package certs

import (
	"context"
	"encoding/json"
	"net"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/miekg/dns"

	"steward/internal/config"
	"steward/internal/jarl"
)

// fakeJarl is Jarl's API as far as Steward uses it, and the DNS server
// that serves what it writes (both the "public resolver" and the zone's
// name server).
type fakeJarl struct {
	mu        sync.Mutex
	txt       map[string][]string // name -> values
	canWrite  bool
	token     string
	served    bool // the DNS server serves what is written
	zones     []jarl.Zone
	writes    int
	dryRuns   int
	nsHasIPv6 bool
}

func (f *fakeJarl) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Header.Get("Authorization") != "Bearer "+f.token {
		w.WriteHeader(401)
		w.Write([]byte(`{"error":{"code":"unauthenticated","message":"invalid API token: unknown token"}}`))
		return
	}
	switch r.URL.Path {
	case "/api/v1/auth/whoami":
		w.Write([]byte(`{"user":{"username":"steward"},"build":{"label":"v0.6.1"}}`))
	case "/api/v1/zones":
		json.NewEncoder(w).Encode(f.zones)
	case "/api/v1/apply":
		var b struct {
			Ops []struct {
				Op   string         `json:"op"`
				Data map[string]any `json:"data"`
			} `json:"ops"`
			DryRun bool `json:"dry_run"`
		}
		json.NewDecoder(r.Body).Decode(&b)
		if !f.canWrite {
			w.WriteHeader(403)
			w.Write([]byte(`{"error":{"code":"forbidden","message":"permission denied: this needs records:write"}}`))
			return
		}
		f.mu.Lock()
		defer f.mu.Unlock()
		if b.DryRun {
			f.dryRuns++
			w.Write([]byte(`{}`))
			return
		}
		f.writes++
		for _, op := range b.Ops {
			name, v := op.Data["name"].(string), op.Data["data"].(string)
			var keep []string
			for _, x := range f.txt[name] {
				if x != v {
					keep = append(keep, x)
				}
			}
			if op.Op == "record.create" {
				keep = append(keep, v)
			}
			f.txt[name] = keep
		}
		w.Write([]byte(`{}`))
	default:
		w.WriteHeader(404)
	}
}

func (f *fakeJarl) dns(w dns.ResponseWriter, r *dns.Msg) {
	m := new(dns.Msg)
	m.SetReply(r)
	q := r.Question[0]
	hdr := dns.RR_Header{Name: q.Name, Class: dns.ClassINET, Ttl: 60}
	switch q.Qtype {
	case dns.TypeNS:
		if q.Name == "adbraun.test." {
			hdr.Rrtype = dns.TypeNS
			m.Answer = append(m.Answer, &dns.NS{Hdr: hdr, Ns: "ns1.adbraun.test."})
		} else {
			m.Rcode = dns.RcodeNameError
		}
	case dns.TypeA:
		hdr.Rrtype = dns.TypeA
		m.Answer = append(m.Answer, &dns.A{Hdr: hdr, A: net.ParseIP("127.0.0.1")})
	case dns.TypeAAAA:
		// An IPv6 address nothing answers on (the check must not fail
		// because of it).
		if f.nsHasIPv6 {
			hdr.Rrtype = dns.TypeAAAA
			m.Answer = append(m.Answer, &dns.AAAA{Hdr: hdr, AAAA: net.ParseIP("100::1")})
		}
	case dns.TypeCNAME:
		if q.Name == "_acme-challenge.dhcp.other.test." {
			hdr.Rrtype = dns.TypeCNAME
			m.Answer = append(m.Answer, &dns.CNAME{Hdr: hdr, Target: "dhcp.acme.adbraun.test."})
		}
	case dns.TypeTXT:
		f.mu.Lock()
		if f.served {
			for _, v := range f.txt[q.Name] {
				hdr.Rrtype = dns.TypeTXT
				m.Answer = append(m.Answer, &dns.TXT{Hdr: hdr, Txt: []string{v}})
			}
		}
		f.mu.Unlock()
	}
	w.WriteMsg(m)
}

func setup(t *testing.T, f *fakeJarl, edit func(a *config.ACME)) (*Manager, string) {
	t.Helper()
	pc, err := net.ListenPacket("udp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	srv := &dns.Server{PacketConn: pc, Handler: dns.HandlerFunc(f.dns)}
	go srv.ActivateAndServe()
	t.Cleanup(func() { srv.Shutdown() })
	hs := httptest.NewServer(f)
	t.Cleanup(hs.Close)
	addr := pc.LocalAddr().String()
	_, port, _ := net.SplitHostPort(addr)
	oldPort, oldWait, oldPoll := nsPort, propagationWait, pollEvery
	nsPort, propagationWait, pollEvery = port, 2*time.Second, 100*time.Millisecond
	t.Cleanup(func() { nsPort, propagationWait, pollEvery = oldPort, oldWait, oldPoll })
	a := config.ACME{Domain: "dhcp.adbraun.test", Resolvers: []string{addr}, CheckPropagation: true}
	if edit != nil {
		edit(&a)
	}
	jc, _ := jarl.New(hs.URL, "steward_good", "", false)
	m := &Manager{cfg: Config{ACME: a}, jarl: jc, now: time.Now}
	return m, addr
}

func steps(c *Check) string {
	var out []string
	for _, s := range c.Steps {
		out = append(out, s.Name+"="+s.Status)
	}
	return strings.Join(out, " ")
}

func newFake() *fakeJarl {
	return &fakeJarl{txt: map[string][]string{}, canWrite: true, token: "steward_good", served: true,
		zones: []jarl.Zone{{Name: "adbraun.test.", View: "internal", LinkGroup: 7}, {Name: "adbraun.test.", View: "external", LinkGroup: 7}, {Name: "other.test.", View: "internal"}}}
}

func TestPreflightOK(t *testing.T) {
	f := newFake()
	f.nsHasIPv6 = true
	m, _ := setup(t, f, nil)
	c := m.Preflight(context.Background())
	want := "Jarl=ok Zone=ok Permission=ok Write=ok Name servers=ok Public resolvers=ok Clean up=ok"
	if !c.OK || steps(c) != want {
		t.Fatalf("got %s\n%+v", steps(c), c.Steps)
	}
	if !strings.Contains(c.Steps[1].Detail, "views internal, external") {
		t.Errorf("zone step: %s", c.Steps[1].Detail)
	}
	// Linked zones are written once; the test record is gone afterwards.
	if f.dryRuns != 1 || f.writes != 2 || len(f.txt["_acme-challenge.dhcp.adbraun.test."]) != 0 {
		t.Errorf("dry runs %d writes %d records %v", f.dryRuns, f.writes, f.txt)
	}
}

func TestPreflightFailures(t *testing.T) {
	cases := []struct {
		name string
		edit func(f *fakeJarl, a *config.ACME)
		want string
		text string
	}{
		{"bad token", func(f *fakeJarl, a *config.ACME) { f.token = "other" }, "Jarl=fail", "check jarl.token"},
		{"no zone", func(f *fakeJarl, a *config.ACME) { a.Domain = "dhcp.example.net" }, "Jarl=ok Zone=fail", "no primary zone the token can see"},
		{"no permission", func(f *fakeJarl, a *config.ACME) { f.canWrite = false }, "Jarl=ok Zone=ok Permission=fail",
			"records:write zones=adbraun.test names=_acme-challenge.dhcp.adbraun.test types=TXT"},
		{"not served", func(f *fakeJarl, a *config.ACME) { f.served = false },
			"Jarl=ok Zone=ok Permission=ok Write=ok Name servers=fail Public resolvers=fail Clean up=ok", "still don't serve it"},
		{"not delegated", func(f *fakeJarl, a *config.ACME) { f.zones[0].Name, f.zones[1].Name = "test.", "test." },
			"Jarl=ok Zone=ok Permission=ok Write=ok Name servers=fail Public resolvers=ok Clean up=ok", "know no name servers for test"},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			f := newFake()
			var am *config.ACME
			m, _ := setup(t, f, func(a *config.ACME) { am = a })
			tc.edit(f, am)
			m.cfg.ACME = *am
			c := m.Preflight(context.Background())
			if c.OK || steps(c) != tc.want {
				t.Fatalf("got %s, want %s\n%+v", steps(c), tc.want, c.Steps)
			}
			all := ""
			for _, s := range c.Steps {
				all += s.Detail + "\n"
			}
			if !strings.Contains(all, tc.text) {
				t.Errorf("details lack %q:\n%s", tc.text, all)
			}
		})
	}
}

func TestResolversOnlyWarnWhenNameServersServe(t *testing.T) {
	f := newFake()
	m, _ := setup(t, f, nil)
	// The "public resolver" is another server that never sees the record.
	pc, _ := net.ListenPacket("udp", "127.0.0.1:0")
	srv := &dns.Server{PacketConn: pc, Handler: dns.HandlerFunc(func(w dns.ResponseWriter, r *dns.Msg) {
		mm := new(dns.Msg)
		mm.SetReply(r)
		if r.Question[0].Qtype == dns.TypeTXT {
			mm.Rcode = dns.RcodeNameError
		} else {
			f.dns(w, r)
			return
		}
		w.WriteMsg(mm)
	})}
	go srv.ActivateAndServe()
	defer srv.Shutdown()
	m.cfg.ACME.Resolvers = []string{pc.LocalAddr().String()}
	c := m.Preflight(context.Background())
	if !c.OK || !strings.Contains(steps(c), "Public resolvers=warn") {
		t.Fatalf("got %s %+v", steps(c), c.Steps)
	}
}

func TestPreflightFollowsCNAME(t *testing.T) {
	f := newFake()
	m, _ := setup(t, f, func(a *config.ACME) { a.Domain = "dhcp.other.test" })
	c := m.Preflight(context.Background())
	if !c.OK || !strings.Contains(c.Steps[2].Detail, "dhcp.acme.adbraun.test") {
		t.Fatalf("got %s %+v", steps(c), c.Steps)
	}
}

func TestZonesFor(t *testing.T) {
	zs := []jarl.Zone{{Name: "lol.", View: "a"}, {Name: "adbraun.lol.", View: "internal", LinkGroup: 3}, {Name: "adbraun.lol.", View: "external", LinkGroup: 3},
		{Name: "adbraun.lol.", View: "guest"}, {Name: "notadbraun.lol.", View: "internal"}}
	got := jarl.ZonesFor("_acme-challenge.dhcp.adbraun.lol.", zs, "")
	if len(got) != 2 || got[0].View != "internal" || got[1].View != "guest" {
		t.Errorf("got %+v", got)
	}
	if n := jarl.ChallengeName("*.Dhcp.adbraun.lol."); n != "_acme-challenge.dhcp.adbraun.lol." {
		t.Errorf("challenge name %q", n)
	}
}