sourceafPegger::NamedRules.fan

using afBeanUtils

** A helper class that lets you reference Rules before they're defined.
class NamedRules {
    private Str:Rule rules := Str:Rule[:] { caseInsensitive = true } 
    
    ** Returns a proxy to the named rule.
    @Operator
    Rule get(Str name) {
        ProxyRule(this, name)
    }
    
    ** Sets the real implementation of the named rule.
    @Operator
    Rule set(Str name, Rule rule) {
        rules[name] = rule
        return rule
    }
    
    internal Rule getForReal(Str name) {
        rules[name] ?: throw ArgNotFoundErr("Could not find rule '$name'", rules.keys)
    }
    
    override Str toStr() {
        rules.reduce("") |Str str, rule->Str| { str += rule.definition + "\n" }
    }
}

internal class ProxyRule : Rule {
    private NamedRules  rules
    private Rule?       ruleForReal

    new make(NamedRules rules, Str name) {
        this.name       = name
        this.rules      = rules
    }
    
    override |Str|? action {
        get { rule.action }
        set { rule.action = it }
    }
    
    override Bool doProcess(PegCtx ctx) {
        rule.doProcess(ctx)
    }
    
    override Str expression() {
        rule.expression
    }
    
    override Str toStr() {
        rule.toStr
    }
    
    internal Rule rule() {
        if (ruleForReal == null) {
            ruleForReal = rules.getForReal(name)
            if (ruleForReal.name == null)
                ruleForReal.name = name
            else
                name = ruleForReal.name
            action = ruleForReal.action
        }
        return ruleForReal
    }
}