008-caesar_cipher/docs/plan.md

Plan: Caesar Cipher project (Udemy Day 8)

Context

Repo 008-caesar_cipher (remote: git.tirsystem.com/Tirsvad-Udemy-100_days_of_code) holds only LICENSE (AGPL-3), a Python .gitignore (already ignores .env, .venv), a stub README and an untracked .env (GITEA_TOKEN, GITHUB_PAT, GITHUB_USER). Goal: build the Caesar cipher in the three course parts below, set up the repo metadata, and track steps via PR branches. Files only; no commit/push.

Files to create (inside the repo root)

• pyproject.toml – setuptools backend, requires-python = ">=3.13", no runtime deps, [project.scripts] caesar-cipher = "caesar_cipher.main:main", optional-deps dev = ["pytest"], [tool.pytest.ini_options] pythonpath=["src"], testpaths=["tests"], src layout.
• src/caesar_cipher/__init__.py
• src/caesar_cipher/constants.py – ALPHABET (a–z list), DIRECTION_ENCODE/DECODE, prompts.
• src/caesar_cipher/cipher.py – encrypt(text, shift), decrypt(text, shift), shared _shift(text, shift) using ALPHABET.index and modulo % len(ALPHABET); non-letters pass through unchanged; case preserved. Doxygen comments (## @brief, @param, @return).
• src/caesar_cipher/main.py – interactive loop (direction, text, shift) + main(); python -m caesar_cipher via __main__.py.
• src/caesar_cipher/env.py – tiny .env loader (no python-dotenv dependency; stdlib only) used for tokens; tokens are never printed/committed. The cipher itself needs none; loader exists for repo tooling per "get tokens from .env".
• tests/test_cipher.py – pytest: shift 3, wrap-around (shift > 26), decrypt round-trip, non-letters, case, negative shift.
• docs/ – docs/index.md (usage/design notes) and Doxygen output target docs/doxygen/ (gitignored generated output).
• Doxyfile – PROJECT_NAME, INPUT=src README.md, OUTPUT_DIRECTORY=docs/doxygen, EXTRACT_ALL, OPTIMIZE_OUTPUT_JAVA... (Python-friendly), GENERATE_LATEX=NO.
• .env.example – placeholder variable names only.
• README.md – replace stub using the given template (Overview, Requirements Python ≥3.13, Setup with python -m venv .venv, activation for PowerShell/bash, python -m pip install --upgrade pip, pip install -e ".[dev]"; Run; Tests pytest; License AGPL-3.0 → LICENSE; Links with repo URL, docs/issue-tracker URLs pointing to repo wiki/issues).
• Append docs/doxygen/ to .gitignore.

Steps (one branch + PR each)

1. part-1-encryption – project scaffold (pyproject.toml, .venv docs, Doxyfile, .env.example, README, constants.py) and encrypt(text, shift) using ALPHABET.index + modulo, with tests.
2. part-2-decryption – decrypt(text, shift) (shift by -shift), round-trip tests.
3. part-3-reorganising-code – merge into one shared caesar(text, shift, direction) function, interactive loop in main.py with encode/decode prompt and "go again", non-letters pass through; refactor tests.

Repo description/topics

Via the Gitea API with GITEA_TOKEN from .env (description + topics: python, udemy, 100-days-of-code, caesar-cipher, cryptography, beginner). Outward-facing: run only after explicit go-ahead. No commits/pushes are made by Claude.

Verification

• python -m venv .venv, activate, python -m pip install --upgrade pip, pip install -e ".[dev]"
• pytest passes; python -m caesar_cipher manual run (encode "hello" shift 5 → "mjqqt")
• doxygen Doxyfile (installed) builds without warnings