package server_test

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"math/big"
	"net/http"
	"net/http/httptest"
	"net/url"
	"path/filepath"
	"strings"
	"testing"

	"misaki/db"
	"misaki/server"
)

const (
	oidcIssuer   = "https://misaki.test"
	oidcSecret   = "pix-secret-pix-secret"
	oidcRedirect = "https://pix.test/auth/oidc/callback"
)

func newOIDCServer(t *testing.T) (http.Handler, *db.DB) {
	t.Helper()
	d := newTestDB(t)
	sum := sha256.Sum256([]byte(oidcSecret))
	srv := server.New(d, server.ServiceURLs{}, nil, server.SMTPConfig{}, server.Config{
		BaseDomain:  "misaki.test",
		TOTPKeyFile: filepath.Join(t.TempDir(), "totp.key"),
		OIDC: &server.OIDCConfig{
			Issuer:  oidcIssuer,
			KeyFile: filepath.Join(t.TempDir(), "oidc.pem"),
			Clients: []server.OIDCClient{
				{ID: "pix", SecretSHA256: hex.EncodeToString(sum[:]), RedirectURIs: []string{oidcRedirect}, Service: "pixelfed", RequireEmail: true},
				{ID: "social", SecretSHA256: hex.EncodeToString(sum[:]), RedirectURIs: []string{"https://social.test/oauth/misaki/callback"}, Service: "akkoma"},
			},
		},
	})
	return srv, d
}

// oidcLogin skips the empty cookie-clearing Set-Cookie sent when BaseDomain is set.
func oidcLogin(t *testing.T, srv http.Handler, user string) *http.Cookie {
	t.Helper()
	rr := doPost(srv, "/login", url.Values{"username": {user}, "password": {"hunter2hunter2"}}, nil)
	for _, c := range rr.Result().Cookies() {
		if c.Name == "session" && c.Value != "" {
			return c
		}
	}
	t.Fatalf("login %s failed: %d", user, rr.Code)
	return nil
}

func authorizeURL(extra url.Values) string {
	v := url.Values{
		"response_type": {"code"}, "client_id": {"pix"}, "redirect_uri": {oidcRedirect},
		"scope": {"openid profile email"}, "state": {"st8"}, "nonce": {"n0nce"},
	}
	for k, vs := range extra {
		v[k] = vs
	}
	return "/oauth/authorize?" + v.Encode()
}

func grantedUser(t *testing.T, srv http.Handler, d *db.DB, name string) *http.Cookie {
	t.Helper()
	id := makeApprovedUser(t, d, name, "hunter2hunter2")
	d.SetUserServiceEnabled(id, "pixelfed", true)
	d.SetUserEmail(id, name+"@thirdculture.diy")
	return oidcLogin(t, srv, name)
}

func getCode(t *testing.T, srv http.Handler, c *http.Cookie, extra url.Values) string {
	t.Helper()
	rr := doGet(srv, authorizeURL(extra), c)
	if rr.Code != http.StatusFound {
		t.Fatalf("authorize: got %d (%s)", rr.Code, rr.Header().Get("Location"))
	}
	loc, _ := url.Parse(rr.Header().Get("Location"))
	if !strings.HasPrefix(loc.String(), oidcRedirect+"?") || loc.Query().Get("state") != "st8" || loc.Query().Get("iss") != oidcIssuer {
		t.Fatalf("authorize redirect: %s", loc)
	}
	return loc.Query().Get("code")
}

func exchange(srv http.Handler, form url.Values, basic bool) *httptest.ResponseRecorder {
	if form.Get("grant_type") == "" {
		form.Set("grant_type", "authorization_code")
	}
	if form.Get("redirect_uri") == "" {
		form.Set("redirect_uri", oidcRedirect)
	}
	req := httptest.NewRequest(http.MethodPost, "/oauth/token", strings.NewReader(form.Encode()))
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	if basic {
		req.SetBasicAuth("pix", oidcSecret)
	}
	rr := httptest.NewRecorder()
	srv.ServeHTTP(rr, req)
	return rr
}

type tokenResp struct {
	AccessToken string `json:"access_token"`
	IDToken     string `json:"id_token"`
	Error       string `json:"error"`
}

func verifyIDToken(t *testing.T, srv http.Handler, tok string) map[string]any {
	t.Helper()
	var jwks struct{ Keys []map[string]string }
	json.NewDecoder(doGet(srv, "/oauth/jwks", nil).Body).Decode(&jwks)
	if len(jwks.Keys) != 1 {
		t.Fatalf("jwks: %+v", jwks)
	}
	k := jwks.Keys[0]
	b := base64.RawURLEncoding
	x, _ := b.DecodeString(k["x"])
	y, _ := b.DecodeString(k["y"])
	pub := &ecdsa.PublicKey{Curve: elliptic.P256(), X: new(big.Int).SetBytes(x), Y: new(big.Int).SetBytes(y)}

	parts := strings.Split(tok, ".")
	if len(parts) != 3 {
		t.Fatalf("id_token parts: %d", len(parts))
	}
	var hdr map[string]string
	h, _ := b.DecodeString(parts[0])
	json.Unmarshal(h, &hdr)
	if hdr["alg"] != "ES256" || hdr["kid"] != k["kid"] {
		t.Fatalf("header: %v", hdr)
	}
	sig, _ := b.DecodeString(parts[2])
	sum := sha256.Sum256([]byte(parts[0] + "." + parts[1]))
	if len(sig) != 64 || !ecdsa.Verify(pub, sum[:], new(big.Int).SetBytes(sig[:32]), new(big.Int).SetBytes(sig[32:])) {
		t.Fatal("id_token signature does not verify against jwks")
	}
	var claims map[string]any
	body, _ := b.DecodeString(parts[1])
	json.Unmarshal(body, &claims)
	return claims
}

func TestOIDCDiscovery(t *testing.T) {
	srv, _ := newOIDCServer(t)
	rr := doGet(srv, "/.well-known/openid-configuration", nil)
	assertStatus(t, rr, http.StatusOK)
	var d map[string]any
	json.NewDecoder(rr.Body).Decode(&d)
	if d["issuer"] != oidcIssuer || d["token_endpoint"] != oidcIssuer+"/oauth/token" {
		t.Errorf("discovery: %v", d)
	}
}

func TestOIDCDisabledWithoutConfig(t *testing.T) {
	srv, _ := newTestServer(t)
	if rr := doGet(srv, "/.well-known/openid-configuration", nil); rr.Code == http.StatusOK {
		t.Error("discovery should not exist without oidc config")
	}
}

func TestOIDCAuthorizeRejects(t *testing.T) {
	srv, d := newOIDCServer(t)

	rr := doGet(srv, authorizeURL(url.Values{"redirect_uri": {"https://evil.test/cb"}}), nil)
	assertStatus(t, rr, http.StatusBadRequest)
	rr = doGet(srv, authorizeURL(url.Values{"client_id": {"nope"}}), nil)
	assertStatus(t, rr, http.StatusBadRequest)

	rr = doGet(srv, authorizeURL(nil), nil)
	assertRedirectTo(t, rr, "/login?next="+url.QueryEscape(oidcIssuer+"/oauth/authorize?"))

	id := makeApprovedUser(t, d, "nogrant", "hunter2hunter2")
	c := oidcLogin(t, srv, "nogrant")
	assertRedirectTo(t, doGet(srv, authorizeURL(nil), c), "/dashboard?err=request+access")

	d.SetUserServiceEnabled(id, "pixelfed", true)
	assertRedirectTo(t, doGet(srv, authorizeURL(nil), c), "/dashboard?err=add+a+contact+email")

	d.SetUserEmail(id, "x@thirdculture.diy")
	for name, extra := range map[string]url.Values{
		"plain pkce": {"code_challenge": {"abc"}, "code_challenge_method": {"plain"}},
		"no openid":  {"scope": {"profile"}},
		"implicit":   {"response_type": {"token"}},
		"huge state": {"state": {strings.Repeat("a", 600)}},
	} {
		rr := doGet(srv, authorizeURL(extra), c)
		loc, _ := url.Parse(rr.Header().Get("Location"))
		if rr.Code != http.StatusFound || loc.Query().Get("error") == "" || loc.Query().Get("code") != "" {
			t.Errorf("%s: want error redirect, got %d %s", name, rr.Code, loc)
		}
	}
}

func TestOIDCFlow(t *testing.T) {
	srv, d := newOIDCServer(t)
	c := grantedUser(t, srv, d, "Misaki_fan")

	code := getCode(t, srv, c, nil)

	if rr := exchange(srv, url.Values{"code": {code}, "client_id": {"pix"}, "client_secret": {"wrong"}}, false); rr.Code != http.StatusUnauthorized {
		t.Errorf("wrong secret: got %d", rr.Code)
	}
	// the failed attempt above did not consume the code (client auth runs first)
	if rr := exchange(srv, url.Values{"code": {code}, "redirect_uri": {"https://pix.test/other"}}, true); rr.Code != http.StatusBadRequest {
		t.Errorf("redirect mismatch: got %d", rr.Code)
	}
	// ...but a mismatched redirect does burn it
	if rr := exchange(srv, url.Values{"code": {code}}, true); rr.Code != http.StatusBadRequest {
		t.Errorf("burnt code reused: got %d", rr.Code)
	}

	code = getCode(t, srv, c, nil)
	rr := exchange(srv, url.Values{"code": {code}, "client_id": {"pix"}, "client_secret": {oidcSecret}}, false)
	assertStatus(t, rr, http.StatusOK)
	if cc := rr.Header().Get("Cache-Control"); cc != "no-store" {
		t.Errorf("token Cache-Control: %q", cc)
	}
	var tr tokenResp
	json.NewDecoder(rr.Body).Decode(&tr)
	claims := verifyIDToken(t, srv, tr.IDToken)
	for k, want := range map[string]any{"iss": oidcIssuer, "aud": "pix", "nonce": "n0nce", "preferred_username": "Misaki_fan", "nickname": "Misaki_fan", "email": "Misaki_fan@thirdculture.diy"} {
		if claims[k] != want {
			t.Errorf("claim %s: got %v, want %v", k, claims[k], want)
		}
	}
	if s, _ := claims["sub"].(string); s == "" || s == "Misaki_fan" {
		t.Errorf("sub should be the stable id, got %v", claims["sub"])
	}

	if rr := exchange(srv, url.Values{"code": {code}}, true); rr.Code != http.StatusBadRequest {
		t.Errorf("code reuse: got %d", rr.Code)
	}

	req := httptest.NewRequest(http.MethodGet, "/oauth/userinfo", nil)
	req.Header.Set("Authorization", "Bearer "+tr.AccessToken)
	ui := httptest.NewRecorder()
	srv.ServeHTTP(ui, req)
	assertStatus(t, ui, http.StatusOK)
	var info map[string]any
	json.NewDecoder(ui.Body).Decode(&info)
	if info["sub"] != claims["sub"] || info["email"] != "Misaki_fan@thirdculture.diy" {
		t.Errorf("userinfo: %v", info)
	}

	u, _ := d.GetUserByUsername("Misaki_fan")
	d.SetUserServiceEnabled(u.ID, "pixelfed", false)
	ui = httptest.NewRecorder()
	srv.ServeHTTP(ui, req)
	assertStatus(t, ui, http.StatusUnauthorized)
}

func TestOIDCPKCE(t *testing.T) {
	srv, d := newOIDCServer(t)
	c := grantedUser(t, srv, d, "pkceuser")
	verifier := "a-verifier-that-is-long-enough-to-be-realistic-0123456789"
	sum := sha256.Sum256([]byte(verifier))
	challenge := base64.RawURLEncoding.EncodeToString(sum[:])
	pkce := url.Values{"code_challenge": {challenge}, "code_challenge_method": {"S256"}}

	code := getCode(t, srv, c, pkce)
	if rr := exchange(srv, url.Values{"code": {code}, "code_verifier": {"wrong"}}, true); rr.Code != http.StatusBadRequest {
		t.Errorf("bad verifier: got %d", rr.Code)
	}
	code = getCode(t, srv, c, pkce)
	if rr := exchange(srv, url.Values{"code": {code}}, true); rr.Code != http.StatusBadRequest {
		t.Errorf("missing verifier: got %d", rr.Code)
	}
	code = getCode(t, srv, c, pkce)
	if rr := exchange(srv, url.Values{"code": {code}, "code_verifier": {verifier}}, true); rr.Code != http.StatusOK {
		t.Errorf("good verifier: got %d", rr.Code)
	}
}

func TestOIDCCodeBoundToClient(t *testing.T) {
	srv, d := newOIDCServer(t)
	c := grantedUser(t, srv, d, "bound")
	u, _ := d.GetUserByUsername("bound")
	d.SetUserServiceEnabled(u.ID, "akkoma", true)
	code := getCode(t, srv, c, nil)
	// a different (valid) client may not redeem pix's code
	form := url.Values{"code": {code}, "grant_type": {"authorization_code"}, "redirect_uri": {"https://social.test/oauth/misaki/callback"},
		"client_id": {"social"}, "client_secret": {oidcSecret}}
	if rr := exchange(srv, form, false); rr.Code != http.StatusBadRequest {
		t.Errorf("cross-client redemption: got %d", rr.Code)
	}
}

func TestOIDCApplyNeedsEmail(t *testing.T) {
	srv, d := newOIDCServer(t)
	makeApprovedUser(t, d, "applicant", "hunter2hunter2")
	c := oidcLogin(t, srv, "applicant")

	assertRedirectTo(t, doPost(srv, "/dashboard/apply", url.Values{"service": {"pixelfed"}}, c), "/dashboard?err=an+email")
	assertRedirectTo(t, doPost(srv, "/dashboard/apply", url.Values{"service": {"pixelfed"}, "email": {"nope"}}, c), "/dashboard?err=invalid+email")
	assertRedirectTo(t, doPost(srv, "/dashboard/apply", url.Values{"service": {"pixelfed"}, "email": {"me@thirdculture.diy"}}, c), "/dashboard?msg=applied")
	// akkoma doesn't need one
	assertRedirectTo(t, doPost(srv, "/dashboard/apply", url.Values{"service": {"akkoma"}}, c), "/dashboard?msg=applied")

	u, _ := d.GetUserByUsername("applicant")
	if e, _ := d.GetUserEmail(u.ID); e != "me@thirdculture.diy" {
		t.Errorf("stored email: %q", e)
	}
}