Add UI core color parser tests

src/ui_core/color.cpp

@@ -0,0 +1,95 @@
+#include "ui_core/color.h"
+
+namespace pp::ui {
+
+namespace {
+
+[[nodiscard]] int hex_value(char ch) noexcept
+{
+    if (ch >= '0' && ch <= '9') {
+        return ch - '0';
+    }
+    if (ch >= 'a' && ch <= 'f') {
+        return 10 + (ch - 'a');
+    }
+    if (ch >= 'A' && ch <= 'F') {
+        return 10 + (ch - 'A');
+    }
+    return -1;
+}
+
+[[nodiscard]] pp::foundation::Result<std::uint8_t> parse_hex_byte(std::string_view value) noexcept
+{
+    const auto high = hex_value(value[0]);
+    const auto low = hex_value(value[1]);
+    if (high < 0 || low < 0) {
+        return pp::foundation::Result<std::uint8_t>::failure(
+            pp::foundation::Status::invalid_argument("color contains a non-hex character"));
+    }
+
+    return pp::foundation::Result<std::uint8_t>::success(
+        static_cast<std::uint8_t>((high << 4) | low));
+}
+
+[[nodiscard]] pp::foundation::Result<std::uint8_t> parse_hex_nibble(char value) noexcept
+{
+    const auto nibble = hex_value(value);
+    if (nibble < 0) {
+        return pp::foundation::Result<std::uint8_t>::failure(
+            pp::foundation::Status::invalid_argument("color contains a non-hex character"));
+    }
+
+    return pp::foundation::Result<std::uint8_t>::success(
+        static_cast<std::uint8_t>((nibble << 4) | nibble));
+}
+
+}
+
+pp::foundation::Result<ColorRgba8> parse_hex_color(std::string_view value) noexcept
+{
+    if (value.empty()) {
+        return pp::foundation::Result<ColorRgba8>::failure(
+            pp::foundation::Status::invalid_argument("color must not be empty"));
+    }
+
+    if (value.front() != '#') {
+        return pp::foundation::Result<ColorRgba8>::failure(
+            pp::foundation::Status::invalid_argument("color must start with #"));
+    }
+
+    const auto hex = value.substr(1);
+    if (hex.size() != 3U && hex.size() != 4U && hex.size() != 6U && hex.size() != 8U) {
+        return pp::foundation::Result<ColorRgba8>::failure(
+            pp::foundation::Status::invalid_argument("color must use #rgb, #rgba, #rrggbb, or #rrggbbaa"));
+    }
+
+    ColorRgba8 color;
+    if (hex.size() == 3U || hex.size() == 4U) {
+        const auto r = parse_hex_nibble(hex[0]);
+        const auto g = parse_hex_nibble(hex[1]);
+        const auto b = parse_hex_nibble(hex[2]);
+        const auto a = hex.size() == 4U ? parse_hex_nibble(hex[3])
+                                        : pp::foundation::Result<std::uint8_t>::success(255);
+        if (!r || !g || !b || !a) {
+            return pp::foundation::Result<ColorRgba8>::failure(
+                pp::foundation::Status::invalid_argument("color contains a non-hex character"));
+        }
+        color = ColorRgba8 { .r = r.value(), .g = g.value(), .b = b.value(), .a = a.value() };
+        return pp::foundation::Result<ColorRgba8>::success(color);
+    }
+
+    const auto r = parse_hex_byte(hex.substr(0, 2));
+    const auto g = parse_hex_byte(hex.substr(2, 2));
+    const auto b = parse_hex_byte(hex.substr(4, 2));
+    const auto a = hex.size() == 8U ? parse_hex_byte(hex.substr(6, 2))
+                                    : pp::foundation::Result<std::uint8_t>::success(255);
+    if (!r || !g || !b || !a) {
+        return pp::foundation::Result<ColorRgba8>::failure(
+            pp::foundation::Status::invalid_argument("color contains a non-hex character"));
+    }
+
+    color = ColorRgba8 { .r = r.value(), .g = g.value(), .b = b.value(), .a = a.value() };
+    return pp::foundation::Result<ColorRgba8>::success(color);
+}
+
+}

src/ui_core/color.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "foundation/result.h"
+
+#include <cstdint>
+#include <string_view>
+
+namespace pp::ui {
+
+struct ColorRgba8 {
+    std::uint8_t r = 0;
+    std::uint8_t g = 0;
+    std::uint8_t b = 0;
+    std::uint8_t a = 255;
+};
+
+[[nodiscard]] pp::foundation::Result<ColorRgba8> parse_hex_color(std::string_view value) noexcept;
+
+}