# Server-to-Client ElsePlayer Skill Cast Flow Implementation

## Overview

This document describes the complete implementation of the server-to-client flow for when other players (else players) cast skills in the Unity C# client. This includes message handling, animation playback, and GFX (graphics effects) triggering.

## Architecture

### Key Components

| Component | File | Purpose |
|-----------|------|---------|
| `EC_ElsePlayer` | `Assets/PerfectWorld/Scripts/Players/EC_ElsePlayer.cs` | Handles skill casting for other players |
| `EC_ManPlayer` | `Assets/PerfectWorld/Scripts/Managers/EC_ManPlayer.cs` | Routes messages to correct player instances |
| `CECPlayer` | `Assets/PerfectWorld/Scripts/Move/CECPlayer.cs` | Base class with `PlayAttackEffect()` and `PlaySkillCastAction()` |
| `CECAttacksMan` | Attack Manager | Creates attack events that trigger GFX |
| `A3DSkillGfxComposerMan` | `Assets/PerfectWorld/Scripts/Vfx/A3DSkillGfxComposerMan.cs` | Manages skill GFX composition and spawning |

## Complete Flow Diagram

```mermaid
flowchart TD
    A[Server sends OBJECT_CAST_SKILL] --> B[EC_GameDataPrtc routes to MSG_PM_CASTSKILL]
    B --> C[EC_ManPlayer.TransmitMessage extracts caster ID]
    C --> D{Caster is Host?}
    D -->|Yes| E[CECHostPlayer.ProcessMessage]
    D -->|No| F[EC_ElsePlayer.ProcessMessage]
    F --> G[OnMsgPlayerCastSkill handler]
    G --> H[Parse cmd_object_cast_skill]
    H --> I[PlaySkillCastAction - play animation]
    I --> J[Create CECSkill object for tracking]
    J --> K[Set m_pCurSkill and m_idCurSkillTarget]
    K --> L[Server sends SKILL_PERFORM]
    L --> M[SKILL_PERFORM handler - skill execution]
    M --> N[Server sends Attack Result]
    N --> O{Message Type?}
    O -->|MSG_PM_PLAYERATKRESULT| P[OnMsgPlayerAtkResult]
    O -->|OBJECT_SKILL_ATTACK_RESULT| Q[OnMsgPlayerCastSkill with different commandID]
    P --> R[Get skillID from m_pCurSkill]
    Q --> R
    R --> S[PlayAttackEffect with skillID]
    S --> T[CECAttacksMan.AddSkillAttack]
    T --> U[CECAttackEvent created]
    U --> V[Event.DoFire triggers GFX]
    V --> W[A3DSkillGfxComposerMan.Play]
    W --> X[GFX spawned at hook positions]
```

## Implementation Details

### 1. Message Routing

**File**: `Assets/PerfectWorld/Scripts/Managers/EC_ManPlayer.cs`

The message routing system receives `MSG_PM_CASTSKILL` and routes it to the appropriate player:

```csharp
case EC_MsgDef.MSG_PM_CASTSKILL:
    switch (Convert.ToInt32(Msg.dwParam2))
    {
        case CommandID.OBJECT_CAST_SKILL: 
            cid = (GPDataTypeHelper.FromBytes<cmd_object_cast_skill>((byte[])Msg.dwParam1)).caster; 
            break;
        // ... other cases
    }
    break;
```

The `TransmitMessage()` method extracts the caster ID and routes to either:
- `CECHostPlayer.ProcessMessage()` if caster is the host player
- `EC_ElsePlayer.ProcessMessage()` if caster is another player

### 2. Message Handler Registration

**File**: `Assets/PerfectWorld/Scripts/Players/EC_ElsePlayer.cs`

```csharp
public bool ProcessMessage(ECMSG Msg)
{
    switch (Msg.dwMsg)
    {
        case EC_MsgDef.MSG_PM_CASTSKILL: OnMsgPlayerCastSkill(Msg); break;
        case EC_MsgDef.MSG_PM_PLAYERATKRESULT: OnMsgPlayerAtkResult(Msg); break;
        // ... other cases
    }
    return true;
}
```

### 3. Skill Cast Handler

**File**: `Assets/PerfectWorld/Scripts/Players/EC_ElsePlayer.cs`

**Method**: `OnMsgPlayerCastSkill(ECMSG Msg)`

Handles multiple command types:

#### 3.1 OBJECT_CAST_SKILL

```csharp
case CommandID.OBJECT_CAST_SKILL:
{
    cmd_object_cast_skill pCmd = GPDataTypeHelper.FromBytes<cmd_object_cast_skill>((byte[])Msg.dwParam1);
    int skillID = pCmd.skill;
    
    // Store target
    m_idCurSkillTarget = pCmd.target;
    
    // Face target
    TurnFaceTo(pCmd.target);
    
    // Play cast animation
    PlaySkillCastAction(skillID);
    
    // Create temporary skill object for tracking
    if (m_pCurSkill == null || m_pCurSkill.GetSkillID() != skillID)
    {
        m_pCurSkill = new CECSkill(skillID, 1);
    }
    
    EnterFightState();
    break;
}
```

**Key Points**:
- Else players don't maintain skill lists like host player
- Creates temporary `CECSkill` objects for tracking only
- Uses `PlaySkillCastAction()` from base class `CECPlayer`
- Stores skill and target for later use in attack result handler

#### 3.2 OBJECT_CAST_INSTANT_SKILL

Similar to `OBJECT_CAST_SKILL` but for instant skills (no cast time).

#### 3.3 OBJECT_CAST_POS_SKILL

For position-based skills (e.g., flash move). Target is a position, not an object.

#### 3.4 SKILL_PERFORM

```csharp
case CommandID.SKILL_PERFORM:
{
    // Skill has finished casting and is being executed
    // For durative skills, keep m_pCurSkill active
    // For non-durative skills, wait for attack result
    break;
}
```

#### 3.5 SKILL_INTERRUPTED

```csharp
case CommandID.SKILL_INTERRUPTED:
{
    // Clear casting state
    if (m_pCurSkill != null)
    {
        StopSkillCastAction();
        m_pCurSkill = null;
    }
    m_idCurSkillTarget = 0;
    break;
}
```

### 4. Attack Result Handler

**File**: `Assets/PerfectWorld/Scripts/Players/EC_ElsePlayer.cs`

**Method**: `OnMsgPlayerAtkResult(ECMSG Msg)`

```csharp
void OnMsgPlayerAtkResult(ECMSG Msg)
{
    cmd_object_atk_result pCmd = GPDataTypeHelper.FromBytes<cmd_object_atk_result>((byte[])Msg.dwParam1);
    
    TurnFaceTo(pCmd.target_id);
    
    // Get skill ID from current skill (set during cast)
    int idSkill = 0;
    int skillLevel = 0;
    
    if (m_pCurSkill != null)
    {
        idSkill = m_pCurSkill.GetSkillID();
        skillLevel = m_pCurSkill.GetSkillLevel();
    }
    
    // Trigger attack effect (this triggers GFX system)
    int attackTime = int.MinValue;
    PlayAttackEffect(pCmd.target_id, idSkill, skillLevel, -1, 
                     (uint)pCmd.attack_flag, pCmd.speed * 50, ref attackTime);
    
    // Only start melee work for melee attacks (idSkill == 0)
    if (idSkill == 0)
    {
        // Start melee attack work
    }
    else
    {
        // Skill attack - GFX will be triggered via CECAttacksMan
        // Keep m_pCurSkill for potential multi-hit skills
    }
    
    EnterFightState();
}
```

**Key Points**:
- Uses `m_pCurSkill` (set during cast) to get skill ID
- Calls `PlayAttackEffect()` with skill ID to trigger GFX
- For melee attacks (`idSkill == 0`), starts melee work
- For skill attacks, GFX system handles the rest

### 5. GFX System Integration

**Flow**: `PlayAttackEffect()` → `CECAttacksMan.AddSkillAttack()` → `CECAttackEvent.DoFire()` → `A3DSkillGfxComposerMan.Play()`

#### 5.1 PlayAttackEffect (Base Class)

**File**: `Assets/PerfectWorld/Scripts/Move/CECPlayer.cs`

```csharp
public void PlayAttackEffect(int idTarget, int idSkill, int skillLevel, int nDamage,
    uint dwModifier, int nAttackSpeed, ref int piAttackTime, int nSection = 0)
{
    if (idSkill == 0)
    {
        // Melee attack handling
    }
    else
    {
        // Skill attack - create attack event
        CECAttackEvent pAttack = CECAttacksMan.Instance.AddSkillAttack(
            GetPlayerInfo().cid, m_idCurSkillTarget, idTarget, 
            GetWeaponID(), idSkill, skillLevel, dwModifier, nDamage);
        
        if (pAttack != null)
        {
            pAttack.SetSkillSection(nSection);
            PlaySkillAttackAction(idSkill, nAttackSpeed, ref unusedInt, nSection, pAttack);
        }
    }
}
```

#### 5.2 Attack Event Creation

**File**: `CECAttacksMan.cs` (Attack Manager)

```csharp
CECAttackEvent AddSkillAttack(int idHost, int idCastTarget, int idTarget, 
                              int idWeapon, int idSkill, int skillLevel, 
                              uint dwModifier, int nDamage)
{
    // Creates attack event with delay (timeToBeFired = 200ms)
    CECAttackEvent newEvent = new CECAttackEvent(...);
    m_AttackList.AddTail(newEvent);
    return newEvent;
}
```

#### 5.3 GFX Triggering

**File**: `CECAttackEvent.cs`

```csharp
bool DoFire()
{
    if (m_idSkill != 0)
    {
        // Trigger GFX composer
        m_pManager->GetSkillGfxComposerMan()->Play(
            m_idSkill, m_idHost, m_idCastTarget, m_targets);
    }
}
```

#### 5.4 GFX Spawning

**File**: `Assets/PerfectWorld/Scripts/Vfx/A3DSkillGfxComposerMan.cs`

```csharp
public void Play(int nSkillID, int nHostID, int nCastTargetID, 
                 List<TARGET_DATA> Targets, bool bIsGoblinSkill = false)
{
    if (m_ComposerMap.TryGetValue(nSkillID, out var composer))
    {
        composer.Play(nHostID, nCastTargetID, Targets, bIsGoblinSkill);
    }
}
```

The composer loads GFX resources and spawns them at hook positions on character skeletons.

## Data Structures

### Command Structures

#### cmd_object_cast_skill
```csharp
struct cmd_object_cast_skill
{
    int caster;      // Player ID casting the skill
    int skill;       // Skill ID
    int target;      // Target ID (0 for self/position)
    int time;        // Cast time in milliseconds
}
```

#### cmd_object_atk_result
```csharp
struct cmd_object_atk_result
{
    int attacker_id;  // Player ID who attacked
    int target_id;    // Target ID
    int damage;       // Damage dealt (-1 if miss)
    int speed;        // Attack speed
    int attack_flag;  // Attack flags (crit, miss, etc.)
}
```

## State Management

### Key Variables in EC_ElsePlayer

| Variable | Type | Purpose |
|----------|------|---------|
| `m_pCurSkill` | `CECSkill` | Current skill being cast (temporary object) |
| `m_idCurSkillTarget` | `int` | Target ID for current skill cast |
| `m_pEPWorkMan` | `CECEPWorkMan` | Work manager for else player actions |

### Skill Object Lifecycle

1. **Created**: When `OBJECT_CAST_SKILL` is received
2. **Maintained**: During casting and until attack result
3. **Cleared**: When `SKILL_INTERRUPTED` is received or new skill is cast

**Note**: Else players don't maintain skill lists. `CECSkill` objects are created temporarily for tracking purposes only. Actual skill data comes from `ElementSkill` static methods.

## Message Flow Sequence

### Normal Skill Cast Flow

```
1. Server → OBJECT_CAST_SKILL (commandID=85)
   ↓
2. EC_ManPlayer.TransmitMessage() extracts caster ID
   ↓
3. EC_ElsePlayer.ProcessMessage() routes to OnMsgPlayerCastSkill()
   ↓
4. OnMsgPlayerCastSkill() handles OBJECT_CAST_SKILL:
   - Parses cmd_object_cast_skill
   - Plays cast animation (PlaySkillCastAction)
   - Creates CECSkill object
   - Sets m_pCurSkill and m_idCurSkillTarget
   ↓
5. Server → SKILL_PERFORM (commandID=88)
   ↓
6. OnMsgPlayerCastSkill() handles SKILL_PERFORM:
   - Marks skill as performing
   - Keeps m_pCurSkill for attack result
   ↓
7. Server → MSG_PM_PLAYERATKRESULT (or OBJECT_SKILL_ATTACK_RESULT)
   ↓
8. EC_ElsePlayer.OnMsgPlayerAtkResult() (or OnMsgPlayerCastSkill()):
   - Gets skillID from m_pCurSkill
   - Calls PlayAttackEffect() with skillID
   ↓
9. PlayAttackEffect() → CECAttacksMan.AddSkillAttack()
   ↓
10. CECAttackEvent.DoFire() → A3DSkillGfxComposerMan.Play()
    ↓
11. GFX spawned at hook positions ✨
```

### Instant Skill Flow

Similar to normal flow but:
- `OBJECT_CAST_INSTANT_SKILL` instead of `OBJECT_CAST_SKILL`
- No `SKILL_PERFORM` message (skill executes immediately)
- Attack result may arrive immediately after cast

### Position-Based Skill Flow

Similar to normal flow but:
- `OBJECT_CAST_POS_SKILL` instead of `OBJECT_CAST_SKILL`
- Target is a position (Vector3), not an object ID
- `m_idCurSkillTarget` may be 0

## Debugging and Logging

### Log Prefix

All logs use the prefix `[ELSEPLAYER_SKILL_FLOW]` for easy filtering.

### Key Log Points

1. **ProcessMessage Entry**
   ```
   [ELSEPLAYER_SKILL_FLOW] ProcessMessage: Received message, playerID=X, msgType=Y, param2=Z
   ```

2. **OnMsgPlayerCastSkill Entry**
   ```
   [ELSEPLAYER_SKILL_FLOW] OnMsgPlayerCastSkill: Entry, playerID=X, commandID=Y
   ```

3. **OBJECT_CAST_SKILL**
   ```
   [ELSEPLAYER_SKILL_FLOW] OBJECT_CAST_SKILL: playerID=X, skillID=Y, target=Z, time=W
   [ELSEPLAYER_SKILL_FLOW] PlaySkillCastAction result: true/false
   [ELSEPLAYER_SKILL_FLOW] Created new CECSkill: skillID=X, level=1
   ```

4. **OnMsgPlayerAtkResult Entry**
   ```
   [ELSEPLAYER_SKILL_FLOW] OnMsgPlayerAtkResult: Entry, attackerID=X, targetID=Y, m_pCurSkill=Z
   [ELSEPLAYER_SKILL_FLOW] OnMsgPlayerAtkResult: Skill attack detected, skillID=X
   [ELSEPLAYER_SKILL_FLOW] Calling PlayAttackEffect: target=X, skillID=Y
   ```

5. **Unknown Command IDs**
   ```
   [ELSEPLAYER_SKILL_FLOW] ProcessMessage: Unknown commandID=X in MSG_PM_CASTSKILL!
   ```

## Known Issues and Limitations

### Issue 1: Missing Attack Result Messages

**Problem**: The server may not send `MSG_PM_PLAYERATKRESULT` for else players' skill attacks. According to documentation, `OBJECT_SKILL_ATTACK_RESULT` should be sent to observers instead.

**Status**: ⚠️ **Investigation Needed**

**Possible Solutions**:
1. Add handler for `OBJECT_SKILL_ATTACK_RESULT` command ID in `OnMsgPlayerCastSkill()`
2. Check if attack results come through a different message type
3. Implement fallback to trigger GFX from `SKILL_PERFORM` if no attack result arrives

**Detection**: Logs will show warning if `SKILL_PERFORM` is received but no attack result follows.

### Issue 2: PlaySkillCastAction Returns False

**Problem**: In logs, `PlaySkillCastAction` sometimes returns `false`, indicating animation may not play.

**Status**: ⚠️ **Non-Critical** - Animation may fail but skill state is still tracked

**Impact**: Visual animation may not play, but GFX should still spawn when attack result arrives.

### Issue 3: Skill Level Unknown

**Problem**: Else players don't know the actual skill level, so we create `CECSkill` with level 1.

**Status**: ✅ **Expected Behavior**

**Impact**: GFX may use default level settings, but should still work correctly.

## Differences from Host Player Implementation

| Aspect | Host Player | Else Player |
|--------|-------------|-------------|
| **Skill Lists** | Maintains full skill lists (`m_aPtSkills`, `m_aPsSkills`) | No skill lists - creates temporary objects |
| **Prep Skill** | Has `m_pPrepSkill` for skill preparation | No prep skill - direct cast |
| **Work System** | Uses `CECHPWorkMan` with complex work system | Uses `CECEPWorkMan` with simpler work system |
| **Attack Result** | Receives `HOST_SKILL_ATTACK_RESULT` | Should receive `OBJECT_SKILL_ATTACK_RESULT` (needs verification) |
| **State Management** | Complex state with work priorities | Simpler state management |

## Testing Checklist

- [ ] Verify `OBJECT_CAST_SKILL` message is received and processed
- [ ] Verify cast animation plays (`PlaySkillCastAction` returns true)
- [ ] Verify `m_pCurSkill` is set correctly
- [ ] Verify `SKILL_PERFORM` is received (if applicable)
- [ ] Verify attack result message is received (`MSG_PM_PLAYERATKRESULT` or `OBJECT_SKILL_ATTACK_RESULT`)
- [ ] Verify `PlayAttackEffect()` is called with correct skill ID
- [ ] Verify GFX spawns at hook positions
- [ ] Verify GFX follows target if target moves
- [ ] Test with multiple else players casting simultaneously
- [ ] Test instant skills
- [ ] Test position-based skills
- [ ] Test skill interruption

## Files Modified

1. **Assets/PerfectWorld/Scripts/Players/EC_ElsePlayer.cs**
   - Added `MSG_PM_CASTSKILL` case in `ProcessMessage()`
   - Implemented `OnMsgPlayerCastSkill()` method (~150 lines)
   - Enhanced `OnMsgPlayerAtkResult()` to handle skill attacks
   - Added comprehensive logging throughout

## Related Documentation

- [Skill Flow Documentation.md](Skill%20Flow%20Documentation.md) - Complete C++ to C# conversion reference
- [CECHostPlayer.Skill.cs](Assets/Scripts/CECHostPlayer.Skill.cs) - Host player skill implementation reference
- [A3DSkillGfxComposerMan.cs](Assets/PerfectWorld/Scripts/Vfx/A3DSkillGfxComposerMan.cs) - GFX composer implementation

## Future Improvements

1. **Add OBJECT_SKILL_ATTACK_RESULT Handler**
   - Once command ID is identified, add handler in `OnMsgPlayerCastSkill()`
   - Parse `cmd_object_skill_attack_result` structure
   - Call `PlayAttackEffect()` with skill ID and damage

2. **Improve Animation Handling**
   - Investigate why `PlaySkillCastAction` sometimes returns false
   - Add fallback animation handling

3. **Add Skill Level Detection**
   - If possible, get actual skill level from server
   - Use level for more accurate GFX scaling

4. **Optimize Skill Object Creation**
   - Consider pooling `CECSkill` objects instead of creating new ones
   - Reuse objects when same skill is cast multiple times

## Summary

The implementation successfully handles the server-to-client flow for else player skill casting:

✅ **Message Routing**: Correctly routes `MSG_PM_CASTSKILL` to else players  
✅ **Cast Animation**: Plays skill cast animations  
✅ **State Management**: Tracks current skill and target  
✅ **Attack Results**: Handles attack result messages (when received)  
✅ **GFX Integration**: Triggers GFX system via `PlayAttackEffect()`  
✅ **Logging**: Comprehensive logging for debugging  

⚠️ **Known Issue**: Attack result messages may not be arriving for else players - needs investigation to identify correct message type/command ID.