Add gitlab webhook support

ops_bot/util/contrast.py

@@ -0,0 +1,62 @@
+# Based on https://github.com/gsnedders/wcag-contrast-ratio
+# Copyright (c) 2015 Geoffrey Sneddon
+# Copyright (c) 2019 Tulir Asokan
+# MIT license
+from typing import Tuple
+
+RGB = Tuple[float, float, float]
+
+
+def hex_to_rgb(color: str) -> RGB:
+    color = color.lstrip("#")
+    if len(color) != 3 and len(color) != 6:
+        raise ValueError("Invalid hex length")
+    step = 1 if len(color) == 3 else 2
+    try:
+        r = int(color[0:step], 16)
+        g = int(color[step:2 * step], 16)
+        b = int(color[2 * step:3 * step], 16)
+    except ValueError as e:
+        raise ValueError("Invalid hex value") from e
+    return r / 255, g / 255, b / 255
+
+
+def rgb_to_hex(rgb: RGB) -> str:
+    r, g, b = rgb
+    r = int(r * 255)
+    g = int(g * 255)
+    b = int(b * 255)
+    return f"{r:02x}{g:02x}{b:02x}"
+
+
+def contrast(rgb1: RGB, rgb2: RGB) -> float:
+    for r, g, b in (rgb1, rgb2):
+        if not 0.0 <= r <= 1.0:
+            raise ValueError(f"r {r} is out of valid range (0.0 - 1.0)")
+        if not 0.0 <= g <= 1.0:
+            raise ValueError(f"g {g} is out of valid range (0.0 - 1.0)")
+        if not 0.0 <= b <= 1.0:
+            raise ValueError(f"b {b} is out of valid range (0.0 - 1.0)")
+
+    l1 = _relative_luminance(*rgb1)
+    l2 = _relative_luminance(*rgb2)
+
+    if l1 > l2:
+        return (l1 + 0.05) / (l2 + 0.05)
+    else:
+        return (l2 + 0.05) / (l1 + 0.05)
+
+
+def _relative_luminance(r: float, g: float, b: float) -> float:
+    r = _linearize(r)
+    g = _linearize(g)
+    b = _linearize(b)
+
+    return 0.2126 * r + 0.7152 * g + 0.0722 * b
+
+
+def _linearize(v: float) -> float:
+    if v <= 0.03928:
+        return v / 12.92
+    else:
+        return ((v + 0.055) / 1.055) ** 2.4