[aerogear-dev] Client Paging Strawman

[Kris Borchers]

OK folks, below is the contents of this gist https://gist.github.com/4531575. I may have missed a number of things, gotten too specific in places or not specific enough in others. This should hopefully get a good discussion going on how we want to handle paging across all of the client libraries. Let's keep all comments on the list and not the gist as much as possible to avoid breaking up the conversation.

Below is a pipe configuration showing the different paging options. Defaults are just suggestions and are up for discussion as much as the rest of it

    var pagedPipe = AeroGear.Pipeline({
        name: "pager",
        settings: {
            paged: {String}, // Default is "headers", can also be "content", or undefined for no paging
            pageConfig: { // Only required if paged is not undefined
                // which page, header default is "AG-Paging-Offset", content default is "paging.offset"
                offset: {String},
                offsetVal: {Number}, // Default 0 for first page
                
                // items per page, header default is "AG-Paging-Limit", content default is "paging.limit"
                limit: {String},
                limitVal: {Number}, // Default 5 items per page
                
                // total number of items, header default is "AG-Paging-Total", content default is "paging.total"
                total: {String},
                
                // link to next page, default in both cases is undefined
                next: {String},
                
                // link to previous page, default in both cases is undefined
                prev: {String}
            }
        }   
    }).pipes.pager;

Getter/Setter methods should be provided for getting and updating the offsetVal and limitVal defaults

    var defaultOffset = pagedPipe.getOffsetVal();
    pagedPipe.setOffsetVal( defaultOffset + 1 ); // by default the second page would be returned
    
    var defaultLimit = pagedPipe.getLimitVal();
    pagedPipe.setLimitVal( defaultLimit + 5 ); // by default, 10 items would be returned per page

## read()
By default, a read() against a paged pipe will return the first page based on the default offsetVal and limitVal. We could possible add an option that doesn't effect unpaged pipes but on a paged pipe, it can be used to turn off paging for that read() and get all data

    // Get first page
    pagedPipe.read({success callback handles data});
    
    // Get all data from paged pipe
    pagedPipe.read({
        page: false,
        success: handle the data
    });
    
To avoid code duplication, **next**, **prev**, **first** and **last** pages can be retrieved by passing an option to the read method of a paged pipe since other than some paging housekeeping, the code would be the same. We can also use that same option as above that was used to get all data from a paged pipe. One question, when requesting prev from first page or next from last page, should it throw an error that needs to be handled or just return and empty data set? I see advantages and disadvantages of both.

    // Get next page
    pagedPipe.read({
        page: "next",
        success: handle the data
    });
    
    // Get previous page
    pagedPipe.read({
        page: "prev",
        success: handle the data
    });
    
    // Get first page
    pagedPipe.read({
        page: "first",
        success: handle the data
    });
    
    // Get last page
    pagedPipe.read({
        page: "last",
        success: handle the data
    });
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