first commit of restructured project

trahn-trade-backend/internal/risk/guardian.go

@@ -0,0 +1,69 @@
+package risk
+
+import (
+	"context"
+	"fmt"
+)
+
+// DailyTradeCounter abstracts the trade-counting dependency so Guardian
+// can be tested without a real database.
+type DailyTradeCounter interface {
+	CountToday(ctx context.Context) (int, error)
+}
+
+// Limits holds the four risk thresholds from config.
+// A zero value for any field means that check is disabled.
+type Limits struct {
+	MaxDailyTrades     int
+	MaxPositionSizeUSD float64
+	StopLossPercent    float64
+	TakeProfitPercent  float64
+}
+
+type Guardian struct {
+	limits  Limits
+	counter DailyTradeCounter
+}
+
+func NewGuardian(limits Limits, counter DailyTradeCounter) *Guardian {
+	return &Guardian{limits: limits, counter: counter}
+}
+
+// PreTradeCheck validates per-trade constraints before execution.
+// Returns nil if the trade is allowed, a descriptive error if blocked.
+func (g *Guardian) PreTradeCheck(ctx context.Context, tradeUSDValue float64) error {
+	if g.limits.MaxPositionSizeUSD > 0 && tradeUSDValue > g.limits.MaxPositionSizeUSD {
+		return fmt.Errorf("trade blocked: position size $%.2f exceeds max $%.2f",
+			tradeUSDValue, g.limits.MaxPositionSizeUSD)
+	}
+
+	if g.limits.MaxDailyTrades > 0 && g.counter != nil {
+		count, err := g.counter.CountToday(ctx)
+		if err != nil {
+			return fmt.Errorf("trade blocked: unable to verify daily trade count: %w", err)
+		}
+		if count >= g.limits.MaxDailyTrades {
+			return fmt.Errorf("trade blocked: daily limit of %d trades reached (%d executed today)",
+				g.limits.MaxDailyTrades, count)
+		}
+	}
+
+	return nil
+}
+
+// PortfolioCheck evaluates portfolio-level circuit breakers.
+// pnlPercent is the unrealized P&L as a percentage (e.g. -8.5 means down 8.5%).
+// Returns nil if trading should continue, a descriptive error if a breaker tripped.
+func (g *Guardian) PortfolioCheck(pnlPercent float64) error {
+	if g.limits.StopLossPercent > 0 && pnlPercent <= -g.limits.StopLossPercent {
+		return fmt.Errorf("STOP-LOSS triggered: portfolio down %.2f%% (threshold: -%.2f%%)",
+			pnlPercent, g.limits.StopLossPercent)
+	}
+
+	if g.limits.TakeProfitPercent > 0 && pnlPercent >= g.limits.TakeProfitPercent {
+		return fmt.Errorf("TAKE-PROFIT triggered: portfolio up %.2f%% (threshold: +%.2f%%)",
+			pnlPercent, g.limits.TakeProfitPercent)
+	}
+
+	return nil
+}