import java.io.FileInputStream;
import java.io.PrintWriter;
import java.nio.charset.StandardCharsets;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class DropFks {
    static class Fk {
        String name, schema, parentTable, refTable, delAction, updAction;
        List<String[]> cols = new ArrayList<>(); // {parentCol, refCol}
    }

    public static void main(String[] args) throws Exception {
        Properties props = new Properties();
        try (FileInputStream in = new FileInputStream(args[0])) { props.load(in); }
        String url = props.getProperty("url");
        String user = props.getProperty("username");
        String pass = props.getProperty("password");

        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        try (Connection conn = DriverManager.getConnection(url, user, pass)) {
            conn.setAutoCommit(false);
            List<Fk> fks = new ArrayList<>();

            String sql =
                "SELECT fk.name AS fk_name, " +
                "OBJECT_SCHEMA_NAME(fk.parent_object_id) AS sch, " +
                "OBJECT_NAME(fk.parent_object_id) AS parent_tbl, " +
                "OBJECT_NAME(fk.referenced_object_id) AS ref_tbl, " +
                "fk.delete_referential_action_desc AS del, " +
                "fk.update_referential_action_desc AS upd " +
                "FROM sys.foreign_keys fk ORDER BY fk.name";
            try (Statement st = conn.createStatement(); ResultSet rs = st.executeQuery(sql)) {
                while (rs.next()) {
                    Fk f = new Fk();
                    f.name = rs.getString("fk_name");
                    f.schema = rs.getString("sch");
                    f.parentTable = rs.getString("parent_tbl");
                    f.refTable = rs.getString("ref_tbl");
                    f.delAction = rs.getString("del");
                    f.updAction = rs.getString("upd");
                    fks.add(f);
                }
            }
            String colSql =
                "SELECT fk.name AS fk_name, " +
                "COL_NAME(fkc.parent_object_id, fkc.parent_column_id) AS pc, " +
                "COL_NAME(fkc.referenced_object_id, fkc.referenced_column_id) AS rc " +
                "FROM sys.foreign_keys fk " +
                "JOIN sys.foreign_key_columns fkc ON fkc.constraint_object_id = fk.object_id " +
                "ORDER BY fk.name, fkc.constraint_column_id";
            try (Statement st = conn.createStatement(); ResultSet rs = st.executeQuery(colSql)) {
                while (rs.next()) {
                    String n = rs.getString("fk_name");
                    for (Fk f : fks) {
                        if (f.name.equals(n)) {
                            f.cols.add(new String[]{rs.getString("pc"), rs.getString("rc")});
                            break;
                        }
                    }
                }
            }

            // 1. Write restore script
            String restorePath = "restore_fks.sql";
            try (PrintWriter w = new PrintWriter(restorePath, StandardCharsets.UTF_8)) {
                w.println("-- Restore script for G3HD (FMS-NEW) physical foreign keys");
                w.println("-- Generated: " + new Timestamp(System.currentTimeMillis()));
                w.println("USE [FMS-NEW];");
                w.println("GO");
                for (Fk f : fks) {
                    StringBuilder pcols = new StringBuilder(), rcols = new StringBuilder();
                    for (int i = 0; i < f.cols.size(); i++) {
                        if (i > 0) { pcols.append(", "); rcols.append(", "); }
                        pcols.append("[").append(f.cols.get(i)[0]).append("]");
                        rcols.append("[").append(f.cols.get(i)[1]).append("]");
                    }
                    w.printf("ALTER TABLE [%s].[%s] WITH CHECK ADD CONSTRAINT [%s] FOREIGN KEY(%s)%n",
                            f.schema, f.parentTable, f.name, pcols);
                    w.printf("REFERENCES [%s].[%s] (%s) ON DELETE %s ON UPDATE %s;%n",
                            f.schema, f.refTable, rcols, f.delAction, f.updAction);
                    w.println("GO");
                }
                w.println("-- End of restore script");
            }
            System.out.println("Restore script written to: " + restorePath + "  (" + fks.size() + " FKs)");

            // 2. Drop all FKs in one transaction
            int dropped = 0;
            for (Fk f : fks) {
                String ddl = String.format("ALTER TABLE [%s].[%s] DROP CONSTRAINT [%s]",
                        f.schema, f.parentTable, f.name);
                try (Statement st = conn.createStatement()) {
                    st.executeUpdate(ddl);
                    dropped++;
                    System.out.println("DROPPED: " + f.name + " (on " + f.parentTable + ")");
                }
            }
            conn.commit();
            System.out.println("\nCommitted. Dropped " + dropped + " foreign keys.");

            // 3. Verify
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT COUNT(*) FROM sys.foreign_keys")) {
                rs.next();
                System.out.println("REMAINING FK COUNT = " + rs.getInt(1));
            }
        }
    }
}