internal/api: ingestion handler; wire normalization pipeline

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I1890a039b874fcc76ac4a545c2901d4e6a6a6964

internal/api/handler.go

@@ -0,0 +1,118 @@
+package api
+
+import (
+	"log"
+	"net/http"
+
+	"notashelf.dev/watchdog/internal/aggregate"
+	"notashelf.dev/watchdog/internal/config"
+	"notashelf.dev/watchdog/internal/normalize"
+)
+
+// Handles incoming analytics events
+type IngestionHandler struct {
+	cfg          config.Config
+	pathNorm     *normalize.PathNormalizer
+	pathRegistry *aggregate.PathRegistry
+	refRegistry  *normalize.ReferrerRegistry
+	metricsAgg   *aggregate.MetricsAggregator
+}
+
+// Creates a new ingestion handler
+func NewIngestionHandler(
+	cfg config.Config,
+	pathNorm *normalize.PathNormalizer,
+	pathRegistry *aggregate.PathRegistry,
+	refRegistry *normalize.ReferrerRegistry,
+	metricsAgg *aggregate.MetricsAggregator,
+) *IngestionHandler {
+	return &IngestionHandler{
+		cfg:          cfg,
+		pathNorm:     pathNorm,
+		pathRegistry: pathRegistry,
+		refRegistry:  refRegistry,
+		metricsAgg:   metricsAgg,
+	}
+}
+
+func (h *IngestionHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Only accept POST requests
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	// Parse event from request body
+	event, err := ParseEvent(r.Body)
+	if err != nil {
+		log.Printf("Failed to parse event: %v", err)
+		http.Error(w, "Bad request", http.StatusBadRequest)
+		return
+	}
+
+	// Validate event
+	if err := event.Validate(h.cfg.Site.Domain); err != nil {
+		log.Printf("Event validation failed: %v", err)
+		http.Error(w, "Bad request", http.StatusBadRequest)
+		return
+	}
+
+	// Normalize path and check if path can be added to the registry.
+	normalizedPath := h.pathNorm.Normalize(event.Path)
+	if !h.pathRegistry.Add(normalizedPath) {
+		// Path was rejected due to cardinality limit
+		h.metricsAgg.RecordPathOverflow()
+		log.Printf("Path overflow: rejected %s", normalizedPath)
+
+		// Still return success to client
+		w.WriteHeader(http.StatusNoContent)
+
+		return
+	}
+
+	// Process based on event type
+	if event.Event != "" {
+		// Custom event
+		h.metricsAgg.RecordCustomEvent(event.Event)
+	} else {
+		// Pageview; process with full normalization pipeline
+		var country, device, referrer string
+
+		// Device classification
+		if h.cfg.Site.Collect.Device {
+			device = classifyDevice(event.Width)
+		}
+
+		// Referrer classification
+		if h.cfg.Site.Collect.Referrer == "domain" {
+			refDomain := normalize.ExtractReferrerDomain(event.Referrer, h.cfg.Site.Domain)
+			if refDomain != "" {
+				referrer = h.refRegistry.Add(refDomain)
+			}
+		}
+
+		// FIXME: Country would be extracted from IP here. For now, we skip country extraction
+		// because I have neither the time nor the patience to look into it. Return later.
+
+		// Record pageview
+		h.metricsAgg.RecordPageview(normalizedPath, country, device, referrer)
+	}
+
+	// Return success
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// Classifies screen width into device categories
+func classifyDevice(width int) string {
+	// FIXME: probably not the best logic for this...
+	if width == 0 {
+		return "unknown"
+	}
+	if width < 768 {
+		return "mobile"
+	}
+	if width < 1024 {
+		return "tablet"
+	}
+	return "desktop"
+}