to normal run.
+    mState = TRADE_RUN;
+}
diff --git a/src/game-server/trade.hpp b/src/game-server/trade.hpp
new file mode 100644
index 00000000..ec5239d0
--- /dev/null
+++ b/src/game-server/trade.hpp
@@ -0,0 +1,90 @@
+/*
+ *  The Mana World Server
+ *  Copyright 2007 The Mana World Development Team
+ *
+ *  This file is part of The Mana World.
+ *
+ *  The Mana World is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  any later version.
+ *
+ *  The Mana World is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with The Mana World; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *  $Id$
+ */
+
+#ifndef _TMSERV_GAMESERVER_TRADE_HPP_
+#define _TMSERV_GAMESERVER_TRADE_HPP_
+
+#include <vector>
+
+class Character;
+
+enum TradeState
+{
+    TRADE_INIT = 0, /**< Waiting for an ack from player 2. */
+    TRADE_RUN,      /**< Currently trading. */
+    TRADE_EXIT      /**< Waiting for an ack from player 2. */
+};
+
+struct TradedItem
+{
+    unsigned short id;
+    unsigned char slot, amount;
+};
+
+typedef std::vector< TradedItem > TradedItems;
+
+class Trade
+{
+    public:
+
+        /**
+         * Sets up a trade between two characters.
+         * Asks for an acknowledgment from the second one.
+         */
+        Trade(Character *, Character *);
+
+        ~Trade();
+
+        /**
+         * Cancels a trade by a given character (optional).
+         * Warns the other character the trade is cancelled.
+         * Takes care of cleaning afterwards.
+         */
+        void cancel(Character *);
+
+        /**
+         * Requests a trade to start with given public ID.
+         * Continues the current trade if the ID is correct, cancels it
+         * otherwise.
+         * @return true if the current trade keeps going.
+         */
+        bool request(Character *, int);
+
+        /**
+         * Agrees to complete the trade.
+         */
+        void accept(Character *);
+
+        /**
+         * Adds some items to the trade.
+         */
+        void addItem(Character *, int slot, int amount);
+
+    private:
+
+        Character *mChar1, *mChar2; /**< Characters involved. */
+        TradedItems mItems1, mItems2; /**< Traded items. */
+        TradeState mState;
+};
+
+#endif