package model.asn1;

import model.asn1.exceptions.ParseException;
import model.asn1.parsing.BytesReader;
import ui.Utils;

import java.nio.charset.StandardCharsets;
import java.util.Arrays;

/**
 * Represents an ASN.1 IA5String type. It is a string that is restricted to ISO 646 / T.50 characters.
 */
public class IA5String extends ASN1String {
    /**
     * The X.680 universal class tag assignment.
     */
    public static final Tag TAG = new Tag(TagClass.UNIVERSAL, false, 0x16);

    /**
     * EFFECTS: Constructs an IA5String with the given tag and string.
     *   Throws {@link ParseException} if the string is invalid. It must only contain T.50 chars.
     * REQUIRES: For the requirements of tag and parentTag, consult {@link ASN1Object}.
     */
    public IA5String(Tag tag, Tag parentTag, String string) throws ParseException {
        super(tag, parentTag, string);
    }

    /**
     * EFFECTS: Parse from user input. Tags are parsed as-per {@link ASN1Object}. The value will be parsed as UTF-8 big
     * endian.
     *   Throws {@link ParseException} if the encoded data is invalid:
     *     - Illegal string (containing non-T.50 chars)
     *     - Early EOF
     *     - Other cases in {@link ASN1Object}
     * MODIFIES: this, encoded
     */
    public IA5String(BytesReader encoded, boolean hasParentTag) throws ParseException {
        super(encoded, hasParentTag);
        setString(new String(Utils.byteToByte(encoded.require(getLength(), true)),
                StandardCharsets.UTF_8));
    }

    /**
     * EFFECTS: Checks whether the given string only contains ISO 646 / T.50 chars.
     */
    @Override
    protected boolean validate(String newString) {
        // Java doesn't have unsigned bytes - that is, bytes greater than 0x7F will
        // overflow and become < 0. Thus, just compare b >= 0 will suffice.
        return Arrays.stream(Utils.byteToByte(newString.getBytes(StandardCharsets.UTF_8)))
                .noneMatch(b -> b < 0);
    }
}