import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

/**
 * 只读探针：按主键逐行比对两个库的同名表，回答「同一主键在两边是不是同一份内容」。
 *
 * <p>用法：java RowCompare &lt;左库url&gt; &lt;右库url&gt; [表名,表名...]
 * 默认比对内置的核心业务表清单。不做任何写入。
 */
public class RowCompare {

    private static final String[] DEFAULT_TABLES = {
            "merchant", "merchant_store", "merchant_product", "merchant_operator",
            "merchant_onboarding_application", "merchant_onboarding_progress", "merchant_bank_card",
            "merchant_verification_attempt", "merchant_agreement_acceptance",
            "benefit_order", "verify_record", "payment_transaction", "order_refund",
            "payment_reconciliation_issue", "payment_callback_event",
            "talent_user", "talent_card", "talent_dynamic_code",
            "admin_user", "merchant_coupon", "news_article",
    };

    public static void main(String[] args) throws Exception {
        try (Connection left = DriverManager.getConnection(args[0], "root", "123456");
             Connection right = DriverManager.getConnection(args[1], "root", "123456")) {
            String[] tables = args.length > 2 ? args[2].split(",") : DEFAULT_TABLES;
            System.out.printf("%-34s %7s %7s %7s %7s %7s %7s%n",
                    "表", "总数L", "总数R", "同内容", "内容不同", "仅左", "仅右");
            for (String table : tables) {
                compare(left, right, table.trim());
            }
        }
    }

    private static void compare(Connection left, Connection right, String table) {
        try {
            List<String> keys = primaryKey(left, table);
            if (keys.isEmpty()) {
                System.out.printf("%-34s %7s%n", table, "（无单列主键，跳过）");
                return;
            }
            String key = keys.get(0);
            // 只比对两边都有的列：本机库可能还没应用某些迁移，列集合不同不代表行内容不同。
            List<String> leftColumns = columns(left, table);
            List<String> rightColumns = columns(right, table);
            List<String> shared = new ArrayList<>(leftColumns);
            shared.retainAll(rightColumns);
            if (!shared.contains(key)) {
                System.out.printf("%-34s %7s%n", table, "（主键列不在共有列里）");
                return;
            }
            Map<String, List<String>> leftRows = fingerprint(left, table, key, shared);
            Map<String, List<String>> rightRows = fingerprint(right, table, key, shared);
            int same = 0;
            int different = 0;
            List<String> conflicts = new ArrayList<>();
            List<String> example = null;
            for (Map.Entry<String, List<String>> entry : leftRows.entrySet()) {
                List<String> other = rightRows.get(entry.getKey());
                if (other == null) continue;
                if (other.equals(entry.getValue())) same++;
                else {
                    different++;
                    if (conflicts.size() < 8) conflicts.add(entry.getKey());
                    if (example == null) example = differingColumns(shared, entry.getValue(), other);
                }
            }
            int onlyLeft = 0;
            for (String id : leftRows.keySet()) if (!rightRows.containsKey(id)) onlyLeft++;
            int onlyRight = 0;
            for (String id : rightRows.keySet()) if (!leftRows.containsKey(id)) onlyRight++;
            System.out.printf("%-34s %7d %7d %7d %7d %7d %7d%n",
                    table, leftRows.size(), rightRows.size(), same, different, onlyLeft, onlyRight);
            if (!conflicts.isEmpty()) {
                System.out.println("      主键相同但内容不同：" + String.join(", ", conflicts)
                        + (different > conflicts.size() ? " ...（共 " + different + " 条）" : ""));
                if (example != null) System.out.println("      差异列（示例）：" + String.join(", ", example));
            }
        } catch (Exception exception) {
            System.out.printf("%-34s %7s%n", table, "（" + exception.getMessage() + "）");
        }
    }

    private static List<String> differingColumns(List<String> columns, List<String> left, List<String> right) {
        List<String> differing = new ArrayList<>();
        for (int index = 0; index < columns.size(); index++) {
            if (!left.get(index).equals(right.get(index))) differing.add(columns.get(index));
        }
        return differing;
    }

    private static List<String> columns(Connection connection, String table) throws Exception {
        List<String> columns = new ArrayList<>();
        try (PreparedStatement statement = connection.prepareStatement("""
                select column_name from information_schema.columns
                where table_schema = database() and table_name = ? order by ordinal_position
                """)) {
            statement.setString(1, table);
            try (ResultSet rows = statement.executeQuery()) {
                while (rows.next()) columns.add(rows.getString(1));
            }
        }
        return columns;
    }

    private static List<String> primaryKey(Connection connection, String table) throws Exception {
        List<String> keys = new ArrayList<>();
        try (PreparedStatement statement = connection.prepareStatement("""
                select column_name from information_schema.key_column_usage
                where table_schema = database() and table_name = ? and constraint_name = 'PRIMARY'
                order by ordinal_position
                """)) {
            statement.setString(1, table);
            try (ResultSet rows = statement.executeQuery()) {
                while (rows.next()) keys.add(rows.getString(1));
            }
        }
        return keys;
    }

    /** 主键 -> 共有列的内容指纹（按列顺序拼串，null 用特殊标记）。 */
    private static Map<String, List<String>> fingerprint(Connection connection, String table, String key,
                                                         List<String> columns) throws Exception {
        Map<String, List<String>> rows = new TreeMap<>();
        String selection = String.join(", ", columns.stream().map(column -> "`" + column + "`").toList());
        try (PreparedStatement statement = connection.prepareStatement(
                "select " + selection + " from `" + table + "`");
             ResultSet result = statement.executeQuery()) {
            while (result.next()) {
                List<String> content = new ArrayList<>(columns.size());
                for (int index = 1; index <= columns.size(); index++) {
                    Object value = result.getObject(index);
                    content.add(value == null ? "\u0000" : String.valueOf(value));
                }
                rows.put(String.valueOf(result.getObject(key)), content);
            }
        }
        return rows;
    }
}