"""把 drawio 框图渲染成 PNG，供原理图第一页当插图（n10 硬要求）。

两种 drawio 格式都吃：
  * SVG 外壳（drawio MCP / 导出的 .drawio.svg）：headless Chrome 直接截 SVG；
  * 纯 mxfile XML（drawio 桌面版存的 .drawio）：套一层 HTML，用 diagrams.net 的
    viewer-static.min.js 在 headless Chrome 里渲染后截图（需要能上网取 JS）。

不用 draw.io.exe --export：G-0022 实测它在 Windows 上报 input file not found，还会挂起。

    python -m schgen.diagram <in.drawio> <out.png> [--scale 2]
"""
import html
import io
import os
import re
import struct
import subprocess
import sys
import tempfile

from .env import chrome

VIEWER_JS = "https://viewer.diagrams.net/js/viewer-static.min.js"


def _png_size(p):
    d = io.open(p, "rb").read(32)
    return struct.unpack(">II", d[16:24])


def _page_size(xml):
    m = re.search(r'pageWidth="(\d+)"[^>]*pageHeight="(\d+)"', xml)
    if m:
        return int(m.group(1)), int(m.group(2))
    return 1600, 1200


def _bounds(xml):
    """所有顶点几何的外包框，用来裁掉页面空白。"""
    xs, ys = [], []
    for m in re.finditer(r'<mxGeometry\s+([^>]*?)/?>', xml):
        a = dict(re.findall(r'(\w+)="([^"]*)"', m.group(1)))
        if a.get("relative") == "1" or "width" not in a:
            continue
        x, y = float(a.get("x", 0)), float(a.get("y", 0))
        w, h = float(a["width"]), float(a["height"])
        xs += [x, x + w]; ys += [y, y + h]
    if not xs:
        return None
    return min(xs), min(ys), max(xs), max(ys)


def render(src, png, scale=2, margin=20):
    raw = io.open(src, encoding="utf-8", errors="replace").read()
    tmpdir = tempfile.mkdtemp(prefix="kf_diag_")
    if raw.lstrip().startswith("<svg") or "<svg" in raw[:500]:
        m = re.search(r'<svg[^>]*\swidth="([\d.]+)(?:px)?"[^>]*\sheight="([\d.]+)', raw)
        w, h = (int(float(m.group(1))), int(float(m.group(2)))) if m else (1600, 1200)
        url = "file:///" + os.path.abspath(src).replace("\\", "/")
        budget = []
    else:
        xml = raw
        bb = _bounds(xml)
        if bb:
            w, h = int(bb[2] - bb[0] + 2 * margin), int(bb[3] - bb[1] + 2 * margin)
        else:
            w, h = _page_size(xml)
        cfg = '{"highlight":"#0000ff","nav":false,"resize":false,"toolbar":"","edit":null,' \
              '"lightbox":false,"border":%d,"xml":%s}' % (margin, _json_str(xml))
        page = ('<!DOCTYPE html><html><head><meta charset="utf-8">'
                '<style>html,body{margin:0;padding:0;background:#fff}</style></head><body>'
                '<div class="mxgraph" style="max-width:100%%" data-mxgraph="%s"></div>'
                '<script src="%s"></script></body></html>' % (html.escape(cfg, quote=True), VIEWER_JS))
        hp = os.path.join(tmpdir, "d.html")
        io.open(hp, "w", encoding="utf-8").write(page)
        url = "file:///" + hp.replace("\\", "/")
        budget = ["--virtual-time-budget=15000"]
    if os.path.exists(png):
        os.remove(png)
    os.makedirs(os.path.dirname(os.path.abspath(png)), exist_ok=True)
    cmd = [chrome(), "--headless", "--disable-gpu", "--hide-scrollbars",
           "--force-device-scale-factor=%d" % scale, "--default-background-color=FFFFFFFF",
           "--window-size=%d,%d" % (w, h), "--screenshot=%s" % os.path.abspath(png)] + budget + [url]
    subprocess.run(cmd, check=True, capture_output=True, timeout=120)
    if not os.path.exists(png):
        raise SystemExit("截图失败：%s" % png)
    pw, ph = _png_size(png)
    print("框图 -> %s  %dx%d px（KiCad 按 300DPI 解释：scale=1 时 %.0fx%.0f mm）"
          % (png, pw, ph, pw / 300.0 * 25.4, ph / 300.0 * 25.4))
    return png


def _json_str(s):
    import json
    return json.dumps(s)


if __name__ == "__main__":
    a = sys.argv[1:]
    sc = 2
    if "--scale" in a:
        i = a.index("--scale"); sc = int(a[i + 1]); del a[i:i + 2]
    render(a[0], a[1], scale=sc)