package com.baiyue.common.event;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

/**
 * 将 JSON 负载转换为稳定字节序列，避免对象字段顺序不同导致摘要不一致。
 */
public final class EventPayloadCanonicalizer {
    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
            .configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);

    private EventPayloadCanonicalizer() {
    }

    /**
     * 递归排序对象字段并输出 UTF-8 JSON 字节。
     */
    public static byte[] canonicalize(JsonNode payload) {
        if (payload == null || payload.isNull()) {
            throw new IllegalArgumentException("事件负载不能为空");
        }
        return write(sort(payload));
    }

    /** 仅用于接收规范化数字规则上线前已经生成的历史摘要。 */
    public static byte[] canonicalizeLegacy(JsonNode payload) {
        if (payload == null || payload.isNull()) {
            throw new IllegalArgumentException("事件负载不能为空");
        }
        return write(sortLegacy(payload));
    }

    private static byte[] write(JsonNode payload) {
        try {
            return OBJECT_MAPPER.writeValueAsBytes(payload);
        } catch (JsonProcessingException exception) {
            throw new IllegalArgumentException("事件负载无法规范化", exception);
        }
    }

    private static JsonNode sort(JsonNode node) {
        if (node.isObject()) {
            var names = new java.util.ArrayList<String>();
            node.fieldNames().forEachRemaining(names::add);
            names.sort(String::compareTo);
            var result = OBJECT_MAPPER.createObjectNode();
            names.forEach(name -> result.set(name, sort(node.get(name))));
            return result;
        }
        if (node.isArray()) {
            var result = OBJECT_MAPPER.createArrayNode();
            node.forEach(child -> result.add(sort(child)));
            return result;
        }
        if (node.isNumber()) {
            return com.fasterxml.jackson.databind.node.DecimalNode.valueOf(node.decimalValue().stripTrailingZeros());
        }
        return node;
    }

    private static JsonNode sortLegacy(JsonNode node) {
        if (node.isObject()) {
            var names = new java.util.ArrayList<String>();
            node.fieldNames().forEachRemaining(names::add);
            names.sort(String::compareTo);
            var result = OBJECT_MAPPER.createObjectNode();
            names.forEach(name -> result.set(name, sortLegacy(node.get(name))));
            return result;
        }
        if (node.isArray()) {
            var result = OBJECT_MAPPER.createArrayNode();
            node.forEach(child -> result.add(sortLegacy(child)));
            return result;
        }
        return node;
    }
}