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

/**
 * 导出该 SQL Server 实例上任意数据库的用户表与视图结构为 Markdown 文档。
 *
 * 典型用途：
 *   - 导出旧库 G3HY2025 的表结构（历史对照）
 *   - 导出新库 FMS 的表结构（V2 核心表 / 业务表 / 视图）
 * 新库的 s_module.b_view_table 大多指向视图，因此视图与表一并导出，
 * 视图标注为「视图」且无主键信息。
 *
 * 用法：
 *   javac -encoding UTF-8 -cp "mssql-jdbc-13.4.0.jre11.jar" SchemaDumpMarkdown.java
 *   java -Dstdout.encoding=UTF-8 -cp ".;mssql-jdbc-13.4.0.jre11.jar" SchemaDumpMarkdown <输出文件绝对路径> [数据库名，默认 G3HY2025] [--tables-only]
 *
 *   --tables-only    只导出表，不含视图（旧行为）
 */
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 {
        boolean tablesOnly = false;
        List<String> positional = new ArrayList<>();
        for (String raw : args) {
            String arg = raw.trim();
            if (arg.equalsIgnoreCase("--tables-only")) {
                tablesOnly = true;
            } else {
                positional.add(arg);
            }
        }

        String out = positional.size() > 0 ? positional.get(0) : "Fms旧系统表结构.md";
        String db = positional.size() > 1 ? positional.get(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<>();
        List<String> tables = new ArrayList<>();
        List<String> views = new ArrayList<>();

        try (Connection conn = DriverManager.getConnection(url, USER, PASSWORD)) {
            // 对象清单（表在前，视图在后）
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT TABLE_NAME, TABLE_TYPE FROM INFORMATION_SCHEMA.TABLES "
                         + "WHERE TABLE_TYPE IN ('BASE TABLE','VIEW') ORDER BY TABLE_TYPE, TABLE_NAME")) {
                while (rs.next()) {
                    if ("VIEW".equalsIgnoreCase(rs.getString(2))) views.add(rs.getString(1));
                    else tables.add(rs.getString(1));
                }
            }

            // 字段（表与视图共用）
            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（仅表有）
            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（仅表有）
            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) + ")");
                }
            }

            List<String> listedViews = tablesOnly ? Collections.emptyList() : views;

            StringBuilder sb = new StringBuilder();
            sb.append("# 表结构导出 — ").append(db).append(" 库\n\n");
            sb.append("> 来源库：`").append(db).append("`（").append(url).append("）\n");
            sb.append("> 包含用户表").append(tablesOnly ? "" : "和视图")
              .append("；字段「备注」列留空，供后续补充含义。").append("\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：该库定义了 ").append(fk.size()).append(" 张表的外键约束；")
              .append(pk.size()).append(" 张表定义了主键，").append(tables.size() - pk.size())
              .append(" 张表无主键。\n");
            if (!tablesOnly) {
                sb.append("> 视图无主键和默认值，字段来源见视图定义。\n");
            }
            sb.append("\n共 **").append(tables.size()).append("** 张表");
            if (!tablesOnly) sb.append("、**").append(listedViews.size()).append("** 个视图");
            sb.append("。\n\n");

            sb.append("## 对象清单（索引）\n\n");
            sb.append("| # | 名称 | 类型 | 字段数 | 主键 |\n| --- | --- | --- | --- | --- |\n");
            int i = 1;
            for (String t : tables) {
                sb.append("| ").append(i++).append(" | `").append(t).append("` | 表 | ")
                  .append(cols.getOrDefault(t, Collections.emptyList()).size())
                  .append(" | ").append(esc(pk.getOrDefault(t, ""))).append(" |\n");
            }
            for (String v : listedViews) {
                sb.append("| ").append(i++).append(" | `").append(v).append("` | 视图 | ")
                  .append(cols.getOrDefault(v, Collections.emptyList()).size())
                  .append(" |  |\n");
            }

            sb.append("\n## 表字段结构\n");
            for (String t : tables) {
                appendObject(sb, t, pk, fk, cols);
            }

            if (!listedViews.isEmpty()) {
                sb.append("\n## 视图字段结构\n");
                for (String v : listedViews) {
                    appendObject(sb, v, pk, fk, cols);
                }
            }

            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"
                + (listedViews.isEmpty() ? "" : "、" + listedViews.size() + " 个视图") + " -> " + out);
        }
    }

    static void appendObject(StringBuilder sb, String name,
                            Map<String, String> pk, Map<String, List<String>> fk,
                            Map<String, List<Col>> cols) {
        List<Col> cs = cols.getOrDefault(name, Collections.emptyList());
        sb.append("\n### ").append(name).append("\n\n");
        if (pk.containsKey(name)) sb.append("**主键：** ").append(esc(pk.get(name))).append("\n\n");
        List<String> fs = fk.get(name);
        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");
        }
    }

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