Chess Game

It is the end of a chess game (human vs human), and only kings and pawns are left. Write a program that takes in a CSV file (from local file system) with the current positions of the pieces, e.g.:

king, white, d3
pawn, white, d4
king, black, b5
pawn, black, a4
pawn, black, c4

and then allows the players to legally move their pieces. You are only implementing the logic, not the UI. The only requirements are that there needs to be one exposed function that lets a player move his/her piece and another function to get the current state of the board.

Please don’t spend more than a couple hours on this. If there are features or edge cases that you don’t have time to include, take note of them, and we can discuss how you would tackle them afterward. Let me know if you have any questions.

Approach

Given the time constraints, I aimed to make problem (listed above) smaller by first solving for the "black pawn" located at "c4". While solving for the "black pawn" first, moved quickly with well tested code. As I begin working on other pieces, I will aim to continue a test driven approach while enhancing the structure, descriptive nature and dynamic pattern of the source code.

Initial Steps

read file
create Pieces
convert position to something that can be represented on x & y coordinates
add ability for pawn to move
- [x, y] = [column, row]
- black: move forward [x, y] + [0, -1]
- black: move diagonally
  - condition: if there is a piece in diagonal position
  - diagonal left: [x, y] + [-1, -1]
  - diagonal right: [x, y] + [1, -1]
- white: move forward [x, y] + [0, 1]
- white: move diagonally
  - condition: if there is a piece in diagonal position
  - diagonal left: [x, y] + [-1, 1]
  - diagonal right: [x, y] + [1, 1]
- cannot move back or horizontally
- cannot move forward if piece is in that position

Run project

clone project
assuming you have bundler installed, run bundle install from root directory of project
- run tests: bundle exec rspec
- You can run the code without bundler but you may not be able to run the tests.
run program: ruby ./main.rb
see Spec directory for tests

Move

To move a piece: call move on an instance of Board and pass in the current board position of the piece (eg 'c4') and the new preferred board position (eg 'c3').

To-do

finish implementing logic described in "Initial Steps"
add logic for white pawn, black king and white king
re-factor method for placing pieces now that a method for calculating the list location from given coordinates exists. (See find_list_position)
remove excessive if else statements and create new methods for logic
add tests for entering a destination that is off the board (logic already exists)
make code descriptive enough where notes would not be (or very minimally) needed
make add_piece and remove_piece private methods, per instructions above
Thoughts: 'Piece' could inherit from 'Square'

Results

running the program with ruby main.rb and the tests with bundle exec rspec should result in the following:

Discussion

How do you handle the case of someone trying to move a king into check?

how to tell if a king is about to be in check?
if a king is in check, what are the available moves?

Example, a king is about to move into check.

Setup: [black, pawn, c5], [white, king, d4]

black pawn move to c4
- for squares located at diagonal left and diagonal right
  - if white king is in diagonal left or diagonal right
    - print "check"
  - else
    - add white king to a property called invalid pieces
after successful move
- remove invalid pieces that were placed on squares by black pawn based on the previous location of black pawn
prepare to move, remove invalid pieces that were placed by white king, from surrounding squares
- white king move to d3
  - for surrounding squares if black king is
  - if the square located at d3 contains white king in the invalid pieces list
    - return "invalid move, king would be in check"
after successful move
- remove invalid pieces that were placed on squares by white king based on the previous location of white king

Additional edge case:

track turns to ensure one person doesn't move twice
piece should be able to kill another piece
after a king is killed, game should end

LauraKirby/chess_game