draw on terminal with python

You are to implement a terminal-based drawing program

C 5 10
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|     |
|     |
|     |
|     |
|     |
|     |
|     |
|     |
|     |
|     |
-------

L 0 0 0 5 x
-------
|x    |
|x    |
|x    |
|x    |
|x    |
|x    |
|     |
|     |
|     |
|     |
-------

R 0 0 3 3 y
-------
|yyyy |
|y  y |
|y  y |
|yyyy |
|x    |
|x    |
|     |
|     |
|     |
|     |
-------

R 2 2 4 4 z
-------
|yyyy |
|y  y |
|y zzz|
|yyzyz|
|x zzz|
|x    |
|     |
|     |
|     |
|     |
-------

B 3 3 z
-------
|yyyy |
|y  y |
|y zzz|
|yyzzz|
|x zzz|
|x    |
|     |
|     |
|     |
|     |
-------

B 0 1 y
-------
|yyyy |
|y  y |
|y zzz|
|yyzzz|
|y zzz|
|y    |
|     |
|     |
|     |
|     |
------- （nothing happened）

L 0 6 4 9 d
-------
|yyyy |
|y  y |
|y zzz|
|yyzzz|
|y zzz|
|y    |
|d    |
| dd  |
|   d |
|    d|
------- (diagonal line, bresenham line;s algo from googling )

B 0 6 c
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|yyyy |
|y  y |
|y zzz|
|yyzzz|
|y zzz|
|y    |
|c    |
| cc  |
|   c |
|    c|
-------

Q
Quitting. (then application quit)

• The program will prompt for input, and render the response to the screen, before prompting for more input, up to the point it is terminated with “Q”.
• A readme explaining how to run the code
• Adequate test coverage. We recommend a test-driven approach
• Where requirements are unclear, make a choice and document if necessary

pip install behave # (or pip install -r requirements.txt)
behave # if you want to test all feature file
behave features/command_basic_check.feature # if you want to test a single feature file

python draw.py

• consult scenarios (.feature files) under folder features if you find any confliction and then raise an issue about this confliction

• (0,0) is at the left top of the canvas, larger x means more close to right, larger y means more close to bottom, all coordinates can not be negative

• you must create a canvas board before drawing anything

• all coordinates cannot exceed the canvas, otherwise an error message will throw but application continue to run

• for invalid command input, and error message will throw out but application continue to run

• virtual z axis for rectangles and lines objects (I learnt it from computer graphic, it's called z-buffer)

  • only colors of largest z (min depth, cloest to the "camera") will be rendered on canvas
  • we maintain coordinate z in-house, i.e when a command pass in, an increasing z coordinate is generated for any object that is being created
  • theoretically two polygons will never be overlapping with each other given increasing z coordinates, but it can be confused to look at what's being printing out since we can only look through z axis

• Any command that specifies coordinates outside the current canvas dimensions

  • returns an error message:
    "Invalid coordinates. Coordinates exceed canvas size."

• Any command that specifies negative coordinates

  • returns an error message:
    "Invalid coordinates. Coordinates must be non-negative."

• Zero-length lines or rectangles (start == end)

  • return an error message:
    "Invalid line. ..."
    or
    "Invalid rectangle. ..."

• Bucket-fill (B x1 y1 c):

  • If (x1,y1) is on a standalone line → only that line segment is filled.
  • If (x1,y1) is inside a rectangle → only the interior is filled (borders remain).
  • If (x1,y1) is on the border of a rectangle → no fill is performed.
  • If a line crosses a rectangle and (x1,y1) is on that line → only the line is filled, interior of the rectangle stays unchanged.
  • More scenarios are covered in features/color_filling_overlap.feature

• Rectangle drawing (R x1 y1 x2 y2 c) should always draw borders only; the inside remains blank until a bucket-fill command is applied.

• Purpose of this application (aka behavior of this application ) is clear but interface and api definition is not known up front
• Feature file has higher readability and easy to understand when elaborating numerous hypothesis and can use as a check when evolving features development, failing feature test means some missing behavior of the application that needs to be developed