package model.x501;

import annotations.Assoc;
import model.asn1.*;
import model.asn1.exceptions.ParseException;
import model.asn1.parsing.BytesReader;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * Represents an X.501 directory Name (a.k.a. RDNSequence).
 * <pre>
 *     Name ::= CHOICE { -- only one possibility for now -- rdnSequence RDNSequence }
 *     RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
 *     DistinguishedName ::= RDNSequence
 * </pre>
 */
public class Name extends ASN1Object {
    @Assoc(partOf = true)
    private final RelativeDistinguishedName[] rdnSequence;

    /**
     * EFFECT: Initialize the Name with the given tags and rdnSequence. For tag and parentTag, consult
     * {@link ASN1Object}.
     * REQUIRES: Items should have SET tag.
     */
    public Name(Tag tag, Tag parentTag, RelativeDistinguishedName[] rdnSequence) {
        super(tag, parentTag);
        this.rdnSequence = rdnSequence;
    }

    /**
     * EFFECT: Parse the Name from input DER bytes. For details on parsing, refer to {@link ASN1Object}.
     * Throws {@link ParseException} for invalid input.
     * MODIFIES: this, encoded
     */
    public Name(BytesReader encoded, boolean hasParentTag) throws ParseException {
        super(encoded, hasParentTag);
        final List<RelativeDistinguishedName> list = new ArrayList<>();
        for (int i = 0; i < getLength(); ) {
            int index = encoded.getIndex();
            final RelativeDistinguishedName name = new RelativeDistinguishedName(encoded, false);
            name.getTag().enforce(TAG_SET);
            list.add(name);
            index = encoded.getIndex() - index;
            i += index;
        }
        this.rdnSequence = list.toArray(new RelativeDistinguishedName[0]);
    }

    /**
     * EFFECTS: Parse OID after last KV and clear context if input is '='. Otherwise add to context.
     *          Throws {@link ParseException} if input is '+' or ',', or if the oid cannot be recognized.
     * MODIFIES: context
     */
    private static ObjectIdentifier handleKey(char c, List<Character> context) throws ParseException {
        if (c == '=') {
            if (context.isEmpty()) {
                throw new ParseException("Unterminated key");
            }
            final ObjectIdentifier oid = new ObjectIdentifier(ObjectIdentifier.TAG, null,
                    ObjectIdentifier.getKnown(
                            context.stream().map(Object::toString).collect(Collectors.joining(""))));
            context.clear();
            return oid;
        } else if (c == '+' || c == ',') {
            throw new ParseException("Unterminated key part: " + context);
        } else {
            context.add(c);
            return null;
        }
    }

    /**
     * EFFECTS: Parse KV after '='. Clear context.
     *          Throws {@link ParseException} if context is empty.
     * MODIFIES: context
     * REQUIRES: curKey to be a valid OID
     */
    private static AttributeTypeAndValue flushKV(ObjectIdentifier curKey, List<Character> context)
            throws ParseException {
        if (context.isEmpty()) {
            throw new ParseException("Unterminated value");
        }
        final AttributeTypeAndValue tv = new AttributeTypeAndValue(ASN1Object.TAG_SEQUENCE, null, curKey,
                new PrintableString(PrintableString.TAG, null,
                        context.stream().map(Object::toString).collect(Collectors.joining(""))));
        context.clear();
        return tv;
    }

    /**
     * EFFECTS: Handle value after =, optionally flush to rdns after ',', or add to curListKT if after '+'. Clears
     * context if flushed, otherwise add to context. Returns whether switch to the state of reading key.
     *          Throws {@link ParseException} if c is '=' or context is empty.
     * MODIFIES: context, curListKT, rdns
     * REQUIRES: curKey to be a valid OID
     */
    private static boolean handleValue(char c, List<Character> context, List<AttributeTypeAndValue> curListKT,
                                    ObjectIdentifier curKey, List<RelativeDistinguishedName> rdns)
            throws ParseException {
        if (c == ',') {
            if (context.isEmpty()) {
                throw new ParseException("Unterminated value");
            }
            curListKT.add(flushKV(curKey, context));
            rdns.add(new RelativeDistinguishedName(ASN1Object.TAG_SET, null,
                    curListKT.toArray(AttributeTypeAndValue[]::new)));
            curListKT.clear();
            return true;
        } else if (c == '+') {
            curListKT.add(flushKV(curKey, context));
            return true;
        } else if (c == '=') {
            throw new ParseException("Unterminated value part: " + context);
        } else {
            context.add(c);
            return false;
        }
    }

    /**
     * EFFECTS: Parse the given DN string into structural X.509 RDN Sequence.
     *          Character literals = + , must be escaped.
     *          Values will always be PrintableString.
     *          Throws {@link ParseException} if invalid.
     */
    public static Name parseString(String dn) throws ParseException {
        char state = 0; // 0 - Key, 1 - Value; MSB: Escaped
        List<RelativeDistinguishedName> rdns = new ArrayList<>();
        List<AttributeTypeAndValue> curListKT = new ArrayList<>();
        ObjectIdentifier curKey = null;
        List<Character> context = new ArrayList<>();
        for (char c : (dn + ",").toCharArray()) {
            if ((state >> 7) == 1) {
                context.add(c);
                state &= 127;
                continue;
            } else if (c == '\\') {
                state |= 128;
                continue;
            }
            if (state == 0) {
                if ((curKey = handleKey(c, context)) != null) {
                    state = 1;
                }
            } else if (handleValue(c, context, curListKT, curKey, rdns)) {
                state = 0;
            }
        }
        return new Name(ASN1Object.TAG_SEQUENCE, null, rdns.toArray(RelativeDistinguishedName[]::new));
    }

    /**
     * EFFECTS: Encode the SEQUENCE OF into DER, keep order. RDNs will be encoded one-by-one.
     */
    @Override
    public Byte[] encodeValueDER() {
        return Stream.of(rdnSequence)
                .map(Encodable::encodeDER)
                .flatMap(Arrays::stream)
                .toArray(Byte[]::new);
    }

    /**
     * EFFECT: Convert the name into directory string, like CN=yuuta,OU=users,DC=yuuta,DC=moe
     */
    @Override
    public String toString() {
        return Stream.of(rdnSequence)
                .map(RelativeDistinguishedName::toString)
                .collect(Collectors.joining(","));
    }

    public RelativeDistinguishedName[] getRdnSequence() {
        return rdnSequence;
    }
}