Billing Calculator

Description

This project is a simple implementation of a solution to a sample exercise.

Exercise Description

You have a set of projects, and you need to calculate a reimbursement amount for the set. Each project has a start date and an end date. The first day of a project and the last day of a project are always "travel" days. Days in the middle of a project are "full" days. There are also two types of cities a project can be in, high cost cities and low cost cities.

Domain Rules

First day and last day of a project, or sequence of projects, is a travel day.
Any day in the middle of a project, or sequence of projects, is considered a full day.
If there is a gap between projects, then the days on either side of that gap are travel days.
If two projects push up against each other, or overlap, then those days are full days as well.
Any given day is only ever counted once, even if two projects are on the same day.
A travel day is reimbursed at a rate of 45 dollars per day in a low cost city.
A travel day is reimbursed at a rate of 55 dollars per day in a high cost city.
A full day is reimbursed at a rate of 75 dollars per day in a low cost city.
A full day is reimbursed at a rate of 85 dollars per day in a high cost city.

Getting Started

This getting started guide is tailored for MacOS users.

If you don't have it, install Homebrew by running the following command in your terminal:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Install dotnet 8 via: brew install dotnet@8
Run the app by executing the following command from the root directory of the project:
```
dotnet run --project ./Billing.Console/Billing.Console.csproj
```
If you run into issues with any missing dependencies, you may need to download them (although dotnet run should handle this for you). Restore the dependencies by running the following command:
```
dotnet restore
```

Running the Tests

From the root directory of the project, run the following command:

dotnet test

Other Considerations

I found logical omissions in the requirements:

The requirements do not specify how to handle the case where a travel day is shared between a high and low cost city; this creates ambiguity in the requirements, as the cost of the travel day cannot be determined because there is no rule for a prevailing rate. To cover this case, I have added a configuration option, OverlapConfiguration, which allows the developer to specify one of these four mechanisms to handle the case:
- Take First Day: Take the billable day of the project that starts first.
- Take Last Day: Take the billable day of the project starts last.
- Take Greater Amount: Take the billable day of the project with the greater amount.
- Take Lesser Amount: Take the billable day of the project with the lesser amount .
Since a date can only be billed once, there is another issue when a travel day is shared between two projects. There is no clear rule for which project should be billed for the travel day. This impacts the total project cost, where costs may be understated.