Access Summary Geoprocessing Task for Chubbs Spatial Server

gistfile1.js

//10.17.2013 - Ryan Whitley
var flow = require('flow');
var pg = require('pg'),
        common = require("../../../common"),
        settings = require('../../../settings');

//Takes in a where clause, buffers, dissolves and zonal stats.  Return table of zonal stats.
//Arguments are:
//1. The points (or at least a where clause to query a particular table).
//2. Buffer Radius

var operation = {};
var countries = { 'TZA': { name: 'tanzania', srid: '32747' }, 'BGD': { srid: '32645', name: 'bangladesh' }, 'UGA': { srid: '32747', name: 'uganda' }, 'NGA': { name: 'nigeria', srid: '32747' } };

/* METADATA */

operation.name = "AccessSummary";
operation.description = "Calculates the number of people living within a certain radius of given access ponits, broken down by urban and rural locations.";
operation.inputs = {};

operation.outputImage = true;

operation.inputs["where_clause"] = { };
operation.inputs["buffer_distance"] = { value: 0, units: "" }; //how far and what units?
operation.inputs["country_code"] = []; //Let user specify input country code

//This will execute for cell coverage, Land Use and buffers ~ 33 seconds for all points in bangladesh
//operation.Query = "with cc_lu as(" +
//"select " +
//"  a.coverage, " +
//"  b.landuse, " +
//"   (st_dump(st_intersection(a.geom,b.geom))).geom as geom" +
//"		from bangladesh_coverage a " +
//"		inner join bangladesh_urbanareas b on " +
//"		st_intersects(a.geom,b.geom) " +
//") " +
//", " +
//"--add the intersection between cell coverage, land use and buffers " +
//"cc_lu_5km as " +
//"( " +
//"select  " +
//"            a.coverage, " +
//"            a.landuse, " +
//"            b.featuretype, " +
//"            (st_dump(st_intersection(a.geom,b.geom))).geom as geom " +
//"from cc_lu a " +
//"inner join (SELECT ST_Union(ST_transform( ST_BUFFER( ST_transform(geom, 32645), 5000 ), 4326 )) as geom, featuretype " +
//"FROM bangladesh_cicos " +
//"WHERE featuretype = 'Post Offices' GROUP BY featuretype) b on " +
//"st_intersects(a.geom, b.geom) " +
//")" +
//"select coverage, landuse, featuretype, ST_AsGeoJSON(geom) as geom from cc_lu_5km;";


//This will execute just for Land Use and buffers - ~ 18 seconds for all points in bangladesh
//operation.Query = "with cc_lu_5km as " +
//"( " +
//"select  " +
//"            a.landuse, " +
//"            b.featuretype, " +
//"            (st_dump(st_intersection(a.geom,b.geom))).geom as geom " +
//"from {country}_urbanareas a " +
//"inner join (SELECT ST_Union(ST_transform( ST_BUFFER( ST_transform(geom, {srid}), 5000 ), 4326 )) as geom, featuretype " +
//"FROM {country}_cicos " +
//"WHERE {where_clause} GROUP BY featuretype) b on " +
//"st_intersects(a.geom, b.geom) " +
//")" +
//"select landuse, featuretype, ST_AsGeoJSON(geom) as geom from cc_lu_5km;"


//This will execute just for Land Use and buffers - ~ 18 seconds for all points in bangladesh
operation.Query = "DO $$DECLARE " +
"orig_srid int; " +
"BEGIN " +
"drop table if exists _gptemp; " +
"--create all polygons " +
"create temporary table _gptemp as " +
"select  " +
"a.landuse, " +
"b.featuretype, " +
"ST_AsGeoJSON((st_dump(st_intersection(a.geom,b.geom))).geom) as geom " +
"from {country}_urbanareas a " +
"inner join (SELECT ST_Union(ST_transform( ST_BUFFER( ST_transform(geom, {srid}), 5000 ), 4326 )) as geom, featuretype " +
"FROM {country}_cicos " +
"WHERE {where_clause} GROUP BY featuretype) b on " +
"st_intersects(a.geom, b.geom); " +
"END$$; " +
"select * from _gptemp;"



operation.execute = flow.define(
    function (args, callback) {
        this.args = args;
        this.callback = callback;
        //Step 1
        //See if inputs are set. Incoming arguments should contain the same properties as the input parameters.
        if (operation.isInputValid(args) === true) {
            operation.inputs["where_clause"] = args.where_clause;
            operation.inputs["buffer_distance"] = args.buffer_distance;
            operation.inputs["country_code"] = args.country_code;

            //Take the point and buffer it in PostGIS
            var query = { text: operation.Query.replace("{where_clause}", operation.inputs["where_clause"]).split("{country}").join(countries[operation.inputs["country_code"]].name).replace("{srid}", countries[operation.inputs["country_code"]].srid), values: []};
            common.executePgQuery(query, this);//Flow to next function when done.

        }
        else {
            //Invalid arguments
            //return message
            callback({ status: "Missing required arguments", rows: []});
        }
    },
    function (results) {
        //Step 2 - get the results and pass back to calling function
        this.callback(results);
    }
)

//Make sure arguments are tight before executing
operation.isInputValid = function (input) {
    //Test to see if inputs are specified
    var isValid = false;

    if (input) {
        //make sure we have a where clause, buffer disatance and the country code is found in the country object.
        if (input["where_clause"] && input["buffer_distance"] && countries[input["country_code"]]) {
            //It's got everything we need.
            return true;
        }
    }

    return isValid;
}

module.exports = operation;