/*
 * Copyright (c) 2023 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
 *
 *      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.networknt.schema;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.nio.charset.StandardCharsets;
import java.util.Objects;

/**
 * The schema location is the canonical IRI of the schema object plus a JSON
 * Pointer fragment indicating the subschema that produced a result. In contrast
 * with the evaluation path, the schema location MUST NOT include by-reference
 * applicators such as $ref or $dynamicRef.
 */
public class SchemaLocation {
    private static final JsonNodePath JSON_POINTER = new JsonNodePath(PathType.JSON_POINTER);
    private static final JsonNodePath ANCHOR = new JsonNodePath(PathType.URI_REFERENCE);

    /**
     * Represents a relative schema location to the current document.
     */
    public static final SchemaLocation DOCUMENT = new SchemaLocation(null, JSON_POINTER);

    private final AbsoluteIri absoluteIri;
    private final JsonNodePath fragment;

    private volatile String value = null; // computed lazily

    /**
     * Constructs a new {@link SchemaLocation}.
     * 
     * @param absoluteIri canonical absolute IRI of the schema object
     * @param fragment    the fragment
     */
    public SchemaLocation(AbsoluteIri absoluteIri, JsonNodePath fragment) {
        this.absoluteIri = absoluteIri;
        this.fragment = fragment;
    }

    /**
     * Constructs a new {@link SchemaLocation}.
     * 
     * @param absoluteIri canonical absolute IRI of the schema object
     */
    public SchemaLocation(AbsoluteIri absoluteIri) {
        this(absoluteIri, JSON_POINTER);
    }

    /**
     * Gets the canonical absolute IRI of the schema object.
     * <p>
     * This is a unique identifier indicated by the $id property or id property in
     * Draft 4 and earlier. This does not have to be network accessible.
     *
     * @return the canonical absolute IRI of the schema object.
     */
    public AbsoluteIri getAbsoluteIri() {
        return this.absoluteIri;
    }

    /**
     * Gets the fragment.
     * 
     * @return the fragment
     */
    public JsonNodePath getFragment() {
        return this.fragment;
    }

    /**
     * Appends the token to the fragment.
     * 
     * @param token the segment
     * @return a new schema location with the segment
     */
    public SchemaLocation append(String token) {
        return new SchemaLocation(this.absoluteIri, this.fragment.append(token));
    }

    /**
     * Appends the index to the fragment.
     * 
     * @param index the segment
     * @return a new schema location with the segment
     */
    public SchemaLocation append(int index) {
        return new SchemaLocation(this.absoluteIri, this.fragment.append(index));
    }

    /**
     * Parses a string representing an IRI of the schema location.
     * 
     * @param iri the IRI
     * @return the schema location
     */
    public static SchemaLocation of(String iri) {
        if (iri == null) {
            return null;
        }
        if ("#".equals(iri)) {
            return DOCUMENT;
        }
        AbsoluteIri absoluteIri = null;
        JsonNodePath fragment = JSON_POINTER;
        int index = iri.indexOf('#');
        if (index == -1) {
            absoluteIri = AbsoluteIri.of(iri);
        } else {
            absoluteIri = AbsoluteIri.of(iri.substring(0, index));
            if (iri.length() > index + 1) {
                fragment = Fragment.of(iri.substring(index + 1));
            }
        }
        return new SchemaLocation(absoluteIri, fragment);
    }

    /**
     * Resolves against a absolute IRI reference or fragment.
     * 
     * @param absoluteIriReferenceOrFragment to resolve
     * @return the resolved schema location
     */
    public SchemaLocation resolve(String absoluteIriReferenceOrFragment) {
        if (absoluteIriReferenceOrFragment == null) {
            return this;
        }
        if ("#".equals(absoluteIriReferenceOrFragment)) {
            return new SchemaLocation(this.getAbsoluteIri(), JSON_POINTER);
        }
        JsonNodePath fragment = JSON_POINTER;
        int index = absoluteIriReferenceOrFragment.indexOf('#');
        AbsoluteIri absoluteIri = this.getAbsoluteIri();
        String part0 = index == -1 ? absoluteIriReferenceOrFragment
                : absoluteIriReferenceOrFragment.substring(0, index);
        if (absoluteIri != null) {
            if (!part0.isEmpty()) {
                absoluteIri = absoluteIri.resolve(part0);
            }
        } else {
            absoluteIri = AbsoluteIri.of(part0);
        }
        if (index != -1) {
            if (absoluteIriReferenceOrFragment.length() > index + 1) {
                String part1 = absoluteIriReferenceOrFragment.substring(index + 1);
                if (!part1.isEmpty()) {
                    fragment = Fragment.of(part1);
                }
            }
        }
        return new SchemaLocation(absoluteIri, fragment);
    }

    /**
     * Resolves against a absolute IRI reference or fragment.
     * 
     * @param schemaLocation                 the parent
     * @param absoluteIriReferenceOrFragment to resolve
     * @return the resolved schema location
     */
    public static String resolve(SchemaLocation schemaLocation, String absoluteIriReferenceOrFragment) {
        if ("#".equals(absoluteIriReferenceOrFragment)) {
            return schemaLocation.getAbsoluteIri().toString() + "#";
        }
        int index = absoluteIriReferenceOrFragment.indexOf('#');
        AbsoluteIri absoluteIri = schemaLocation.getAbsoluteIri();
        String part0 = index == -1 ? absoluteIriReferenceOrFragment
                : absoluteIriReferenceOrFragment.substring(0, index);
        String resolved = part0;
        if (absoluteIri != null) {
            if (!part0.isEmpty()) {
                resolved = absoluteIri.resolve(part0).toString();
            } else {
                resolved = absoluteIri.toString();
            }
        }
        String part1 = "";
        if (index != -1) {
            if (absoluteIriReferenceOrFragment.length() > index + 1) {
                part1 = absoluteIriReferenceOrFragment.substring(index + 1);
            }
        }
        if (!part1.isEmpty()) {
            resolved = resolved + "#" + part1;
        } else {
            resolved = resolved + "#";
        }
        return resolved;
    }

    /**
     * The fragment can be a JSON pointer to the document or an anchor.
     */
    public static class Fragment {
        /**
         * Parses a string representing a fragment.
         * 
         * @param fragmentString the fragment
         * @return the path
         */
        public static JsonNodePath of(String fragmentString) {
            if (fragmentString.startsWith("#")) {
                fragmentString = fragmentString.substring(1);
            }
            JsonNodePath fragment = JSON_POINTER;
            String[] fragmentParts = fragmentString.split("/");

            boolean jsonPointer = false;
            if (fragmentString.startsWith("/")) {
                // json pointer
                jsonPointer = true;
            } else {
                // anchor
                fragment = ANCHOR;
            }

            int index = -1;
            for (int fragmentPartIndex = 0; fragmentPartIndex < fragmentParts.length; fragmentPartIndex++) {
                if (fragmentPartIndex == 0 && jsonPointer) {
                    continue;
                }
                String fragmentPart = fragmentParts[fragmentPartIndex];
                for (int x = 0; x < fragmentPart.length(); x++) {
                    char ch = fragmentPart.charAt(x);
                    if (ch >= '0' && ch <= '9') {
                        if (x == 0) {
                            index = 0;
                        } else {
                            index = index * 10;
                        }
                        index += (ch - '0');
                    } else {
                        index = -1; // Not an index
                        break;
                    }
                }
                if (index != -1) {
                    fragment = fragment.append(index);
                } else {
                    String fragmentPartString = fragmentPart;
                    if (PathType.JSON_POINTER.equals(fragment.getPathType())) {
                        if (fragmentPartString.contains("~")) {
                            fragmentPartString = fragmentPartString.replace("~1", "/");
                            fragmentPartString = fragmentPartString.replace("~0", "~");
                        }
                        if (fragmentPartString.contains("%")) {
                            try {
                                fragmentPartString = URLDecoder.decode(fragmentPartString, StandardCharsets.UTF_8.toString());
                            } catch (UnsupportedEncodingException e) {
                                // Do nothing
                            }
                        }
                    }
                    fragment = fragment.append(fragmentPartString);
                }
            }
            if (index == -1 && fragmentString.endsWith("/")) {
                // Trailing / in fragment
                fragment = fragment.append("");
            }
            return fragment;
        }

        /**
         * Determine if the string is a fragment.
         * 
         * @param fragmentString to evaluate
         * @return true if it is a fragment
         */
        public static boolean isFragment(String fragmentString) {
            return fragmentString.startsWith("#");
        }

        /**
         * Determine if the string is a JSON Pointer fragment.
         * 
         * @param fragmentString to evaluate
         * @return true if it is a JSON Pointer fragment
         */
        public static boolean isJsonPointerFragment(String fragmentString) {
            return fragmentString.startsWith("#/");
        }

        /**
         * Determine if the string is an anchor fragment.
         * 
         * @param fragmentString to evaluate
         * @return true if it is an anchor fragment
         */
        public static boolean isAnchorFragment(String fragmentString) {
            return isFragment(fragmentString) && !isDocumentFragment(fragmentString)
                    && !isJsonPointerFragment(fragmentString);
        }

        /**
         * Determine if the string is a fragment referencing the document.
         * 
         * @param fragmentString to evaluate
         * @return true if it is a fragment
         */
        public static boolean isDocumentFragment(String fragmentString) {
            return "#".equals(fragmentString);
        }
    }

    /**
     * Returns a builder for building {@link SchemaLocation}.
     * 
     * @return the builder
     */
    public static Builder builder() {
        return new Builder();
    }

    /**
     * Builder for building {@link SchemaLocation}.
     */
    public static class Builder {
        private AbsoluteIri absoluteIri;
        private JsonNodePath fragment = JSON_POINTER;

        /**
         * Sets the canonical absolute IRI of the schema object.
         * <p>
         * This is a unique identifier indicated by the $id property or id property in
         * Draft 4 and earlier. This does not have to be network accessible.
         *
         * @param absoluteIri the canonical IRI of the schema object
         * @return the builder
         */
        protected Builder absoluteIri(AbsoluteIri absoluteIri) {
            this.absoluteIri = absoluteIri;
            return this;
        }

        /**
         * Sets the canonical absolute IRI of the schema object.
         * <p>
         * This is a unique identifier indicated by the $id property or id property in
         * Draft 4 and earlier. This does not have to be network accessible.
         *
         * @param absoluteIri the canonical IRI of the schema object
         * @return the builder
         */
        protected Builder absoluteIri(String absoluteIri) {
            return absoluteIri(AbsoluteIri.of(absoluteIri));
        }

        /**
         * Sets the fragment.
         * 
         * @param fragment the fragment
         * @return the builder
         */
        protected Builder fragment(JsonNodePath fragment) {
            this.fragment = fragment;
            return this;
        }

        /**
         * Sets the fragment.
         * 
         * @param fragment the fragment
         * @return the builder
         */
        protected Builder fragment(String fragment) {
            return fragment(Fragment.of(fragment));
        }

        /**
         * Builds a {@link SchemaLocation}.
         * 
         * @return the schema location
         */
        public SchemaLocation build() {
            return new SchemaLocation(absoluteIri, fragment);
        }

    }

    @Override
    public String toString() {
        if (this.value == null) {
            if (this.absoluteIri != null && this.fragment == null) {
                this.value = this.absoluteIri.toString();
            } else {
                StringBuilder result = new StringBuilder();
                if (this.absoluteIri != null) {
                    result.append(this.absoluteIri);
                }
                result.append("#");
                if (this.fragment != null) {
                    result.append(this.fragment);
                }
                this.value = result.toString();
            }
        }
        return this.value;
    }

    @Override
    public int hashCode() {
        return Objects.hash(fragment, absoluteIri);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        SchemaLocation other = (SchemaLocation) obj;
        return Objects.equals(fragment, other.fragment) && Objects.equals(absoluteIri, other.absoluteIri);
    }
}
