#!/usr/bin/env python3

import os
from collections.abc import Iterator


def good_file_paths(top_dir: str = ".") -> Iterator[str]:
    for dir_path, dir_names, filenames in os.walk(top_dir):
        dir_names[:] = [
            d
            for d in dir_names
            if d != "scripts" and d[0] not in "._" and "venv" not in d
        ]
        for filename in filenames:
            if filename == "__init__.py":
                continue
            if os.path.splitext(filename)[1] in (".py", ".ipynb"):
                yield os.path.join(dir_path, filename).lstrip("./")


def md_prefix(indent: int) -> str:
    """
    Markdown prefix based on indent for bullet points

    >>> md_prefix(0)
    '\\n##'
    >>> md_prefix(1)
    '  *'
    >>> md_prefix(2)
    '    *'
    >>> md_prefix(3)
    '      *'
    """
    return f"{indent * '  '}*" if indent else "\n##"


def md_anchor(heading: str) -> str:
    """
    GitHub-style anchor slug for a section heading, so the table of contents
    can link to it.

    >>> md_anchor("Audio Filters")
    'audio-filters'
    >>> md_anchor("Bit Manipulation")
    'bit-manipulation'
    >>> md_anchor("Computer Vision")
    'computer-vision'
    """
    return heading.strip().lower().replace(" ", "-")


def print_path(old_path: str, new_path: str) -> str:
    old_parts = old_path.split(os.sep)
    for i, new_part in enumerate(new_path.split(os.sep)):
        if (i + 1 > len(old_parts) or old_parts[i] != new_part) and new_part:
            title = new_part.replace("_", " ").title()
            if i == 0:
                # Link each top-level section heading to its algorithm
                # directory, so readers can click the title and jump straight
                # to the folder (no leading pound sign, unlike the ToC links).
                print(f"{md_prefix(i)} [{title}]({new_part})")
            else:
                print(f"{md_prefix(i)} {title}")
    return new_path


def print_directory_md(top_dir: str = ".") -> None:
    filepaths = sorted(good_file_paths(top_dir))

    # Top-level sections, in the order they appear, for the table of contents.
    sections = list(
        dict.fromkeys(
            fp.split(os.sep)[0].replace("_", " ").title()
            for fp in filepaths
            if os.sep in fp
        )
    )
    print("## Table of Contents")
    for index, section in enumerate(sections, start=1):
        # Numbered list so the final number is the total count of algorithm
        # folders, visible at a glance.
        print(f"{index}. [{section}](#{md_anchor(section)})")

    old_path = ""
    for filepath in filepaths:
        filepath, filename = os.path.split(filepath)
        if filepath != old_path:
            old_path = print_path(old_path, filepath)
        indent = (filepath.count(os.sep) + 1) if filepath else 0
        url = f"{filepath}/{filename}".replace(" ", "%20")
        filename = os.path.splitext(filename.replace("_", " ").title())[0]
        print(f"{md_prefix(indent)} [{filename}]({url})")


if __name__ == "__main__":
    print_directory_md(".")