package com.btk5h.skriptdb.skript;

import ch.njol.skript.Skript;
import ch.njol.skript.effects.Delay;
import ch.njol.skript.lang.*;
import ch.njol.skript.variables.Variables;
import ch.njol.util.Kleenean;
import ch.njol.util.Pair;
import com.btk5h.skriptdb.SkriptDB;
import com.btk5h.skriptdb.SkriptUtil;
import com.zaxxer.hikari.HikariDataSource;
import org.bukkit.Bukkit;
import org.bukkit.event.Event;

import javax.sql.DataSource;
import javax.sql.rowset.CachedRowSet;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.*;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Executes a statement on a database and optionally stores the result in a variable. Expressions
 * embedded in the query will be escaped to avoid SQL injection.
 * <p>
 * If a single variable, such as `{test}`, is passed, the variable will be set to the number of
 * affected rows.
 * <p>
 * If a list variable, such as `{test::*}`, is passed, the query result will be mapped to the list
 * variable in the form `{test::<column name>::<row number>}`
 *
 * @name Execute Statement
 * @pattern [synchronously] execute %string% (in|on) %datasource% [and store [[the] (output|result)[s]] (to|in)
 * [the] [var[iable]] %-objects%]
 * @example execute "select * from table" in {sql} and store the result in {output::*}
 * @example execute "select * from %{table variable}%" in {sql} and store the result in {output::*}
 * @since 0.1.0
 */
public class EffExecuteStatement extends Effect {
  static {
    Skript.registerEffect(EffExecuteStatement.class,
        "execute %string% (in|on) %datasource% " +
            "[and store [[the] (output|result)[s]] (to|in) [the] [var[iable]] %-objects%]", "synchronously execute %string% (in|on) %datasource% " +
            "[and store [[the] (output|result)[s]] (to|in) [the] [var[iable]] %-objects%]");
  }

  static String lastError;

  private static final ExecutorService threadPool =
      Executors.newFixedThreadPool(SkriptDB.getInstance().getConfig().getInt("thread-pool-size"));

  private Expression<String> query;
  private Expression<HikariDataSource> dataSource;
  private VariableString var;
  private boolean isLocal;
  private boolean isList;
  private boolean isSync;

  private void continueScriptExecution(Event e, Object populatedVariables) {
    lastError = null;
    if (populatedVariables instanceof String) {
      lastError = (String) populatedVariables;
    } else {

      if (getNext() != null) {
        ((Map<String, Object>) populatedVariables).forEach((name, value) -> setVariable(e, name, value));
      }
    }
    TriggerItem.walk(getNext(), e);
  }
  @Override
  protected void execute(Event e) {
    DataSource ds = dataSource.getSingle(e);
    Pair<String, List<Object>> query = parseQuery(e);
    String baseVariable = var != null ? var.toString(e).toLowerCase(Locale.ENGLISH) : null;

    //if data source isn't set
    if (ds == null)
      return;


    if (isSync) {
      Object populatedVariables = executeStatement(ds, baseVariable, query);
      continueScriptExecution(e, populatedVariables);
    } else {
      Object locals = Variables.removeLocals(e);

      //execute SQL statement
      CompletableFuture<Object> sql =
          CompletableFuture.supplyAsync(() -> executeStatement(ds, baseVariable, query), threadPool);

      //when SQL statement is completed
      sql.whenComplete((res, err) -> {
        if (err != null) {
          err.printStackTrace();
        }

        Bukkit.getScheduler().runTask(SkriptDB.getInstance(), () -> {

          //handle last error syntax data
          lastError = null;
          if (res instanceof String) {
            lastError = (String) res;
          }

          if (getNext() != null) {
            //if local variables are present
            if (locals != null)

              //bring back local variables
              Variables.setLocalVariables(e, locals);

            //populate SQL data into variables
            if (!(res instanceof String)) {
              ((Map<String, Object>) res).forEach((name, value) -> setVariable(e, name, value));
            }
            TriggerItem.walk(getNext(), e);
            //let's try with this commented, as it may be not needed? let's test!
            //Variables.removeLocals(e);
          }
        });
      });
    }
  }

  @Override
  protected TriggerItem walk(Event e) {
    debug(e, true);
    if (!isSync) {
      Delay.addDelayedEvent(e);
    }
    execute(e);
    return null;
  }

  private Pair<String, List<Object>> parseQuery(Event e) {
    if (!(query instanceof VariableString)) {
      return new Pair<>(query.getSingle(e), null);
    }
    VariableString q = (VariableString) query;
    if (q.isSimple()) {
      return new Pair<>(q.toString(e), null);
    }

    StringBuilder sb = new StringBuilder();
    List<Object> parameters = new ArrayList<>();
    Object[] objects = SkriptUtil.getTemplateString(q);

    for (int i = 0; i < objects.length; i++) {
      Object o = objects[i];
      if (o instanceof String) {
        sb.append(o);
      } else {
        Expression<?> expr = SkriptUtil.getExpressionFromInfo(o);

        String before = getString(objects, i - 1);
        String after = getString(objects, i + 1);
        boolean standaloneString = false;

        if (before != null && after != null) {
          if (before.endsWith("'") && after.endsWith("'")) {
            standaloneString = true;
          }
        }

        Object expressionValue = expr.getSingle(e);

        if (expr instanceof ExprUnsafe) {
          sb.append(expressionValue);

          if (standaloneString && expressionValue instanceof String) {
            String rawExpression = ((ExprUnsafe) expr).getRawExpression();
            Skript.warning(
                String.format("Unsafe may have been used unnecessarily. Try replacing 'unsafe %1$s' with %1$s",
                    rawExpression));
          }
        } else {
          parameters.add(expressionValue);
          sb.append('?');

          if (standaloneString) {
            Skript.warning("Do not surround expressions with quotes!");
          }
        }
      }
    }
    return new Pair<>(sb.toString(), parameters);
  }

  private Object executeStatement(DataSource ds, String baseVariable, Pair<String, List<Object>> query) {
    if (ds == null) {
      return "Data source is not set";
    }
    Map<String, Object> variableList = new HashMap<>();
    try (Connection conn = ds.getConnection();
         PreparedStatement stmt = createStatement(conn, query)) {

      boolean hasResultSet = stmt.execute();

      if (baseVariable != null) {
        if (isList) {
          baseVariable = baseVariable.substring(0, baseVariable.length() - 1);
        }

        if (hasResultSet) {
          CachedRowSet crs = SkriptDB.getRowSetFactory().createCachedRowSet();
          crs.populate(stmt.getResultSet());

          if (isList) {
              ResultSetMetaData meta = crs.getMetaData();
              int columnCount = meta.getColumnCount();

              for (int i = 1; i <= columnCount; i++) {
                String label = meta.getColumnLabel(i);
                variableList.put(baseVariable + label, label);
              }

              int rowNumber = 1;
              try {
                while (crs.next()) {
                  for (int i = 1; i <= columnCount; i++) {
                    variableList.put(baseVariable + meta.getColumnLabel(i).toLowerCase(Locale.ENGLISH)
                        + Variable.SEPARATOR + rowNumber, crs.getObject(i));
                  }
                  rowNumber++;
                }
              } catch (SQLException ex) {
                return ex.getMessage();
              }
          } else {
            crs.last();
            variableList.put(baseVariable, crs.getRow());
          }
        } else if (!isList) {
          //if no results are returned and the specified variable isn't a list variable, put the affected rows count in the variable
          variableList.put(baseVariable, stmt.getUpdateCount());
        }
      }
    } catch (SQLException ex) {
      return ex.getMessage();
    }
    return variableList;
  }

  private PreparedStatement createStatement(Connection conn, Pair<String, List<Object>> query) throws SQLException {
    PreparedStatement stmt = conn.prepareStatement(query.getFirst());
    List<Object> parameters = query.getSecond();

    if (parameters != null) {
      for (int i = 0; i < parameters.size(); i++) {
        stmt.setObject(i + 1, parameters.get(i));
      }
    }

    return stmt;
  }

  private String getString(Object[] objects, int index) {
    if (index < 0 || index >= objects.length) {
      return null;
    }

    Object object = objects[index];

    if (object instanceof String) {
      return (String) object;
    }

    return null;
  }

  private void setVariable(Event e, String name, Object obj) {
    Variables.setVariable(name.toLowerCase(Locale.ENGLISH), obj, e, isLocal);
  }

  @Override
  public String toString(Event e, boolean debug) {
    return "execute " + query.toString(e, debug) + " in " + dataSource.toString(e, debug);
  }

  @SuppressWarnings("unchecked")
  @Override
  public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed,
                      SkriptParser.ParseResult parseResult) {
    Expression<String> statementExpr = (Expression<String>) exprs[0];
    if (statementExpr instanceof VariableString || statementExpr instanceof ExprUnsafe) {
      query = statementExpr;
    } else {
      Skript.error("Database statements must be string literals. If you must use an expression, " +
          "you may use \"%unsafe (your expression)%\", but keep in mind, you may be vulnerable " +
          "to SQL injection attacks!");
      return false;
    }
    dataSource = (Expression<HikariDataSource>) exprs[1];
    Expression<?> expr = exprs[2];
    isSync = matchedPattern == 1;
    if (expr instanceof Variable) {
      Variable<?> varExpr = (Variable<?>) expr;
      var = varExpr.getName();
      isLocal = varExpr.isLocal();
      isList = varExpr.isList();
    } else if (expr != null) {
      Skript.error(expr + " is not a variable");
      return false;
    }
    return true;
  }
}