worg / rslv

rslv - Resuelve invoice tool

Problem

We need to fetch the total invoice count within a date span from a limited API, the API returns more than 100 results if the query exceedes that count.

Solution

I used a divide and conquer algorithm, if the first call exceedes the result count, I'll split the date in two ranges, and make two calls, one for each range, This process repeats until we get the total count.

Running

I choosed docker to deploy this utility. for this makes easier to not depend on the user environment for running this program. I'll assume the user has docker in her/his system.

Options

rslv takes three options, either as command line flags or environment variables:

Option	Environment Variable	Command Line Flag	Description	Format
ID	USER_ID	id	User id to fetch invoices	GUID
Start	START_DATE	finish	Start of date range to find invoices	[YYYY-MM-DD]
Finish	END_DATE	start	End of date range to find invoices	[YYYY-MM-DD]

Building the image

In order to have an usable base image with rslv and its dependencies we'll build an image containing golang and our dependencies.

• Clone the repository.
• Navigate to the repository root.
• Execute docker build -t {TAG_NAME} . and wait for our image to be built.
  • Where {TAG_NAME} is a name for our image, for example: rslv_img

This will fetch our tool dependencies and build a binary

Running rslv

Once built the image we can run our tool

Execute

docker run --rm --name rslv {TAG_NAME} -id={USER_ID} -start={START_DATE} -finish={END_DATE}

Replacing:

• {TAG_NAME} with the tag defined in the build step
• {USER_ID} with the user id to find invoices
• {START_DATE} with the start of date range within invoices must be searched
• {END_DATE} with the end of the date range to perfotm the search

I prefer to use --rm option to discard our container after execution is done.

Output

At the end of execution rslv will output the total invoice count and how many requests it took.

{X} invoices were found, using {Y} requests

Debugging

Executing with RSLV_DEBUG environment variable distinct of empty string will output the requests made and their results, in the following format:

-- REQUEST: "http://U.R.L/path?query=args"
 - RESPONSE: "HTTP_RESPONSE"

Testing

Test results are available on travis-ci [see badge], alternatively one can run locally the tests. Assuming a working golang setup:

• cd cmd/rslv from the repository root
• go get -t ./... to fetch the project dependencies
• go test -v -cover to display the test results using the command line
• goconvey -cover . to display test results using the browser