// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package oauth2

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"net/url"
	"testing"
	"time"

	"gitea.dev/modules/setting"
	"gitea.dev/modules/test"

	"github.com/markbates/goth/providers/openidConnect"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	go_oauth2 "golang.org/x/oauth2"
)

func TestOpenIDConnectPKCEProvider(t *testing.T) {
	var codeChallenge string
	var codeVerifier string
	var serverURL string

	server := httptest.NewServer(http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
		switch request.URL.Path {
		case "/.well-known/openid-configuration":
			response.Header().Set("Content-Type", "application/json")
			require.NoError(t, json.NewEncoder(response).Encode(map[string]string{
				"issuer":                 serverURL,
				"authorization_endpoint": serverURL + "/authorize",
				"token_endpoint":         serverURL + "/token",
			}))
		case "/token":
			require.NoError(t, request.ParseForm())
			codeVerifier = request.Form.Get("code_verifier")
			if codeVerifier == "" || go_oauth2.S256ChallengeFromVerifier(codeVerifier) != codeChallenge {
				http.Error(response, "invalid PKCE verifier", http.StatusBadRequest)
				return
			}
			claims, err := json.Marshal(map[string]any{
				"aud": "client-id",
				"exp": time.Now().Add(time.Hour).Unix(),
				"iss": serverURL,
				"sub": "person-1",
			})
			require.NoError(t, err)
			response.Header().Set("Content-Type", "application/json")
			require.NoError(t, json.NewEncoder(response).Encode(map[string]any{
				"access_token": "access-token",
				"expires_in":   3600,
				"id_token":     "e30." + base64.RawURLEncoding.EncodeToString(claims) + ".signature",
				"token_type":   "Bearer",
			}))
		default:
			http.NotFound(response, request)
		}
	}))
	defer server.Close()
	serverURL = server.URL

	defer test.MockVariableValue(&setting.OAuth2Client.EnableOpenIDConnectPKCE, true)()
	createdProvider, err := (&OpenIDProvider{}).CreateGothProvider(
		"example",
		"https://git.example.com/user/oauth2/example/callback",
		&Source{
			ClientID:                      "client-id",
			ClientSecret:                  "client-secret",
			OpenIDConnectAutoDiscoveryURL: server.URL + "/.well-known/openid-configuration",
			Scopes:                        []string{"openid"},
		},
	)
	require.NoError(t, err)
	pkceProvider, ok := createdProvider.(*openIDConnectPKCEProvider)
	require.True(t, ok)
	pkceProvider.Provider.SkipUserInfoRequest = true
	pkceProvider.SetName("example")
	session, err := pkceProvider.BeginAuth("test-state")
	require.NoError(t, err)
	authURL, err := session.GetAuthURL()
	require.NoError(t, err)
	parsedAuthURL, err := url.Parse(authURL)
	require.NoError(t, err)
	assert.Equal(t, "S256", parsedAuthURL.Query().Get("code_challenge_method"))
	codeChallenge = parsedAuthURL.Query().Get("code_challenge")
	assert.NotEmpty(t, codeChallenge)

	restoredSession, err := pkceProvider.UnmarshalSession(session.Marshal())
	require.NoError(t, err)
	accessToken, err := restoredSession.Authorize(pkceProvider, url.Values{"code": {"authorization-code"}})
	require.NoError(t, err)
	assert.Equal(t, "access-token", accessToken)
	assert.NotEmpty(t, codeVerifier)

	user, err := pkceProvider.FetchUser(restoredSession)
	require.NoError(t, err)
	assert.Equal(t, "person-1", user.UserID)
	assert.Equal(t, "example", user.Provider)
}

func TestOpenIDConnectPKCESessionRejectsMissingVerifier(t *testing.T) {
	provider := &openIDConnectPKCEProvider{Provider: &openidConnect.Provider{}}
	session := &openIDConnectPKCESession{}

	_, err := session.Authorize(provider, url.Values{"code": {"authorization-code"}})
	assert.EqualError(t, err, "OpenID Connect PKCE session is missing the code verifier")
	_, err = provider.UnmarshalSession(fmt.Sprintf(`{"session":{"AuthURL":%q}}`, "https://id.example.com/authorize"))
	assert.EqualError(t, err, "OpenID Connect PKCE session is missing the code verifier")
}

func TestAsOpenIDConnectProvider(t *testing.T) {
	provider := &openidConnect.Provider{}

	actual, ok := asOpenIDConnectProvider(provider)
	require.True(t, ok)
	assert.Same(t, provider, actual)

	actual, ok = asOpenIDConnectProvider(newOpenIDConnectPKCEProvider(provider))
	require.True(t, ok)
	assert.Same(t, provider, actual)
}