#!/usr/bin/env python3
"""Regenerate the logo mask in site.css from logo.txt.

The site draws the logo as geometry -- an SVG of rects used as a CSS mask --
because the half-block glyphs the ascii original is typed in do not survive
every platform's font fallback (Android's default monospace has none of
them). This script turns logo.txt into that SVG and splices it into
site.css's --logo-svg custom property in place.

Each character cell is 6x10 units; ▀ fills the top half, ▄ the bottom, █
both. Horizontal runs merge into single rects, and every rect is drawn with
a little vertical overlap (EPS): stacked halves land on fractional pixels
when the mask scales, and the seams read as pinstripes without it.
"""

import os
import re
import sys

HERE = os.path.dirname(os.path.abspath(__file__))
LOGO = os.path.join(os.path.dirname(HERE), "logo.txt")
CSS = os.path.join(HERE, "site.css")

CW, CH, EPS = 6, 10, 0.4


def runs(row, want):
    out, start = [], None
    for i, ch in enumerate(row + " "):
        hit = ch in want
        if hit and start is None:
            start = i
        if not hit and start is not None:
            out.append((start, i))
            start = None
    return out


def num(v):
    return f"{v:.1f}".rstrip("0").rstrip(".")


lines = open(LOGO).read().rstrip("\n").splitlines()
rects = []
for j, row in enumerate(lines):
    for a, b in runs(row, "\u2580\u2588"):
        rects.append((a * CW, j * CH - EPS, (b - a) * CW, CH / 2 + 2 * EPS))
    for a, b in runs(row, "\u2584\u2588"):
        rects.append((a * CW, j * CH + CH / 2 - EPS, (b - a) * CW, CH / 2 + 2 * EPS))

w = max(len(l) for l in lines) * CW
h = len(lines) * CH
body = "".join(
    f"<rect x='{num(x)}' y='{num(y)}' width='{num(rw)}' height='{num(rh)}'/>"
    for x, y, rw, rh in rects
)
svg = f"<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 {w} {h}'>{body}</svg>"
uri = svg.replace("<", "%3C").replace(">", "%3E").replace("#", "%23")

css = open(CSS).read()
out = re.sub(
    r'--logo-svg: url\("data:image/svg\+xml,[^"]*"\);',
    f'--logo-svg: url("data:image/svg+xml,{uri}");',
    css,
    count=1,
)
if out == css and "--logo-svg" not in css:
    sys.exit("gen-logo-mask: no --logo-svg property in site.css to replace")
open(CSS, "w").write(out)
print(
    f"gen-logo-mask: {len(rects)} rects, viewBox 0 0 {w} {h}, "
    f"{len(uri)} URI bytes -> site.css"
)