// Package health provides standard health check implementations for
// Metacircular services, supporting both REST and gRPC.
package health

import (
	"database/sql"
	"encoding/json"
	"net/http"

	"google.golang.org/grpc"
	"google.golang.org/grpc/health"
	healthpb "google.golang.org/grpc/health/grpc_health_v1"
)

// Handler returns an http.HandlerFunc that checks database connectivity.
// It returns 200 {"status":"ok"} if the database is reachable, or
// 503 {"status":"unhealthy","error":"..."} if the ping fails.
//
// Mount it on whatever path the service uses (typically /healthz or
// /v1/health).
func Handler(database *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "application/json")

		if err := database.Ping(); err != nil {
			w.WriteHeader(http.StatusServiceUnavailable)
			_ = json.NewEncoder(w).Encode(map[string]string{
				"status": "unhealthy",
				"error":  err.Error(),
			})
			return
		}

		w.WriteHeader(http.StatusOK)
		_ = json.NewEncoder(w).Encode(map[string]string{
			"status": "ok",
		})
	}
}

// RegisterGRPC registers the standard gRPC health checking service
// (grpc.health.v1.Health) on the given gRPC server. The health server
// is set to SERVING status immediately.
func RegisterGRPC(srv *grpc.Server) {
	hs := health.NewServer()
	hs.SetServingStatus("", healthpb.HealthCheckResponse_SERVING)
	healthpb.RegisterHealthServer(srv, hs)
}