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Provenance static analysis

There is a newer version: 1.7.0

package fr.insee.vtl.prov;

import org.antlr.v4.runtime.ParserRuleContext;
import org.antlr.v4.runtime.Token;
import org.antlr.v4.runtime.misc.Interval;

import java.util.Optional;

public class Variable {

    /**
     * Returns the text of a context with empty space (aka. all channels).
     */
    private static String getText(ParserRuleContext ctx) {
        Token start = ctx.getStart();
        Token stop = ctx.getStop();
        return start.getInputStream().getText(new Interval(start.getStartIndex(), stop.getStopIndex()));
    }

    // Identifier of the variable.
    private final ParserRuleContext nameCtx;

    // Expression of the variable, if any.
    private final ParserRuleContext exprCtx;

    // Version of the variable.
    private Integer version = 0;

    // Previous version.
    private Variable previous;

    Variable(ParserRuleContext name, ParserRuleContext expression) {
        this.nameCtx = name;
        this.exprCtx = expression;
    }

    public Variable(ParserRuleContext name) {
        this.nameCtx = name;
        this.exprCtx = null;
    }

    public String getName() {
        return getText(this.nameCtx);
    }

    public String getVersion() {
        return getName() + "_" + this.version;
    }

    public Optional getExpression() {
        return Optional.ofNullable(exprCtx)
                .map(Variable::getText);
    }

    public Optional getPrevious() {
        return Optional.ofNullable(previous);
    }

    public Variable newVersion() {
        Variable copy = new Variable(this.nameCtx, this.exprCtx);
        copy.version = this.version + 1;
        copy.previous = this;
        return copy;
    }

    @Override
    public String toString() {
        return getVersion();
    }

    public final boolean isSame(Variable other) {
        return nameCtx.equals(other.nameCtx);
    }

    @Override
    public final boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Variable)) return false;

        Variable variable = (Variable) o;
        return getVersion().equals(variable.getVersion());
    }

    @Override
    public int hashCode() {
        return nameCtx.hashCode();
    }
}