module.exports = installMethod;

function installMethod(model, methodName, filterCb) {
    model.remoteMethod(methodName, {
        description: 'List items using a filter',
        accessType: 'READ',
        accepts: [
            {
                arg: 'filter',
                type: 'object',
                required: true,
                description: 'Filter defining where',
                http: function(ctx) {
                    return ctx.req.query;
                }
            }
        ],
        returns: {
            arg: 'data', 
            type: [model.modelName],
            root: true
        },
        http: {
            verb: 'get',
            path: `/${methodName}`
        }
    });
    
    model.filter = function(params, cb) {
        let filter = removeEmpty(filterCb(params));
        model.find(filter, function(err, instances) {
            if(!err) {
                cb(null, instances);
            }
        })
    };
}

function removeEmpty(o) {
    if(Array.isArray(o)) {
        let array = [];
        for(let item of o) {
            let i = removeEmpty(item);
            if(!isEmpty(item))
                array.push(item);
        };
        if(array.length > 0)
            return array;
    }
    else if (typeof o === 'object') {
        let object = {};
        for(let key in o) {
            let i = removeEmpty(o[key]);
            if(!isEmpty(i))
                object[key] = i;                
        }
        if(Object.keys(object).length > 0)
            return object;
    }
    else if (!isEmpty(o))
        return o;

    return undefined;
}

function isEmpty(value) {
    return value === undefined || value === "";
}