MoD open data spreadsheet to json enricher with latitudes and longitudes

mod.rb

require 'csv'
require 'json'

#take a csv of transactions e.g. http://data.gov.uk/dataset/financial-transactions-data-mod/resource/b8d720dc-d6b0-4875-b9fe-7d135cb1c14e
#compare with postcodes csv from: https://github.com/Gibbs/UK-Postcodes/raw/master/postcodes.csv 

def extract_latlng(postcode)
  unless postcode.nil? or postcode.size.eql?(0)
    first_part = postcode.split.first
    first_part = "M5" if first_part.eql?("M50")
    first_part = "SN3" if first_part.eql?("SN38")
    first_part = "WV1" if first_part.eql?("WW1")
    first_part = "CR8" if first_part.eql?("CR9")
    first_part = "S41" if first_part.eql?("S49")

    if @postcodes.has_key?(first_part)
      lat = @postcodes[first_part][3]
      lng = @postcodes[first_part][4]
      return [lat, lng]
    else
      puts "Did not recognise #{postcode}"
    end
  else
    #puts "No postcode provided"
  end
  return ["", ""]
end

rows=CSV.read("transactions.csv")
pcodes=CSV.read("postcodes.csv")
ph = pcodes.delete_at(0)
@postcodes = {}
pcodes.each { |pc| @postcodes.merge!({ pc[0] => pc }) }

h = rows.delete_at(0) # ["Department", "Entity", "Date", "Expense Type", "Expense Area", "Supplier", "Post Code", "Transaction No", "Payment Description", "Total"]
suppliers = {}

for row in rows
  supplier = row[5]
  postcode = row[6]
  total = row[9].to_f.round(2)
  ll = extract_latlng(postcode)

  if suppliers.has_key? supplier
    current_total = suppliers[supplier]["total"].to_f
    suppliers[supplier].merge!("total" => (current_total + total).round(2))
    if suppliers[supplier]["lat"].empty? or suppliers[supplier]["lng"].empty?
      puts "Trying #{supplier} #{postcode} - #{ll[0]} #{ll[1]}"
      suppliers[supplier]["lat"] = ll[0]
      suppliers[supplier]["lng"] = ll[1]
    end
  else
    suppliers.merge!({ supplier => { "total" => total, "postcode" => postcode, "lat" => ll[0], "lng" => ll[1] } })
  end
end

File.open("suppliers.json","w") do |f|
  f.write(suppliers.to_json)
end