import Role from './Role';
class Frame {
    roles: Role[];
    constructor(roles: Role[]) {
        const predCount = roles.filter(role=>role.isPredicate).length;
        if(predCount !== 1) {
            throw new Error("A frame must have exactly 1 predicate. got "+predCount);
        }
        this.roles = roles.sort(function(a,b){
            return a.beginTokenIndex - b.beginTokenIndex;
        });
        Object.freeze(this);
    }
    static getPredicateIndex(frame:Frame):number {
        for(let i=0; i<frame.roles.length; i++) {
            if(frame.roles[i].isPredicate) return i;
        }
        throw new Error("Frame.getPredicateIndex: predicate not found");
    }
    /**
     * get the token index span covered by this frame
     * @param frame {Frame}
     * @returns {[number, number]} [begin, end)
     */
    static getTokenSpan(frame: Frame):[number,number] {
        const beginRole = frame.roles[0];
        const endRole = frame.roles[frame.roles.length - 1];
        const beginTokenIndex = beginRole.beginTokenIndex;
        const endTokenIndex = endRole.beginTokenIndex + endRole.length;
        return [beginTokenIndex, endTokenIndex];
    }
}
export default Frame;