feat(scaffold): add main.go [skip ci]

main.go

@@ -0,0 +1,215 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
+	"go.opentelemetry.io/otel/propagation"
+	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+)
+
+// ---------------------------------------------------------------------------
+// Domain model
+// ---------------------------------------------------------------------------
+
+type Item struct {
+	ID          int    `json:"id"`
+	Name        string `json:"name"`
+	Description string `json:"description"`
+}
+
+type ItemRequest struct {
+	Name        string `json:"name"`
+	Description string `json:"description"`
+}
+
+// ---------------------------------------------------------------------------
+// In-memory store
+// ---------------------------------------------------------------------------
+
+var (
+	store   sync.Map
+	counter atomic.Int64
+)
+
+func nextID() int {
+	return int(counter.Add(1))
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func writeJSON(w http.ResponseWriter, status int, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(v)
+}
+
+func itemIDFromPath(path string) (int, bool) {
+	parts := strings.Split(strings.TrimSuffix(path, "/"), "/")
+	if len(parts) < 3 {
+		return 0, false
+	}
+	id, err := strconv.Atoi(parts[len(parts)-1])
+	return id, err == nil
+}
+
+// ---------------------------------------------------------------------------
+// Handlers
+// ---------------------------------------------------------------------------
+
+func healthHandler(w http.ResponseWriter, _ *http.Request) {
+	writeJSON(w, http.StatusOK, map[string]string{"status": "UP"})
+}
+
+func itemsHandler(w http.ResponseWriter, r *http.Request) {
+	// Route: /api/items  or  /api/items/{id}
+	hasSub := strings.Count(strings.TrimSuffix(r.URL.Path, "/"), "/") >= 3
+
+	if hasSub {
+		id, ok := itemIDFromPath(r.URL.Path)
+		if !ok {
+			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid id"})
+			return
+		}
+		switch r.Method {
+		case http.MethodGet:
+			v, exists := store.Load(id)
+			if !exists {
+				writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
+				return
+			}
+			writeJSON(w, http.StatusOK, v)
+		case http.MethodPut:
+			var req ItemRequest
+			if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+				writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
+				return
+			}
+			existingRaw, exists := store.Load(id)
+			if !exists {
+				writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
+				return
+			}
+			existing := existingRaw.(Item)
+			if req.Name == "" {
+				req.Name = existing.Name
+			}
+			if req.Description == "" {
+				req.Description = existing.Description
+			}
+			updated := Item{ID: id, Name: req.Name, Description: req.Description}
+			store.Store(id, updated)
+			writeJSON(w, http.StatusOK, updated)
+		case http.MethodDelete:
+			store.Delete(id)
+			writeJSON(w, http.StatusOK, map[string]int{"deleted": id})
+		default:
+			w.WriteHeader(http.StatusMethodNotAllowed)
+		}
+		return
+	}
+
+	// /api/items — list or create
+	switch r.Method {
+	case http.MethodGet:
+		var items []Item
+		store.Range(func(_, v any) bool {
+			items = append(items, v.(Item))
+			return true
+		})
+		if items == nil {
+			items = []Item{}
+		}
+		writeJSON(w, http.StatusOK, items)
+	case http.MethodPost:
+		var req ItemRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
+			return
+		}
+		if req.Name == "" {
+			req.Name = "unnamed"
+		}
+		item := Item{ID: nextID(), Name: req.Name, Description: req.Description}
+		store.Store(item.ID, item)
+		writeJSON(w, http.StatusCreated, item)
+	default:
+		w.WriteHeader(http.StatusMethodNotAllowed)
+	}
+}
+
+// ---------------------------------------------------------------------------
+// OpenTelemetry setup
+// ---------------------------------------------------------------------------
+
+// setupOTel initialises the OTLP trace and metric pipelines from OTEL_* env
+// vars (injected by score.yaml / Humanitec). Returns a no-op shutdown func
+// when OTEL_EXPORTER_OTLP_ENDPOINT is not set (local dev).
+func setupOTel(ctx context.Context) func() {
+	if os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT") == "" {
+		return func() {}
+	}
+	svcName := os.Getenv("OTEL_SERVICE_NAME")
+	if svcName == "" {
+		svcName = "unknown"
+	}
+	res, _ := resource.New(ctx,
+		resource.WithAttributes(semconv.ServiceName(svcName)),
+		resource.WithFromEnv(),
+	)
+	traceExp, _ := otlptracehttp.New(ctx)
+	tp := sdktrace.NewTracerProvider(sdktrace.WithBatcher(traceExp), sdktrace.WithResource(res))
+	otel.SetTracerProvider(tp)
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{}, propagation.Baggage{},
+	))
+	metricExp, _ := otlpmetrichttp.New(ctx)
+	mp := sdkmetric.NewMeterProvider(
+		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(metricExp)),
+		sdkmetric.WithResource(res),
+	)
+	otel.SetMeterProvider(mp)
+	return func() {
+		_ = tp.Shutdown(context.Background())
+		_ = mp.Shutdown(context.Background())
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Main
+// ---------------------------------------------------------------------------
+
+func main() {
+	ctx := context.Background()
+	shutdownOTel := setupOTel(ctx)
+	defer shutdownOTel()
+
+	mux := http.NewServeMux()
+
+	mux.HandleFunc("/health", healthHandler)
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/api/items/", itemsHandler)
+	mux.HandleFunc("/api/items", itemsHandler)
+
+	addr := ":8080"
+	fmt.Printf("sonar-test-go3 listening on %s\n", addr)
+	log.Fatal(http.ListenAndServe(addr, otelhttp.NewHandler(mux, "")))
+}