/*
 * oauth2-oidc-sdk
 *
 * Copyright 2020, Connect2id Ltd and contributors.
 *
 * 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
 *
 *    http://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 com.nimbusds.common.contenttype;


import java.nio.charset.Charset;
import java.text.ParseException;
import java.util.*;


/**
 * Content (media) type.
 *
 * <p>To create a new content type {@code application/json} without character
 * set parameter:
 *
 * <pre>
 * ContentType ct = new ContentType("application", "json");
 *
 * // Prints out "application/json"
 * System.out.println(ct.toString());
 * </pre>
 *
 * <p>With a character set parameter {@code application/json; charset=UTF-8}:
 *
 * <pre>
 * ContentType ct = new ContentType("application", "json", new ContentType.Parameter("charset", "UTF-8"));
 *
 * // Prints out "application/json; charset=UTF-8"
 * System.out.println(ct.toString());
 * </pre>
 *
 * <p>To parse a content type:
 *
 * <pre>
 * try {
 *         ContentType.parse("application/json; charset=UTF-8");
 * } catch (java.text.ParseException e) {
 *         System.err.println(e.getMessage());
 * }
 * </pre>
 *
 * <p>See RFC 2045, section 5.1.
 *
 * @author vd
 */
public final class ContentType {
        
        
        /**
         * Optional content type parameter, for example {@code charset=UTF-8}.
         */
        public static final class Parameter {
                
                
                /**
                 * A {@code charset=UTF-8} parameter.
                 */
                public static final Parameter CHARSET_UTF_8 = new Parameter("charset", "UTF-8");
                
                
                /**
                 * The parameter name.
                 */
                private final String name;
                
                
                /**
                 * The parameter value.
                 */
                private final String value;
                
                
                /**
                 * Creates a new content type parameter.
                 *
                 * @param name  The name. Must not be {@code null} or empty.
                 * @param value The value. Must not be {@code null} or empty.
                 */
                public Parameter(final String name, final String value) {
                        
                        if (name == null || name.trim().isEmpty()) {
                                throw new IllegalArgumentException("The parameter name must be specified");
                        }
                        this.name = name;
                        
                        if (value == null || value.trim().isEmpty()) {
                                throw new IllegalArgumentException("The parameter value must be specified");
                        }
                        this.value = value;
                }
                
                
                /**
                 * Returns the parameter name.
                 *
                 * @return The name.
                 */
                public String getName() {
                        return name;
                }
                
                
                /**
                 * Returns the parameter value.
                 *
                 * @return The value.
                 */
                public String getValue() {
                        return value;
                }
                
                
                @Override
                public String toString() {
                        return name + "=" + value;
                }
                
                
                @Override
                public boolean equals(Object o) {
                        if (this == o) return true;
                        if (!(o instanceof Parameter)) return false;
                        Parameter parameter = (Parameter) o;
                        return getName().equalsIgnoreCase(parameter.getName()) &&
                                getValue().equalsIgnoreCase(parameter.getValue());
                }
                
                
                @Override
                public int hashCode() {
                        return Objects.hash(getName().toLowerCase(), getValue().toLowerCase());
                }
        }
        
        
        /**
         * Content type {@code application/json; charset=UTF-8}.
         */
        public static final ContentType APPLICATION_JSON = new ContentType("application", "json", Parameter.CHARSET_UTF_8);
        
        
        /**
         * Content type {@code application/jose; charset=UTF-8}.
         */
        public static final ContentType APPLICATION_JOSE = new ContentType("application", "jose", Parameter.CHARSET_UTF_8);
        
        
        /**
         * Content type {@code application/jwt; charset=UTF-8}.
         */
        public static final ContentType APPLICATION_JWT = new ContentType("application", "jwt", Parameter.CHARSET_UTF_8);
        
        
        /**
         * Content type {@code application/x-www-form-urlencoded; charset=UTF-8}.
         */
        public static final ContentType APPLICATION_URLENCODED = new ContentType("application", "x-www-form-urlencoded", Parameter.CHARSET_UTF_8);
        
        
        /**
         * Content type {@code text/plain; charset=UTF-8}.
         */
        public static final ContentType TEXT_PLAIN = new ContentType("text", "plain", Parameter.CHARSET_UTF_8);
        
        
        /**
         * The base type.
         */
        private final String baseType;
        
        
        /**
         * The sub type.
         */
        private final String subType;
        
        
        /**
         * The optional parameters.
         */
        private final List<Parameter> params;
        
        
        /**
         * Creates a new content type.
         *
         * @param baseType The type. E.g. "application" from
         *                 "application/json".Must not be {@code null} or
         *                 empty.
         * @param subType  The subtype. E.g. "json" from "application/json".
         *                 Must not be {@code null} or empty.
         * @param param    Optional parameters.
         */
        public ContentType(final String baseType, final String subType, final Parameter ... param) {
                
                if (baseType == null || baseType.trim().isEmpty()) {
                        throw new IllegalArgumentException("The base type must be specified");
                }
                this.baseType = baseType;
                
                if (subType == null || subType.trim().isEmpty()) {
                        throw new IllegalArgumentException("The subtype must be specified");
                }
                this.subType = subType;
                
                
                if (param != null && param.length > 0) {
                        params = Collections.unmodifiableList(Arrays.asList(param));
                } else {
                        params = Collections.emptyList();
                }
        }
        
        
        /**
         * Creates a new content type with the specified character set.
         *
         * @param baseType The base type. E.g. "application" from
         *                 "application/json".Must not be {@code null} or
         *                 empty.
         * @param subType  The subtype. E.g. "json" from "application/json".
         *                 Must not be {@code null} or empty.
         * @param charset  The character set to use for the {@code charset}
         *                 parameter. Must not be {@code null}.
         */
        public ContentType(final String baseType, final String subType, final Charset charset) {
                
                this(baseType, subType, new Parameter("charset", charset.toString()));
        }
        
        
        /**
         * Returns the base type. E.g. "application" from "application/json".
         *
         * @return The base type.
         */
        public String getBaseType() {
                return baseType;
        }
        
        
        /**
         * Returns the subtype. E.g. "json" from "application/json".
         *
         * @return The subtype.
         */
        public String getSubType() {
                return subType;
        }
        
        
        /**
         * Returns the type. E.g. "application/json".
         *
         * @return The type, any optional parameters are omitted.
         */
        public String getType() {
                
                StringBuilder sb = new StringBuilder();
                sb.append(getBaseType());
                sb.append("/");
                sb.append(getSubType());
                return sb.toString();
        }
        
        
        /**
         * Returns the optional parameters.
         *
         * @return The parameters, as unmodifiable list, empty list if none.
         */
        public List<Parameter> getParameters() {
                return params;
        }
        
        
        /**
         * Returns {@code true} if the types and subtypes match. The
         * parameters, if any, are ignored.
         *
         * @param other The other content type, {@code null} if not specified.
         *
         * @return {@code true} if the types and subtypes match, else
         *         {@code false}.
         */
        public boolean matches(final ContentType other) {
                
                return other != null
                        && getBaseType().equalsIgnoreCase(other.getBaseType())
                        && getSubType().equalsIgnoreCase(other.getSubType());
        }
        
        
        @Override
        public String toString() {
                
                StringBuilder sb = new StringBuilder(getType());
                
                if (! getParameters().isEmpty()) {
                        for (Parameter p: getParameters()) {
                                sb.append("; ");
                                sb.append(p.getName());
                                sb.append("=");
                                sb.append(p.getValue());
                        }
                }
                
                return sb.toString();
        }
        
        
        @Override
        public boolean equals(Object o) {
                if (this == o) return true;
                if (!(o instanceof ContentType)) return false;
                ContentType that = (ContentType) o;
                return getBaseType().equalsIgnoreCase(that.getBaseType()) &&
                        getSubType().equalsIgnoreCase(that.getSubType()) &&
                        params.equals(that.params);
        }
        
        
        @Override
        public int hashCode() {
                return Objects.hash(getBaseType().toLowerCase(), getSubType().toLowerCase(), params);
        }
        
        
        /**
         * Parses a content type from the specified string.
         *
         * @param s The string to parse.
         *
         * @return The content type.
         *
         * @throws ParseException If parsing failed or the string is
         *                        {@code null} or empty.
         */
        public static ContentType parse(final String s)
                throws ParseException {
                
                if (s == null || s.trim().isEmpty()) {
                        throw new ParseException("Null or empty content type string", 0);
                }
                
                StringTokenizer st = new StringTokenizer(s, "/");
                
                if (! st.hasMoreTokens()) {
                        throw new ParseException("Invalid content type string", 0);
                }
                
                String type = st.nextToken().trim();
                
                if (type.trim().isEmpty()) {
                        throw new ParseException("Invalid content type string", 0);
                }
                
                if (! st.hasMoreTokens()) {
                        throw new ParseException("Invalid content type string", 0);
                }
                
                String subtypeWithOptParams = st.nextToken().trim();
                
                st = new StringTokenizer(subtypeWithOptParams, ";");
                
                if (! st.hasMoreTokens()) {
                        // No params
                        return new ContentType(type, subtypeWithOptParams.trim());
                }
                
                String subtype = st.nextToken().trim();
                
                if (! st.hasMoreTokens()) {
                        // No params
                        return new ContentType(type, subtype);
                }
                
                List<Parameter> params = new LinkedList<>();
                
                while (st.hasMoreTokens()) {
                        
                        String paramToken = st.nextToken().trim();
                        
                        StringTokenizer paramTokenizer = new StringTokenizer(paramToken, "=");
                        
                        if (! paramTokenizer.hasMoreTokens()) {
                                throw new ParseException("Invalid parameter", 0);
                        }
                        
                        String paramName = paramTokenizer.nextToken().trim();
                        
                        if (! paramTokenizer.hasMoreTokens()) {
                                throw new ParseException("Invalid parameter", 0);
                        }
                        
                        String paramValue = paramTokenizer.nextToken().trim();
                        
                        try {
                                params.add(new Parameter(paramName, paramValue));
                        } catch (IllegalArgumentException e) {
                                throw new ParseException("Invalid parameter: " + e.getMessage(), 0);
                        }
                }
                
                return new ContentType(type, subtype, params.toArray(new Parameter[0]));
        }
}