input domain parsing

src/mdns.zig

@@ -1,8 +1,8 @@
 const std = @import("std");
 const util = @import("util.zig");
 
-pub fn get_mdns(domain: [:0]const u8) !util.IPs {
-    std.debug.print("{s}\n", .{domain});
+pub fn get_mdns(domain: util.Domain) !util.IPs {
+    std.debug.print("{}\n", .{domain});
     return util.IPs{
         .v4 = "stub v4",
         .v6 = "stub v6",

src/util.zig

@@ -1,15 +1,45 @@
 const std = @import("std");
 
+const ArgError = error{
+    NotEnoughArgs,
+    BadDomain,
+};
+
 pub const IPs = struct {
     v4: [:0]const u8,
     v6: [:0]const u8,
 };
 
+pub const Domain = struct {
+    name: [:0]const u8,
+    labels: u8,
+};
+
 pub fn check_perms() !void {
     var f = try std.fs.openFileAbsolute("/etc/hosts", .{ .mode = .write_only });
     f.close();
 }
 
-pub fn get_input() ![:0]const u8 {
-    return "stub";
+pub fn get_input() !Domain {
+    var args = std.process.args();
+    _ = args.next();
+    const domain = args.next() orelse return ArgError.NotEnoughArgs;
+    return check_domain(domain);
+}
+
+fn check_domain(domain_str: [:0]const u8) !Domain {
+    var domain = Domain{
+        .name = domain_str,
+        .labels = 0,
+    };
+    var labels = std.mem.split(u8, domain_str, ".");
+    var last: []const u8 = "";
+    while (labels.next()) |segment| {
+        last = segment;
+        domain.labels += 1;
+    }
+    if (domain.labels <= 1 or !std.mem.eql(u8, last, "local")) {
+        return ArgError.BadDomain;
+    }
+    return domain;
 }