Function resolveBoundWithSubst

engine/temporal.go:519–567

resolveBoundWithSubst resolves a temporal bound, substituting variables and handling 'now'.

(bound ast.TemporalBound, subst unionfind.UnionFind, evalTime time.Time)

// resolveBoundWithSubst resolves a temporal bound, substituting variables and handling 'now'.
func resolveBoundWithSubst(bound ast.TemporalBound, subst unionfind.UnionFind, evalTime time.Time) (ast.TemporalBound, error) {
	switch bound.Type {
	case ast.TimestampBound:
		return bound, nil

	case ast.VariableBound:
		// Look up the variable in the substitution
		term := subst.Get(bound.Variable)
		if term == nil {
			return ast.TemporalBound{}, fmt.Errorf("variable %v not bound in substitution", bound.Variable.Symbol)
		}

		// The term should be a constant (either a number representing nanoseconds or a pair for an interval)
		switch t := term.(type) {
		case ast.Constant:
			// If it's a number, interpret as nanoseconds since epoch
			if t.Type == ast.NumberType {
				nano, err := t.NumberValue()
				if err != nil {
					return ast.TemporalBound{}, fmt.Errorf("failed to get number value: %w", err)
				}
				return ast.TemporalBound{Type: ast.TimestampBound, Timestamp: nano}, nil
			}
			if t.Type == ast.TimeType {
				nano, err := t.TimeValue()
				if err != nil {
					return ast.TemporalBound{}, fmt.Errorf("failed to get time value: %w", err)
				}
				return ast.TemporalBound{Type: ast.TimestampBound, Timestamp: nano}, nil
			}
			return ast.TemporalBound{}, fmt.Errorf("expected number or time constant for temporal bound, got %v", t.Type)
		case ast.Variable:
			// Variable is still unbound
			return ast.TemporalBound{}, fmt.Errorf("variable %v not fully resolved", t.Symbol)
		default:
			return ast.TemporalBound{}, fmt.Errorf("unexpected term type for temporal bound: %T", term)
		}

	case ast.NegativeInfinityBound, ast.PositiveInfinityBound:
		return bound, nil

	case ast.NowBound:
		// 'now' resolves to the current evaluation time
		return ast.NewTimestampBound(evalTime), nil

	default:
		return ast.TemporalBound{}, fmt.Errorf("unknown bound type: %v", bound.Type)
	}
}

// DerivedTemporalFact represents a temporal fact derived from a rule.
type DerivedTemporalFact struct {