Heads-I-Lose

# Heads I Lose

This started as a little learning exercise in Erlang, but I've been building on it to make it more useful for my cycle commute. It looks up the wind direction ([via the MetOffice Datapoint API](http://www.metoffice.gov.uk/datapoint/api)) and for a given route (a polyline from [OSRM](http://project-osrm.org/)) determines how much of the route is a headwind sidewind or tailwind. 

## Usage

Since it has just been developed for personal use installation is not very polished.

1. Get a MetOffice Datapoint [API key](http://www.metoffice.gov.uk/datapoint/support/API) and save in a file called `~/.datapoint`.
2. Get/install [Jiffy](https://github.com/davisp/jiffy). (I just cloned the repository, issued `make` and copied the `ebin` and `priv` directories to my `heads-I-lose` directory).
3. Within the `heads-I-lose` directory, compile with `erlc headsilose.erl; erlc weather_types.erl; erlc osrm.erl; erlc polyline.erl`.
4. Run `erl -run headsilose get_locations <Optional search term> -noshell -s init stop` to get a list of locations and Ids. The optional search term cannot contain spaces.

	Weather type: Cloudy
	Temperature: 4 deg C

_Note1:_ Since the route is from OSRM there is the option to specify `alternative_geometries` as an argument. In theory OSRM can return more than one alternative route, but in practice (at least as far as I can tell) I think it only ever returns one alternative route so although the argument is `alternative_geometries` it is actually the first alternative that is used. If `alternative_geometries` is not specified then the default route is used. If you'd like to see visually which route is the default and which is the alternative you can see them at [Project OSRM](http://map.project-osrm.org/) as routes A (default) and B (alternative).

_Note2:_ I don't use [init stop](http://erlangcentral.org/wiki/index.php?title=Running_Erlang_Code_From_The_Command_Line&oldid=2293) in my main command line call as I have that in my script instead. Otherwise, if `headsilose` errors out then `init stop` will crash out (I guess because it is trying to stop something that isn't running).

## Credits

Various posts I've found that have helped me out:

- Initial inspiration from [PragDave - A First Erlang Program](http://pragdave.pragprog.com/pragdave/2007/04/a_first_erlang_.html)
- Putting initial inspiration to practice (i.e. `inets:start`) from [Andrew Locatelli Woodcock - Connecting to Cloudant from Erlang: a quick example of using HTTPS from httpc:request](http://andrewlocatelliwoodcock.com/2012/06/12/connecting-to-cloudant-from-erlang-a-quick-example-of-using-https-from-httpcrequest-17-2/)
- The recursive parsing of XML from [Sam Ruby - Parsing Atom with Erlang](http://intertwingly.net/blog/2007/08/28/Parsing-Atom-with-Erlang)
- Formating dates with leading zeroes from [Warren Young on Stack Overflow](http://stackoverflow.com/a/7599506/208793)
- Figuring out command line arguments from [Cody on Stack Overflow](http://stackoverflow.com/a/8498073/208793)
- Figuring out [Jiffy](http://www.snip2code.com/Snippet/51463/how-to-support-chinese-in-http-request-b/)
- [Rounding numbers](http://www.codecodex.com/wiki/index.php?title=Round_a_number_to_a_specific_decimal_place#Erlang)
- [Converting between binary and decimal](http://erlangcentral.org/wiki/index.php/Converting_Between_Binary_and_Decimal)

I did read through a [number](http://www.mathworks.com/matlabcentral/fileexchange/32341-google-maps-api-polyline-decoder) [of](http://jeffreysambells.com/2010/05/27/decoding-polylines-from-google-maps-direction-api-with-java) [posts](http://seewah.blogspot.co.uk/2009/11/gpolyline-decoding-in-python.html)/[implementations](http://unitstep.net/blog/2008/08/02/decoding-google-maps-encoded-polylines-using-php/) [of](https://github.com/Project-OSRM/osrm-frontend/blob/master/WebContent/routing/OSRM.RoutingGeometry.js) polyline decoders, but they didn't really help me in Erlang so I just worked backwards through the [specification](https://developers.google.com/maps/documentation/utilities/polylinealgorithm) and wrote my own, much less concise, version rather than porting an existing implementation.

## Todo

_I should really put these as issues_

- Sort the list of locations?
- Finish off implementing the list of client "supposed to"s from the OSRM API, such as checksum and hint data, but this would mean caching all previous requests made.
- Use postcodes to get the latitudes and longitudes via [UK Postcodes](http://www.uk-postcodes.com/)
- Figure out how to pass negative numbers on the command line (perhaps use [getopt](http://github.com/jcomellas/getopt)?)
- Use tuples instead of lists where it makes sense