/*
 * Copyright 2002-2021 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.web.util.pattern;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.springframework.http.server.PathContainer.PathSegment;
import org.springframework.web.util.pattern.PathPattern.MatchingContext;

/**
 * A regex path element. Used to represent any complicated element of the path.
 * For example in '<tt>/foo/&ast;_&ast;/&ast;_{foobar}</tt>' both <tt>*_*</tt> and <tt>*_{foobar}</tt>
 * are {@link RegexPathElement} path elements. Derived from the general
 * {@link org.springframework.util.AntPathMatcher} approach.
 *
 * @author Andy Clement
 * @since 5.0
 */
class RegexPathElement extends PathElement {

	private static final Pattern GLOB_PATTERN = Pattern.compile("\\?|\\*|\\{((?:\\{[^/]+?\\}|[^/{}]|\\\\[{}])+?)\\}");

	private static final String DEFAULT_VARIABLE_PATTERN = "(.*)";


	private final char[] regex;

	private final boolean caseSensitive;

	private final Pattern pattern;

	private int wildcardCount;

	private final List<String> variableNames = new ArrayList<>();


	RegexPathElement(int pos, char[] regex, boolean caseSensitive, char[] completePattern, char separator) {
		super(pos, separator);
		this.regex = regex;
		this.caseSensitive = caseSensitive;
		this.pattern = buildPattern(regex, completePattern);
	}


	public Pattern buildPattern(char[] regex, char[] completePattern) {
		StringBuilder patternBuilder = new StringBuilder();
		String text = new String(regex);
		Matcher matcher = GLOB_PATTERN.matcher(text);
		int end = 0;

		while (matcher.find()) {
			patternBuilder.append(quote(text, end, matcher.start()));
			String match = matcher.group();
			if ("?".equals(match)) {
				patternBuilder.append('.');
			}
			else if ("*".equals(match)) {
				patternBuilder.append(".*");
				int pos = matcher.start();
				if (pos < 1 || text.charAt(pos-1) != '.') {
					// To be compatible with the AntPathMatcher comparator,
					// '.*' is not considered a wildcard usage
					this.wildcardCount++;
				}
			}
			else if (match.startsWith("{") && match.endsWith("}")) {
				int colonIdx = match.indexOf(':');
				if (colonIdx == -1) {
					patternBuilder.append(DEFAULT_VARIABLE_PATTERN);
					String variableName = matcher.group(1);
					if (this.variableNames.contains(variableName)) {
						throw new PatternParseException(this.pos, completePattern,
								PatternParseException.PatternMessage.ILLEGAL_DOUBLE_CAPTURE, variableName);
					}
					this.variableNames.add(variableName);
				}
				else {
					String variablePattern = match.substring(colonIdx + 1, match.length() - 1);
					patternBuilder.append('(');
					patternBuilder.append(variablePattern);
					patternBuilder.append(')');
					String variableName = match.substring(1, colonIdx);
					if (this.variableNames.contains(variableName)) {
						throw new PatternParseException(this.pos, completePattern,
								PatternParseException.PatternMessage.ILLEGAL_DOUBLE_CAPTURE, variableName);
					}
					this.variableNames.add(variableName);
				}
			}
			end = matcher.end();
		}

		patternBuilder.append(quote(text, end, text.length()));
		if (this.caseSensitive) {
			return Pattern.compile(patternBuilder.toString());
		}
		else {
			return Pattern.compile(patternBuilder.toString(), Pattern.CASE_INSENSITIVE);
		}
	}

	public List<String> getVariableNames() {
		return this.variableNames;
	}

	private String quote(String s, int start, int end) {
		if (start == end) {
			return "";
		}
		return Pattern.quote(s.substring(start, end));
	}

	@Override
	public boolean matches(int pathIndex, MatchingContext matchingContext) {
		String textToMatch = matchingContext.pathElementValue(pathIndex);
		Matcher matcher = this.pattern.matcher(textToMatch);
		boolean matches = matcher.matches();

		if (matches) {
			if (isNoMorePattern()) {
				if (matchingContext.determineRemainingPath &&
						(this.variableNames.isEmpty() || textToMatch.length() > 0)) {
					matchingContext.remainingPathIndex = pathIndex + 1;
					matches = true;
				}
				else {
					// No more pattern, is there more data?
					// If pattern is capturing variables there must be some actual data to bind to them
					matches = (pathIndex + 1 >= matchingContext.pathLength) &&
							(this.variableNames.isEmpty() || textToMatch.length() > 0);
					if (!matches && matchingContext.isMatchOptionalTrailingSeparator()) {
						matches = (this.variableNames.isEmpty() || textToMatch.length() > 0) &&
								(pathIndex + 2 >= matchingContext.pathLength) &&
								matchingContext.isSeparator(pathIndex + 1);
					}
				}
			}
			else {
				matches = (this.next != null && this.next.matches(pathIndex + 1, matchingContext));
			}
		}

		if (matches && matchingContext.extractingVariables) {
			// Process captures
			if (this.variableNames.size() != matcher.groupCount()) {  // SPR-8455
				throw new IllegalArgumentException("The number of capturing groups in the pattern segment " +
						this.pattern + " does not match the number of URI template variables it defines, " +
						"which can occur if capturing groups are used in a URI template regex. " +
						"Use non-capturing groups instead.");
			}
			for (int i = 1; i <= matcher.groupCount(); i++) {
				String name = this.variableNames.get(i - 1);
				String value = matcher.group(i);
				matchingContext.set(name, value,
						(i == this.variableNames.size())?
								((PathSegment)matchingContext.pathElements.get(pathIndex)).parameters():
								NO_PARAMETERS);
			}
		}
		return matches;
	}

	@Override
	public int getNormalizedLength() {
		int varsLength = 0;
		for (String variableName : this.variableNames) {
			varsLength += variableName.length();
		}
		return (this.regex.length - varsLength - this.variableNames.size());
	}

	@Override
	public char[] getChars() {
		return this.regex;
	}

	@Override
	public int getCaptureCount() {
		return this.variableNames.size();
	}

	@Override
	public int getWildcardCount() {
		return this.wildcardCount;
	}

	@Override
	public int getScore() {
		return (getCaptureCount() * CAPTURE_VARIABLE_WEIGHT + getWildcardCount() * WILDCARD_WEIGHT);
	}


	@Override
	public String toString() {
		return "Regex(" + String.valueOf(this.regex) + ")";
	}

}
