feat: add terminal-scoped transaction analytics

internal/analytics/terminals.go

@@ -0,0 +1,54 @@
+package analytics
+
+import (
+	"context"
+	"errors"
+	"fmt"
+)
+
+var ErrUnknownTerminal = errors.New("analytics: unknown terminal")
+
+type Terminal struct {
+	TerminalID   string `json:"terminalId"`
+	DisplayName  string `json:"displayName"`
+	SessionCount int64  `json:"sessionCount"`
+	IsDefault    bool   `json:"isDefault"`
+}
+
+func (s *Service) Terminals(ctx context.Context, merchantID int64) ([]Terminal, error) {
+	rows, err := s.pool.Query(ctx, `SELECT t.source_key,count(ps.id) FROM terminals t
+		LEFT JOIN payment_sessions ps ON ps.terminal_id=t.id
+		WHERE t.merchant_id=$1 GROUP BY t.id ORDER BY count(ps.id) DESC,t.source_key`, merchantID)
+	if err != nil {
+		return nil, fmt.Errorf("querying merchant terminals: %w", err)
+	}
+	defer rows.Close()
+	terminals := make([]Terminal, 0, 8)
+	for rows.Next() {
+		var terminal Terminal
+		if err := rows.Scan(&terminal.TerminalID, &terminal.SessionCount); err != nil {
+			return nil, fmt.Errorf("scanning merchant terminal: %w", err)
+		}
+		terminal.DisplayName = terminalDisplayName(terminal.TerminalID)
+		terminal.IsDefault = len(terminals) == 0
+		terminals = append(terminals, terminal)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("iterating merchant terminals: %w", err)
+	}
+	return terminals, nil
+}
+
+func (s *Service) validateTerminal(ctx context.Context, merchantID int64, terminalID string) error {
+	if terminalID == "" {
+		return nil
+	}
+	var exists bool
+	if err := s.pool.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM terminals WHERE merchant_id=$1 AND source_key=$2)`, merchantID, terminalID).Scan(&exists); err != nil {
+		return fmt.Errorf("validating merchant terminal: %w", err)
+	}
+	if !exists {
+		return ErrUnknownTerminal
+	}
+	return nil
+}