#!/usr/bin/env python3
"""Encode a .drawio XML file into a diagrams.net browser URL.

Used as the browser fallback when the draw.io desktop CLI is unavailable.
The diagram XML is carried in the URL fragment (after `#`), so nothing is
uploaded to any server.

Two modes:
  (default)  read-only viewer  -> https://viewer.diagrams.net/...#R<payload>
  --edit     editable editor   -> https://app.diagrams.net/...#create=<payload>

Usage: python3 encode_drawio_url.py [--edit] <path/to/input.drawio>
"""
import base64
import json
import sys
import urllib.parse
import zlib


def _deflate_b64(xml: str) -> str:
    # draw.io's loader runs JS decodeURIComponent on the inflated string, so the
    # XML MUST be percent-encoded (encodeURIComponent) BEFORE deflate — otherwise
    # a literal `%` or any non-ASCII (e.g. CJK) label makes the browser throw
    # "URI malformed" and the diagram never opens. encodeURIComponent leaves
    # only A-Za-z0-9 and -_.!~*'() unescaped, which `quote` reproduces here.
    pre = urllib.parse.quote(xml, safe="!~*'()")
    c = zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS)
    compressed = c.compress(pre.encode("utf-8")) + c.flush()
    # Standard base64 (atob rejects url-safe -/_); strip newlines.
    return base64.b64encode(compressed).decode("utf-8").replace("\n", "")


def encode(xml: str) -> str:
    """Read-only viewer URL (mxGraph `#R` raw-inflate format)."""
    return (
        "https://viewer.diagrams.net/?tags=%7B%7D&lightbox=1&edit=_blank#R"
        + urllib.parse.quote(_deflate_b64(xml), safe="")
    )


def edit_url(xml: str) -> str:
    """Editable editor URL — opens directly in the draw.io editor."""
    payload = json.dumps({"type": "xml", "compressed": True, "data": _deflate_b64(xml)})
    return (
        "https://app.diagrams.net/?grid=0&pv=0&border=10&edit=_blank#create="
        + urllib.parse.quote(payload, safe="")
    )


if __name__ == "__main__":
    args = [a for a in sys.argv[1:] if a != "--edit"]
    if len(args) != 1:
        print("usage: encode_drawio_url.py [--edit] <path>", file=sys.stderr)
        sys.exit(2)
    with open(args[0], "r", encoding="utf-8") as f:
        xml = f.read()
    print(edit_url(xml) if "--edit" in sys.argv[1:] else encode(xml))