Advent of Code -- Go

Architecture

This program uses Go's plugin to dynamically load the solution code for a given day's puzzle. The puzzles directory contains subdirectories for each year of AOC puzzles, each of which contains subdirectories for each day's puzzle. Within a given day's directory, there is a main.go and an input.txt file. main.go implements a Solve() function with the signature Solve(fname string), which is loaded in by AOC.go. Solve() calls functions inside of the puzzle's main.go file to parse the input provided and solve the puzzle, and then prints out the solution.

Because of Go's plugin system, each plugin is its own main package that is built with

$ go build -buildmode=plugin

to produce a .so (shared object) file. Because each plugin has to be its own main package, I implement an empty main() function in each so that Go doesn't complain that function main is undeclared in the main package.

Within AOC.go, I parse and validate the command line arguments to get the year and day of the desired puzzle. If a solution has been implemented (i.e. if there is a .so file in the puzzle's directory), I load it in and use plugin.Lookup("Solve") to be able to use that function. The caller function must provide a type assertion for the looked-up symbol, which in this case is func(string). Once that's all taken care of, we can finally call the function, which in turn calls whatever functions the plugin has implemented to read the input file and solve the puzzle.

Usage

First, build all of the .so files for the puzzle solutions:

$ bash build_all_plugins.sh

Then, build the binary for the main AOC program:

$ go build -o AOC

Finally, run AOC with the desired year and day:

$ ./AOC 2018 1