// Copyright (C) 2009 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.gerrit.server.schema;

import com.google.gerrit.reviewdb.CurrentSchemaVersion;
import com.google.gerrit.reviewdb.ReviewDb;
import com.google.gwtorm.client.OrmException;
import com.google.gwtorm.client.StatementExecutor;
import com.google.gwtorm.jdbc.JdbcExecutor;
import com.google.gwtorm.jdbc.JdbcSchema;
import com.google.inject.AbstractModule;
import com.google.inject.Provider;

import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/** A version of the database schema. */
public abstract class SchemaVersion {
  /** The current schema version. */
  private static final Class<? extends SchemaVersion> C = Schema_42.class;

  public static class Module extends AbstractModule {
    @Override
    protected void configure() {
      bind(SchemaVersion.class).annotatedWith(Current.class).to(C);
    }
  }

  private final Provider<? extends SchemaVersion> prior;
  private final int versionNbr;

  protected SchemaVersion(final Provider<? extends SchemaVersion> prior) {
    this.prior = prior;
    this.versionNbr = guessVersion(getClass());
  }

  private static int guessVersion(Class<?> c) {
    String n = c.getName();
    n = n.substring(n.lastIndexOf('_') + 1);
    while (n.startsWith("0"))
      n = n.substring(1);
    return Integer.parseInt(n);
  }

  protected SchemaVersion(final Provider<? extends SchemaVersion> prior,
      final int versionNbr) {
    this.prior = prior;
    this.versionNbr = versionNbr;
  }

  /** @return the {@link CurrentSchemaVersion#versionNbr} this step targets. */
  public final int getVersionNbr() {
    return versionNbr;
  }

  public final void check(UpdateUI ui, CurrentSchemaVersion curr, ReviewDb db, boolean toTargetVersion)
      throws OrmException, SQLException {
    if (curr.versionNbr == versionNbr) {
      // Nothing to do, we are at the correct schema.
      //
    } else {
      upgradeFrom(ui, curr, db, toTargetVersion);
    }
  }

  /** Runs check on the prior schema version, and then upgrades. */
  protected void upgradeFrom(UpdateUI ui, CurrentSchemaVersion curr, ReviewDb db, boolean toTargetVersion)
      throws OrmException, SQLException {
    final JdbcSchema s = (JdbcSchema) db;

    prior.get().check(ui, curr, db, false);

    ui.message("Upgrading database schema from version " + curr.versionNbr
        + " to " + versionNbr + " ...");

    preUpdateSchema(db);
    final JdbcExecutor e = new JdbcExecutor(s);
    try {
      s.updateSchema(e);
      migrateData(db, ui);

      if (toTargetVersion) {
        final List<String> pruneList = new ArrayList<String>();
        s.pruneSchema(new StatementExecutor() {
          public void execute(String sql) {
            pruneList.add(sql);
          }
        });

        if (!pruneList.isEmpty()) {
          ui.pruneSchema(e, pruneList);
        }
      }
    } finally {
      e.close();
    }
    finish(curr, db);
  }

  /** Invoke before updateSchema adds new columns/tables. */
  protected void preUpdateSchema(ReviewDb db) throws OrmException, SQLException {
  }

  /**
   * Invoked between updateSchema (adds new columns/tables) and pruneSchema
   * (removes deleted columns/tables).
   */
  @SuppressWarnings("unused")
  protected void migrateData(ReviewDb db, UpdateUI ui) throws OrmException, SQLException {
  }

  /** Mark the current schema version. */
  protected void finish(CurrentSchemaVersion curr, ReviewDb db)
      throws OrmException {
    curr.versionNbr = versionNbr;
    db.schemaVersion().update(Collections.singleton(curr));
  }

  /** Rename an existing column. */
  protected void renameColumn(ReviewDb db, String table, String from, String to)
      throws OrmException {
    final JdbcSchema s = (JdbcSchema) db;
    final JdbcExecutor e = new JdbcExecutor(s);
    try {
      s.renameField(e, table, from, to);
    } finally {
      e.close();
    }
  }

  /** Execute a SQL statement. */
  protected void execute(ReviewDb db, String sql) throws SQLException {
    Statement s = ((JdbcSchema) db).getConnection().createStatement();
    try {
      s.execute(sql);
    } finally {
      s.close();
    }
  }
}