package main

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

const (
	addr              = ":9090"
	readHeaderTimeout = 5 * time.Second
)

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/healthz", health)
	mux.HandleFunc("/api/v1/query", prometheusQuery)
	mux.HandleFunc("/api/v1/query_range", prometheusQuery)

	log.Printf("cp9 o11y stub listening on %s", addr)
	server := &http.Server{
		Addr:              addr,
		Handler:           mux,
		ReadHeaderTimeout: readHeaderTimeout,
	}
	if err := server.ListenAndServe(); err != nil {
		log.Fatal(err)
	}
}

func health(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	writeJSON(w, map[string]string{"status": "ok"})
}

func prometheusQuery(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	writeJSON(w, map[string]any{
		"status": "success",
		"data": map[string]any{
			"resultType": "vector",
			"result":     []any{},
		},
	})
}

func writeJSON(w http.ResponseWriter, value any) {
	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(value); err != nil {
		log.Printf("encode response: %v", err)
	}
}