Quick Start

// Example: Blacksmith merchant
Config:
  bHasStock = true
  bBuysAnything = false
  bHasBuyList = true
  bReplenishOnBuyback = false          // Doesn't resell bought items
  MarketFeePercent = 10.0              // 10% transaction fee
  BuybackPercent = 30.0                // Buys at 30% value
  AcceptedCurrency = GoldCoinAsset
  MaxInteractionDistance = 500.0

StockItems:
  [0] Iron Sword
      MaxStock = 5
      CurrentStock = 5
      UnitPriceOverride = 150.0        // Custom price (overrides item default)
      ReplenishMode = NeverReplenish   // Don't resell

  [1] Steel Armor
      MaxStock = 3
      CurrentStock = 3
      UnitPriceOverride = -1.0         // Use item's base price
      ReplenishMode = NeverReplenish

  [2] Health Potion
      MaxStock = 20
      CurrentStock = 20
      UnitPriceOverride = -1.0
      ReplenishMode = UseVendorDefault

BuyList:
  - Ore_Iron
  - Ore_Steel
  - Weapon_Damaged (for repairs)

// On player interaction
FMerchantSnapshot Snapshot = MerchantComponent->OpenVendor(PlayerController);

// Display UI with:
// - Snapshot.Config (merchant settings)
// - Snapshot.StockItems (items for sale)
// - Snapshot.BuyList (items merchant buys)

// Step 1: Get quote
FPurchaseQuote Quote = MerchantComponent->QuotePurchase(PlayerController, ItemData, Quantity);

if (Quote.bSuccess)
{
    // Display to player:
    // - Quote.UnitPrice
    // - Quote.Subtotal
    // - Quote.Fee
    // - Quote.Total

    // Step 2: Confirm purchase
    MerchantComponent->Server_ConfirmPurchase(
        PlayerController,
        ItemData,
        Quantity,
        Quote.Total,      // For validation
        Quote.QuoteNonce  // For idempotency
    );
}
else
{
    // Handle error: Quote.ErrorCode
    switch (Quote.ErrorCode)
    {
        case ERR_NO_STOCK:
            DisplayMessage("Out of stock!");
            break;
        case ERR_INSUFFICIENT_FUNDS:
            DisplayMessage("Not enough gold!");
            break;
        case ERR_INVENTORY_FULL:
            DisplayMessage("Inventory full!");
            break;
    }
}

// Step 1: Get quote
FSellQuote Quote = MerchantComponent->QuoteSell(PlayerController, ItemData, Quantity);

if (Quote.bSuccess)
{
    // Display offer to player:
    // - Quote.UnitBuyPrice
    // - Quote.Total (what player receives)

    // Step 2: Confirm sale
    MerchantComponent->Server_ConfirmSell(
        PlayerController,
        ItemData,
        Quantity,
        Quote.Total,
        Quote.QuoteNonce
    );
}
else
{
    // Handle error
    switch (Quote.ErrorCode)
    {
        case ERR_NOT_BUYING:
            DisplayMessage("Merchant doesn't buy items.");
            break;
        case ERR_NOT_IN_BUYLIST:
            DisplayMessage("Merchant doesn't want this item.");
            break;
    }
}