import java.io.*;
import java.nio.charset.StandardCharsets;
import java.sql.*;
import java.util.*;

/**
 * 导出旧系统库（FMS）的用户表结构为 Markdown 文档。
 *
 * 用法：
 *   javac -encoding UTF-8 -cp "mssql-jdbc-13.4.0.jre11.jar" SchemaDumpMarkdown.java
 *   java -cp ".;mssql-jdbc-13.4.0.jre11.jar" SchemaDumpMarkdown <输出文件绝对路径> [数据库名，默认 G3HY2025]
 */
public class SchemaDumpMarkdown {

    static final String BASE_URL = "jdbc:sqlserver://118.89.70.199:1433;encrypt=true;trustServerCertificate=true";
    static final String USER = "sa";
    static final String PASSWORD = "zhang520..";

    static class Col {
        String name, type, len, precScale, nullable, def;
    }

    public static void main(String[] args) throws Exception {
        String out = args.length > 0 ? args[0] : "Fms旧系统表结构.md";
        String db = args.length > 1 ? args[1] : "G3HY2025";
        String url = BASE_URL + ";databaseName=" + db;

        Map<String, List<Col>> cols = new LinkedHashMap<>();
        Map<String, String> pk = new LinkedHashMap<>();
        Map<String, List<String>> fk = new LinkedHashMap<>();

        try (Connection conn = DriverManager.getConnection(url, USER, PASSWORD)) {
            // 表清单
            List<String> tables = new ArrayList<>();
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES "
                         + "WHERE TABLE_TYPE='BASE TABLE' ORDER BY TABLE_NAME")) {
                while (rs.next()) tables.add(rs.getString(1));
            }

            // 字段
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT TABLE_NAME, COLUMN_NAME, DATA_TYPE, "
                         + "CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, NUMERIC_SCALE, IS_NULLABLE, COLUMN_DEFAULT "
                         + "FROM INFORMATION_SCHEMA.COLUMNS ORDER BY TABLE_NAME, ORDINAL_POSITION")) {
                while (rs.next()) {
                    Col c = new Col();
                    c.name = rs.getString(2);
                    c.type = rs.getString(3);
                    int maxLen = rs.getInt(4);
                    c.len = rs.wasNull() ? "" : (maxLen == -1 ? "MAX" : String.valueOf(maxLen));
                    Object p = rs.getObject(5);
                    if (p != null) c.precScale = p + "," + rs.getObject(6);
                    else c.precScale = "";
                    c.nullable = rs.getString(7);
                    c.def = rs.getString(8);
                    cols.computeIfAbsent(rs.getString(1), k -> new ArrayList<>()).add(c);
                }
            }

            // 主键
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT OBJECT_NAME(k.parent_object_id), c.name "
                         + "FROM sys.key_constraints k "
                         + "JOIN sys.index_columns ic ON ic.object_id = k.parent_object_id AND ic.index_id = k.unique_index_id "
                         + "JOIN sys.columns c ON c.object_id = ic.object_id AND c.column_id = ic.column_id "
                         + "WHERE k.type = 'PK' "
                         + "ORDER BY 1, ic.key_ordinal")) {
                while (rs.next()) {
                    String t = rs.getString(1);
                    pk.merge(t, rs.getString(2), (a, b) -> a + ", " + b);
                }
            }

            // 外键
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT OBJECT_NAME(f.parent_object_id), "
                         + "COL_NAME(fc.parent_object_id, fc.parent_column_id), "
                         + "OBJECT_NAME(f.referenced_object_id), "
                         + "COL_NAME(fc.referenced_object_id, fc.referenced_column_id) "
                         + "FROM sys.foreign_keys f JOIN sys.foreign_key_columns fc ON f.object_id = fc.constraint_object_id "
                         + "ORDER BY 1, 2")) {
                while (rs.next()) {
                    fk.computeIfAbsent(rs.getString(1), k -> new ArrayList<>())
                      .add(rs.getString(2) + " -> " + rs.getString(3) + "(" + rs.getString(4) + ")");
                }
            }

            StringBuilder sb = new StringBuilder();
            sb.append("# Fms 旧系统表结构（G3HY2025 库）\n\n");
            sb.append("> 来源库：`").append(db).append("`（jdbc:sqlserver://118.89.70.199:1433;databaseName=").append(db).append("）\n");
            sb.append("> 仅包含用户表（BASE TABLE），不含视图。字段「备注」列留空，供后续补充含义。\n");
            sb.append("> 拉取时间：").append(new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new java.util.Date())).append("\n");
            sb.append("> 约束情况：该库未定义外键约束（`sys.foreign_keys` = 0）；")
              .append(pk.size()).append(" 张表定义了主键，").append(tables.size() - pk.size())
              .append(" 张表无主键。\n\n");
            sb.append("共 **").append(tables.size()).append("** 张表。\n\n");

            sb.append("## 表清单（索引）\n\n");
            sb.append("| # | 表名 | 字段数 | 主键 |\n| --- | --- | --- | --- |\n");
            int i = 1;
            for (String t : tables) {
                List<Col> cs = cols.getOrDefault(t, Collections.emptyList());
                sb.append("| ").append(i++).append(" | `").append(t).append("` | ").append(cs.size())
                  .append(" | ").append(esc(pk.getOrDefault(t, ""))).append(" |\n");
            }

            sb.append("\n## 各表字段结构\n");
            for (String t : tables) {
                List<Col> cs = cols.getOrDefault(t, Collections.emptyList());
                sb.append("\n### ").append(t).append("\n\n");
                if (pk.containsKey(t)) sb.append("**主键：** ").append(esc(pk.get(t))).append("\n\n");
                List<String> fs = fk.get(t);
                if (fs != null && !fs.isEmpty()) {
                    sb.append("**外键：**\n");
                    for (String f : fs) sb.append("- ").append(esc(f)).append("\n");
                    sb.append("\n");
                }
                sb.append("| 字段名 | 类型 | 长度 | 精度,小数位 | 可空 | 默认值 | 备注 |\n");
                sb.append("| --- | --- | --- | --- | --- | --- | --- |\n");
                for (Col c : cs) {
                    sb.append("| `").append(c.name).append("` | ").append(c.type).append(" | ").append(c.len)
                      .append(" | ").append(c.precScale).append(" | ").append(c.nullable)
                      .append(" | ").append(c.def == null ? "" : esc(c.def)).append(" |  |\n");
                }
            }

            try (Writer w = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(out), StandardCharsets.UTF_8))) {
                w.write(sb.toString());
            }
            System.out.println("已写出 " + tables.size() + " 张表 -> " + out);
        }
    }

    static String esc(String s) {
        return s == null ? "" : s.replace("|", "\\|");
    }
}