/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */
package org.elasticsearch.xcontent;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;

/**
 * Both {@link String} and {@link UTF8Bytes} representation of the text. Starts with one of those, and if
 * the other is requested, caches the other one in a local reference so no additional conversion will be needed.
 */
public final class Text implements XContentString, Comparable<Text>, ToXContentFragment {

    public static final Text[] EMPTY_ARRAY = new Text[0];

    public static Text[] convertFromStringArray(String[] strings) {
        if (strings.length == 0) {
            return EMPTY_ARRAY;
        }
        Text[] texts = new Text[strings.length];
        for (int i = 0; i < strings.length; i++) {
            texts[i] = new Text(strings[i]);
        }
        return texts;
    }

    private UTF8Bytes bytes;
    private String string;
    private int hash;
    private int stringLength = -1;

    /**
     * Construct a Text from encoded UTF8Bytes. Since no string length is specified, {@link #stringLength()}
     * will perform a string conversion to measure the string length.
     */
    public Text(UTF8Bytes bytes) {
        this.bytes = bytes;
    }

    /**
     * Construct a Text from encoded UTF8Bytes and an explicit string length. Used to avoid string conversion
     * in {@link #stringLength()}. The provided stringLength should match the value that would
     * be calculated by {@link Text#Text(UTF8Bytes)}.
     */
    public Text(UTF8Bytes bytes, int stringLength) {
        this.bytes = bytes;
        this.stringLength = stringLength;
    }

    public Text(String string) {
        this.string = string;
    }

    /**
     * Whether an {@link UTF8Bytes} view of the data is already materialized.
     */
    public boolean hasBytes() {
        return bytes != null;
    }

    @Override
    public UTF8Bytes bytes() {
        if (bytes == null) {
            var byteBuff = StandardCharsets.UTF_8.encode(string);
            assert byteBuff.hasArray();
            bytes = new UTF8Bytes(byteBuff.array(), byteBuff.arrayOffset() + byteBuff.position(), byteBuff.remaining());
        }
        return bytes;
    }

    /**
     * Whether a {@link String} view of the data is already materialized.
     */
    public boolean hasString() {
        return string != null;
    }

    @Override
    public String string() {
        if (string == null) {
            var byteBuff = ByteBuffer.wrap(bytes.bytes(), bytes.offset(), bytes.length());
            string = StandardCharsets.UTF_8.decode(byteBuff).toString();
            assert (stringLength < 0) || (string.length() == stringLength);
        }
        return string;
    }

    @Override
    public int stringLength() {
        if (stringLength < 0) {
            stringLength = string().length();
        }
        return stringLength;
    }

    @Override
    public String toString() {
        return string();
    }

    @Override
    public int hashCode() {
        if (hash == 0) {
            hash = bytes().hashCode();
        }
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        return bytes().equals(((Text) obj).bytes());
    }

    @Override
    public int compareTo(Text text) {
        return bytes().compareTo(text.bytes());
    }

    @Override
    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
        if (hasString()) {
            return builder.value(this.string());
        } else {
            // TODO: TextBytesOptimization we can use a buffer here to convert it? maybe add a
            // request to jackson to support InputStream as well?
            return builder.utf8Value(bytes.bytes(), bytes.offset(), bytes.length());
        }
    }
}