mod(structure): update project structure

Remove examples, add description for design goals in README.md and
apply re-names and naming changes accordingly for the project structure.
Implement a flat hierachry, as the library shall remain pretty simple.

src/color.zig

@@ -0,0 +1,86 @@
+const std = @import("std");
+
+pub const Color = union(enum) {
+    default,
+    index: u8,
+    rgb: [3]u8,
+
+    pub fn eql(a: Color, b: Color) bool {
+        switch (a) {
+            .default => return b == .default,
+            .index => |a_idx| {
+                switch (b) {
+                    .index => |b_idx| return a_idx == b_idx,
+                    else => return false,
+                }
+            },
+            .rgb => |a_rgb| {
+                switch (b) {
+                    .rgb => |b_rgb| return a_rgb[0] == b_rgb[0] and
+                        a_rgb[1] == b_rgb[1] and
+                        a_rgb[2] == b_rgb[2],
+                    else => return false,
+                }
+            },
+        }
+    }
+
+    pub fn rgbFromUint(val: u24) Color {
+        const r_bits = val & 0b11111111_00000000_00000000;
+        const g_bits = val & 0b00000000_11111111_00000000;
+        const b_bits = val & 0b00000000_00000000_11111111;
+        const rgb = [_]u8{
+            @truncate(r_bits >> 16),
+            @truncate(g_bits >> 8),
+            @truncate(b_bits),
+        };
+        return .{ .rgb = rgb };
+    }
+
+    /// parse an XParseColor-style rgb specification into an rgb Color. The spec
+    /// is of the form: rgb:rrrr/gggg/bbbb. Generally, the high two bits will always
+    /// be the same as the low two bits.
+    pub fn rgbFromSpec(spec: []const u8) !Color {
+        var iter = std.mem.splitScalar(u8, spec, ':');
+        const prefix = iter.next() orelse return error.InvalidColorSpec;
+        if (!std.mem.eql(u8, "rgb", prefix)) return error.InvalidColorSpec;
+
+        const spec_str = iter.next() orelse return error.InvalidColorSpec;
+
+        var spec_iter = std.mem.splitScalar(u8, spec_str, '/');
+
+        const r_raw = spec_iter.next() orelse return error.InvalidColorSpec;
+        if (r_raw.len != 4) return error.InvalidColorSpec;
+
+        const g_raw = spec_iter.next() orelse return error.InvalidColorSpec;
+        if (g_raw.len != 4) return error.InvalidColorSpec;
+
+        const b_raw = spec_iter.next() orelse return error.InvalidColorSpec;
+        if (b_raw.len != 4) return error.InvalidColorSpec;
+
+        const r = try std.fmt.parseUnsigned(u8, r_raw[2..], 16);
+        const g = try std.fmt.parseUnsigned(u8, g_raw[2..], 16);
+        const b = try std.fmt.parseUnsigned(u8, b_raw[2..], 16);
+
+        return .{
+            .rgb = [_]u8{ r, g, b },
+        };
+    }
+
+    test "rgbFromSpec" {
+        const spec = "rgb:aaaa/bbbb/cccc";
+        const actual = try rgbFromSpec(spec);
+        switch (actual) {
+            .rgb => |rgb| {
+                try std.testing.expectEqual(0xAA, rgb[0]);
+                try std.testing.expectEqual(0xBB, rgb[1]);
+                try std.testing.expectEqual(0xCC, rgb[2]);
+            },
+            else => try std.testing.expect(false),
+        }
+    }
+};
+
+test {
+    _ = Color;
+}