= S3XRC Mini-Tutorial =

  - [wiki:S3XRC_Recipes S3XRC Recipes and Tutorials]
== Report Function for your Resource ==

=== The idea ===

You have a module {{{xxx}}} and within it a resource {{{yyy}}}, which has a number of components. You're providing CRUD functions for the resource and its components using {{{shn_rest_controller()}}}.

Now you want to provide a reporting function for this resource, where the user can select records using a search form and then generate a summary report that can be exported in various formats, among others XLS, PDF and SVG.

This tutorial shows you how this can be integrated in the REST interface of your resource.

=== Techniques to use ===

==== Creating a custom method handler ====

Reporting is a method of your resource, the reporting function will therefore be implemented as a custom method handler.

Add the reporting function to your model file, and add it as a method to your resource, like:

{{{
def s3_xxx_yyy_report(r, **attr):

    # Report generating code goes here

s3xrc.model.set_method("xxx", "yyy", method="report", action=s3_xxx_yyy_report)
}}}

A custom method handler has to take two arguments:

  - {{{r}}} is the respective S3Request object, which represents the current request
  - {{{attr}}} is the same dict of named arguments that have been passed to shn_rest_controller

Once you have done this, you can invoke your method handler from the URL:

{{{
http://localhost:8000/eden/xxx/yyy/report
}}}

The advantage of this is that this even understands URLs like:

{{{
http://localhost:8000/eden/xxx/yyy/1/report
http://localhost:8000/eden/xxx/yyy/report?yyy.id=1,2,3
http://localhost:8000/eden/xxx/yyy/report?yyy.field1__like=abc
}}}

meaning, it already implements a RESTful API for your reporting function, e.g. does the parsing/validating of the URL for you, implements the full range of URL queries for your resource and so forth. Nothing you need to care about now.

==== Providing different Report Formats ====

You want to provide the report in various formats, hence you need to know what format the user has requested. The best way is to check for the format that has been specified in the URL.

To know which format has been specified, simply use r.representation inside the method handler:

{{{
def s3_xxx_yyy_report(r, **attr):

    if r.representation == "html":
        # HTML report generating code goes here:
        # "output" gets a dict of variables to be passed to the view

        response.view = "xxx/yyy_report.html" # <== choose the view template

        return output # <== return the output to the view

    elif r.representation == "xls":
        # XLS report generating code goes here
        # "output" gets the XLS contents

        return output # <== return the output to the view

    elif r.representation == "pdf":
        # PDF report generating code goes here
        # "output" takes the PDF contents

        return output # <== return the output to the view

    elif r.representation == "svg":
        # SVG report generating code goes here
        # "output" takes the SVG as a string

        return output # <== return the output to the view

    else:
        # Unsupported format
        raise HTTP(501, body=s3xrc.ERROR.BAD_FORMAT)

s3xrc.model.set_method("xxx", "yyy", method="report", action=s3_xxx_yyy_report)
}}}

Now your method handler recognises the requested format as specified in the URL by either a filename extension or the {{{format}}} variable:

{{{
http://localhost:8000/eden/xxx/yyy/4/report.xls
http://localhost:8000/eden/xxx/yyy.pdf/6
http://localhost:8000/eden/xxx/yyy/report?format=svg
}}}

==== How to get at the data ====

How can you find out which data have to be processed by your reporting function, and yet more important: how can you get at them?

{{{r}}} (the {{{S3Request}}} object) contains an interface to your resource as {{{S3Resource}}} object in: {{{r.resource}}}

And this is what you can use to easily access the resource data. Some examples:

{{{
def s3_xxx_yyy_report(r, **attr):

    resource = r.resource # <== Get the resource

    if r.representation == "html":

        resource.load()
        rows = resource.records() # <== get all records

    elif r.representation == "xls":

        for record in resource: # <== interate through the records
            ...

    elif r.representation == "pdf":

        # Access components record-wise:
        for record in resource:
            component_set = resource(record, component="component_name")
            for component_record in component_set:
                ...

    elif r.representation == "svg":

        # Modifying the resource query before accessing records
        filter = resource.get_query()
        filter = filter & (db.xxx_yyy.field5 == "value")
        resource.build_query(filter = filter)

        # ...and then iterate through the records:
        for record in resource:
            ...

    else:
        # Unsupported format
        raise HTTP(501, body=s3xrc.ERROR.BAD_FORMAT)

s3xrc.model.set_method("xxx", "yyy", method="report", action=s3_xxx_yyy_report)
}}}


=== The concrete case: Total costs within a time interval ===

Your resource contains a "timestmp" field (type datetime) and a field "cost" (type double), and now the user shall select a time interval in aform, and your report function shall provide the sum of all "cost" for those records with a timestmp within the selected time interval.

Let's go:
First of all, we implement our method handler as before:

{{{
def s3_xxx_yyy_report(r, **attr):

    # Report generating code goes here

s3xrc.model.set_method("xxx", "yyy", method="report", action=s3_xxx_yyy_report)
}}}

Then we add the HTML representation:

{{{
def s3_xxx_yyy_report(r, **attr):

    if r.representation == "html":
        output = dict()
        return output

s3xrc.model.set_method("xxx", "yyy", method="report", action=s3_xxx_yyy_report)
}}}

The next step would be to provide a form to select the first and the last date of the interval. This would look like that:

{{{
    if r.representation == "html":

        # Filter form
        form = FORM(
                 TABLE(
                   TR(
                     T("Date from:"),
                     INPUT(_type="text", _name="date_from", _class="date", _value=datetime.now().date(), requires=IS_DATE()),
                     T("until:"),
                     INPUT(_type="text", _name="date_until", _class="date", _value=datetime.now().date(), requires=IS_DATE())
                   )
                 )
               )

        output = dict(form=form)

        if form.accepts(request.vars, session, keepvalues=True):
            # Processing of the form data goes here

        return output

}}}

From this, we need to process the form data into two dates. We use {{{datetime}}} for that:

{{{
        if form.accepts(request.vars, session, keepvalues=True):

            from datetime import date, datetime, time

            # Date from
            if form.vars.date_from:
                from = datetime.combine(form.vars.date_from, time(0,0,0))

            # Date until
            if form.vars.date_until:
                until = datetime.combine(form.vars.date_until+timedelta(days=1), time(0,0,0))

}}}

To select the corresponding records, we need to extend our query:

{{{
        if form.accepts(request.vars, session, keepvalues=True):

            # Get the initial query from the resource
            # => this implements authorisation as well as URL queries
            resource = r.resource
            table = resource.table
            filter = resource.get_query()

            from datetime import date, datetime, time

            # Date from
            if form.vars.date_from:
                from = datetime.combine(form.vars.date_from, time(0,0,0))
                date_query = (table.timestmp >= from)

            # Date until
            if form.vars.date_until:
                until = datetime.combine(form.vars.date_until+timedelta(days=1), time(0,0,0))
                q = (table.timetmp <= until)
                if date_query:
                    date_query = date_query & q
                else:
                    date_query = q

            # Add our filter and rebuild the resource query
            filter = filter & date_query
            resource.build_query(filter=filter)

}}}

From there, it is easy to select the sum of the "cost" field:

{{{
        if form.accepts(request.vars, session, keepvalues=True):

            # Get the initial query from the resource
            # => this implements authorisation as well as URL queries
            resource = r.resource
            table = resource.table
            filter = resource.get_query()

            from datetime import date, datetime, time

            # Date from
            if form.vars.date_from:
                from = datetime.combine(form.vars.date_from, time(0,0,0))
                date_query = (table.timestmp >= from)

            # Date until
            if form.vars.date_until:
                until = datetime.combine(form.vars.date_until+timedelta(days=1), time(0,0,0))
                q = (table.timetmp <= until)
                if date_query:
                    date_query = date_query & q
                else:
                    date_query = q

            # Add our filter and rebuild the resource query
            filter = filter & date_query
            resource.build_query(filter=filter)

            # Get the total costs
            costs = table.costs.sum()
            total = db(query).select(costs)

            # Build the result string
            result = "%s: %s" % (T("The total costs of the selected projects are"), total)

            output.update(result=result)
}}}

Done with the method handler! Here at a glance:

{{{

def s3_xxx_yyy_report(r, **attr):

    if r.representation == "html":

        # Filter form
        form = FORM(
                 TABLE(
                   TR(
                     T("Date from:"),
                     INPUT(_type="text", _name="date_from", _class="date", _value=datetime.now().date(), requires=IS_DATE()),
                     T("until:"),
                     INPUT(_type="text", _name="date_until", _class="date", _value=datetime.now().date(), requires=IS_DATE())
                   )
                 )
               )

        output = dict(form=form)

        if form.accepts(request.vars, session, keepvalues=True):

            # Get the initial query from the resource
            # => this implements authorisation as well as URL queries
            resource = r.resource
            table = resource.table
            filter = resource.get_query()

            from datetime import date, datetime, time

            # Date from
            if form.vars.date_from:
                from = datetime.combine(form.vars.date_from, time(0,0,0))
                date_query = (table.timestmp >= from)

            # Date until
            if form.vars.date_until:
                until = datetime.combine(form.vars.date_until+timedelta(days=1), time(0,0,0))
                q = (table.timetmp <= until)
                if date_query:
                    date_query = date_query & q
                else:
                    date_query = q

            # Add our filter and rebuild the resource query
            filter = filter & date_query
            resource.build_query(filter=filter)

            # Get the total costs
            costs = table.costs.sum()
            total = db(query).select(costs)

            # Build the result string
            result = "%s: %s" % (T("The total costs of the selected projects are"), total)

            output.update(result=result)

            # Select the corresponding view:
            response.view = "xxx/report.html"

    else:
        raise HTTP(501, body=s3xrc.ERROR.BAD_FORMAT)

    return output

s3xrc.model.set_method("xxx", "yyy", method="report", action=s3_xxx_yyy_report)
}}}

We have added a line to raise an HTTP error in case an unsupported format gets requested, and added a line to select a proper view template "xxx/report.html", which would look like that:

{{{
{{extend 'layout.html'}}
<div class='form-container'>
{{try:}}{{=form}}{{except:}}{{pass}}
</div>
<div id='table-container'>
{{try:}}{{=result}}{{except:}}{{pass}}
</div>
}}}

...and that's all.

...to be continued...
...to be continued...