RidesElixir

A proof-of-concept Elixir application which performs a few Geolocation operations.

Execution

First make sure you have all dependencies:

# Fetch dependencies
$ mix deps.get

The easyest way to try it out is by running iex -S mix:

$ iex -S mix
Erlang/OTP 20 [erts-9.3] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Interactive Elixir (1.6.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> RidesElixir.run()
:ok

This will perform two actions:

• Process pairs.csv file and create bounding boxes for each pair or coordinates (i.e. line 1 + line 2, line 2 + line 3, line 3 + line 4 etc.).
• Process coordinates.csv files and assign each of its coordinates to a a previously created bounding box. Unmatched coordinates are discarded.

After this processing you can interact with data using both %RidesElixir.Geo.Point{} and %RidesElixir.Geo.Box{} structs. For your convenience, run the following lines in iex:

iex(2)> alias RidesElixir.Geo.Box
RidesElixir.Geo.Box
iex(3)> alias RidesElixir.Geo.Point
RidesElixir.Geo.Point

%Point{} is the representation of a lon/lat coordinate, while %Box{} is the representation of the bounding box of two %Point{}s. %Box{} also holds a list of %Point{}s which are within its boundaries.

Operations

%Box{} has several operations for manipulating data. You can list previously processed boxes with list/0:

iex(4)> Box.list()
[
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 14.756699999999999, lon: 120.99206},
      %RidesElixir.Geo.Point{lat: 14.75659, lon: 120.99287}
    ]
  },
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 14.756939999999998, lon: 120.99203999999999},
      %RidesElixir.Geo.Point{lat: 14.756699999999999, lon: 120.99206}
    ]
  },
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 14.757139999999998, lon: 120.99203999999999},
      %RidesElixir.Geo.Point{lat: 14.756939999999998, lon: 120.99207999999999}
    ]
  },
  ...

You can create a new Box with new/1, which receives a pair of %Point{} and calculates the upper-left and bottom-right coordinates of the bounding box:

iex(5)> Box.new([%Point{lon: 120, lat: 14}, %Point{lon: 121, lat: 15}])
%RidesElixir.Geo.Box{
  list: #MapSet<[]>,
  pair: [
    %RidesElixir.Geo.Point{lat: 15, lon: 120},
    %RidesElixir.Geo.Point{lat: 14, lon: 121}
  ]
}

Please note that new/1 only creates the structure of a %Box{} and does not persist it locally. If you want to do so, use put/1:

iex(6)> Box.new([%Point{lon: 120, lat: 14}, %Point{lon: 121, lat: 15}]) |> Box.put()
:ok

You can search for the first matching box of a given %Point{} using find/1, which returns a tuple with the index of the Box and the %Box{} struct itself:

iex(7)> Box.find(%Point{lon: 120, lat: 14})
{327,
 %RidesElixir.Geo.Box{
   list: #MapSet<[]>,
   pair: [
     %RidesElixir.Geo.Point{lat: 15, lon: 120},
     %RidesElixir.Geo.Point{lat: 14, lon: 121}
   ]
 }}

You can also use find/1 to look for a specific %Box{}:

iex(8)> [%Point{lon: 120.99844000000004, lat: 14.65445}, %Point{lon: 120.99775000000004, lat: 14.65323}] |> Box.new() |> Box.find()
{101,
 %RidesElixir.Geo.Box{
   list: #MapSet<[]>,
   pair: [
     %RidesElixir.Geo.Point{lat: 14.65445, lon: 120.99775000000004},
     %RidesElixir.Geo.Point{lat: 14.65323, lon: 120.99844000000004}
   ]
 }}

Assign a particular %Point{} to the first matching box with find_and_assign/1. It leverages MapSet to make sure that no duplicates will occur -- trying to add a duplicated %Point{} is a no-op:

iex(10)> %Point{lon: 120.9984, lat: 14.65445} |> Box.find_and_assign()
:ok
iex(12)> %Point{lon: 120.9984, lat: 14.65445} |> Box.find()
{101,
 %RidesElixir.Geo.Box{
   list: #MapSet<[%RidesElixir.Geo.Point{lat: 14.65445, lon: 120.9984}]>,
   pair: [
     %RidesElixir.Geo.Point{lat: 14.65445, lon: 120.99775000000004},
     %RidesElixir.Geo.Point{lat: 14.65323, lon: 120.99844000000004}
   ]
 }}

filter/1 retrieves every %Box{} that matches a given %Point{}:

iex(13)> %Point{lat: 14.65445, lon: 120.99775000000004} |> Box.filter()
[
  %RidesElixir.Geo.Box{
    list: #MapSet<[%RidesElixir.Geo.Point{lat: 14.65445, lon: 120.9984}]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 14.65445, lon: 120.99775000000004},
      %RidesElixir.Geo.Point{lat: 14.65323, lon: 120.99844000000004}
    ]
  },
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 15, lon: 120},
      %RidesElixir.Geo.Point{lat: 14, lon: 121}
    ]
  }
]

Finally, find_and_put/1 receives a pair of %Point{} and retrieves a Keyword list with matching boxes for each one of them (i.e. origin and destination). It also creates the bounding box for the received pair if it does not exist already:

iex(14)> [%Point{lon: 121.0111, lat: 14.787}, %Point{lon: 120.9853, lat: 14.6097}] |> Box.find_and_put()
[
  origin: [
    %RidesElixir.Geo.Box{
      list: #MapSet<[]>,
      pair: [
        %RidesElixir.Geo.Point{lat: 14.787, lon: 120.9853},
        %RidesElixir.Geo.Point{lat: 14.6097, lon: 121.0111}
      ]
    }
  ],
  destination: [
    %RidesElixir.Geo.Box{
      list: #MapSet<[]>,
      pair: [
        %RidesElixir.Geo.Point{lat: 15, lon: 120},
        %RidesElixir.Geo.Point{lat: 14, lon: 121}
      ]
    },
    %RidesElixir.Geo.Box{
      list: #MapSet<[]>,
      pair: [
        %RidesElixir.Geo.Point{lat: 14.787, lon: 120.9853},
        %RidesElixir.Geo.Point{lat: 14.6097, lon: 121.0111}
      ]
    }
  ]
]

Your can call find_and_put/2 with :origin or :destination to receive only the matching boxes of the first or second %Point{} respectively:

iex(15)> [%Point{lon: 121.0111, lat: 14.787}, %Point{lon: 120.9853, lat: 14.6097}] |> Box.find_and_put(:origin)
[
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 14.787, lon: 120.9853},
      %RidesElixir.Geo.Point{lat: 14.6097, lon: 121.0111}
    ]
  }
]
iex(16)> [%Point{lon: 121.0111, lat: 14.787}, %Point{lon: 120.9853, lat: 14.6097}] |> Box.find_and_put(:destination)
[
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 15, lon: 120},
      %RidesElixir.Geo.Point{lat: 14, lon: 121}
    ]
  },
  %RidesElixir.Geo.Box{
    list: #MapSet<[]>,
    pair: [
      %RidesElixir.Geo.Point{lat: 14.787, lon: 120.9853},
      %RidesElixir.Geo.Point{lat: 14.6097, lon: 121.0111}
    ]
  }
]

Tests & static analysis

Run mix test to run the test suite:

$ mix test
..................

Finished in 0.3 seconds
18 tests, 0 failures

Randomized with seed 67962

Run mix credo for static code analysis:

$ mix credo
Checking 8 source files ...

Please report incorrect results: https://github.com/rrrene/credo/issues

Analysis took 0.5 seconds (0.02s to load, 0.4s running checks)
25 mods/funs, found no issues.

Use `--strict` to show all issues, `--help` for options.