package agentcore

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"cloudipvalidator/internal/config"
)

// echoServer answers every request with body (an IP-echo stand-in).
func echoServer(t *testing.T, body string) *httptest.Server {
	t.Helper()
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprint(w, body)
	}))
	t.Cleanup(ts.Close)
	return ts
}

// controlAPIServer plays control-api's observed-ip route: it answers with ip
// (status 200) or with the given error status when ip is empty.
func controlAPIServer(t *testing.T, ip string, status int) *httptest.Server {
	t.Helper()
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path != "/api/v1/agents/val-1/observed-ip" {
			http.NotFound(w, r)
			return
		}
		if ip == "" {
			w.WriteHeader(status)
			return
		}
		fmt.Fprintf(w, `{"ip":%q,"source":"remote_addr"}`, ip)
	}))
	t.Cleanup(ts.Close)
	return ts
}

func selfCheckAgent(controlAPIURL string, methods []string, echoURLs ...string) *Agent {
	return &Agent{
		cfg: &config.ValidatorAgent{
			ValidatorID:   "val-1",
			ControlAPIURL: controlAPIURL,
			SelfCheck:     config.SelfCheckCfg{TimeoutSeconds: 2, Methods: methods, IPEchoURLs: echoURLs},
		},
		log: testLogger(),
	}
}

func TestSelfCheckControlAPIFirstWins(t *testing.T) {
	capi := controlAPIServer(t, "1.2.3.4", 0)
	var echoCalls int32
	echo := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		atomic.AddInt32(&echoCalls, 1)
		fmt.Fprint(w, "1.2.3.4")
	}))
	defer echo.Close()

	a := selfCheckAgent(capi.URL, []string{config.SelfCheckControlAPI, config.SelfCheckIPEcho}, echo.URL)
	ip, method, detail, ok := a.runSelfCheckMethods(context.Background(), "1.2.3.4")
	if !ok || ip != "1.2.3.4" || method != config.SelfCheckControlAPI || detail != "matched (control_api)" {
		t.Fatalf("got ip=%q method=%q detail=%q ok=%v", ip, method, detail, ok)
	}
	if n := atomic.LoadInt32(&echoCalls); n != 0 {
		t.Fatalf("ip_echo was called %d times although control_api already confirmed", n)
	}
}

// Any one confirming method is enough: control-api answers with a different
// address, ip_echo confirms.
func TestSelfCheckFallsThroughOnMismatch(t *testing.T) {
	capi := controlAPIServer(t, "5.5.5.5", 0)
	echo := echoServer(t, "1.2.3.4")

	a := selfCheckAgent(capi.URL, []string{config.SelfCheckControlAPI, config.SelfCheckIPEcho}, echo.URL)
	ip, method, _, ok := a.runSelfCheckMethods(context.Background(), "1.2.3.4")
	if !ok || ip != "1.2.3.4" || method != config.SelfCheckIPEcho {
		t.Fatalf("got ip=%q method=%q ok=%v, want a pass via ip_echo", ip, method, ok)
	}
}

// An old control-api without the route (404) or a failing one (5xx) must not
// stop the self-check: the next method decides.
func TestSelfCheckFallsThroughOnControlAPIError(t *testing.T) {
	for _, status := range []int{http.StatusNotFound, http.StatusInternalServerError} {
		capi := controlAPIServer(t, "", status)
		echo := echoServer(t, "1.2.3.4")
		a := selfCheckAgent(capi.URL, []string{config.SelfCheckControlAPI, config.SelfCheckIPEcho}, echo.URL)
		_, method, _, ok := a.runSelfCheckMethods(context.Background(), "1.2.3.4")
		if !ok || method != config.SelfCheckIPEcho {
			t.Fatalf("status %d: method=%q ok=%v, want a pass via ip_echo", status, method, ok)
		}
	}
}

func TestSelfCheckFailsWhenNoMethodConfirms(t *testing.T) {
	capi := controlAPIServer(t, "10.0.0.5", 0) // private address: internal-network case
	echo := echoServer(t, "6.6.6.6")

	a := selfCheckAgent(capi.URL, []string{config.SelfCheckControlAPI, config.SelfCheckIPEcho}, echo.URL)
	ip, method, detail, ok := a.runSelfCheckMethods(context.Background(), "1.2.3.4")
	if ok || method != "" {
		t.Fatalf("expected a failure, got ok=%v method=%q", ok, method)
	}
	if ip != "6.6.6.6" {
		t.Fatalf("detected ip = %q, want the last reported address 6.6.6.6", ip)
	}
	for _, want := range []string{
		`control_api: egress ip "10.0.0.5" does not match assigned fip "1.2.3.4"`,
		"private address", // the hint for the internal-network case
		`ip_echo: egress ip "6.6.6.6" does not match`,
	} {
		if !strings.Contains(detail, want) {
			t.Fatalf("detail %q does not contain %q", detail, want)
		}
	}
}

func TestSelfCheckPrivateHintOnlyForControlAPI(t *testing.T) {
	echo := echoServer(t, "10.1.1.1")
	a := selfCheckAgent("http://unused", []string{config.SelfCheckIPEcho}, echo.URL)
	_, _, detail, ok := a.runSelfCheckMethods(context.Background(), "1.2.3.4")
	if ok || strings.Contains(detail, "private address") {
		t.Fatalf("ok=%v detail=%q: the control_api hint must not appear for ip_echo", ok, detail)
	}
}

// With nothing configured (a config built without the loader) the agent
// behaves as before: ip_echo only, control-api is never asked.
func TestSelfCheckDefaultsToIPEcho(t *testing.T) {
	var capiCalls int32
	capi := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		atomic.AddInt32(&capiCalls, 1)
	}))
	defer capi.Close()
	echo := echoServer(t, "1.2.3.4")

	a := selfCheckAgent(capi.URL, nil, echo.URL)
	_, method, _, ok := a.runSelfCheckMethods(context.Background(), "1.2.3.4")
	if !ok || method != config.SelfCheckIPEcho || atomic.LoadInt32(&capiCalls) != 0 {
		t.Fatalf("method=%q ok=%v control-api calls=%d", method, ok, atomic.LoadInt32(&capiCalls))
	}
}

// A hung control-api must not use up the time of the fallback: each method
// has its own timeout.
func TestSelfCheckHungControlAPIDoesNotStarveFallback(t *testing.T) {
	release := make(chan struct{})
	capi := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		<-release
	}))
	defer capi.Close()
	defer close(release)
	echo := echoServer(t, "1.2.3.4")

	a := selfCheckAgent(capi.URL, []string{config.SelfCheckControlAPI, config.SelfCheckIPEcho}, echo.URL)
	a.cfg.SelfCheck.TimeoutSeconds = 1

	start := time.Now()
	// The outer context mirrors handleSelfCheckAndRun: timeout x methods.
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	_, method, detail, ok := a.runSelfCheckMethods(ctx, "1.2.3.4")
	if !ok || method != config.SelfCheckIPEcho {
		t.Fatalf("method=%q ok=%v detail=%q, want a pass via ip_echo after control_api timed out", method, ok, detail)
	}
	if elapsed := time.Since(start); elapsed > 1900*time.Millisecond {
		t.Fatalf("took %s: the hung method consumed the fallback's time", elapsed)
	}
}

// Every control-api request must use a new TCP connection: a connection
// opened before the floating IP was attached would report the old address.
func TestDetectViaControlAPIDialsNewConnectionEachTime(t *testing.T) {
	var conns int32
	ts := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprint(w, `{"ip":"1.2.3.4","source":"remote_addr"}`)
	}))
	ts.Config.ConnState = func(_ net.Conn, s http.ConnState) {
		if s == http.StateNew {
			atomic.AddInt32(&conns, 1)
		}
	}
	ts.Start()
	defer ts.Close()

	a := selfCheckAgent(ts.URL, nil)
	for i := 0; i < 3; i++ {
		if _, err := a.detectViaControlAPI(context.Background()); err != nil {
			t.Fatalf("call %d: %v", i, err)
		}
	}
	if n := atomic.LoadInt32(&conns); n != 3 {
		t.Fatalf("3 calls opened %d connections, want 3 (no keep-alive reuse)", n)
	}
}

func TestDetectViaControlAPIRejectsBadAnswers(t *testing.T) {
	for name, body := range map[string]string{"not json": "oops", "not an ip": `{"ip":"abc"}`, "empty": `{}`} {
		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { fmt.Fprint(w, body) }))
		a := selfCheckAgent(ts.URL, nil)
		if ip, err := a.detectViaControlAPI(context.Background()); err == nil {
			t.Fatalf("%s: expected an error, got %q", name, ip)
		}
		ts.Close()
	}
}

// The agent token must never be sent on this request (the route is open and
// the token is meant for control-api writes only).
func TestDetectViaControlAPISendsNoToken(t *testing.T) {
	var auth string
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		auth = r.Header.Get("Authorization")
		fmt.Fprint(w, `{"ip":"1.2.3.4"}`)
	}))
	defer ts.Close()
	a := selfCheckAgent(ts.URL, nil)
	if _, err := a.detectViaControlAPI(context.Background()); err != nil {
		t.Fatal(err)
	}
	if auth != "" {
		t.Fatalf("Authorization header sent: %q", auth)
	}
}