// SPDX-License-Identifier: MIT

package netdetect

import (
	"context"
	"strings"
	"testing"

	"prx/internal/execx"
)

func fake(handler func(name string, args []string) (string, error)) *execx.Fake {
	return &execx.Fake{Handler: func(name string, args []string, _ []byte) (execx.Result, error) {
		out, err := handler(name, args)
		if err != nil {
			return execx.Result{}, err
		}
		return execx.Result{Stdout: []byte(out)}, nil
	}}
}

func TestDetect(t *testing.T) {
	r := fake(func(name string, args []string) (string, error) {
		joined := strings.Join(args, " ")
		switch {
		case joined == "-j route show default":
			return `[{"dst":"default","gateway":"192.168.1.1","dev":"wlan0","metric":600}]`, nil
		case joined == "-6 -j route show default":
			return `[]`, nil
		case joined == "-j addr show dev wlan0":
			return `[{"ifname":"wlan0","addr_info":[
				{"family":"inet","local":"192.168.1.100","prefixlen":24,"scope":"global"},
				{"family":"inet6","local":"fe80::abcd","prefixlen":64,"scope":"link"}]}]`, nil
		}
		return "", nil
	})

	wan, err := Detect(context.Background(), r, "", "", "")
	if err != nil {
		t.Fatalf("Detect: %v", err)
	}
	if wan.Interface != "wlan0" {
		t.Errorf("interface = %q", wan.Interface)
	}
	if wan.Gateway4 != "192.168.1.1" {
		t.Errorf("gateway4 = %q", wan.Gateway4)
	}
	if wan.Gateway6 != "" {
		t.Errorf("gateway6 = %q, want empty", wan.Gateway6)
	}
	if len(wan.Local4) != 1 || wan.Local4[0] != "192.168.1.100" {
		t.Errorf("local4 = %v", wan.Local4)
	}
	if len(wan.Local6) != 0 {
		t.Errorf("local6 = %v, want none (link-local excluded)", wan.Local6)
	}
}

func TestDetectPrefersLowestMetric(t *testing.T) {
	r := fake(func(_ string, args []string) (string, error) {
		joined := strings.Join(args, " ")
		if joined == "-j route show default" {
			return `[{"dst":"default","gateway":"10.0.0.1","dev":"eth9","metric":900},
			         {"dst":"default","gateway":"192.168.1.1","dev":"wlan0","metric":100}]`, nil
		}
		if strings.Contains(joined, "addr show dev wlan0") {
			return `[{"ifname":"wlan0","addr_info":[{"family":"inet","local":"192.168.1.100","prefixlen":24,"scope":"global"}]}]`, nil
		}
		return `[]`, nil
	})
	wan, err := Detect(context.Background(), r, "", "", "")
	if err != nil {
		t.Fatalf("Detect: %v", err)
	}
	if wan.Interface != "wlan0" || wan.Gateway4 != "192.168.1.1" {
		t.Fatalf("picked %s/%s, want wlan0/192.168.1.1", wan.Interface, wan.Gateway4)
	}
}

func TestDetectOverride(t *testing.T) {
	r := fake(func(_ string, args []string) (string, error) {
		if strings.Join(args, " ") == "-j route show default" {
			return `[{"dst":"default","gateway":"192.168.1.1","dev":"wlan0","metric":100}]`, nil
		}
		if strings.Contains(strings.Join(args, " "), "addr show dev wlan0") {
			return `[{"ifname":"wlan0","addr_info":[{"family":"inet","local":"192.168.1.100","prefixlen":24,"scope":"global"}]}]`, nil
		}
		return `[]`, nil
	})
	wan, err := Detect(context.Background(), r, "wlan0", "10.9.9.9", "")
	if err != nil {
		t.Fatalf("Detect: %v", err)
	}
	if wan.Gateway4 != "10.9.9.9" {
		t.Fatalf("gateway override not applied: %q", wan.Gateway4)
	}
}

func TestDetectNoDefaultRoute(t *testing.T) {
	r := fake(func(_ string, _ []string) (string, error) { return `[]`, nil })
	if _, err := Detect(context.Background(), r, "", "", ""); err == nil {
		t.Fatal("expected error when no default route exists")
	}
}

func TestDetectIPv6OnlyUplink(t *testing.T) {
	r := fake(func(_ string, args []string) (string, error) {
		joined := strings.Join(args, " ")
		switch {
		case joined == "-j route show default":
			return `[]`, nil
		case joined == "-6 -j route show default":
			return `[{"dst":"default","gateway":"2001:db8::1","dev":"eth0","metric":100}]`, nil
		case joined == "-j addr show dev eth0":
			return `[{"ifname":"eth0","addr_info":[{"family":"inet6","local":"2001:db8::5","prefixlen":64,"scope":"global"}]}]`, nil
		}
		return `[]`, nil
	})
	wan, err := Detect(context.Background(), r, "", "", "")
	if err != nil {
		t.Fatalf("Detect: %v", err)
	}
	if wan.Interface != "eth0" || wan.Gateway4 != "" || wan.Gateway6 != "2001:db8::1" {
		t.Fatalf("ipv6-only detection = %+v", wan)
	}
}