/*
 * #%L
 * HAPI FHIR - Core Library
 * %%
 * Copyright (C) 2014 - 2025 Smile CDR, Inc.
 * %%
 * 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.
 * #L%
 */
package ca.uhn.fhir.util;

import ca.uhn.fhir.context.FhirContext;
import ca.uhn.fhir.context.RuntimeResourceDefinition;
import ca.uhn.fhir.i18n.Msg;
import ca.uhn.fhir.model.primitive.IdDt;
import ca.uhn.fhir.parser.DataFormatException;
import ca.uhn.fhir.rest.api.Constants;
import ca.uhn.fhir.rest.server.exceptions.InvalidRequestException;
import com.google.common.escape.Escaper;
import com.google.common.net.PercentEscaper;
import jakarta.annotation.Nonnull;
import jakarta.annotation.Nullable;
import org.apache.commons.lang3.StringUtils;
import org.hl7.fhir.instance.model.api.IPrimitiveType;

import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLDecoder;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.StringTokenizer;
import java.util.stream.Collectors;

import static org.apache.commons.lang3.StringUtils.defaultIfBlank;
import static org.apache.commons.lang3.StringUtils.defaultString;
import static org.apache.commons.lang3.StringUtils.endsWith;
import static org.apache.commons.lang3.StringUtils.isBlank;
import static org.apache.commons.lang3.StringUtils.isNotBlank;

@SuppressWarnings("JavadocLinkAsPlainText")
public class UrlUtil {
        private static final org.slf4j.Logger ourLog = org.slf4j.LoggerFactory.getLogger(UrlUtil.class);

        private static final String URL_FORM_PARAMETER_OTHER_SAFE_CHARS = "-_.*";
        private static final Escaper PARAMETER_ESCAPER_NO_SLASH =
                        new PercentEscaper(URL_FORM_PARAMETER_OTHER_SAFE_CHARS + "/", false);
        private static final Escaper PARAMETER_ESCAPER = new PercentEscaper(URL_FORM_PARAMETER_OTHER_SAFE_CHARS, false);

        /**
         * Non instantiable
         */
        private UrlUtil() {}

        /**
         * Cleans up a value that will be serialized as an HTTP header. This method:
         * <p>
         * - Strips any newline (\r or \n) characters
         *
         * @since 6.2.0
         */
        public static String sanitizeHeaderValue(String theHeader) {
                return theHeader.replace("\n", "").replace("\r", "");
        }

        public static String sanitizeBaseUrl(String theBaseUrl) {
                return theBaseUrl.replaceAll("[^a-zA-Z0-9:/._-]", "");
        }

        /**
         * Resolve a relative URL - THIS METHOD WILL NOT FAIL but will log a warning and return theEndpoint if the input is invalid.
         */
        public static String constructAbsoluteUrl(String theBase, String theEndpoint) {
                if (theEndpoint == null) {
                        return null;
                }
                if (isAbsolute(theEndpoint)) {
                        return theEndpoint;
                }
                if (theBase == null) {
                        return theEndpoint;
                }

                try {
                        return new URL(new URL(theBase), theEndpoint).toString();
                } catch (MalformedURLException e) {
                        ourLog.warn(
                                        "Failed to resolve relative URL[" + theEndpoint + "] against absolute base[" + theBase + "]", e);
                        return theEndpoint;
                }
        }

        public static String constructRelativeUrl(String theParentExtensionUrl, String theExtensionUrl) {
                if (theParentExtensionUrl == null) {
                        return theExtensionUrl;
                }
                if (theExtensionUrl == null) {
                        return null;
                }

                int parentLastSlashIdx = theParentExtensionUrl.lastIndexOf('/');
                int childLastSlashIdx = theExtensionUrl.lastIndexOf('/');

                if (parentLastSlashIdx == -1 || childLastSlashIdx == -1) {
                        return theExtensionUrl;
                }

                if (parentLastSlashIdx != childLastSlashIdx) {
                        return theExtensionUrl;
                }

                if (!theParentExtensionUrl
                                .substring(0, parentLastSlashIdx)
                                .equals(theExtensionUrl.substring(0, parentLastSlashIdx))) {
                        return theExtensionUrl;
                }

                if (theExtensionUrl.length() > parentLastSlashIdx) {
                        return theExtensionUrl.substring(parentLastSlashIdx + 1);
                }

                return theExtensionUrl;
        }

        /**
         * Given a FHIR resource URL, extracts the associated resource type. Supported formats
         * include the following inputs, all of which will return {@literal Patient}. If no
         * resource type can be determined, {@literal null} will be returned.
         * <ul>
         * <li>Patient
         * <li>Patient?
         * <li>Patient?identifier=foo
         * <li>/Patient
         * <li>/Patient?
         * <li>/Patient?identifier=foo
         * <li>http://foo/base/Patient?identifier=foo
         * <li>http://foo/base/Patient/1
         * <li>http://foo/base/Patient/1/_history/2
         * <li>Patient/1
         * <li>Patient/1/_history/2
         * <li>/Patient/1
         * <li>/Patient/1/_history/2
         * </ul>
         */
        @Nullable
        public static String determineResourceTypeInResourceUrl(FhirContext theFhirContext, String theUrl) {
                if (theUrl == null) {
                        return null;
                }
                if (theUrl.startsWith("urn:")) {
                        return null;
                }

                String resourceType = null;
                int qmIndex = theUrl.indexOf("?");
                if (qmIndex > 0) {
                        String urlResourceType = theUrl.substring(0, qmIndex);
                        int slashIdx = urlResourceType.lastIndexOf('/');
                        if (slashIdx != -1) {
                                urlResourceType = urlResourceType.substring(slashIdx + 1);
                        }
                        if (isNotBlank(urlResourceType)) {
                                resourceType = urlResourceType;
                        }
                } else {
                        resourceType = theUrl;
                        int slashIdx = resourceType.indexOf('/');
                        if (slashIdx == 0) {
                                resourceType = resourceType.substring(1);
                        }

                        slashIdx = resourceType.indexOf('/');
                        if (slashIdx != -1) {
                                resourceType = new IdDt(resourceType).getResourceType();
                        }
                }

                try {
                        if (isNotBlank(resourceType)) {
                                theFhirContext.getResourceDefinition(resourceType);
                        }
                } catch (DataFormatException e) {
                        return null;
                }

                return resourceType;
        }

        /**
         * URL encode a value according to RFC 3986, except for the following
         * characters: <code>-_.*</code>.
         * <p>
         * This method is intended to be applied to an individual parameter
         * name or value. For example, if you are creating the URL
         * <code>http://example.com/fhir/Patient?key=føø</code>
         * it would be appropriate to pass the string "føø" to this method,
         * but not appropriate to pass the entire URL since characters
         * such as "/" and "?" would also be escaped.
         * </p>
         *
         * @see #escapeUrlParam(String, boolean)
         */
        public static String escapeUrlParam(String theUnescaped) {
                return escapeUrlParam(theUnescaped, true);
        }

        /**
         * URL encode a value according to RFC 3986, except for the following
         * characters: <code>-_.*</code>, and optionally <code>/</code>.
         * <p>
         * This method is intended to be applied to an individual parameter
         * name or value. For example, if you are creating the URL
         * <code>http://example.com/fhir/Patient?key=føø</code>
         * it would be appropriate to pass the string "føø" to this method,
         * but not appropriate to pass the entire URL since characters
         * such as "?" and possibly "/" would also be escaped.
         * </p>
         *
         * @param theEscapeSlash If <code>true</code>, the slash character will be percent-escaped.
         *                       Set this to false if you are escaping a query parameter value, since slashes
         *                       will be more readable in the URL than the percent-encoded version. If you
         *                       aren't sure where the escaped version will appear, always set this to
         *                       <code>false</code>, or just call {@link #escapeUrlParam(String)} instead.
         * @since 8.6.0
         */
        public static String escapeUrlParam(String theUnescaped, boolean theEscapeSlash) {
                if (theUnescaped == null) {
                        return null;
                }
                if (theEscapeSlash) {
                        return PARAMETER_ESCAPER.escape(theUnescaped);
                } else {
                        return PARAMETER_ESCAPER_NO_SLASH.escape(theUnescaped);
                }
        }

        /**
         * Applies the same encodong as {@link #escapeUrlParam(String)} but against all
         * values in a collection
         */
        public static List<String> escapeUrlParams(@Nonnull Collection<String> theUnescaped) {
                return theUnescaped.stream().map(t -> PARAMETER_ESCAPER.escape(t)).collect(Collectors.toList());
        }

        public static boolean isAbsolute(String theValue) {
                String value = theValue.toLowerCase();
                return value.startsWith("http://") || value.startsWith("https://");
        }

        public static boolean isNeedsSanitization(CharSequence theString) {
                if (theString != null) {
                        for (int i = 0; i < theString.length(); i++) {
                                char nextChar = theString.charAt(i);
                                switch (nextChar) {
                                        case '\'':
                                        case '"':
                                        case '<':
                                        case '>':
                                        case '\n':
                                        case '\r':
                                                return true;
                                }
                                if (nextChar < ' ') {
                                        return true;
                                }
                        }
                }
                return false;
        }

        public static boolean isValid(String theUrl) {
                if (theUrl == null || theUrl.length() < 8) {
                        return false;
                }

                String url = theUrl.toLowerCase();
                if (url.charAt(0) != 'h') {
                        return false;
                }
                if (url.charAt(1) != 't') {
                        return false;
                }
                if (url.charAt(2) != 't') {
                        return false;
                }
                if (url.charAt(3) != 'p') {
                        return false;
                }
                int slashOffset;
                if (url.charAt(4) == ':') {
                        slashOffset = 5;
                } else if (url.charAt(4) == 's') {
                        if (url.charAt(5) != ':') {
                                return false;
                        }
                        slashOffset = 6;
                } else {
                        return false;
                }

                if (url.charAt(slashOffset) != '/') {
                        return false;
                }
                if (url.charAt(slashOffset + 1) != '/') {
                        return false;
                }

                return true;
        }

        public static RuntimeResourceDefinition parseUrlResourceType(FhirContext theCtx, String theUrl)
                        throws DataFormatException {
                String url = theUrl;
                int paramIndex = url.indexOf('?');

                // Change pattern of "Observation/?param=foo" into "Observation?param=foo"
                if (paramIndex > 0 && url.charAt(paramIndex - 1) == '/') {
                        url = url.substring(0, paramIndex - 1) + url.substring(paramIndex);
                        paramIndex--;
                }

                String resourceName = url.substring(0, paramIndex);
                if (resourceName.contains("/")) {
                        resourceName = resourceName.substring(resourceName.lastIndexOf('/') + 1);
                }
                return theCtx.getResourceDefinition(resourceName);
        }

        @Nonnull
        public static Map<String, String[]> parseQueryString(String theQueryString) {
                HashMap<String, List<String>> map = new HashMap<>();
                parseQueryString(theQueryString, map);
                return toQueryStringMap(map);
        }

        private static void parseQueryString(String theQueryString, HashMap<String, List<String>> map) {
                String query = defaultString(theQueryString);

                int questionMarkIdx = query.indexOf('?');
                if (questionMarkIdx != -1) {
                        query = query.substring(questionMarkIdx + 1);
                }

                StringTokenizer tok = new StringTokenizer(query, "&");
                while (tok.hasMoreTokens()) {
                        String nextToken = tok.nextToken();
                        if (isBlank(nextToken)) {
                                continue;
                        }

                        int equalsIndex = nextToken.indexOf('=');
                        String nextValue;
                        String nextKey;
                        if (equalsIndex == -1) {
                                nextKey = nextToken;
                                nextValue = "";
                        } else {
                                nextKey = nextToken.substring(0, equalsIndex);
                                nextValue = nextToken.substring(equalsIndex + 1);
                        }

                        nextKey = unescape(nextKey);
                        nextValue = unescape(nextValue);

                        List<String> list = map.computeIfAbsent(nextKey, k -> new ArrayList<>());
                        list.add(nextValue);
                }
        }

        public static Map<String, String[]> parseQueryStrings(String... theQueryString) {
                HashMap<String, List<String>> map = new HashMap<>();
                for (String next : theQueryString) {
                        parseQueryString(next, map);
                }
                return toQueryStringMap(map);
        }

        /**
         * Normalizes canonical URLs for comparison. Trailing "/" is stripped,
         * and any version identifiers or fragment hash is removed
         */
        public static String normalizeCanonicalUrlForComparison(String theUrl) {
                String retVal;
                try {
                        retVal = new URI(theUrl).normalize().toString();
                } catch (URISyntaxException e) {
                        retVal = theUrl;
                }
                while (endsWith(retVal, "/")) {
                        retVal = retVal.substring(0, retVal.length() - 1);
                }
                int hashOrPipeIndex = StringUtils.indexOfAny(retVal, '#', '|');
                if (hashOrPipeIndex != -1) {
                        retVal = retVal.substring(0, hashOrPipeIndex);
                }
                return retVal;
        }

        /**
         * Parse a URL in one of the following forms:
         * <ul>
         * <li>[Resource Type]?[Search Params]
         * <li>[Resource Type]/[Resource ID]
         * <li>[Resource Type]/[Resource ID]/_history/[Version ID]
         * </ul>
         */
        public static UrlParts parseUrl(String theUrl) {
                String url = theUrl;
                UrlParts retVal = new UrlParts();
                if (url.startsWith("http")) {
                        int qmIdx = url.indexOf('?');
                        if (qmIdx != -1) {
                                retVal.setParams(defaultIfBlank(url.substring(qmIdx + 1), null));
                                url = url.substring(0, qmIdx);
                        }

                        IdDt id = new IdDt(url);
                        retVal.setResourceType(id.getResourceType());
                        retVal.setResourceId(id.getIdPart());
                        retVal.setVersionId(id.getVersionIdPart());
                        return retVal;
                }

                int parsingStart = 0;
                if (url.length() > 2) {
                        if (url.charAt(0) == '/') {
                                if (Character.isLetter(url.charAt(1))) {
                                        parsingStart = 1;
                                }
                        }
                }

                int nextStart = parsingStart;
                boolean nextIsHistory = false;

                for (int idx = parsingStart; idx < url.length(); idx++) {
                        char nextChar = url.charAt(idx);
                        boolean atEnd = (idx + 1) == url.length();
                        if (nextChar == '?' || nextChar == '/' || atEnd) {
                                int endIdx = (atEnd && nextChar != '?') ? idx + 1 : idx;
                                String nextSubstring = url.substring(nextStart, endIdx);
                                if (retVal.getResourceType() == null) {
                                        retVal.setResourceType(nextSubstring);
                                } else if (retVal.getResourceId() == null) {
                                        retVal.setResourceId(nextSubstring);
                                } else if (nextIsHistory) {
                                        retVal.setVersionId(nextSubstring);
                                } else {
                                        if (nextSubstring.equals(Constants.URL_TOKEN_HISTORY)) {
                                                nextIsHistory = true;
                                        } else {
                                                throw new InvalidRequestException(Msg.code(1742) + "Invalid FHIR resource URL: " + url);
                                        }
                                }
                                if (nextChar == '?') {
                                        if (url.length() > idx + 1) {
                                                retVal.setParams(url.substring(idx + 1));
                                        }
                                        break;
                                }
                                nextStart = idx + 1;
                        }
                }

                return retVal;
        }

        /**
         * This method specifically HTML-encodes the &quot; and
         * &lt; characters in order to prevent injection attacks
         */
        public static String sanitizeUrlPart(IPrimitiveType<?> theString) {
                String retVal = null;
                if (theString != null) {
                        retVal = sanitizeUrlPart(theString.getValueAsString());
                }
                return retVal;
        }

        /**
         * This method specifically HTML-encodes the &quot; and
         * &lt; characters in order to prevent injection attacks.
         * <p>
         * The following characters are escaped:
         * <ul>
         *    <li>&apos;</li>
         *    <li>&quot;</li>
         *    <li>&lt;</li>
         *    <li>&gt;</li>
         *    <li>\n (newline)</li>
         * </ul>
         */
        public static String sanitizeUrlPart(CharSequence theString) {
                if (theString == null) {
                        return null;
                }

                boolean needsSanitization = isNeedsSanitization(theString);

                if (needsSanitization) {
                        // Ok, we're sanitizing
                        StringBuilder buffer = new StringBuilder(theString.length() + 10);
                        for (int j = 0; j < theString.length(); j++) {

                                char nextChar = theString.charAt(j);
                                switch (nextChar) {
                                                /*
                                                 * NB: If you add a constant here, you also need to add it
                                                 * to isNeedsSanitization()!!
                                                 */
                                        case '\'':
                                                buffer.append("&apos;");
                                                break;
                                        case '"':
                                                buffer.append("&quot;");
                                                break;
                                        case '<':
                                                buffer.append("&lt;");
                                                break;
                                        case '>':
                                                buffer.append("&gt;");
                                                break;
                                        case '\n':
                                                buffer.append("&#10;");
                                                break;
                                        case '\r':
                                                buffer.append("&#13;");
                                                break;
                                        default:
                                                if (nextChar >= ' ') {
                                                        buffer.append(nextChar);
                                                }
                                                break;
                                }
                        } // for build escaped string

                        return buffer.toString();
                }

                return theString.toString();
        }

        /**
         * Applies the same logic as {@link #sanitizeUrlPart(CharSequence)} but against an array, returning an array with the
         * same strings as the input but with sanitization applied
         */
        public static String[] sanitizeUrlPart(String[] theParameterValues) {
                String[] retVal = null;
                if (theParameterValues != null) {
                        retVal = new String[theParameterValues.length];
                        for (int i = 0; i < theParameterValues.length; i++) {
                                retVal[i] = sanitizeUrlPart(theParameterValues[i]);
                        }
                }
                return retVal;
        }

        private static Map<String, String[]> toQueryStringMap(HashMap<String, List<String>> map) {
                HashMap<String, String[]> retVal = new HashMap<>();
                for (Entry<String, List<String>> nextEntry : map.entrySet()) {
                        retVal.put(nextEntry.getKey(), nextEntry.getValue().toArray(new String[0]));
                }
                return retVal;
        }

        public static String unescape(String theString) {
                if (theString == null) {
                        return null;
                }
                // If the user passes "_outputFormat" as a GET request parameter directly in the URL:
                final boolean shouldEscapePlus = !theString.startsWith("application/");

                for (int i = 0; i < theString.length(); i++) {
                        char nextChar = theString.charAt(i);
                        if (nextChar == '%' || (nextChar == '+' && shouldEscapePlus)) {
                                return URLDecoder.decode(theString, StandardCharsets.UTF_8);
                        }
                }
                return theString;
        }

        /**
         * Creates list of sub URIs candidates for search with :above modifier
         * Example input: http://[host]/[pathPart1]/[pathPart2]
         * Example output: http://[host], http://[host]/[pathPart1], http://[host]/[pathPart1]/[pathPart2]
         *
         * @param theUri String URI parameter
         * @return List of URI candidates
         */
        public static List<String> getAboveUriCandidates(String theUri) {
                try {
                        URI uri = new URI(theUri);
                        if (uri.getScheme() == null || uri.getHost() == null) {
                                throwInvalidRequestExceptionForNotValidUri(theUri, null);
                        }
                } catch (URISyntaxException theCause) {
                        throwInvalidRequestExceptionForNotValidUri(theUri, theCause);
                }

                List<String> candidates = new ArrayList<>();
                Path path = Paths.get(theUri);
                candidates.add(path.toString().replace(":/", "://"));
                while (path.getParent() != null && path.getParent().toString().contains("/")) {
                        candidates.add(path.getParent().toString().replace(":/", "://"));
                        path = path.getParent();
                }
                return candidates;
        }

        private static void throwInvalidRequestExceptionForNotValidUri(String theUri, Exception theCause) {
                throw new InvalidRequestException(
                                Msg.code(2419) + String.format("Provided URI is not valid: %s", theUri), theCause);
        }

        public static class UrlParts {
                private String myParams;
                private String myResourceId;
                private String myResourceType;
                private String myVersionId;

                public String getParams() {
                        return myParams;
                }

                public void setParams(String theParams) {
                        myParams = theParams;
                }

                public String getResourceId() {
                        return myResourceId;
                }

                public void setResourceId(String theResourceId) {
                        myResourceId = theResourceId;
                }

                public String getResourceType() {
                        return myResourceType;
                }

                public void setResourceType(String theResourceType) {
                        myResourceType = theResourceType;
                }

                public String getVersionId() {
                        return myVersionId;
                }

                public void setVersionId(String theVersionId) {
                        myVersionId = theVersionId;
                }
        }
}