import ngModule from '../../module';
import ModelProxy from '../model-proxy/model-proxy';

export default class CrudModel extends ModelProxy {
    constructor($http, $q) {
        super();
        this.$http = $http;
        this.$q = $q;
        this.primaryKey = 'id';
        this.autoLoad = true;
    }

    get isLoading() {
        return this.canceler != null;
    }

    $onInit() {
        if (this.autoLoad)
            this.refresh();
    }

    refresh(usFilter) {
        if (!this.url) return;

        let myFilter = {
            fields: this.fields,
            where: mergeWhere(this.link, this.where),
            include: this.include,
            order: this.order,
            limit: this.limit
        };

        let filter = this.filter;
        filter = mergeFilters(myFilter, filter);
        filter = mergeFilters(usFilter, filter);
        return this.sendRequest(filter);
    }

    cancelRequest() {
        if (this.canceler) {
            this.canceler.resolve();
            this.canceler = null;
        }
    }

    sendRequest(filter, append) {
        this.cancelRequest();
        this.canceler = this.$q.defer();

        let options = {
            timeout: this.canceler.promise,
            params: {filter: filter}
        };

        if (this.userParams instanceof Object)
            Object.assign(options.params, this.userParams);

        return this.$http.get(this.url, options).then(
            json => this.onRemoteDone(json, filter, append),
            json => this.onRemoteError(json)
        );
    }

    onRemoteDone(json, filter, append) {
        let data = json.data;

        if (append)
            this.orgData = this.orgData.concat(data);
        else
            this.orgData = data;

        this.currentFilter = filter;
        this.moreRows = filter.limit && data.length == filter.limit;
        this.onRequestEnd();
        this.dataChanged();
    }

    onRemoteError(err) {
        this.onRequestEnd();
        throw err;
    }

    onRequestEnd() {
        this.canceler = null;
    }

    loadMore() {
        if (this.moreRows) {
            let filter = Object.assign({}, this.currentFilter);
            filter.skip = (filter.skip || 0) + filter.limit;
            this.sendRequest(filter, true);
        }
    }

    getChanges() {
        let create = [];
        let update = [];
        let remove = [];

        for (let row of this.removed)
            remove.push(row.$data[this.primaryKey]);

        for (let row of this._data) {
            if (row.$isNew)
                create.push(row.$data);
            else if (row.$oldData)
                update.push(row.$data);
        }

        let isChanged =
            create.length > 0 ||
            update.length > 0 ||
            remove.length > 0;

        if (!isChanged)
            return null;

        let changes = {
            create: create,
            update: update,
            delete: remove
        };

        return changes;
    }

    save() {
        let changes = this.getChanges();

        if (!changes)
            return this.$q.resolve();

        let url = this.saveUrl ? this.saveUrl : `${this.url}/crud`;
        return this.$http.post(url, changes)
            .then(() => this.resetChanges);
    }
}
CrudModel.$inject = ['$http', '$q'];

ngModule.component('vnCrudModel', {
    controller: CrudModel,
    bindings: {
        orgData: '<?',
        data: '=?',
        onDataChange: '&?',
        fields: '<?',
        link: '<?',
        url: '@?',
        saveUrl: '@?',
        where: '<?',
        include: '<?',
        order: '@?',
        limit: '<?',
        filter: '<?',
        userParams: '<?',
        primaryKey: '@?',
        autoLoad: '<?'
    }
});

/**
 * Passes a loopback fields filter to an object.
 *
 * @param {Object} fields The fields object or array
 * @return {Object} The fields as object
 */
function fieldsToObject(fields) {
    let fieldsObj = {};

    if (Array.isArray(fields))
        for (let field of fields)
            fieldsObj[field] = true;
    else if (typeof fields == 'object')
        for (let field in fields)
            if (fields[field])
                fieldsObj[field] = true;

    return fieldsObj;
}

/**
 * Merges two loopback fields filters.
 *
 * @param {Object|Array} src The source fields
 * @param {Object|Array} dst The destination fields
 * @return {Array} The merged fields as an array
 */
function mergeFields(src, dst) {
    let fields = {};
    Object.assign(fields,
        fieldsToObject(src),
        fieldsToObject(dst)
    );
    return Object.keys(fields);
}

/**
 * Merges two loopback where filters.
 *
 * @param {Object|Array} src The source where
 * @param {Object|Array} dst The destination where
 * @return {Array} The merged wheres
 */
function mergeWhere(src, dst) {
    let and = [];
    if (src) and.push(src);
    if (dst) and.push(dst);
    return and.length > 1 ? {and} : and[0];
}

/**
 * Merges two loopback filters returning the merged filter.
 *
 * @param {Object} src The source filter
 * @param {Object} dst The destination filter
 * @return {Object} The result filter
 */
function mergeFilters(src, dst) {
    let res = Object.assign({}, dst);

    if (!src)
        return res;

    if (src.fields)
        res.fields = mergeFields(src.fields, res.fields);
    if (src.where)
        res.where = mergeWhere(res.where, src.where);
    if (src.include)
        res.include = src.include;
    if (src.order)
        res.order = src.order;
    if (src.limit)
        res.limit = src.limit;

    return res;
}