package software.amazon.event.ruler.input;

import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Set;

/**
 * A parser to be used specifically for equals-ignore-case rules. For Java characters where lower and upper case UTF-8
 * representations do not differ, we will parse into InputBytes. Otherwise, we will use InputMultiByteSet.
 *
 * Note that there are actually characters whose upper-case/lower-case UTF-8 representations differ in number of bytes.
 * One example where length differs by 1: ⱥ, Ⱥ
 * One example where length differs by 4: ΰ, Ϋ́
 * InputMultiByteSet handles differing byte lengths per Java character.
 */
public class EqualsIgnoreCaseParser {

    EqualsIgnoreCaseParser() { }

    public InputCharacter[] parse(String value) {
        List<InputCharacter> result = new ArrayList<>(value.length());
        for (char c : value.toCharArray()) {
            byte[] lowerCaseUtf8bytes = String.valueOf(c).toLowerCase(Locale.ROOT).getBytes(StandardCharsets.UTF_8);
            byte[] upperCaseUtf8bytes = String.valueOf(c).toUpperCase(Locale.ROOT).getBytes(StandardCharsets.UTF_8);
            if (Arrays.equals(lowerCaseUtf8bytes, upperCaseUtf8bytes)) {
                for (int i = 0; i < lowerCaseUtf8bytes.length; i++) {
                    result.add(new InputByte(lowerCaseUtf8bytes[i]));
                }
            } else {
                Set<MultiByte> multiBytes = new HashSet<>();
                multiBytes.add(new MultiByte(lowerCaseUtf8bytes));
                multiBytes.add(new MultiByte(upperCaseUtf8bytes));
                result.add(new InputMultiByteSet(multiBytes));
            }
        }
        return result.toArray(new InputCharacter[0]);
    }
}