[Refactor]: Core/API Split (#1506)

Refactors api folder to core, creates firm split between backend code and api frontend.

core/http/endpoints/localai/metrics.go

@@ -0,0 +1,42 @@
+package localai
+
+import (
+	"time"
+
+	"github.com/go-skynet/LocalAI/pkg/schema"
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/adaptor"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+func MetricsHandler() fiber.Handler {
+	return adaptor.HTTPHandler(promhttp.Handler())
+}
+
+type apiMiddlewareConfig struct {
+	Filter  func(c *fiber.Ctx) bool
+	metrics *schema.LocalAIMetrics
+}
+
+func MetricsAPIMiddleware(metrics *schema.LocalAIMetrics) fiber.Handler {
+	cfg := apiMiddlewareConfig{
+		metrics: metrics,
+		Filter: func(c *fiber.Ctx) bool {
+			return c.Path() == "/metrics"
+		},
+	}
+
+	return func(c *fiber.Ctx) error {
+		if cfg.Filter != nil && cfg.Filter(c) {
+			return c.Next()
+		}
+		path := c.Path()
+		method := c.Method()
+
+		start := time.Now()
+		err := c.Next()
+		elapsed := float64(time.Since(start)) / float64(time.Second)
+		cfg.metrics.ObserveAPICall(method, path, elapsed)
+		return err
+	}
+}