package com.heaerie.server.auth201.Auth201Server.config;

import com.nimbusds.jose.jwk.JWKSet;
import com.nimbusds.jose.jwk.RSAKey;
import com.nimbusds.jose.jwk.source.ImmutableJWKSet;
import com.nimbusds.jose.jwk.source.JWKSource;
import com.nimbusds.jose.proc.SecurityContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.Customizer;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.oauth2.core.AuthorizationGrantType;
import org.springframework.security.oauth2.core.ClientAuthenticationMethod;
import org.springframework.security.oauth2.core.oidc.OidcScopes;
import org.springframework.security.oauth2.jwt.JwtDecoder;
import org.springframework.security.oauth2.jwt.NimbusJwtDecoder;
import org.springframework.security.oauth2.server.authorization.client.InMemoryRegisteredClientRepository;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClient;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClientRepository;
import org.springframework.security.oauth2.server.authorization.settings.AuthorizationServerSettings;
import org.springframework.security.oauth2.server.authorization.settings.ClientSettings;
import org.springframework.security.oauth2.server.authorization.settings.TokenSettings;
import org.springframework.security.provisioning.InMemoryUserDetailsManager;
import org.springframework.security.web.SecurityFilterChain;

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.time.Duration;
import java.util.UUID;

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    /**
     * Default Security Filter Chain for authentication
     * Handles login and OAuth 2.1 authorization
     */
    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http
            .authorizeHttpRequests(authorize -> authorize
                .requestMatchers("/", "/h2-console/**").permitAll()
                .anyRequest().authenticated()
            )
            .formLogin(Customizer.withDefaults())
            .oauth2ResourceServer(oauth2 -> oauth2
                .jwt(Customizer.withDefaults())
            );
        
        // Allow H2 console access (development only)
        http.csrf(csrf -> csrf
            .ignoringRequestMatchers("/h2-console/**")
        );
        http.headers(headers -> headers
            .frameOptions(frame -> frame.sameOrigin())
        );

        return http.build();
    }

    /**
     * Registered Client Repository with OAuth 2.1 compliant configuration
     * This example uses in-memory storage, but you can implement database storage
     */
    @Bean
    public RegisteredClientRepository registeredClientRepository() {
        // OAuth 2.1 Public Client with PKCE (recommended for SPAs and mobile apps)
        RegisteredClient publicClient = RegisteredClient.withId(UUID.randomUUID().toString())
            .clientId("public-client")
            // No client secret for public clients (OAuth 2.1 requirement)
            .clientAuthenticationMethod(ClientAuthenticationMethod.NONE)
            .authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE)
            .authorizationGrantType(AuthorizationGrantType.REFRESH_TOKEN)
            .redirectUri("http://127.0.0.1:8080/login/oauth2/code/public-client")
            .redirectUri("http://127.0.0.1:8080/authorized")
            .postLogoutRedirectUri("http://127.0.0.1:8080/logged-out")
            .scope(OidcScopes.OPENID)
            .scope(OidcScopes.PROFILE)
            .scope(OidcScopes.EMAIL)
            .scope("read")
            .scope("write")
            .clientSettings(ClientSettings.builder()
                .requireAuthorizationConsent(true)
                .requireProofKey(true) // PKCE is required (OAuth 2.1)
                .build())
            .tokenSettings(TokenSettings.builder()
                .accessTokenTimeToLive(Duration.ofMinutes(15))
                .refreshTokenTimeToLive(Duration.ofHours(24))
                .reuseRefreshTokens(false) // OAuth 2.1: Refresh token rotation
                .build())
            .build();

        // OAuth 2.1 Confidential Client (for server-to-server)
        RegisteredClient confidentialClient = RegisteredClient.withId(UUID.randomUUID().toString())
            .clientId("confidential-client")
            .clientSecret("{bcrypt}$2a$10$MJJhX9K8bGqVHJwF8X8o6O5fF5F5F5F5F5F5F5F5F5F5F5F5F5F5F") // "secret"
            .clientAuthenticationMethod(ClientAuthenticationMethod.CLIENT_SECRET_BASIC)
            .clientAuthenticationMethod(ClientAuthenticationMethod.CLIENT_SECRET_POST)
            .authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE)
            .authorizationGrantType(AuthorizationGrantType.REFRESH_TOKEN)
            .authorizationGrantType(AuthorizationGrantType.CLIENT_CREDENTIALS)
            .redirectUri("http://127.0.0.1:8080/login/oauth2/code/confidential-client")
            .redirectUri("http://127.0.0.1:8080/authorized")
            .postLogoutRedirectUri("http://127.0.0.1:8080/logged-out")
            .scope(OidcScopes.OPENID)
            .scope(OidcScopes.PROFILE)
            .scope(OidcScopes.EMAIL)
            .scope("read")
            .scope("write")
            .clientSettings(ClientSettings.builder()
                .requireAuthorizationConsent(true)
                .requireProofKey(true) // PKCE recommended even for confidential clients
                .build())
            .tokenSettings(TokenSettings.builder()
                .accessTokenTimeToLive(Duration.ofMinutes(15))
                .refreshTokenTimeToLive(Duration.ofHours(24))
                .reuseRefreshTokens(false) // OAuth 2.1: Refresh token rotation
                .build())
            .build();

        return new InMemoryRegisteredClientRepository(publicClient, confidentialClient);
    }

    /**
     * User Details Service for authentication
     * In production, this should be backed by a database
     */
    @Bean
    public UserDetailsService userDetailsService() {
        UserDetails user = User.builder()
            .username("user")
            .password(passwordEncoder().encode("password"))
            .roles("USER")
            .build();

        UserDetails admin = User.builder()
            .username("admin")
            .password(passwordEncoder().encode("admin"))
            .roles("USER", "ADMIN")
            .build();

        return new InMemoryUserDetailsManager(user, admin);
    }

    /**
     * Password Encoder
     */
    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }

    /**
     * JWK Source for signing JWT tokens
     */
    @Bean
    public JWKSource<SecurityContext> jwkSource() {
        KeyPair keyPair = generateRsaKey();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        RSAKey rsaKey = new RSAKey.Builder(publicKey)
            .privateKey(privateKey)
            .keyID(UUID.randomUUID().toString())
            .build();
        JWKSet jwkSet = new JWKSet(rsaKey);
        return new ImmutableJWKSet<>(jwkSet);
    }

    /**
     * Generate RSA key pair for JWT signing
     */
    private static KeyPair generateRsaKey() {
        KeyPair keyPair;
        try {
            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
            keyPairGenerator.initialize(2048);
            keyPair = keyPairGenerator.generateKeyPair();
        } catch (Exception ex) {
            throw new IllegalStateException(ex);
        }
        return keyPair;
    }

    /**
     * JWT Decoder for validating JWT tokens
     */
    @Bean
    public JwtDecoder jwtDecoder(JWKSource<SecurityContext> jwkSource) {
        return NimbusJwtDecoder.withJwkSetUri("http://localhost:9000/oauth2/jwks").build();
    }

    /**
     * Authorization Server Settings
     * Configures the OAuth 2.1 endpoints
     */
    @Bean
    public AuthorizationServerSettings authorizationServerSettings() {
        return AuthorizationServerSettings.builder()
            .issuer("http://localhost:9000")
            .build();
    }
}