package io.ebeaninternal.dbmigration.model;

import io.ebeaninternal.dbmigration.ddlgeneration.platform.DdlHelp;
import io.ebeaninternal.dbmigration.migration.AddColumn;
import io.ebeaninternal.dbmigration.migration.AddHistoryTable;
import io.ebeaninternal.dbmigration.migration.AddTableComment;
import io.ebeaninternal.dbmigration.migration.AlterColumn;
import io.ebeaninternal.dbmigration.migration.AlterTable;
import io.ebeaninternal.dbmigration.migration.Column;
import io.ebeaninternal.dbmigration.migration.CreateTable;
import io.ebeaninternal.dbmigration.migration.DropColumn;
import io.ebeaninternal.dbmigration.migration.DropHistoryTable;
import io.ebeaninternal.dbmigration.migration.DropTable;
import io.ebeaninternal.dbmigration.migration.ForeignKey;
import io.ebeaninternal.dbmigration.migration.RenameColumn;
import io.ebeaninternal.dbmigration.migration.UniqueConstraint;
import io.ebeaninternal.server.deploy.BeanDescriptor;
import io.ebeaninternal.server.deploy.BeanProperty;
import io.ebeaninternal.server.deploy.IdentityMode;
import io.ebeaninternal.server.deploy.PartitionMeta;
import io.ebeaninternal.server.deploy.TablespaceMeta;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

import static io.ebeaninternal.dbmigration.ddlgeneration.platform.SplitColumns.split;
import static io.ebeaninternal.dbmigration.model.MTableIdentity.fromCreateTable;
import static io.ebeaninternal.dbmigration.model.MTableIdentity.toCreateTable;

/**
 * Holds the logical model for a given Table and everything associated to it.
 * <p>
 * This effectively represents a table, its columns and all associated
 * constraints, foreign keys and indexes.
 * <p>
 * Migrations can be applied to this such that it represents the state
 * of a given table after various migrations have been applied.
 * <p>
 * This table model can also be derived from the EbeanServer bean descriptor
 * and associated properties.
 */
public class MTable {

  private static final Logger logger = LoggerFactory.getLogger(MTable.class);

  private final String name;
  private MTable draftTable;
  /**
   * Marked true for draft tables. These need to have their FK references adjusted
   * after all the draft tables have been identified.
   */
  private boolean draft;
  private PartitionMeta partitionMeta;
  private TablespaceMeta tablespaceMeta;
  private String pkName;
  private String comment;
  private String storageEngine;
  private IdentityMode identityMode;
  private boolean withHistory;
  private final Map<String, MColumn> columns = new LinkedHashMap<>();

  /**
   * Compound unique constraints.
   */
  private final List<MCompoundUniqueConstraint> uniqueConstraints = new ArrayList<>();

  /**
   * Compound foreign keys.
   */
  private final List<MCompoundForeignKey> compoundKeys = new ArrayList<>();

  /**
   * Column name for the 'When created' column. This can be used for the initial effective start date when adding
   * history to an existing table and maps to a @WhenCreated or @CreatedTimestamp column.
   */
  private String whenCreatedColumn;

  /**
   * Temporary - holds addColumn settings.
   */
  private AddColumn addColumn;

  private final List<String> droppedColumns = new ArrayList<>();

  public MTable(BeanDescriptor<?> descriptor) {
    this.name = descriptor.baseTable();
    this.identityMode = descriptor.identityMode();
    this.storageEngine = descriptor.storageEngine();
    this.partitionMeta = descriptor.partitionMeta();
    this.tablespaceMeta = descriptor.tablespaceMeta();
    this.comment = descriptor.dbComment();
    if (descriptor.isHistorySupport()) {
      withHistory = true;
      BeanProperty whenCreated = descriptor.whenCreatedProperty();
      if (whenCreated != null) {
        whenCreatedColumn = whenCreated.dbColumn();
      }
    }
  }

  /**
   * Constructor for test cases only!
   */
  @Deprecated
  public MTable(String name) {
    this(name, null, null);
  }

  /**
   * Construct for element collection or intersection table. They have same table space and storage engine.
   */
  public MTable(String name, BeanDescriptor<?> descriptor) {
    this(name, descriptor.tablespaceMeta(), descriptor.storageEngine());
  }
  
  /**
   * Constructor for dependant tables (draft/element collection or intersection).
   */
  private MTable(String name, TablespaceMeta tablespaceMeta, String storageEngine) {
    this.name = name;
    this.identityMode = IdentityMode.NONE;
    this.tablespaceMeta = tablespaceMeta;
    this.storageEngine = storageEngine;
  }

  /**
   * Create a copy of this table structure as a 'draft' table.
   * <p>
   * Note that both tables contain @DraftOnly MColumns and these are filtered out
   * later when creating the CreateTable object.
   */
  public MTable createDraftTable() {
    draftTable = new MTable(name + "_draft", this.tablespaceMeta, this.storageEngine);
    draftTable.draft = true;
    draftTable.whenCreatedColumn = whenCreatedColumn;
    // compoundKeys
    // compoundUniqueConstraints
    draftTable.identityMode = identityMode;
    for (MColumn col : allColumns()) {
      draftTable.addColumn(col.copyForDraft());
    }
    return draftTable;
  }

  /**
   * Construct for migration.
   */
  public MTable(CreateTable createTable) {
    this.name = createTable.getName();
    this.pkName = createTable.getPkName();
    this.comment = createTable.getComment();
    this.storageEngine = createTable.getStorageEngine();
    if (createTable.getTablespace() != null) {
      this.tablespaceMeta = new TablespaceMeta(createTable.getTablespace(),
          createTable.getIndexTablespace() != null ? createTable.getIndexTablespace() : createTable.getTablespace(),
          createTable.getLobTablespace() != null ? createTable.getLobTablespace() : createTable.getTablespace());
    } else {
      this.tablespaceMeta = null;
    }
    this.withHistory = Boolean.TRUE.equals(createTable.isWithHistory());
    this.draft = Boolean.TRUE.equals(createTable.isDraft());
    this.identityMode = fromCreateTable(createTable);
    List<Column> cols = createTable.getColumn();
    for (Column column : cols) {
      addColumn(column);
    }
    for (UniqueConstraint uq : createTable.getUniqueConstraint()) {
      uniqueConstraints.add(new MCompoundUniqueConstraint(uq));
    }

    for (ForeignKey fk : createTable.getForeignKey()) {
      if (DdlHelp.isDropForeignKey(fk.getColumnNames())) {
        removeForeignKey(fk.getName());
      } else {
        addForeignKey(fk.getName(), fk.getRefTableName(), fk.getIndexName(), fk.getColumnNames(), fk.getRefColumnNames());
      }
    }
  }

  public void addForeignKey(String name, String refTableName, String indexName, String columnNames, String refColumnNames) {
    MCompoundForeignKey foreignKey = new MCompoundForeignKey(name, refTableName, indexName);
    String[] cols = split(columnNames);
    String[] refCols = split(refColumnNames);
    for (int i = 0; i < cols.length && i < refCols.length; i++) {
      foreignKey.addColumnPair(cols[i], refCols[i]);
    }
    addForeignKey(foreignKey);
  }

  /**
   * Return the DropTable migration for this table.
   */
  public DropTable dropTable() {
    DropTable dropTable = new DropTable();
    dropTable.setName(name);
    // we must add pk col name & sequence name, as we have to delete the sequence also.
    if (identityMode.isDatabaseIdentity()) {
      String pkCol = null;
      for (MColumn column : columns.values()) {
        if (column.isPrimaryKey()) {
          if (pkCol == null) {
            pkCol = column.getName();
          } else { // multiple pk cols -> no sequence
            pkCol = null;
            break;
          }
        }
      }
      if (pkCol != null) {
        dropTable.setSequenceCol(pkCol);
        dropTable.setSequenceName(identityMode.getSequenceName());
      }
    }
    return dropTable;
  }

  /**
   * Return the CreateTable migration for this table.
   */
  public CreateTable createTable() {
    CreateTable createTable = new CreateTable();
    createTable.setName(name);
    createTable.setPkName(pkName);
    createTable.setComment(comment);
    if (partitionMeta != null) {
      createTable.setPartitionMode(partitionMeta.getMode().name());
      createTable.setPartitionColumn(partitionMeta.getProperty());
    }
    createTable.setStorageEngine(storageEngine);
    if (tablespaceMeta != null) {
      createTable.setTablespace(tablespaceMeta.getTablespaceName());
      createTable.setIndexTablespace(tablespaceMeta.getIndexTablespace());
      createTable.setLobTablespace(tablespaceMeta.getLobTablespace());
    }
    toCreateTable(identityMode, createTable);
    if (withHistory) {
      createTable.setWithHistory(Boolean.TRUE);
    }
    if (draft) {
      createTable.setDraft(Boolean.TRUE);
    }
    for (MColumn column : allColumns()) {
      // filter out draftOnly columns from the base table
      if (draft || !column.isDraftOnly()) {
        createTable.getColumn().add(column.createColumn());
      }
    }
    for (MCompoundForeignKey compoundKey : compoundKeys) {
      createTable.getForeignKey().add(compoundKey.createForeignKey());
    }
    for (MCompoundUniqueConstraint constraint : uniqueConstraints) {
      createTable.getUniqueConstraint().add(constraint.getUniqueConstraint());
    }
    return createTable;
  }

  /**
   * Compare to another version of the same table to perform a diff.
   */
  public void compare(ModelDiff modelDiff, MTable newTable) {
    if (withHistory != newTable.withHistory) {
      if (withHistory) {
        DropHistoryTable dropHistoryTable = new DropHistoryTable();
        dropHistoryTable.setBaseTable(name);
        modelDiff.addDropHistoryTable(dropHistoryTable);

      } else {
        AddHistoryTable addHistoryTable = new AddHistoryTable();
        addHistoryTable.setBaseTable(name);
        modelDiff.addAddHistoryTable(addHistoryTable);
      }
    }

    compareColumns(modelDiff, newTable);

    if (MColumn.different(comment, newTable.comment)) {
      AddTableComment addTableComment = new AddTableComment();
      addTableComment.setName(name);
      if (newTable.comment == null) {
        addTableComment.setComment(DdlHelp.DROP_COMMENT);
      } else {
        addTableComment.setComment(newTable.comment);
      }
      modelDiff.addTableComment(addTableComment);
    }

    compareCompoundKeys(modelDiff, newTable);
    compareUniqueKeys(modelDiff, newTable);
    compareTableAttrs(modelDiff, newTable);
  
  }

  private void compareColumns(ModelDiff modelDiff, MTable newTable) {
    addColumn = null;
    Map<String, MColumn> newColumnMap = newTable.getColumns();

    // compare newColumns to existing columns (look for new and diff columns)
    for (MColumn newColumn : newColumnMap.values()) {
      MColumn localColumn = getColumn(newColumn.getName());
      if (localColumn == null) {
        // can ignore if draftOnly column and non-draft table
        if (!newColumn.isDraftOnly() || draft) {
          diffNewColumn(newColumn, newTable);
        }
      } else {
        localColumn.compare(modelDiff, this, newColumn);
      }
    }

    // compare existing columns (look for dropped columns)
    for (MColumn existingColumn : allColumns()) {
      MColumn newColumn = newColumnMap.get(existingColumn.getName());
      if (newColumn == null) {
        diffDropColumn(modelDiff, existingColumn);
      } else if (newColumn.isDraftOnly() && !draft) {
        // effectively a drop column (draft only column on a non-draft table)
        logger.trace("... drop column {} from table {} as now draftOnly", newColumn.getName(), name);
        diffDropColumn(modelDiff, existingColumn);
      }
    }

    if (addColumn != null) {
      modelDiff.addAddColumn(addColumn);
    }
  }


  private void compareCompoundKeys(ModelDiff modelDiff, MTable newTable) {
    List<MCompoundForeignKey> newKeys = new ArrayList<>(newTable.getCompoundKeys());
    List<MCompoundForeignKey> currentKeys = new ArrayList<>(getCompoundKeys());

    // remove keys that have not changed
    currentKeys.removeAll(newTable.getCompoundKeys());
    newKeys.removeAll(getCompoundKeys());

    for (MCompoundForeignKey currentKey : currentKeys) {
      modelDiff.addAlterForeignKey(currentKey.dropForeignKey(name));
    }

    for (MCompoundForeignKey newKey : newKeys) {
      modelDiff.addAlterForeignKey(newKey.addForeignKey(name));
    }
  }

  private void compareUniqueKeys(ModelDiff modelDiff, MTable newTable) {
    List<MCompoundUniqueConstraint> newKeys = new ArrayList<>(newTable.getUniqueConstraints());
    List<MCompoundUniqueConstraint> currentKeys = new ArrayList<>(getUniqueConstraints());

    // remove keys that have not changed
    currentKeys.removeAll(newTable.getUniqueConstraints());
    newKeys.removeAll(getUniqueConstraints());

    for (MCompoundUniqueConstraint currentKey : currentKeys) {
      modelDiff.addUniqueConstraint(currentKey.dropUniqueConstraint(name));
    }
    for (MCompoundUniqueConstraint newKey : newKeys) {
      modelDiff.addUniqueConstraint(newKey.addUniqueConstraint(name));
    }
  }
  
  private void compareTableAttrs(ModelDiff modelDiff, MTable newTable) {
    AlterTable alterTable = new AlterTable();
    alterTable.setName(newTable.getName());
    boolean altered = false;

    if (!Objects.equals(tablespaceMeta, newTable.getTablespaceMeta())) {
      if (newTable.getTablespaceMeta() == null) {
        alterTable.setTablespace(DdlHelp.TABLESPACE_DEFAULT);
        alterTable.setIndexTablespace(DdlHelp.TABLESPACE_DEFAULT);
        alterTable.setLobTablespace(DdlHelp.TABLESPACE_DEFAULT);
      } else {
        alterTable.setTablespace(newTable.getTablespaceMeta().getTablespaceName());
        alterTable.setIndexTablespace(newTable.getTablespaceMeta().getIndexTablespace());
        alterTable.setLobTablespace(newTable.getTablespaceMeta().getLobTablespace());
      }
      altered = true;
    }

    if (altered) {
      modelDiff.addAlterTable(alterTable);
    }
  }

  /**
   * Apply AddColumn migration.
   */
  public void apply(AddColumn addColumn) {
    checkTableName(addColumn.getTableName());
    for (Column column : addColumn.getColumn()) {
      addColumn(column);
    }
  }

  /**
   * Apply AddColumn migration.
   */
  public void apply(AlterColumn alterColumn) {
    checkTableName(alterColumn.getTableName());
    String columnName = alterColumn.getColumnName();
    MColumn existingColumn = getColumn(columnName);
    if (existingColumn == null) {
      throw new IllegalStateException("Column [" + columnName + "] does not exist for AlterColumn change?");
    }
    existingColumn.apply(alterColumn);
  }

  /**
   * Apply DropColumn migration.
   */
  public void apply(DropColumn dropColumn) {
    checkTableName(dropColumn.getTableName());
    MColumn removed = columns.remove(dropColumn.getColumnName());
    if (removed == null) {
      throw new IllegalStateException("Column [" + dropColumn.getColumnName() + "] does not exist for DropColumn change on table [" + dropColumn.getTableName() + "]?");
    }
  }

  public void apply(RenameColumn renameColumn) {
    checkTableName(renameColumn.getTableName());
    MColumn column = columns.remove(renameColumn.getOldName());
    if (column == null) {
      throw new IllegalStateException("Column [" + renameColumn.getOldName() + "] does not exist for RenameColumn change on table [" + renameColumn.getTableName() + "]?");
    }
    addColumn(column.rename(renameColumn.getNewName()));
  }

  public String getName() {
    return name;
  }

  public String getSchema() {
    int pos = name.indexOf('.');
    return pos == -1 ? null : name.substring(0, pos);
  }

  /**
   * Return true if this table is a 'Draft' table.
   */
  public boolean isDraft() {
    return draft;
  }

  /**
   * Return true if this table is partitioned.
   */
  public boolean isPartitioned() {
    return partitionMeta != null;
  }

  /**
   * Return the partition meta for this table.
   */
  public PartitionMeta getPartitionMeta() {
    return partitionMeta;
  }

  public String getPkName() {
    return pkName;
  }

  public void setPkName(String pkName) {
    this.pkName = pkName;
  }

  public String getComment() {
    return comment;
  }

  public void setComment(String comment) {
    this.comment = comment;
  }
  
  public void setTablespaceMeta(TablespaceMeta tablespaceMeta) {
    this.tablespaceMeta = tablespaceMeta;
  }
  
  public TablespaceMeta getTablespaceMeta() {
    return tablespaceMeta;
  }

  public boolean isWithHistory() {
    return withHistory;
  }

  public MTable setWithHistory(boolean withHistory) {
    this.withHistory = withHistory;
    return this;
  }

  public List<String> allHistoryColumns(boolean includeDropped) {
    List<String> columnNames = new ArrayList<>(columns.size());
    for (MColumn column : columns.values()) {
      if (column.isIncludeInHistory()) {
        columnNames.add(column.getName());
      }
    }
    if (includeDropped && !droppedColumns.isEmpty()) {
      columnNames.addAll(droppedColumns);
    }
    return columnNames;
  }

  /**
   * Returns true, if there are pending dropped columns.
   */
  public boolean hasDroppedColumns() {
    return !droppedColumns.isEmpty();
  }

  /**
   * Return all the columns (excluding columns marked as dropped).
   */
  public Collection<MColumn> allColumns() {
    return columns.values();
  }

  /**
   * Return the column by name.
   */
  public MColumn getColumn(String name) {
    return columns.get(name);
  }

  private Map<String, MColumn> getColumns() {
    return columns;
  }

  public List<MCompoundUniqueConstraint> getUniqueConstraints() {
    return uniqueConstraints;
  }

  public List<MCompoundForeignKey> getCompoundKeys() {
    return compoundKeys;
  }

  public String getWhenCreatedColumn() {
    return whenCreatedColumn;
  }

  /**
   * Return the list of columns that make the primary key.
   */
  public List<MColumn> primaryKeyColumns() {
    List<MColumn> pk = new ArrayList<>(3);
    for (MColumn column : allColumns()) {
      if (column.isPrimaryKey()) {
        pk.add(column);
      }
    }
    return pk;
  }

  /**
   * Return the primary key column if it is a simple primary key.
   */
  public String singlePrimaryKey() {
    List<MColumn> columns = primaryKeyColumns();
    if (columns.size() == 1) {
      return columns.get(0).getName();
    }
    return null;
  }

  private void checkTableName(String tableName) {
    if (!name.equals(tableName)) {
      throw new IllegalArgumentException("addColumn tableName [" + tableName + "] does not match [" + name + "]");
    }
  }

  /**
   * Add a column via migration data.
   */
  private void addColumn(Column column) {
    columns.put(column.getName(), new MColumn(column));
  }

  /**
   * Add a model column (typically from EbeanServer meta data).
   */
  public void addColumn(MColumn column) {
    columns.put(column.getName(), column);
  }

  /**
   * Add a unique constraint.
   */
  public void addUniqueConstraint(MCompoundUniqueConstraint uniqueConstraint) {
    uniqueConstraints.add(uniqueConstraint);
  }

  /**
   * Add a compound foreign key.
   */
  public void addForeignKey(MCompoundForeignKey compoundKey) {
    compoundKeys.add(compoundKey);
  }

  /**
   * Add a column checking if it already exists and if so return the existing column.
   * Sometimes the case for a primaryKey that is also a foreign key.
   */
  public MColumn addColumn(String dbCol, String columnDefn, boolean notnull) {
    MColumn existingColumn = getColumn(dbCol);
    if (existingColumn != null) {
      if (notnull) {
        existingColumn.setNotnull(true);
      }
      return existingColumn;
    }

    MColumn newCol = new MColumn(dbCol, columnDefn, notnull);
    addColumn(newCol);
    return newCol;
  }

  public MColumn addColumnScalar(String dbColumn, String columnDefn) {
    MColumn existingColumn = getColumn(dbColumn);
    if (existingColumn != null) {
      return existingColumn;
    }
    MColumn newCol = new MColumn(dbColumn, columnDefn);
    addColumn(newCol);
    return newCol;
  }

  /**
   * Add a 'new column' to the AddColumn migration object.
   */
  private void diffNewColumn(MColumn newColumn, MTable newTable) {
    if (addColumn == null) {
      addColumn = new AddColumn();
      addColumn.setTableName(name);
      if (newTable.isWithHistory()) {
        // These addColumns need to occur on the history
        // table as well as the base table
        addColumn.setWithHistory(Boolean.TRUE);
      }
    }

    addColumn.getColumn().add(newColumn.createColumn());
  }

  /**
   * Add a 'drop column' to the diff.
   */
  private void diffDropColumn(ModelDiff modelDiff, MColumn existingColumn) {
    DropColumn dropColumn = new DropColumn();
    dropColumn.setTableName(name);
    dropColumn.setColumnName(existingColumn.getName());
    if (withHistory) {
      // These dropColumns should occur on the history
      // table as well as the base table
      dropColumn.setWithHistory(Boolean.TRUE);
    }
    modelDiff.addDropColumn(dropColumn);
  }

  /**
   * Register a pending un-applied drop column.
   * <p>
   * This means this column still needs to be included in history views/triggers etc even
   * though it is not part of the current model.
   */
  public void registerPendingDropColumn(String columnName) {
    droppedColumns.add(columnName);
  }

  /**
   * Check if there are duplicate foreign keys.
   * <p>
   * This can occur when an ManyToMany relates back to itself.
   * </p>
   */
  public void checkDuplicateForeignKeys() {
    if (hasDuplicateForeignKeys()) {
      int counter = 1;
      for (MCompoundForeignKey fk : compoundKeys) {
        fk.addNameSuffix(counter++);
      }
    }
  }

  /**
   * Return true if the foreign key names are not unique.
   */
  private boolean hasDuplicateForeignKeys() {
    Set<String> fkNames = new HashSet<>();
    for (MCompoundForeignKey fk : compoundKeys) {
      if (!fkNames.add(fk.getName())) {
        return true;
      }
    }
    return false;
  }

  /**
   * Adjust the references (FK) if it should relate to a draft table.
   */
  public void adjustReferences(ModelContainer modelContainer) {
    Collection<MColumn> cols = allColumns();
    for (MColumn col : cols) {
      String references = col.getReferences();
      if (references != null) {
        String baseTable = extractBaseTable(references);
        MTable refBaseTable = modelContainer.getTable(baseTable);
        if (refBaseTable.draftTable != null) {
          // change references to another associated 'draft' table
          String newReferences = deriveReferences(references, refBaseTable.draftTable.getName());
          col.setReferences(newReferences);
        }
      }
    }
  }

  /**
   * Return the base table name from references (table.column).
   */
  private String extractBaseTable(String references) {
    int lastDot = references.lastIndexOf('.');
    return references.substring(0, lastDot);
  }

  /**
   * Return the new references using the given draftTableName.
   * (The referenced column is the same as before).
   */
  private String deriveReferences(String references, String draftTableName) {
    int lastDot = references.lastIndexOf('.');
    return draftTableName + "." + references.substring(lastDot + 1);
  }

  /**
   * This method adds information which columns are nullable or not to the compound indices.
   */
  public void updateCompoundIndices() {
    for (MCompoundUniqueConstraint uniq : uniqueConstraints) {
      List<String> nullableColumns = new ArrayList<>();
      for (String columnName : uniq.getColumns()) {
        MColumn col = getColumn(columnName);
        if (col != null && !col.isNotnull()) {
          nullableColumns.add(columnName);
        }
      }
      uniq.setNullableColumns(nullableColumns.toArray(new String[0]));
    }
  }

  public void removeForeignKey(String name) {
    compoundKeys.removeIf(fk -> fk.getName().equals(name));
  }

  /**
   * Clear the indexes on the foreign keys as they are covered by unique constraints.
   */
  public void clearForeignKeyIndexes() {
    for (MCompoundForeignKey compoundKey : compoundKeys) {
      compoundKey.setIndexName(null);
    }
  }

  /**
   * Clear foreign key as this element collection table logically references
   * back to multiple tables.
   */
  public MIndex setReusedElementCollection() {
    MIndex index = null;
    for (MColumn column : columns.values()) {
      final String references = column.getReferences();
      if (references != null) {
        index = new MIndex(column.getForeignKeyIndex(), name, column.getName());
        column.clearForeignKey();
      }
    }
    return index;
  }
}