MeshCore repeater available public key prefix finder

meshcore-repeater-free-prefix-finder.rb

#!/usr/bin/env ruby

# Prints un-used two letter public key hex prefixes
# for new repeater nodes within a given radius for a location.
#
# This allows for better trace display without repeating hex codes. 
# 
# After finding a prefix, generate a key pair here:
#  https://gessaman.com/mc-keygen/

require 'json'
require 'date'

# Constants

# Seattle: 47.6068836 -122.3260829

LOC_LAT      = 47.6068836
LOC_LON      = -122.3260829
RADIUS_MILES = 20
MAX_AGE_DAYS = 30  # Filter out items not updated within this many days

# Haversine formula to calculate distance between two GPS coordinates in miles
def haversine_miles(lat1, lon1, lat2, lon2)
  rad_per_deg = Math::PI / 180
  earth_radius_miles = 3959.0

  dlat = (lat2 - lat1) * rad_per_deg
  dlon = (lon2 - lon1) * rad_per_deg

  a = Math.sin(dlat / 2)**2 +
      Math.cos(lat1 * rad_per_deg) * Math.cos(lat2 * rad_per_deg) *
      Math.sin(dlon / 2)**2

  c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a))

  earth_radius_miles * c
end


require 'net/http'
require 'json'

filename = 'meshcore-nodes.json'

unless File.exist?(filename)
  uri = URI('https://map.meshcore.dev/api/v1/nodes')
  File.write(filename, Net::HTTP.get(uri))
  puts "Downloaded #{filename}"
else
  puts "#{filename} already exists, skipping download"
end

json_data = JSON.parse(File.read(filename))


cutoff_date = DateTime.now - MAX_AGE_DAYS

near = json_data
  .select { |node| node['type'] == 2 }  # Only repeaters
  .reject do |node|
    # Reject if within 20 miles of location
    lat = node['adv_lat']
    lon = node['adv_lon']
    d = lat && lon && haversine_miles(LOC_LAT, LOC_LON, lat, lon) 
    node['distance'] = d
    d > RADIUS_MILES
  end
  .reject do |node|
    # Reject old items (not updated recently)
    updated = node['updated_date']
    updated.nil? || DateTime.parse(updated) < cutoff_date
  end
  .sort_by{|node| node['distance']}

prefixes = near.map { |node| node['public_key'][0, 2] }.sort  # First two chars of public key

# dump nodes
# near.each do |n|
#  h =  n.slice("adv_name", "params", "updated_date", "distance")
#  params = h.delete "params"
#  h['freq'] = params['freq']
#  puts h.values.join(";  ")
# end

hex = [0,1,2,3,4,5,6,7,8,9] + %w{a b c d e f }
all_prefixes = hex.map{|a| hex.map{|b| a.to_s + b.to_s}}.flatten


unseen = all_prefixes - prefixes
puts unseen