/*
 * Copyright 2004-2008 H2 Group. Multiple-Licensed under the H2 License, 
 * Version 1.0, and under the Eclipse Public License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.expression;

import java.sql.SQLException;
import java.util.HashMap;

import org.h2.command.Parser;
import org.h2.command.dml.Select;
import org.h2.constant.ErrorCode;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.index.IndexCondition;
import org.h2.message.Message;
import org.h2.schema.Constant;
import org.h2.schema.Schema;
import org.h2.table.Column;
import org.h2.table.ColumnResolver;
import org.h2.table.Table;
import org.h2.table.TableFilter;
import org.h2.value.Value;
import org.h2.value.ValueBoolean;

/**
 * A expression that represents a column of a table or view.
 */
public class ExpressionColumn extends Expression {
    private Database database;
    private String schemaName;
    private String tableAlias;
    private String columnName;
    private ColumnResolver resolver;
    private int queryLevel;
    private Column column;
    private boolean evaluatable;

    public ExpressionColumn(Database database, Column column) {
        this.database = database;
        this.column = column;
    }

    public ExpressionColumn(Database database, String schemaName, String tableAlias, String columnName) {
        this.database = database;
        this.schemaName = schemaName;
        this.tableAlias = tableAlias;
        this.columnName = columnName;
    }

    public String getSQL() {
        String sql;
        if (column != null) {
            sql = column.getSQL();
        } else {
            sql = columnName;
        }
        if (tableAlias != null) {
            sql = Parser.quoteIdentifier(tableAlias) + "." + sql;
        }
        if (schemaName != null) {
            sql = Parser.quoteIdentifier(schemaName) + "." + sql;
        }
        return sql;
    }

    public TableFilter getTableFilter() {
        return resolver == null ? null : resolver.getTableFilter();
    }

    public void mapColumns(ColumnResolver resolver, int level) throws SQLException {
        if (tableAlias != null && !tableAlias.equals(resolver.getTableAlias())) {
            return;
        }
        if (schemaName != null && !schemaName.equals(resolver.getSchemaName())) {
            return;
        }
        Column[] columns = resolver.getColumns();
        for (int i = 0; i < columns.length; i++) {
            Column col = columns[i];
            if (columnName.equals(col.getName())) {
                mapColumn(resolver, col, level);
                return;
            }
        }
        columns = resolver.getSystemColumns();
        for (int i = 0; columns != null && i < columns.length; i++) {
            Column col = columns[i];
            if (columnName.equals(col.getName())) {
                mapColumn(resolver, col, level);
                return;
            }
        }
    }

    private void mapColumn(ColumnResolver resolver, Column col, int level) throws SQLException {
        if (this.resolver == null) {
            queryLevel = level;
            column = col;
            this.resolver = resolver;
        } else if (queryLevel == level && this.resolver != resolver) {
            throw Message.getSQLException(ErrorCode.AMBIGUOUS_COLUMN_NAME_1, columnName);
        }
    }

    public Expression optimize(Session session) throws SQLException {
        if (resolver == null) {
            Schema schema = session.getDatabase().findSchema(
                    tableAlias == null ? session.getCurrentSchemaName() : tableAlias);
            if (schema != null) {
                Constant constant = schema.findConstant(columnName);
                if (constant != null) {
                    return constant.getValue();
                }
            }
            String name = columnName;
            if (tableAlias != null) {
                name = tableAlias + "." + name;
                if (schemaName != null) {
                    name = schemaName + "." + name;
                }
            }
            throw Message.getSQLException(ErrorCode.COLUMN_NOT_FOUND_1, name);
        }
        return this;
    }

    public void updateAggregate(Session session) throws SQLException {
        Value now = resolver.getValue(column);
        Select select = resolver.getSelect();
        if (select == null) {
            throw Message.getSQLException(ErrorCode.MUST_GROUP_BY_COLUMN_1, getSQL());
        }
        HashMap values = select.getCurrentGroup();
        if (values == null) {
            // this is a different level (the enclosing query)
            return;
        }
        Value v = (Value) values.get(this);
        if (v == null) {
            values.put(this, now);
        } else {
            if (!database.areEqual(now, v)) {
                throw Message.getSQLException(ErrorCode.MUST_GROUP_BY_COLUMN_1, getSQL());
            }
        }
    }

    public Value getValue(Session session) throws SQLException {
        // TODO refactor: simplify check if really part of an aggregated value /
        // detection of
        // usage of non-grouped by columns without aggregate function
        Select select = resolver.getSelect();
        if (select != null) {
            HashMap values = select.getCurrentGroup();
            if (values != null) {
                Value v = (Value) values.get(this);
                if (v != null) {
                    return v;
                }
            }
        }
        Value value = resolver.getValue(column);
        if (value == null) {
            throw Message.getSQLException(ErrorCode.MUST_GROUP_BY_COLUMN_1, getSQL());
        }
        return value;
    }

    public int getType() {
        return column.getType();
    }

    public void setEvaluatable(TableFilter tableFilter, boolean b) {
        if (resolver != null && tableFilter == resolver.getTableFilter()) {
            evaluatable = b;
        }
    }

    public Column getColumn() {
        return column;
    }

    public int getScale() {
        return column.getScale();
    }

    public long getPrecision() {
        return column.getPrecision();
    }

    public int getDisplaySize() {
        return column.getDisplaySize();
    }

    public String getOriginalColumnName() {
        return columnName;
    }

    public String getOriginalAliasName() {
        return tableAlias;
    }

    public String getColumnName() {
        return columnName != null ? columnName : column.getName();
    }

    public String getSchemaName() {
        Table table = column.getTable();
        return table == null ? null : table.getSchema().getName();
    }

    public String getTableName() {
        Table table = column.getTable();
        return table == null ? null : table.getName();
    }

    public String getAlias() {
        return column.getName();
    }

    public boolean isAutoIncrement() {
        return column.getSequence() != null;
    }

    public int getNullable() {
        return column.getNullable() ? Column.NULLABLE : Column.NOT_NULLABLE;
    }

    public boolean isEverything(ExpressionVisitor visitor) {
        switch (visitor.getType()) {
        case ExpressionVisitor.OPTIMIZABLE_MIN_MAX_COUNT_ALL:
            return false;
        case ExpressionVisitor.READONLY:
        case ExpressionVisitor.DETERMINISTIC:
            return true;
        case ExpressionVisitor.INDEPENDENT:
            return this.queryLevel < visitor.getQueryLevel();
        case ExpressionVisitor.EVALUATABLE:
            // if the current value is known (evaluatable set)
            // or if this columns belongs to a 'higher level' query and is
            // therefore just a parameter
            return evaluatable || visitor.getQueryLevel() < this.queryLevel;
        case ExpressionVisitor.SET_MAX_DATA_MODIFICATION_ID:
            visitor.addDataModificationId(column.getTable().getMaxDataModificationId());
            return true;
        case ExpressionVisitor.NOT_FROM_RESOLVER:
            return resolver != visitor.getResolver();
        case ExpressionVisitor.GET_DEPENDENCIES:
            visitor.addDependency(column.getTable());
            return true;
        default:
            throw Message.getInternalError("type=" + visitor.getType());
        }
    }

    public int getCost() {
        return 2;
    }

    public void createIndexConditions(Session session, TableFilter filter) {
        TableFilter tf = getTableFilter();
        if (filter == tf && column.getType() == Value.BOOLEAN) {
            IndexCondition cond = new IndexCondition(Comparison.EQUAL, this, ValueExpression
                    .get(ValueBoolean.get(true)));
            filter.addIndexCondition(cond);
        }
    }

    public Expression getNotIfPossible(Session session) {
        return new Comparison(session, Comparison.EQUAL, this, ValueExpression.get(ValueBoolean.get(false)));
    }

}
