#!/usr/bin/env python3

"""

Replace the Mermaid block between COMPOSE_MERMAID_AUTO_START/END in README.md

using docker-compose-viz-mermaid (docker-compose.yml → Mermaid text).

Requires Docker. From repo root:

python scripts/update_compose_mermaid_readme.py

Environment:

COMPOSE_VIZ_IMAGE — override image (default: derlin/docker-compose-viz-mermaid)

"""

from __future__ import annotations

import os

import re

import subprocess

import sys

from pathlib import Path

ROOT = Path(__file__).resolve().parent.parent

README = ROOT / "README.md"

COMPOSE_REL = "docker-compose.yml"

IMAGE = os.environ.get("COMPOSE_VIZ_IMAGE", "derlin/docker-compose-viz-mermaid")

START = "<!-- COMPOSE_MERMAID_AUTO_START -->"

END = "<!-- COMPOSE_MERMAID_AUTO_END -->"

def run_viz() -> str:

compose = ROOT / COMPOSE_REL

if not compose.is_file():

sys.exit(f"Missing {compose}")

cmd = [

"docker",

"run",

"--rm",

"-v",

f"{ROOT}:/work",

"-w",

"/work",

IMAGE,

COMPOSE_REL,

"-f",

"text",

]

r = subprocess.run(cmd, capture_output=True, text=True)

if r.returncode != 0:

msg = r.stderr.strip() or r.stdout.strip() or "unknown error"

sys.exit(f"docker-compose-viz-mermaid failed ({r.returncode}): {msg}")

return r.stdout.rstrip("\n")

def main() -> None:

text = README.read_text(encoding="utf-8")

if START not in text or END not in text:

sys.exit(f"{README} must contain {START!r} and {END!r}")

mermaid_body = run_viz().strip()

if not mermaid_body:

sys.exit("Visualizer returned empty Mermaid output")

block = f"```mermaid\n{mermaid_body}\n```"

pattern = re.compile(re.escape(START) + r"\s*.*?\s*" + re.escape(END), re.DOTALL)

new_text, n = pattern.subn(f"{START}\n{block}\n{END}", text, count=1)

if n != 1:

sys.exit("Could not replace exactly one marked region (check markers are unique and paired).")

if new_text == text:

print("README.md already up to date.")

return

README.write_text(new_text, encoding="utf-8", newline="\n")

print("Updated README.md Mermaid diagram.")

if __name__ == "__main__":

main()