package httpapi

import (
	"net/http"
	"net/http/httptest"
	"testing"
)

func TestExtractClientIP(t *testing.T) {
	tests := []struct {
		name       string
		request    *http.Request
		headers    map[string]string
		remoteAddr string
		wantIP     *string
	}{
		{
			name:    "nil request",
			request: nil,
			wantIP:  nil,
		},
		{
			name: "CF-Connecting-IP takes precedence",
			headers: map[string]string{
				"CF-Connecting-IP": "203.0.113.10",
				"X-Real-IP":        "198.51.100.20",
				"X-Forwarded-For":  "192.0.2.30",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("203.0.113.10"),
		},
		{
			name: "True-Client-IP takes precedence over X-Real-IP",
			headers: map[string]string{
				"True-Client-IP":  "203.0.113.11",
				"X-Real-IP":       "198.51.100.20",
				"X-Forwarded-For": "192.0.2.30",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("203.0.113.11"),
		},
		{
			name: "X-Real-IP takes precedence over X-Forwarded-For",
			headers: map[string]string{
				"X-Real-IP":       "198.51.100.20",
				"X-Forwarded-For": "192.0.2.30",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("198.51.100.20"),
		},
		{
			name: "X-Forwarded-For first entry is extracted",
			headers: map[string]string{
				"X-Forwarded-For": "192.0.2.30, 10.0.0.2, 172.16.0.5",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("192.0.2.30"),
		},
		{
			name: "X-Forwarded-For single entry",
			headers: map[string]string{
				"X-Forwarded-For": " 192.0.2.31 ",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("192.0.2.31"),
		},
		{
			name: "X-Forwarded-For skips invalid first entry to find valid IP",
			headers: map[string]string{
				"X-Forwarded-For": "unknown, 192.0.2.32",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("192.0.2.32"),
		},
		{
			name: "Fallback to RemoteAddr with port",
			headers: map[string]string{},
			remoteAddr: "192.168.1.100:12345",
			wantIP:     ptr("192.168.1.100"),
		},
		{
			name: "Fallback to RemoteAddr without port",
			headers: map[string]string{},
			remoteAddr: "192.168.1.101",
			wantIP:     ptr("192.168.1.101"),
		},
		{
			name: "IPv6 in RemoteAddr with port",
			headers: map[string]string{},
			remoteAddr: "[2001:db8::1]:8080",
			wantIP:     ptr("2001:db8::1"),
		},
		{
			name: "IPv6 in header",
			headers: map[string]string{
				"X-Real-IP": "2001:db8::2",
			},
			remoteAddr: "10.0.0.1:54321",
			wantIP:     ptr("2001:db8::2"),
		},
		{
			name: "Invalid headers fall back to RemoteAddr",
			headers: map[string]string{
				"X-Real-IP":       "not-an-ip",
				"X-Forwarded-For": "also-not-an-ip",
			},
			remoteAddr: "192.168.1.102:443",
			wantIP:     ptr("192.168.1.102"),
		},
		{
			name: "No headers and empty RemoteAddr",
			headers: map[string]string{},
			remoteAddr: "",
			wantIP:     nil,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			var req *http.Request
			if tt.name != "nil request" {
				req = httptest.NewRequest(http.MethodGet, "/", nil)
				for k, v := range tt.headers {
					req.Header.Set(k, v)
				}
				req.RemoteAddr = tt.remoteAddr
			}

			got := extractClientIP(req)
			if (got == nil) != (tt.wantIP == nil) {
				t.Fatalf("extractClientIP() = %v, want %v", got, tt.wantIP)
			}
			if got != nil && tt.wantIP != nil && *got != *tt.wantIP {
				t.Errorf("extractClientIP() = %q, want %q", *got, *tt.wantIP)
			}
		})
	}
}

func ptr(s string) *string {
	return &s
}