package seedu.ezdo.logic.parser;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import seedu.ezdo.commons.exceptions.IllegalValueException;
import seedu.ezdo.commons.util.StringUtil;
import seedu.ezdo.model.tag.Tag;
import seedu.ezdo.model.tag.UniqueTagList;
import seedu.ezdo.model.todo.DueDate;
import seedu.ezdo.model.todo.Name;
import seedu.ezdo.model.todo.Priority;
import seedu.ezdo.model.todo.StartDate;
import seedu.ezdo.model.todo.TaskDate;

/**
 * Contains utility methods used for parsing strings in the various *Parser classes
 */
public class ParserUtil {

    private static final Pattern INDEX_ARGS_FORMAT = Pattern.compile("(?<targetIndex>.+)");

    /**
     * Returns the specified index in the {@code command} if it is a positive unsigned integer
     * Returns an {@code Optional.empty()} otherwise.
     */
    public static Optional<Integer> parseIndex(String command) {
        final Matcher matcher = INDEX_ARGS_FORMAT.matcher(command.trim());
        if (!matcher.matches()) {
            return Optional.empty();
        }

        String index = matcher.group("targetIndex");
        if (!StringUtil.isUnsignedInteger(index)) {
            return Optional.empty();
        }
        return Optional.of(Integer.parseInt(index));

    }

    /**
     * Returns a new Set populated by all elements in the given list of strings
     * Returns an empty set if the given {@code Optional} is empty,
     * or if the list contained in the {@code Optional} is empty
     */
    public static Set<String> toSet(Optional<List<String>> list) {
        List<String> elements = list.orElse(Collections.emptyList());
        return new HashSet<>(elements);
    }

    /**
    * Splits a preamble string into ordered fields.
    * @return A list of size {@code numFields} where the ith element is the ith field value if specified in
    *         the input, {@code Optional.empty()} otherwise.
    */
    public static List<Optional<String>> splitPreamble(String preamble, int numFields) {
        return Arrays.stream(Arrays.copyOf(preamble.split("\\s+", numFields), numFields))
                .map(Optional::ofNullable)
                .collect(Collectors.toList());
    }

    /**
     * Parses a {@code Optional<String> name} into an {@code Optional<Name>} if {@code name} is present.
     */
    public static Optional<Name> parseName(Optional<String> name) throws IllegalValueException {
        assert name != null;
        return name.isPresent() ? Optional.of(new Name(name.get())) : Optional.empty();
    }

    /**
     * Parses a {@code Optional<String> priority} into an {@code Optional<Priority>} if {@code priority} is present.
     */
    public static Optional<Priority> parsePriority(Optional<String> priority) throws IllegalValueException {
        assert priority != null;
        return priority.isPresent() ? Optional.of(new Priority(priority.get())) : Optional.empty();
    }

    /**
     * Parses a {@code Optional<String> startDate} into an {@code Optional<StartDate>} if {@code startDate} is present.
     */
    public static Optional<TaskDate> parseStartDate(Optional<String> startDate) throws IllegalValueException {
        assert startDate != null;
        return startDate.isPresent() ? Optional.of(new StartDate(startDate.get())) : Optional.empty();
    }

    /**
     * Parses a {@code Optional<String> dueDate} into an {@code Optional<DueDate>} if {@code dueDate} is present.
     */
    public static Optional<TaskDate> parseDueDate(Optional<String> dueDate) throws IllegalValueException {
        assert dueDate != null;
        return dueDate.isPresent() ? Optional.of(new DueDate(dueDate.get())) : Optional.empty();
    }

    /**
     * Parses {@code Collection<String> tags} into an {@code UniqueTagList}.
     */
    public static UniqueTagList parseTags(Collection<String> tags) throws IllegalValueException {
        assert tags != null;
        final Set<Tag> tagSet = new HashSet<>();
        for (String tagName : tags) {
            tagSet.add(new Tag(tagName));
        }
        return new UniqueTagList(tagSet);
    }
}

@@ -891,16 +891,117 @@
 x%3E.+)%22);
+%0A    private static final Pattern SORT_CRITERIA_ARGS_FORMAT = Pattern.compile(%22(?%3CsortCriteria%3E.+)%22);
 %0A%0A    /*
@@ -1586,32 +1586,544 @@
 ndex));%0A%0A    %7D%0A%0A
+    /**%0A     * Returns the specified index in the %7B@code command%7D if it is a positive unsigned integer%0A     * Returns an %7B@code Optional.empty()%7D otherwise.%0A     */%0A    public static Optional%3CString%3E parseSortCriteria(String command) %7B%0A        final Matcher matcher = SORT_CRITERIA_ARGS_FORMAT.matcher(command.trim());%0A        if (!matcher.matches()) %7B%0A            return Optional.empty();%0A        %7D%0A%0A        String sortCriteria = matcher.group(%22sortCriteria%22);%0A        return Optional.of(sortCriteria);%0A%0A    %7D%0A%0A
     /**%0A     * R

Implement parseSortCriteria for sort command