package auth

import (
	"crypto/rand"
	"crypto/rsa"
	"encoding/base64"
	"net/http"
	"net/http/httptest"
	"strconv"
	"sync/atomic"
	"testing"
	"time"

	"github.com/go-jose/go-jose/v4"
	"github.com/go-jose/go-jose/v4/jwt"

	"git.unkin.net/unkin/artifactapi/internal/testsupport"
)

func serve(h http.Handler, method, token string) int {
	if token == "" {
		return serveAuth(h, method, "")
	}
	return serveAuth(h, method, "Bearer "+token)
}

func serveAuth(h http.Handler, method, authz string) int {
	r := httptest.NewRequest(method, "/x", nil)
	if authz != "" {
		r.Header.Set("Authorization", authz)
	}
	w := httptest.NewRecorder()
	h.ServeHTTP(w, r)
	return w.Code
}

func claims(iss string) jwt.Claims {
	now := time.Now()
	return jwt.Claims{
		Issuer:   iss,
		Subject:  "ci",
		Audience: jwt.Audience{"artifactapi"},
		IssuedAt: jwt.NewNumericDate(now.Add(-time.Minute)),
		Expiry:   jwt.NewNumericDate(now.Add(time.Hour)),
	}
}

func hs256Token(t *testing.T, c jwt.Claims) string {
	sig, err := jose.NewSigner(jose.SigningKey{Algorithm: jose.HS256, Key: []byte("0123456789abcdef0123456789abcdef")},
		(&jose.SignerOptions{}).WithType("JWT").WithHeader("kid", "k1"))
	if err != nil {
		t.Fatal(err)
	}
	tok, err := jwt.Signed(sig).Claims(c).Serialize()
	if err != nil {
		t.Fatal(err)
	}
	return tok
}

func noneToken(iss string) string {
	enc := base64.RawURLEncoding.EncodeToString
	return enc([]byte(`{"alg":"none","typ":"JWT","kid":"k1"}`)) + "." +
		enc([]byte(`{"iss":"`+iss+`","sub":"ci","aud":"artifactapi","exp":`+strconv.FormatInt(time.Now().Add(time.Hour).Unix(), 10)+`}`)) + "."
}

var ok = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(http.StatusNoContent) })

func TestBearerOIDC(t *testing.T) {
	iss := testsupport.NewOIDCIssuer()
	defer iss.Close()
	h := NewBearerOIDC(iss.URL, []string{"other", "artifactapi"}).Require(ok)

	otherKey, _ := rsa.GenerateKey(rand.Reader, 2048)
	cases := []struct {
		name  string
		token string
		want  int
	}{
		{"valid", iss.Token(nil, "artifactapi", "ci", time.Hour), http.StatusNoContent},
		{"missing", "", http.StatusUnauthorized},
		{"garbage", "not.a.jwt", http.StatusUnauthorized},
		{"bad signature", iss.Token(otherKey, "artifactapi", "ci", time.Hour), http.StatusUnauthorized},
		{"wrong aud", iss.Token(nil, "nope", "ci", time.Hour), http.StatusUnauthorized},
		{"expired", iss.Token(nil, "artifactapi", "ci", -time.Hour), http.StatusUnauthorized},
		{"wrong iss", iss.Sign(nil, claims("https://evil.example")), http.StatusUnauthorized},
		{"hs256", hs256Token(t, claims(iss.URL)), http.StatusUnauthorized},
		{"alg none", noneToken(iss.URL), http.StatusUnauthorized},
	}
	for _, c := range cases {
		if got := serve(h, http.MethodPost, c.token); got != c.want {
			t.Errorf("%s: status %d, want %d", c.name, got, c.want)
		}
	}

	valid := iss.Token(nil, "artifactapi", "ci", time.Hour)
	headers := []struct {
		name  string
		authz string
		want  int
	}{
		{"lowercase scheme", "bearer " + valid, http.StatusNoContent},
		{"extra whitespace", "  Bearer   " + valid + " ", http.StatusNoContent},
		{"empty value", "Bearer ", http.StatusUnauthorized},
		{"scheme only", "Bearer", http.StatusUnauthorized},
		{"basic scheme", "Basic " + valid, http.StatusUnauthorized},
	}
	for _, c := range headers {
		if got := serveAuth(h, http.MethodPost, c.authz); got != c.want {
			t.Errorf("%s: status %d, want %d", c.name, got, c.want)
		}
	}
}

func TestBearerOIDCHangingIssuerBacksOff(t *testing.T) {
	var hits atomic.Int32
	release := make(chan struct{})
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		hits.Add(1)
		select {
		case <-r.Context().Done():
		case <-release:
		}
	}))
	defer srv.Close()
	defer close(release)

	b := NewBearerOIDC(srv.URL, nil)
	b.timeout = 100 * time.Millisecond
	b.backoff = time.Hour
	h := b.Require(ok)

	start := time.Now()
	if got := serve(h, http.MethodPost, "x.y.z"); got != http.StatusServiceUnavailable {
		t.Fatalf("hanging issuer: status %d, want 503", got)
	}
	if d := time.Since(start); d > 2*time.Second {
		t.Fatalf("hanging issuer: took %s, timeout not applied", d)
	}
	if got := serve(h, http.MethodPost, "x.y.z"); got != http.StatusServiceUnavailable {
		t.Fatalf("during backoff: status %d, want 503", got)
	}
	if n := hits.Load(); n != 1 {
		t.Fatalf("issuer hit %d times, want 1", n)
	}
}

func TestBearerOIDCRetriesAfterBackoff(t *testing.T) {
	iss := testsupport.NewOIDCIssuer()
	defer iss.Close()
	b := NewBearerOIDC(iss.URL, nil)
	b.failedAt = time.Now()
	b.backoff = 50 * time.Millisecond
	tok := iss.Token(nil, "artifactapi", "ci", time.Hour)
	if got := serve(b.Require(ok), http.MethodPost, tok); got != http.StatusServiceUnavailable {
		t.Fatalf("within backoff: status %d, want 503", got)
	}
	time.Sleep(60 * time.Millisecond)
	if got := serve(b.Require(ok), http.MethodPost, tok); got != http.StatusNoContent {
		t.Fatalf("after backoff: status %d, want 204", got)
	}
}

func TestBearerOIDCIssuerDown(t *testing.T) {
	iss := testsupport.NewOIDCIssuer()
	b := NewBearerOIDC(iss.URL, []string{"artifactapi"})
	tok := iss.Token(nil, "artifactapi", "ci", time.Hour)
	iss.Close()
	if got := serve(b.Require(ok), http.MethodPost, tok); got != http.StatusServiceUnavailable {
		t.Errorf("issuer down: status %d, want 503", got)
	}
}

func TestBearerOIDCDisabled(t *testing.T) {
	if got := serve(NewBearerOIDC("", nil).RequireWrites(ok), http.MethodDelete, ""); got != http.StatusNoContent {
		t.Errorf("disabled: status %d, want 204", got)
	}
}

func TestRequireWritesLeavesReadsOpen(t *testing.T) {
	iss := testsupport.NewOIDCIssuer()
	defer iss.Close()
	h := NewBearerOIDC(iss.URL, []string{"artifactapi"}).RequireWrites(ok)
	for _, m := range []string{http.MethodGet, http.MethodHead, http.MethodOptions} {
		if got := serve(h, m, ""); got != http.StatusNoContent {
			t.Errorf("%s: status %d, want 204", m, got)
		}
	}
	for _, m := range []string{http.MethodPost, http.MethodPut, http.MethodDelete} {
		if got := serve(h, m, ""); got != http.StatusUnauthorized {
			t.Errorf("%s: status %d, want 401", m, got)
		}
	}
}