[hw-1] implement cart service

cart/internal/app/app.go

@@ -0,0 +1,104 @@
+package app
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
+
+	"route256/cart/internal/app/server"
+	"route256/cart/internal/domain/cart/repository"
+	"route256/cart/internal/domain/cart/service"
+	product_service "route256/cart/internal/domain/products/service"
+	"route256/cart/internal/infra/config"
+	"route256/cart/internal/infra/http/middlewares"
+	"route256/cart/internal/infra/http/round_trippers"
+)
+
+const (
+	productsRetryAttemptsDefault   = 3
+	productsInitialDelaySecDefault = 1
+)
+
+type App struct {
+	config *config.Config
+	server http.Server
+}
+
+func NewApp(configPath string) (*App, error) {
+	c, err := config.LoadConfig(configPath)
+	if err != nil {
+		return nil, fmt.Errorf("unable to load config: %w", err)
+	}
+
+	log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
+	zerolog.SetGlobalLevel(zerolog.InfoLevel)
+
+	if c.Service.LogLevel != "" {
+		level, err := zerolog.ParseLevel(c.Service.LogLevel)
+		if err != nil {
+			return nil, fmt.Errorf("unknown log level `%s` provided: %w", c.Service.LogLevel, err)
+		}
+
+		zerolog.SetGlobalLevel(level)
+	}
+
+	log.WithLevel(zerolog.GlobalLevel()).Msgf("using logging level=`%s`", zerolog.GlobalLevel().String())
+
+	app := &App{
+		config: c,
+	}
+	app.server.Handler = app.bootstrapHandlers()
+
+	return app, nil
+}
+
+func (app *App) ListenAndServe() error {
+	address := fmt.Sprintf("%s:%s", app.config.Service.Host, app.config.Service.Port)
+
+	l, err := net.Listen("tcp", address)
+	if err != nil {
+		return err
+	}
+
+	log.Info().Msgf("Serving cart at http://%s", l.Addr())
+
+	return app.server.Serve(l)
+}
+
+func (app *App) bootstrapHandlers() http.Handler {
+	transport := http.DefaultTransport
+	transport = round_trippers.NewLogRoundTripper(transport)
+	transport = round_trippers.NewRetryRoundTripper(transport, productsRetryAttemptsDefault, productsInitialDelaySecDefault)
+
+	httpClient := http.Client{
+		Transport: transport,
+		Timeout:   10 * time.Second,
+	}
+
+	productService := product_service.NewProductService(
+		httpClient,
+		app.config.ProductService.Token,
+		fmt.Sprintf("%s:%s", app.config.ProductService.Host, app.config.ProductService.Port),
+	)
+
+	const userCartCap = 100
+	cartRepository := repository.NewInMemoryRepository(userCartCap)
+	cartService := service.NewCartService(cartRepository, productService)
+
+	s := server.NewServer(cartService)
+
+	mx := http.NewServeMux()
+	mx.HandleFunc("POST /user/{user_id}/cart/{sku_id}", s.AddItemHandler)
+	mx.HandleFunc("GET /user/{user_id}/cart", s.GetItemsByUserIDHandler)
+	mx.HandleFunc("DELETE /user/{user_id}/cart/{sku_id}", s.DeleteItemHandler)
+	mx.HandleFunc("DELETE /user/{user_id}/cart", s.DeleteItemsByUserIDHandler)
+
+	h := middlewares.NewTimerMiddleware(mx)
+
+	return h
+}