package main

import (
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"testing"
)

func write(t *testing.T, body string) string {
	t.Helper()
	path := filepath.Join(t.TempDir(), "routes.json")
	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	return path
}

// A route is a grant: the consumer supplies a target, and where that machine is comes from the
// mesh rather than from a naming convention the proxy has to know.
func TestARouteGoesToWhereTheMeshSaysTheConsumerIs(t *testing.T) {
	routes, err := routesFrom(write(t, `{"contributions":1,"requirement":"route","given":[
	  {"from":"app","node":"laptop","at":"laptop.internal","values":{"name":"App.Example","port":8080}}
	]}`))
	if err != nil {
		t.Fatal(err)
	}
	// Lower-cased, because a Host header is not case-sensitive and a route that only answers the
	// spelling in the manifest answers half the requests made to it.
	if routes["app.example"] != "http://laptop.internal:8080" {
		t.Fatalf("the route does not point at the consumer: %v", routes)
	}
}

// A workload beside the proxy is ordinary, and reaching it over loopback is both correct and the
// only thing that works when there is no private network.
func TestAConsumerOnTheProxysOwnMachineIsReachedOverLoopback(t *testing.T) {
	routes, err := routesFrom(write(t, `{"given":[
	  {"from":"app","node":"anchor","values":{"name":"app.example","port":9000}}
	]}`))
	if err != nil {
		t.Fatal(err)
	}
	if routes["app.example"] != "http://127.0.0.1:9000" {
		t.Fatalf("a workload on this machine was not reachable: %v", routes)
	}
}

// Skipped rather than served wrongly. A route with no port would proxy to :0.
func TestAContributionMissingWhatARouteNeedsIsSkipped(t *testing.T) {
	routes, err := routesFrom(write(t, `{"given":[
	  {"from":"a","node":"n","at":"n.internal","values":{"name":"no-port.example"}},
	  {"from":"b","node":"n","at":"n.internal","values":{"port":8080}},
	  {"from":"c","node":"n","at":"n.internal","values":{"name":"fine.example","port":8080}}
	]}`))
	if err != nil {
		t.Fatal(err)
	}
	if len(routes) != 1 || routes["fine.example"] == "" {
		t.Fatalf("an unusable contribution was served: %v", routes)
	}
}

// End to end through the proxy itself: a request for the name reaches the workload, and a name
// nobody asked for is refused in a way that says what IS served.
func TestTheProxyReachesTheWorkloadAndNamesWhatItServes(t *testing.T) {
	workload := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
		_, _ = w.Write([]byte("the workload"))
	}))
	defer workload.Close()
	target := strings.TrimPrefix(workload.URL, "http://")
	host, port, _ := strings.Cut(target, ":")

	held := newTable()
	held.set(map[string]string{"app.example": "http://" + host + ":" + port})

	proxy := httptest.NewServer(handler(held))
	defer proxy.Close()

	asked, err := http.NewRequest(http.MethodGet, proxy.URL, nil)
	if err != nil {
		t.Fatal(err)
	}
	asked.Host = "app.example"
	answer, err := http.DefaultClient.Do(asked)
	if err != nil {
		t.Fatal(err)
	}
	defer answer.Body.Close()
	if answer.StatusCode != http.StatusOK {
		t.Fatalf("a request for a served name got %d", answer.StatusCode)
	}

	// And a name that is not served says which are — a route withdrawn and a name that never
	// existed are different things, and a bare 404 makes an operator go and read the mesh.
	other, _ := http.NewRequest(http.MethodGet, proxy.URL, nil)
	other.Host = "nobody.example"
	refused, err := http.DefaultClient.Do(other)
	if err != nil {
		t.Fatal(err)
	}
	defer refused.Body.Close()
	if refused.StatusCode != http.StatusNotFound {
		t.Fatalf("a name nobody asked for got %d", refused.StatusCode)
	}
	body := make([]byte, 256)
	n, _ := refused.Body.Read(body)
	if !strings.Contains(string(body[:n]), "app.example") {
		t.Fatalf("the refusal does not say what is served: %s", body[:n])
	}
}

// The file is the whole truth about who has a route, so the table replaces rather than merges.
//
// Merging would keep serving a name whose module was unassigned — the stale-route fault
// 08-connectivity lists as open, reintroduced one level down. A stale public name pointing at
// nothing fails more visibly than a stale grant, which is exactly why it must not survive.
func TestWithdrawingARouteStopsServingIt(t *testing.T) {
	held := newTable()
	held.set(map[string]string{
		"going.example":   "http://a.internal:80",
		"staying.example": "http://b.internal:80",
	})
	held.set(map[string]string{"staying.example": "http://b.internal:80"})

	if _, still := held.find("going.example"); still {
		t.Fatal("a route whose module was unassigned is still served")
	}
	if _, kept := held.find("staying.example"); !kept {
		t.Fatal("withdrawing one route took another with it")
	}
}

// A Host header carries a port and the name does not.
func TestARequestNamingAPortStillFindsItsRoute(t *testing.T) {
	held := newTable()
	held.set(map[string]string{"app.example": "http://a.internal:8080"})
	if _, found := held.find("app.example:8080"); !found {
		t.Fatal("a request to app.example:8080 did not find the route for app.example")
	}
}