package tss

import "fmt"
import "errors"

// Flatten evaluates all variables recursively, thereby eliminating all
// instances of ValueVariable.
func (this *Sheet) Flatten () error {
	if this.flat { return nil }
	this.flat = true
	
	for name, variable := range this.Variables {
		variable, err := this.eval(variable)
		if err != nil { return err }
		this.Variables[name] = variable
	}
	
	for index, rule := range this.Rules {
		for name, attr := range rule.Attrs {
			for index, list := range attr {
				list, err := this.eval(list)
				if err != nil { return err }
				attr[index] = list
			}
			rule.Attrs[name] = attr
		}
		this.Rules[index] = rule
	}
	
	return nil
}

func (this *Sheet) eval (source ValueList) (ValueList, error) {
	destination := make(ValueList, 0, len(source))
	for _, value := range source {
		if name, ok := value.(ValueVariable); ok {
			variable, ok := this.Variables[string(name)]
			if !ok {
				return nil, errors.New(fmt.Sprintf(
					"variable $%s does not exist",
					value))
			}
			variable, err := this.eval(variable)
			if err != nil { return nil, err }
			destination = append(destination, variable...)
			continue
		} else {
			destination = append(destination, value)
		}
	}
	
	return destination, nil
}