// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.text;

import com.yahoo.slime.Slime;
import com.yahoo.slime.SlimeUtils;

import java.util.Map;

/**
 * Static methods for working with JSON.
 *
 * @author bratseth
 */
public final class JSON {

    /** No instances */
    private JSON() {}

    /**
     * Outputs a map as a JSON 'object' string, provided that the map values
     * are either
     * <ul>
     * <li>String
     * <li>Number
     * <li>Any object whose toString returns JSON
     * </ul>
     */
    public static String encode(Map<String, ?> map) {
        StringBuilder b = new StringBuilder("{");
        for (Map.Entry<String,?> entry : map.entrySet()) {
            b.append("\"").append(escape(entry.getKey())).append("\":");
            if (entry.getValue() instanceof String)
                b.append("\"").append(escape(entry.getValue().toString())).append("\"");
            else // Number, or some other object which returns JSON
                b.append(entry.getValue());
            b.append(",");
        }
        if (b.length()>1)
            b.setLength(b.length()-1); // remove last comma
        b.append("}");
        return b.toString();
    }

    /** Returns the given string as a properly json escaped string */
    public static String escape(String s) {
        StringBuilder b = null; // lazy create to optimize for "nothing to do" case

        for (int i=0; i < s.length(); i = s.offsetByCodePoints(i, 1)) {
            final int codepoint = s.codePointAt(i);
            if (codepoint == '"') {
                if (b == null)
                    b = new StringBuilder(s.substring(0, i));
                b.append('\\');
            }

            if (b != null)
                b.appendCodePoint(codepoint);
        }
        return b != null ? b.toString() : s;
    }

    /**
     * Test whether two JSON strings are equal, e.g. the order of fields in an object is irrelevant.
     *
     * <p>When comparing two numbers of the two JSON strings, the result is only guaranteed to be
     * correct if (a) both are integers (without fraction and exponent) and each fits in a long, or
     * (b) both are non-integers, fits in a double, and are syntactically identical. Examples
     * of pairs that may not be equal: 1 and 1.0 (different types), 0.1 and 1e-1, 0.0 and 0.00.</p>
     *
     * @throws RuntimeException on invalid JSON
     */
    public static boolean equals(String left, String right) {
        Slime leftSlime = SlimeUtils.jsonToSlimeOrThrow(left);
        Slime rightSlime = SlimeUtils.jsonToSlimeOrThrow(right);
        return leftSlime.equalTo(rightSlime);
    }

    public static String canonical(String jsonString) {
        return SlimeUtils.jsonToSlimeOrThrow(jsonString).toString();
    }

}