com.github.harbby.dsxparser.tree.DereferenceExpression Maven / Gradle / Ivy

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package com.github.harbby.dsxparser.tree;

import com.github.harbby.dsxparser.Optimizer;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Objects;

import static com.github.harbby.gadtry.base.MoreObjects.checkArgument;

public class DereferenceExpression
        extends Expression {
    private final Expression base;
    private final Identifier field;

    public DereferenceExpression(Expression base, Identifier field) {
        this(null, base, field);
    }

    public DereferenceExpression(NodeLocation location, Expression base, Identifier field) {
        super(location);
        checkArgument(base != null, "base is null");
        checkArgument(field != null, "fieldName is null");
        this.base = base;
        this.field = field;
    }

    @Override
    public List getChildren() {
        return List.of(base);
    }

    public Expression getBase() {
        return base;
    }

    public Identifier getField() {
        return field;
    }

    /**
     * If this DereferenceExpression looks like a QualifiedName, return QualifiedName.
     * Otherwise return null
     */
    public static QualifiedName getQualifiedName(DereferenceExpression expression) {
        List parts = tryParseParts(expression.base, expression.field.getValue().toLowerCase(Locale.ENGLISH));
        return parts == null ? null : QualifiedName.of(parts);
    }

    public static Expression from(QualifiedName name) {
        Expression result = null;

        for (String part : name.getParts()) {
            if (result == null) {
                result = new Identifier(part);
            } else {
                result = new DereferenceExpression(result, new Identifier(part));
            }
        }

        return result;
    }

    private static List tryParseParts(Expression base, String fieldName) {
        if (base instanceof Identifier) {
            return List.of(((Identifier) base).getValue(), fieldName);
        } else if (base instanceof DereferenceExpression) {
            QualifiedName baseQualifiedName = getQualifiedName((DereferenceExpression) base);
            if (baseQualifiedName != null) {
                List newList = new ArrayList<>(baseQualifiedName.getParts());
                newList.add(fieldName);
                return newList;
            }
        }
        return null;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        DereferenceExpression that = (DereferenceExpression) o;
        return Objects.equals(base, that.base) &&
                Objects.equals(field, that.field);
    }

    @Override
    public int hashCode() {
        return Objects.hash(base, field);
    }

    @Override
    public String doGenSql() {
        return String.format("%s.%s", base.doGenSql(), field.doGenSql());
    }

    @Override
    public Expression visit(Optimizer optimizer) {
        return this;
    }
}