feat: Added command structure.

src/root.zig

@@ -2,17 +2,92 @@
 const std = @import("std");
 const Io = std.Io;
 
-/// This is a documentation comment to explain the `printAnotherMessage` function below.
-///
-/// Accepting an `Io.Writer` instance is a handy way to write reusable code.
-pub fn printAnotherMessage(writer: *Io.Writer) Io.Writer.Error!void {
-    try writer.print("Run `zig build test` to run the tests.\n", .{});
+pub const root: Command = .new(.{
+    .name = "envr",
+    .subcommands = &[_]CommandOptions{.{ .name = "version" }},
+});
+
+const CommandOptions = struct {
+    name: []const u8,
+    short: ?[]const u8 = null,
+    long: ?[]const u8 = null,
+    subcommands: []const CommandOptions = &[0]CommandOptions{},
+
+    fn as_enum(self: @This()) type {
+        var field_names: [self.subcommands.len + 1][]const u8 = undefined;
+        var field_values: [self.subcommands.len + 1]u32 = undefined;
+
+        field_names[0] = self.name;
+        field_values[0] = 0;
+
+        inline for (self.subcommands, 1..) |cmd, idx| {
+            field_names[idx] = cmd.name;
+            field_values[idx] = idx;
+        }
+
+        return @Enum(
+            u32,
+            .exhaustive,
+            &field_names,
+            &field_values,
+        );
+    }
+};
+
+pub const Command = struct {
+    name: []const u8,
+    short: ?[]const u8 = null,
+    long: ?[]const u8 = null,
+    subcommands: []const Command = &[0]Command{},
+    Type: type,
+
+    pub fn new(cmd: CommandOptions) Command {
+        const subcommands: [cmd.subcommands.len]Command = blk: {
+            var result: [cmd.subcommands.len]Command = undefined;
+            inline for (cmd.subcommands, 0..) |sub, idx| {
+                result[idx] = new(sub);
+            }
+            break :blk result;
+        };
+
+        return .{
+            .name = cmd.name,
+            .short = cmd.short,
+            .long = cmd.long,
+            .subcommands = &subcommands,
+            .Type = cmd.as_enum(),
+        };
+    }
+
+    pub fn parse(comptime self: @This(), args: []const []const u8) ParseError!self.Type {
+        if (args.len == 0) {
+            return ParseError.InvalidType;
+        }
+        const target = args[0];
+
+        inline for (self.subcommands, 1..) |cmd, idx| {
+            if (std.mem.eql(u8, target, cmd.name)) {
+                return @enumFromInt(idx);
+            }
+        }
+
+        return @enumFromInt(0);
+    }
+};
+
+pub const ParseError = error{
+    InvalidType,
+};
+
+test "enum type" {
+    const got: root.Type = @enumFromInt(1);
+
+    try std.testing.expectEqual(.version, got);
 }
 
-pub fn add(a: i32, b: i32) i32 {
-    return a + b;
-}
+test "parse version" {
+    const args = &[_][]const u8{"version"};
+    const cmd = root.parse(args);
 
-test "basic add functionality" {
-    try std.testing.expect(add(3, 7) == 10);
+    try std.testing.expectEqual(.version, cmd);
 }