first commit. added CI, Docker compose, blank client and server. used unit tests, they pass

server/internal/platform/config/config.go

@@ -0,0 +1,56 @@
+// Package config loads the server configuration from environment
+// variables with sane defaults for local development.
+package config
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+// Config holds all runtime configuration for the API server.
+type Config struct {
+	// HTTPAddr is the listen address, e.g. ":8080".
+	HTTPAddr string
+	// StaticDir points to the built frontend (React/Vite dist).
+	// Empty disables static file serving.
+	StaticDir string
+	// Environment is "development", "staging" or "production".
+	Environment string
+	// AllowedOrigins is a comma-separated list of CORS origins
+	// allowed to call the API from a browser.
+	AllowedOrigins []string
+}
+
+// Load reads configuration from the environment, falling back to
+// development-friendly defaults. Unknown values are validated.
+func Load() (*Config, error) {
+	cfg := &Config{
+		HTTPAddr:    fromEnv("MESSENGER_HTTP_ADDR", ":8080"),
+		StaticDir:   os.Getenv("MESSENGER_STATIC_DIR"),
+		Environment: fromEnv("MESSENGER_ENV", "development"),
+	}
+
+	for _, origin := range strings.Split(fromEnv("MESSENGER_ALLOWED_ORIGINS", ""), ",") {
+		if origin = strings.TrimSpace(origin); origin != "" {
+			cfg.AllowedOrigins = append(cfg.AllowedOrigins, origin)
+		}
+	}
+
+	switch cfg.Environment {
+	case "development", "staging", "production":
+	default:
+		return nil, fmt.Errorf("MESSENGER_ENV must be one of development|staging|production, got %q", cfg.Environment)
+	}
+
+	return cfg, nil
+}
+
+// fromEnv returns the value of the environment variable name, or
+// fallback if the variable is unset or empty.
+func fromEnv(name, fallback string) string {
+	if v := os.Getenv(name); v != "" {
+		return v
+	}
+	return fallback
+}