feat(add solutions reference for challenge 01-concurrent-aggregator)

01-context-cancellation-concurrency/01-concurrent-aggregator/aggregator.go

@@ -0,0 +1,102 @@
+package concurrent_aggregator
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/medunes/go-kata/01-context-cancellation-concurrency/01-concurrent-aggregator/order"
+	"github.com/medunes/go-kata/01-context-cancellation-concurrency/01-concurrent-aggregator/profile"
+
+	"golang.org/x/sync/errgroup"
+)
+
+type Option func(ua *UserAggregator)
+
+func WithLogger(l *slog.Logger) Option {
+	return func(ua *UserAggregator) {
+		ua.logger = l
+	}
+}
+
+func WithTimeout(timeout time.Duration) Option {
+	return func(ua *UserAggregator) {
+		ua.timeout = timeout
+	}
+}
+
+type UserAggregator struct {
+	orderService   order.Service
+	profileService profile.Service
+	timeout        time.Duration
+	logger         *slog.Logger
+}
+
+func NewUserAggregator(os order.Service, ps profile.Service, opts ...Option) *UserAggregator {
+	ua := &UserAggregator{
+		orderService:   os,
+		profileService: ps,
+		logger:         slog.Default(), // avoid nil panics, default writes to stderr
+	}
+	for _, opt := range opts {
+		opt(ua)
+	}
+	return ua
+}
+
+type AggregatedProfile struct {
+	Name string
+	Cost float64
+}
+
+func (ua *UserAggregator) Aggregate(ctx context.Context, id int) ([]*AggregatedProfile, error) {
+	var (
+		localCtx context.Context
+		cancel   context.CancelFunc
+		pr       *profile.Profile
+		or       []*order.Order
+		au       []*AggregatedProfile
+		g        *errgroup.Group
+	)
+	if ua.timeout > 0 {
+		localCtx, cancel = context.WithTimeout(ctx, ua.timeout)
+	} else {
+		localCtx, cancel = context.WithCancel(ctx)
+	}
+	defer cancel()
+	ua.logger.Info("starting aggregation", "user_id", id)
+	g, localCtx = errgroup.WithContext(localCtx)
+	g.Go(func() error {
+		var err error
+		pr, err = ua.profileService.Get(localCtx, id)
+		if err != nil {
+			ua.logger.Warn("failed to fetch profile", "user_id", id, "err", err)
+			return fmt.Errorf("profile fetch failed: %w", err)
+		}
+		return nil
+	})
+	g.Go(func() error {
+		var err error
+		or, err = ua.orderService.GetAll(localCtx, id)
+		if err != nil {
+			ua.logger.Warn("failed to fetch order", "user_id", id, "err", err)
+			return fmt.Errorf("order fetch failed: %w", err)
+		}
+		return nil
+
+	})
+
+	err := g.Wait()
+	if err != nil {
+		ua.logger.Warn("aggregator exited with error", "user_id", id, "err", err)
+		return nil, err
+	}
+	for _, o := range or {
+		if o.UserId == id {
+			au = append(au, &AggregatedProfile{pr.Name, o.Cost})
+		}
+	}
+	ua.logger.Info("aggregation complete successfully", "user_id", id, "count", len(au))
+	return au, nil
+}