package host

import (
	"net"
	"net/http"
	"strings"
	"time"

	"github.com/carlosframework/platform/internal/edgesfile"
)

// imdsAddresses is the AWS adapter of AddressSource (region HA spec 2
// §25): IMDSv2's local-ipv4, public-ipv4, and the VPC's CIDR blocks for
// the primary interface (network/interfaces/macs/<mac>/vpc-ipv4-cidr-blocks),
// read on every call. IMDS reports only addresses this instance holds, so
// once the region's EIP has moved to the load balancer no box reports it
// (A1-12). A leaf that does not answer 200 is blank.
type imdsAddresses struct {
	token func() string
	leaf  func(token, path string) (string, int)
}

func newIMDSAddresses() imdsAddresses {
	client := &http.Client{Timeout: 2 * time.Second}
	return imdsAddresses{
		token: func() string { return imdsToken(client) },
		leaf:  func(token, path string) (string, int) { return imdsLeaf(client, token, path) },
	}
}

func (s imdsAddresses) BoxAddresses() (BoxAddresses, bool) {
	token := s.token()
	if token == "" {
		return BoxAddresses{}, false
	}
	// read is a leaf's answer: its value on 200, blank on 404 (IMDS says the
	// instance has no such leaf: authoritative), and unknown on anything
	// else, a failed or timed-out request included.
	unknown := false
	read := func(path string) string {
		v, code := s.leaf(token, path)
		switch code {
		case http.StatusOK:
			return v
		case http.StatusNotFound:
		default:
			unknown = true
		}
		return ""
	}
	out := BoxAddresses{Public: read("/latest/meta-data/public-ipv4")}
	ip := read("/latest/meta-data/local-ipv4")
	mac := read("/latest/meta-data/mac")
	if unknown {
		return BoxAddresses{}, false
	}
	if ip == "" || mac == "" {
		return out, true
	}
	if _, err := net.ParseMAC(mac); err != nil {
		return out, true
	}
	blocks := strings.Fields(read("/latest/meta-data/network/interfaces/macs/" + mac + "/vpc-ipv4-cidr-blocks"))
	if unknown {
		return BoxAddresses{}, false
	}
	out.Private, out.PrivateCIDR = edgesfile.PrivateAddress(ip, blocks)
	return out, true
}

// boxAddressSource is what the edges file publisher reads with region HA
// on: host.env's settings, then IMDS on EC2. IMDS is asked on every
// publication that host.env does not fully answer; a failed request makes
// that publication unknown, and the pass writes nothing and retries.
func boxAddressSource(getenv func(string) string) AddressSource {
	return envAddresses{getenv: getenv, provider: newIMDSAddresses()}
}