/*
 * Copyright 2004-present the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.security.oauth2.server.resource.authentication;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.convert.converter.Converter;
import org.springframework.core.log.LogMessage;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.oauth2.jwt.Jwt;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Extracts the {@link GrantedAuthority}s from scope attributes typically found in a
 * {@link Jwt}.
 *
 * @author Eric Deandrea
 * @since 5.2
 */
public final class JwtGrantedAuthoritiesConverter implements Converter<Jwt, Collection<GrantedAuthority>> {

	private final Log logger = LogFactory.getLog(getClass());

	private static final String DEFAULT_AUTHORITY_PREFIX = "SCOPE_";

	private static final String DEFAULT_AUTHORITIES_CLAIM_DELIMITER = " ";

	private static final Collection<String> WELL_KNOWN_AUTHORITIES_CLAIM_NAMES = Arrays.asList("scope", "scp");

	private String authorityPrefix = DEFAULT_AUTHORITY_PREFIX;

	private String authoritiesClaimDelimiter = DEFAULT_AUTHORITIES_CLAIM_DELIMITER;

	private Collection<String> authoritiesClaimNames = WELL_KNOWN_AUTHORITIES_CLAIM_NAMES;

	/**
	 * Extract {@link GrantedAuthority}s from the given {@link Jwt}.
	 * @param jwt The {@link Jwt} token
	 * @return The {@link GrantedAuthority authorities} read from the token scopes
	 */
	@Override
	public Collection<GrantedAuthority> convert(Jwt jwt) {
		Collection<GrantedAuthority> grantedAuthorities = new ArrayList<>();
		for (String authority : getAuthorities(jwt)) {
			grantedAuthorities.add(new SimpleGrantedAuthority(this.authorityPrefix + authority));
		}
		return grantedAuthorities;
	}

	/**
	 * Sets the prefix to use for {@link GrantedAuthority authorities} mapped by this
	 * converter. Defaults to
	 * {@link JwtGrantedAuthoritiesConverter#DEFAULT_AUTHORITY_PREFIX}.
	 * @param authorityPrefix The authority prefix
	 * @since 5.2
	 */
	public void setAuthorityPrefix(String authorityPrefix) {
		Assert.notNull(authorityPrefix, "authorityPrefix cannot be null");
		this.authorityPrefix = authorityPrefix;
	}

	/**
	 * Sets the regex to use for splitting the value of the authorities claim into
	 * {@link GrantedAuthority authorities}. Defaults to
	 * {@link JwtGrantedAuthoritiesConverter#DEFAULT_AUTHORITIES_CLAIM_DELIMITER}.
	 * @param authoritiesClaimDelimiter The regex used to split the authorities
	 * @since 6.1
	 */
	public void setAuthoritiesClaimDelimiter(String authoritiesClaimDelimiter) {
		Assert.notNull(authoritiesClaimDelimiter, "authoritiesClaimDelimiter cannot be null");
		this.authoritiesClaimDelimiter = authoritiesClaimDelimiter;
	}

	/**
	 * Sets the name of token claim to use for mapping {@link GrantedAuthority
	 * authorities} by this converter. Defaults to
	 * {@link JwtGrantedAuthoritiesConverter#WELL_KNOWN_AUTHORITIES_CLAIM_NAMES}.
	 * @param authoritiesClaimName The token claim name to map authorities
	 * @since 5.2
	 */
	public void setAuthoritiesClaimName(String authoritiesClaimName) {
		Assert.hasText(authoritiesClaimName, "authoritiesClaimName cannot be empty");
		this.authoritiesClaimNames = Collections.singletonList(authoritiesClaimName);
	}

	private String getAuthoritiesClaimName(Jwt jwt) {
		for (String claimName : this.authoritiesClaimNames) {
			if (jwt.hasClaim(claimName)) {
				return claimName;
			}
		}
		return null;
	}

	private Collection<String> getAuthorities(Jwt jwt) {
		String claimName = getAuthoritiesClaimName(jwt);
		if (claimName == null) {
			this.logger.trace("Returning no authorities since could not find any claims that might contain scopes");
			return Collections.emptyList();
		}
		if (this.logger.isTraceEnabled()) {
			this.logger.trace(LogMessage.format("Looking for scopes in claim %s", claimName));
		}
		Object authorities = jwt.getClaim(claimName);
		if (authorities instanceof String) {
			if (StringUtils.hasText((String) authorities)) {
				return Arrays.asList(((String) authorities).split(this.authoritiesClaimDelimiter));
			}
			return Collections.emptyList();
		}
		if (authorities instanceof Collection) {
			return castAuthoritiesToCollection(authorities);
		}
		return Collections.emptyList();
	}

	@SuppressWarnings("unchecked")
	private Collection<String> castAuthoritiesToCollection(Object authorities) {
		return (Collection<String>) authorities;
	}

}
