terminal sgr attribute parsing

src/terminal/main.zig

@@ -1,6 +1,7 @@
 const stream = @import("stream.zig");
 const ansi = @import("ansi.zig");
 const csi = @import("csi.zig");
+const sgr = @import("sgr.zig");
 
 pub const Terminal = @import("Terminal.zig");
 pub const Parser = @import("Parser.zig");
@@ -8,12 +9,14 @@ pub const Stream = stream.Stream;
 pub const Mode = ansi.Mode;
 pub const EraseDisplay = csi.EraseDisplay;
 pub const EraseLine = csi.EraseLine;
+pub const Attribute = sgr.Attribute;
 
 // Not exported because they're just used for tests.
 
 test {
     _ = ansi;
     _ = csi;
+    _ = sgr;
     _ = stream;
     _ = Parser;
     _ = Terminal;

src/terminal/sgr.zig

@@ -0,0 +1,113 @@
+//! SGR (Select Graphic Rendition) attribute parsing and types.
+
+const std = @import("std");
+const testing = std.testing;
+
+/// Attribute type for SGR
+pub const Attribute = union(enum) {
+    /// Unset all attributes
+    unset: void,
+
+    /// Unknown attribute, the raw CSI command parameters are here.
+    unknown: []const u16,
+
+    /// Set foreground color as RGB values.
+    direct_color_fg: RGB,
+
+    /// Set background color as RGB values.
+    direct_color_bg: RGB,
+
+    pub const RGB = struct {
+        r: u8,
+        g: u8,
+        b: u8,
+    };
+};
+
+/// Parse a set of parameters to a SGR command into an attribute.
+pub fn parse(params: []const u16) Attribute {
+    // No parameters means unset
+    if (params.len == 0) return .{ .unset = {} };
+
+    switch (params[0]) {
+        0 => if (params.len == 1) return .{ .unset = {} },
+
+        38 => if ((params.len == 5 or params.len == 6) and params[1] == 2) {
+            // In the 6-len form, ignore the 3rd param.
+            const rgb = params[params.len - 3 .. params.len];
+
+            // We use @truncate because the value should be 0 to 255. If
+            // it isn't, the behavior is undefined so we just... truncate it.
+            return .{
+                .direct_color_fg = .{
+                    .r = @truncate(u8, rgb[0]),
+                    .g = @truncate(u8, rgb[1]),
+                    .b = @truncate(u8, rgb[2]),
+                },
+            };
+        },
+
+        48 => if ((params.len == 5 or params.len == 6) and params[1] == 2) {
+            // In the 6-len form, ignore the 3rd param.
+            const rgb = params[params.len - 3 .. params.len];
+
+            // We use @truncate because the value should be 0 to 255. If
+            // it isn't, the behavior is undefined so we just... truncate it.
+            return .{
+                .direct_color_bg = .{
+                    .r = @truncate(u8, rgb[0]),
+                    .g = @truncate(u8, rgb[1]),
+                    .b = @truncate(u8, rgb[2]),
+                },
+            };
+        },
+
+        else => {},
+    }
+
+    return .{ .unknown = params };
+}
+
+test "sgr: parse" {
+    try testing.expect(parse(&[_]u16{}) == .unset);
+    try testing.expect(parse(&[_]u16{0}) == .unset);
+    try testing.expect(parse(&[_]u16{ 0, 1 }) == .unknown);
+
+    {
+        const v = parse(&[_]u16{ 38, 2, 40, 44, 52 });
+        try testing.expect(v == .direct_color_fg);
+        try testing.expectEqual(@as(u8, 40), v.direct_color_fg.r);
+        try testing.expectEqual(@as(u8, 44), v.direct_color_fg.g);
+        try testing.expectEqual(@as(u8, 52), v.direct_color_fg.b);
+    }
+
+    {
+        const v = parse(&[_]u16{ 38, 2, 22, 40, 44, 52 });
+        try testing.expect(v == .direct_color_fg);
+        try testing.expectEqual(@as(u8, 40), v.direct_color_fg.r);
+        try testing.expectEqual(@as(u8, 44), v.direct_color_fg.g);
+        try testing.expectEqual(@as(u8, 52), v.direct_color_fg.b);
+    }
+
+    try testing.expect(parse(&[_]u16{ 38, 2, 44, 52 }) == .unknown);
+    try testing.expect(parse(&[_]u16{ 38, 2, 22, 22, 40, 44, 52 }) == .unknown);
+
+    {
+        const v = parse(&[_]u16{ 48, 2, 40, 44, 52 });
+        try testing.expect(v == .direct_color_bg);
+        try testing.expectEqual(@as(u8, 40), v.direct_color_bg.r);
+        try testing.expectEqual(@as(u8, 44), v.direct_color_bg.g);
+        try testing.expectEqual(@as(u8, 52), v.direct_color_bg.b);
+    }
+
+    {
+        const v = parse(&[_]u16{ 48, 2, 22, 40, 44, 52 });
+        try testing.expect(v == .direct_color_bg);
+        try testing.expectEqual(@as(u8, 40), v.direct_color_bg.r);
+        try testing.expectEqual(@as(u8, 44), v.direct_color_bg.g);
+        try testing.expectEqual(@as(u8, 52), v.direct_color_bg.b);
+    }
+
+    try testing.expect(parse(&[_]u16{ 48, 2, 44, 52 }) == .unknown);
+    try testing.expect(parse(&[_]u16{ 48, 2, 22, 22, 40, 44, 52 }) == .unknown);
+}