package main

import (
	"encoding/json"
	"io"
	"log"
	"net/http"
)

func runServer() {
	cfg, err := LoadConfig()
	if err != nil {
		log.Fatal(err)
	}

	metrics := NewMetrics(nil)
	proxy := NewProxy(cfg, metrics)
	mux := http.NewServeMux()

	mux.HandleFunc("GET /", func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		_, _ = w.Write([]byte("Mattermost Push Proxy Router\n"))
	})

	mux.HandleFunc("GET /version", func(w http.ResponseWriter, _ *http.Request) {
		writeJSON(w, map[string]string{"version": version})
	})

	mux.HandleFunc("GET /health", handleHealth)
	mux.Handle("GET /metrics", metrics.Handler())

	mux.HandleFunc("POST /api/v1/send_push", func(w http.ResponseWriter, r *http.Request) {
		handleRoute(w, r, proxy, cfg, "/api/v1/send_push")
	})

	mux.HandleFunc("POST /api/v1/ack", func(w http.ResponseWriter, r *http.Request) {
		handleRoute(w, r, proxy, cfg, "/api/v1/ack")
	})

	addr := ":" + cfg.Port
	log.Printf("Push proxy router listening on %s", addr)
	for _, route := range cfg.Routes {
		log.Printf("Route %v -> %s", route.Prefixes, route.URL)
	}

	if err := http.ListenAndServe(addr, mux); err != nil {
		log.Fatal(err)
	}
}

func handleRoute(w http.ResponseWriter, r *http.Request, proxy *Proxy, cfg Config, path string) {
	body, err := io.ReadAll(r.Body)
	if err != nil {
		proxy.metrics.incRoutingError("read_body")
		writePushError(w, "failed to read request body")
		return
	}

	platform, err := extractPlatform(body)
	if err != nil {
		proxy.metrics.incRoutingError(routingErrorReason(err))
		writePushError(w, err.Error())
		return
	}

	backend, ok := cfg.BackendForPlatform(platform)
	if !ok {
		proxy.metrics.incRoutingError("unknown_platform")
		writePushError(w, "no backend configured for platform="+platform)
		return
	}

	proxy.metrics.incRequest(routePathLabel(path), platform)
	log.Printf("route platform=%s path=%s backend=%s", platform, path, backend)
	proxy.Forward(w, r, backend, path, body, platform)
}

func handleHealth(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, map[string]string{"status": "ok"})
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	enc := json.NewEncoder(w)
	enc.SetEscapeHTML(false)
	_ = enc.Encode(v)
}