package ip

import (
	"net"
	"net/http"
	"reflect"
	"testing"

	ipapi "github.com/oauth2-proxy/oauth2-proxy/v7/pkg/apis/ip"
	"github.com/stretchr/testify/assert"
)

func TestGetRealClientIPParser(t *testing.T) {
	forwardedForType := reflect.TypeOf((*xForwardedForClientIPParser)(nil))

	tests := []struct {
		header     string
		errString  string
		parserType reflect.Type
	}{
		{"X-Forwarded-For", "", forwardedForType},
		{"X-REAL-IP", "", forwardedForType},
		{"x-proxyuser-ip", "", forwardedForType},
		{"x-envoy-external-address", "", forwardedForType},
		{"cf-connecting-ip", "", forwardedForType},
		{"", "the http header key () is either invalid or unsupported", nil},
		{"Forwarded", "the http header key (Forwarded) is either invalid or unsupported", nil},
		{"2#* @##$$:kd", "the http header key (2#* @##$$:kd) is either invalid or unsupported", nil},
	}

	for _, test := range tests {
		p, err := GetRealClientIPParser(test.header)

		if test.errString == "" {
			assert.Nil(t, err)
		} else {
			assert.NotNil(t, err)
			assert.Equal(t, test.errString, err.Error())
		}

		if test.parserType == nil {
			assert.Nil(t, p)
		} else {
			assert.NotNil(t, p)
			assert.Equal(t, test.parserType, reflect.TypeOf(p))
		}

		if xp, ok := p.(*xForwardedForClientIPParser); ok {
			assert.Equal(t, http.CanonicalHeaderKey(test.header), xp.header)
		}
	}
}

func TestXForwardedForClientIPParser(t *testing.T) {
	p := &xForwardedForClientIPParser{header: http.CanonicalHeaderKey("X-Forwarded-For")}

	tests := []struct {
		name        string
		headerValue string
		remoteAddr  net.IP
		trusted     *NetSet
		errString   string
		expectedIP  net.IP
	}{
		// No trusted-proxy restriction configured (nil): behaves exactly like the historical
		// leftmost-picking parser, regardless of remoteAddr.
		{name: "empty header", headerValue: "", expectedIP: nil},
		{name: "single hop", headerValue: "1.2.3.4", expectedIP: net.ParseIP("1.2.3.4")},
		{name: "single hop v6", headerValue: "10::23", expectedIP: net.ParseIP("10::23")},
		{name: "loopback v6", headerValue: "::1", expectedIP: net.ParseIP("::1")},
		{name: "v6 with port", headerValue: "[::1]:1234", expectedIP: net.ParseIP("::1")},
		{name: "v4 with port", headerValue: "10.0.10.11:1234", expectedIP: net.ParseIP("10.0.10.11")},
		{name: "no trusted proxies falls back to leftmost", headerValue: "192.168.10.50, 10.0.0.1, 1.2.3.4", expectedIP: net.ParseIP("192.168.10.50")},
		{name: "unparseable hop", headerValue: "nil", errString: "unable to parse ip (nil) from X-Forwarded-For header"},
		{name: "malformed hop", headerValue: "10000.10000.10000.10000", errString: "unable to parse ip (10000.10000.10000.10000) from X-Forwarded-For header"},

		// The reported attack: a client sends X-Forwarded-For set to an IP it wants to
		// impersonate; the trusted reverse proxy appends the real client IP rather than
		// replacing the header. Only the proxy's own /32 is trusted, so the walk must stop at
		// the rightmost (attacker) hop instead of trusting the client-supplied leftmost value.
		{
			name:        "spoofed leftmost hop behind a trusted proxy",
			headerValue: "9.9.9.9, 6.6.6.6",
			remoteAddr:  net.ParseIP("10.0.0.5"),
			trusted:     mustNetSet(t, "10.0.0.5/32"),
			expectedIP:  net.ParseIP("6.6.6.6"),
		},
		// Direct peer isn't a trusted proxy at all: the header must be ignored entirely and
		// the real connecting peer used, since nothing in the header can be believed.
		{
			name:        "untrusted direct peer ignores header",
			headerValue: "9.9.9.9",
			remoteAddr:  net.ParseIP("6.6.6.6"),
			trusted:     mustNetSet(t, "10.0.0.5/32"),
			expectedIP:  net.ParseIP("6.6.6.6"),
		},
		// A chain of two trusted proxies (client -> ProxyA(10.0.0.6) -> ProxyB(10.0.0.5) ->
		// us) still resolves to the real (untrusted) client hop, skipping past both trusted
		// proxy-appended hops and the attacker's forged leftmost claim.
		{
			name:        "chain of trusted proxies",
			headerValue: "9.9.9.9, 6.6.6.6, 10.0.0.6",
			remoteAddr:  net.ParseIP("10.0.0.5"),
			trusted:     mustNetSet(t, "10.0.0.5/32", "10.0.0.6/32"),
			expectedIP:  net.ParseIP("6.6.6.6"),
		},
		// Degenerate case: every hop (and the direct peer) is itself a trusted proxy; there's
		// no untrusted hop to find, so fall back to the oldest (leftmost) entry.
		{
			name:        "all hops trusted falls back to leftmost",
			headerValue: "10.0.0.7, 10.0.0.6",
			remoteAddr:  net.ParseIP("10.0.0.5"),
			trusted:     mustNetSet(t, "10.0.0.5/32", "10.0.0.6/32", "10.0.0.7/32"),
			expectedIP:  net.ParseIP("10.0.0.7"),
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			h := http.Header{}
			h.Add("X-Forwarded-For", test.headerValue)

			var trusted ipapi.TrustedProxies
			if test.trusted != nil {
				trusted = test.trusted
			}

			ip, err := p.GetRealClientIP(h, test.remoteAddr, trusted)

			if test.errString == "" {
				assert.Nil(t, err)
			} else {
				assert.NotNil(t, err)
				assert.Equal(t, test.errString, err.Error())
			}

			if test.expectedIP == nil {
				assert.Nil(t, ip)
			} else {
				assert.NotNil(t, ip)
				assert.Equal(t, test.expectedIP, ip)
			}
		})
	}
}

func TestXForwardedForClientIPParserIgnoresOthers(t *testing.T) {
	p := &xForwardedForClientIPParser{header: http.CanonicalHeaderKey("X-Forwarded-For")}

	h := http.Header{}
	expectedIPString := "192.168.10.50"
	h.Add("X-Real-IP", "10.0.0.1")
	h.Add("X-ProxyUser-IP", "10.0.0.1")
	h.Add("X-Forwarded-For", expectedIPString)
	ip, err := p.GetRealClientIP(h, nil, nil)
	assert.Nil(t, err)
	assert.NotNil(t, ip)
	assert.Equal(t, ip, net.ParseIP(expectedIPString))
}

// mustNetSet builds a *NetSet from CIDR/IP strings, failing the test on error.
func mustNetSet(t *testing.T, ipStrs ...string) *NetSet {
	t.Helper()
	set, err := ParseNetSet(ipStrs)
	if err != nil {
		t.Fatalf("failed to build NetSet: %v", err)
	}
	return set
}

func TestGetRemoteIP(t *testing.T) {
	tests := []struct {
		remoteAddr string
		errString  string
		expectedIP net.IP
	}{
		// Unix domain sockets set RemoteAddr to "@"
		{"@", "", nil},
		{"", "unable to get ip and port from http.RemoteAddr ()", nil},
		{"nil", "unable to get ip and port from http.RemoteAddr (nil)", nil},
		{"235.28.129.186", "unable to get ip and port from http.RemoteAddr (235.28.129.186)", nil},
		{"90::45", "unable to get ip and port from http.RemoteAddr (90::45)", nil},
		{"192.168.73.165:14976, 10.4.201.15:18453", "unable to get ip and port from http.RemoteAddr (192.168.73.165:14976, 10.4.201.15:18453)", nil},
		{"10000.10000.10000.10000:8080", "unable to parse ip (10000.10000.10000.10000)", nil},
		{"[::1]:48290", "", net.ParseIP("::1")},
		{"10.254.244.165:62750", "", net.ParseIP("10.254.244.165")},
	}

	for _, test := range tests {
		req := &http.Request{RemoteAddr: test.remoteAddr}

		ip, err := getRemoteIP(req)

		if test.errString == "" {
			assert.Nil(t, err)
		} else {
			assert.NotNil(t, err)
			assert.Equal(t, test.errString, err.Error())
		}

		if test.expectedIP == nil {
			assert.Nil(t, ip)
		} else {
			assert.NotNil(t, ip)
			assert.Equal(t, test.expectedIP, ip)
		}
	}
}

func TestGetClientString(t *testing.T) {
	p := &xForwardedForClientIPParser{header: http.CanonicalHeaderKey("X-Forwarded-For")}

	tests := []struct {
		parser             ipapi.RealClientIPParser
		remoteAddr         string
		headerValue        string
		expectedClient     string
		expectedClientFull string
	}{
		// Should fail quietly, only printing warnings to the log
		{nil, "", "", "", ""},
		// Unix domain socket — no IP available
		{nil, "@", "", "", ""},
		{p, "127.0.0.1:11950", "", "127.0.0.1", "127.0.0.1"},
		{p, "[::1]:28660", "99.103.56.12", "99.103.56.12", "::1 (99.103.56.12)"},
		{nil, "10.254.244.165:62750", "", "10.254.244.165", "10.254.244.165"},
		// Parser is nil, the contents of X-Forwarded-For should be ignored in all cases.
		{nil, "[2001:470:26:307:a5a1:1177:2ae3:e9c3]:48290", "127.0.0.1", "2001:470:26:307:a5a1:1177:2ae3:e9c3", "2001:470:26:307:a5a1:1177:2ae3:e9c3"},
	}

	for _, test := range tests {
		h := http.Header{}
		h.Add("X-Forwarded-For", test.headerValue)
		req := &http.Request{
			Header:     h,
			RemoteAddr: test.remoteAddr,
		}

		client := GetClientString(test.parser, req, false, nil)
		assert.Equal(t, test.expectedClient, client)

		clientFull := GetClientString(test.parser, req, true, nil)
		assert.Equal(t, test.expectedClientFull, clientFull)
	}
}