package mirko

import (
	"fmt"
	"net"
	"net/http"
	"strconv"
	"strings"
)

// parsePort parses a string as a port number from 1 to 65535.
func parsePort(s string) (uint16, error) {
	port, err := strconv.ParseUint(s, 10, 16)
	if err != nil {
		return 0, fmt.Errorf("could not parse port %q: %v", s, err)
	}
	if port < 1 || port > 65535 {
		return 0, fmt.Errorf("port %d out of range", port)
	}
	return uint16(port), nil
}

// GetHTTPRemoteClient returns the IP address and source port of the client
// initiating the given HTTP request. This will either interpret the remote
// side of the HTTP connection if not running within a cluster, or the source
// IP/port as reported by the cluster reverse proxy (nginx-ingress-controller).
// An error will be returned if the request is unparseable for this data. In
// this case, the caller should assume that the environment is misconfigured,
// and that the client source cannot be deduced.
func GetHTTPRemoteClient(r *http.Request) (net.IP, uint16, error) {
	if KubernetesClient() == nil {
		// We're not running inside a cluster (we're probably running on a dev
		// machine), so just return whatever net/http says.

		host, portStr, err := net.SplitHostPort(r.RemoteAddr)
		if err != nil {
			return nil, 0, fmt.Errorf("could not split hostport: %v", err)
		}
		ip := net.ParseIP(host)
		if ip == nil {
			return nil, 0, fmt.Errorf("could not parse host %q to IP address", host)
		}
		port, err := parsePort(portStr)
		if err != nil {
			return nil, 0, err
		}
		return ip, uint16(port), nil
	}

	// We are running in a cluster, so we can expect Hscloud-* headers.
	// These are configured in the nginx-ingress-controller, //cluster/kube/lib/nginx.libsonnet.
	nsip := strings.TrimSpace(r.Header.Get("Hscloud-Nic-Source-IP"))
	nsport := strings.TrimSpace(r.Header.Get("Hscloud-Nic-Source-Port"))
	if nsip == "" || nsport == "" {
		return nil, 0, fmt.Errorf("Hscloud-Nic-* headers not set")
	}
	ip := net.ParseIP(nsip)
	if ip == nil {
		return nil, 0, fmt.Errorf("Invalid Hscloud-Nix-Source-IP %q", nsip)
	}
	port, err := parsePort(nsport)
	if err != nil {
		return nil, 0, fmt.Errorf("Invalid Hscloud-Nix-Source-Port: %v", err)
	}
	return ip, port, nil
}