#!/usr/bin/env python3
import os
import sys
import random
import subprocess
from datetime import date, timedelta
from pathlib import Path

# --- Helper functions ---


def ordinal(n: int) -> str:
    """Return ordinal suffix for a given day number."""
    if 10 <= n % 100 <= 20:
        suffix = "th"
    else:
        suffix = {1: "st", 2: "nd", 3: "rd"}.get(n % 10, "th")
    return f"{n}{suffix}"


def get_latest_entry(base_path: Path):
    """Return the latest existing journal file, or None if none exist."""
    entries = sorted(base_path.glob("*/*/*.md"))
    return entries[-1] if entries else None


def next_date_from_latest(latest_path: Path):
    """Compute the next date after the latest entry."""
    year = int(latest_path.parent.parent.name)
    month = int(latest_path.parent.name)
    day = int(latest_path.stem.split("_")[0])
    d = date(year, month, day)
    return d + timedelta(days=1)


def make_entry_path(base_path: Path, entry_date: date):
    year = entry_date.year
    month = entry_date.month
    day = entry_date.day
    weekday = entry_date.strftime("%A").lower()
    folder = base_path / f"{year}" / f"{month:02d}"
    folder.mkdir(parents=True, exist_ok=True)
    filename = f"{day:02d}_{weekday}.md"
    return folder / filename


def write_entry_header(path: Path, entry_date: date):
    """Create new entry file with date header if it doesn’t exist."""
    if path.exists():
        return
    header = f"# {entry_date.strftime('%A')}, {ordinal(entry_date.day)} {entry_date.strftime('%B %Y')}\n\n"
    path.write_text(header, encoding="utf-8")


def pick_random_entry(base_path: Path):
    """Return path to a random existing entry, or None if none exist."""
    entries = sorted(base_path.glob("*/*/*.md"))
    return random.choice(entries) if entries else None


# --- Main logic ---


def main():
    base_path = Path.cwd()
    base_path.mkdir(exist_ok=True)

    arg = sys.argv[1] if len(sys.argv) > 1 else None
    latest = get_latest_entry(base_path)

    if arg == "-t":
        entry_date = date.today()
        entry_path = make_entry_path(base_path, entry_date)
        write_entry_header(entry_path, entry_date)
    elif arg == "-n":
        if latest:
            entry_date = next_date_from_latest(latest)
        else:
            entry_date = date.today()
        entry_path = make_entry_path(base_path, entry_date)
        write_entry_header(entry_path, entry_date)
    elif arg == "-r":
        entry_path = pick_random_entry(base_path)
        if not entry_path:
            print("No journal entries found to review.")
            sys.exit(1)
        today = date.today()
        review_header = f"\n## {today.strftime('%A')}, {ordinal(today.day)} {today.strftime('%B %Y')}\n\n"
        with entry_path.open("a", encoding="utf-8") as f:
            f.write(review_header)
    else:
        if latest:
            entry_date = next_date_from_latest(latest)
        else:
            entry_date = date.today()
        entry_path = make_entry_path(base_path, entry_date)
        write_entry_header(entry_path, entry_date)

    editor = os.environ.get("EDITOR", "nano")
    subprocess.run([editor, str(entry_path)])


if __name__ == "__main__":
    main()