// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package prober

import (
	"context"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/http/httptest"
	"regexp"
	"testing"
	"time"

	"git.ipng.ch/ipng/vpp-maglev/internal/config"
)

// dialAndProbe dials addr directly (bypassing netns/interface binding) and
// exercises the HTTP probe response-checking logic.
func dialAndProbe(ctx context.Context, addr string, cfg ProbeConfig) (bool, error) {
	if cfg.HTTP == nil {
		return false, fmt.Errorf("dialAndProbe requires HTTP params")
	}
	p := cfg.HTTP

	path := p.Path
	if path == "" {
		path = "/"
	}

	conn, err := net.DialTimeout("tcp", addr, cfg.Timeout)
	if err != nil {
		return false, err
	}

	transport := &http.Transport{
		DialContext: func(_ context.Context, _, _ string) (net.Conn, error) {
			return conn, nil
		},
		DisableKeepAlives: true,
	}
	client := &http.Client{
		Transport: transport,
		Timeout:   cfg.Timeout,
		CheckRedirect: func(_ *http.Request, _ []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}

	target := "http://" + addr + path
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, target, nil)
	if err != nil {
		return false, err
	}
	if p.Host != "" {
		req.Host = p.Host
	}

	resp, err := client.Do(req)
	if err != nil {
		return false, err
	}
	defer resp.Body.Close()

	if resp.StatusCode < p.ResponseCodeMin || resp.StatusCode > p.ResponseCodeMax {
		return false, nil
	}
	if p.ResponseRegexp != nil {
		body, _ := io.ReadAll(resp.Body)
		if !p.ResponseRegexp.Match(body) {
			return false, nil
		}
	}
	return true, nil
}

func TestHTTPProbeStatusCode(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, "healthy")
	}))
	defer srv.Close()

	cfg := ProbeConfig{
		Timeout: 2 * time.Second,
		HTTP: &config.HTTPParams{
			Path:            "/healthz",
			ResponseCodeMin: 200,
			ResponseCodeMax: 200,
		},
	}
	ok, err := dialAndProbe(context.Background(), srv.Listener.Addr().String(), cfg)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !ok {
		t.Error("expected probe success")
	}
}

func TestHTTPProbeWrongStatusCode(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusServiceUnavailable)
	}))
	defer srv.Close()

	cfg := ProbeConfig{
		Timeout: 2 * time.Second,
		HTTP: &config.HTTPParams{
			Path:            "/",
			ResponseCodeMin: 200,
			ResponseCodeMax: 200,
		},
	}
	ok, err := dialAndProbe(context.Background(), srv.Listener.Addr().String(), cfg)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if ok {
		t.Error("expected probe failure on wrong status code")
	}
}

func TestHTTPProbeRegexpMatch(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		fmt.Fprint(w, `{"status":"ok"}`)
	}))
	defer srv.Close()

	cfg := ProbeConfig{
		Timeout: 2 * time.Second,
		HTTP: &config.HTTPParams{
			Path:            "/",
			ResponseCodeMin: 200,
			ResponseCodeMax: 200,
			ResponseRegexp:  regexp.MustCompile(`"status":"ok"`),
		},
	}
	ok, err := dialAndProbe(context.Background(), srv.Listener.Addr().String(), cfg)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !ok {
		t.Error("expected probe success with matching regexp")
	}
}

func TestHTTPProbeRegexpNoMatch(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		fmt.Fprint(w, `{"status":"degraded"}`)
	}))
	defer srv.Close()

	cfg := ProbeConfig{
		Timeout: 2 * time.Second,
		HTTP: &config.HTTPParams{
			Path:            "/",
			ResponseCodeMin: 200,
			ResponseCodeMax: 200,
			ResponseRegexp:  regexp.MustCompile(`"status":"ok"`),
		},
	}
	ok, err := dialAndProbe(context.Background(), srv.Listener.Addr().String(), cfg)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if ok {
		t.Error("expected probe failure when regexp does not match")
	}
}

func TestHTTPProbeNoRedirect(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, "/other", http.StatusFound)
	}))
	defer srv.Close()

	// Probe expects 302 — redirect is not followed.
	cfg := ProbeConfig{
		Timeout: 2 * time.Second,
		HTTP: &config.HTTPParams{
			Path:            "/",
			ResponseCodeMin: 302,
			ResponseCodeMax: 302,
		},
	}
	ok, err := dialAndProbe(context.Background(), srv.Listener.Addr().String(), cfg)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !ok {
		t.Error("expected success when probe expects 302 and server returns 302")
	}
}