Current File : //proc/985914/root/data/old/home/stash/stash/atlassian-stash/static/util/page-providers.js
define('util/page-providers', [
'jquery',
'underscore',
'util/ajax',
'exports'
], function(
$,
_,
ajax,
exports
) {
'use strict';
function filterPage(page, filter) {
var values = _.filter(page.values, filter);
return $.extend(page, {
values: values,
size: values.length
});
}
function index(start, values) {
return _.map(values, function (value, index) {
return { value: value, index: start + index };
});
}
function deindex(indexedVals) {
return _.pluck(indexedVals, 'value');
}
/**
* A provider of pages filtered with a predicate
* @param provider the delegate page provider
* @param filter the predicate function to filter the pages provided by the underlying provider
* @constructor
*/
function FilteredPageProvider(provider, filter) {
this.provider = provider;
this.filter = filter;
}
/**
* Fetches a page of results
* @param start the start index
* @param limit the limit on the number of elements in the page
* @returns {Promise}
*/
FilteredPageProvider.prototype.fetch = function(start, limit) {
var self = this;
//fetch twice as many as we need (unfiltered) to minimise round-trips to make up a full filtered page
var multiplier = 2;
return this.provider.fetch(start, limit * multiplier).then(function(page) {
var indexed = index(start, page.values);
var filtered = _.filter(indexed,function (valIndex) {
return self.filter(valIndex.value);
});
var pageValues = filtered.slice(0, limit);
var nextPageFirstValue = filtered.slice(limit, limit + 1);
var result = {
values: deindex(pageValues),
size: pageValues.length,
start: start,
limit: limit,
isLastPage: nextPageFirstValue.length === 0 && page.isLastPage
};
if (!result.isLastPage) {
result.nextPageStart = nextPageFirstValue.length ? nextPageFirstValue[0].index : page.nextPageStart;
}
return result;
});
};
/**
* A provider of pages where the entire set of results are already known up-front
* @param values the entire set of results to be returned as pages
* @constructor
*/
function PreloadedPageProvider(values) {
this.values = values;
}
/**
* Fetches a page of results
* @param start the start index
* @param limit the limit on the number of elements in the page
* @returns {Promise}
*/
PreloadedPageProvider.prototype.fetch = function(start, limit) {
var self = this;
var values = self.values;
//the page request exceeds the boundaries of the values (or there are no values)
if (start >= values.length) {
return $.Deferred().resolve({
start: start,
values: [],
size: 0,
limit: limit,
isLastPage: true
});
}
var end = start + limit;
if (end <= values.length) {
//the page request falls within the page of results
var slice = values.slice(start, end);
var isLastPage = end === values.length;
return $.Deferred().resolve({
start: start,
values: slice,
size: limit,
limit: limit,
isLastPage: isLastPage,
nextPageStart: isLastPage ? undefined : end
});
} else {
//the page exceeds the page of results but starts within it
var partial = values.slice(start, end);
//there are no more results beyond the first page
return $.Deferred().resolve({
start: start,
values: partial,
size: partial.length,
limit: limit,
isLastPage: true
});
}
};
/**
* A provider of pages retrieved via an AJAX request
* @param restBuilder the builder to construct the URL used for the AJAX requests
* @constructor
*/
function AjaxPageProvider(restBuilder) {
this.restBuilder = restBuilder;
}
/**
* Fetches a page of results
* @param start the start index
* @param limit the limit on the number of elements in the page
* @returns {Promise}
*/
AjaxPageProvider.prototype.fetch = function(start, limit) {
var url = this.restBuilder.addParams({ start: start, limit: limit }).buildRelative();
return ajax.rest({ url: url, type: 'GET' });
};
/**
* A provider of pages where the start of each page request to an underlying page provider is offset by a constant number
* @param provider the underlying page provider
* @param offset the fixed offset >= 0
* @constructor
*/
function OffsetPageProvider(provider, offset) {
this.provider = provider;
this.offset = offset;
}
/**
* Fetches a page of results
* @param start the start index
* @param limit the limit on the number of elements in the page
* @returns {Promise}
*/
OffsetPageProvider.prototype.fetch = function(start, limit) {
var self = this;
var offset = self.offset;
return self.provider.fetch(start + offset, limit).then(function(page) {
page.start = start;
if (!page.isLastPage) {
page.nextPageStart = page.nextPageStart - offset;
}
return page;
});
};
/**
* A provider of pages where the entire set of results is composed from the pages of other page providers.
* Fetch requests are delegated to each underlying page providers in turn moving to the next once the current provider
* has exhausted its supply of pages.
*
* Page requests will only ever return page results from the current page provider. In some cases this will result
* in empty pages returned or smaller pages than requested returned but with the result clearly indicated (by way
* of isLastPage and nextPageStart) that subsequent calls are likely to return more result. This is purely to
* simplify the implementation but *is* compatible with our paged table / scrollable protocol.
*
* Note: fetch requests to this page provider must be contiguous or an exception will be thrown.
*
* @param providers the {Array} of composite page providers
* @constructor
*/
function CompositePageProvider(providers) {
this.providers = providers;
this.offset = 0;
this.nextPageStart = 0;
}
/**
* Fetches a page of results.
*
* Note: fetch requests to this page provider must be contiguous or an exception will be thrown.
*
* @param start the start index
* @param limit the limit on the number of elements in the page
* @returns {Promise}
*/
CompositePageProvider.prototype.fetch = function(start, limit) {
var self = this;
var providers = self.providers;
if (self.nextPageStart !== start) {
throw new Error('Page requests must be contiguous (expected start: ' + self.nextPageStart + ', actual start: ' + start + ')');
}
if (!providers.length) {
return $.Deferred().resolve(self._mark({
start: start,
limit: limit,
size: 0,
values: [],
isLastPage: true
}));
}
var offset = self.offset;
var provider = providers[0];
var hasNextProvider = providers.length > 1;
return provider.fetch(start - offset, limit).then(function(page) {
page = $.extend(page, { start: start, limit: limit });
if (page.isLastPage) {
if (hasNextProvider) {
page = $.extend(page, { isLastPage: false, nextPageStart: offset + start + page.size });
providers.shift();
self.offset = start + page.size;
}
} else {
page.nextPageStart = page.nextPageStart + offset;
}
return self._mark(page);
});
};
CompositePageProvider.prototype._mark = function(page) {
this.nextPageStart = page.isLastPage ? page.start + page.size : page.nextPageStart;
return page;
};
exports.AjaxPageProvider = AjaxPageProvider;
exports.CompositePageProvider = CompositePageProvider;
exports.FilteredPageProvider = FilteredPageProvider;
exports.OffsetPageProvider = OffsetPageProvider;
exports.PreloadedPageProvider = PreloadedPageProvider;
exports.filterPage = filterPage;
});
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