Wrote the first version for `dnsresolve`

contracts/main.fc

@@ -127,6 +127,7 @@ slice calculate_nft_item_address(int wc, cell state_init) {
 ;; address new_owner
 ;; address response_destination (can be 0 if no response needed)
 ;; coins to forward + coins to pay the fees
+;; The function transfers the nft to the new owner (+forwards some coins) and (optionally) sends the excess balance to `response_destination`
 () transfer_ownership(int my_balance, cell collection_content, cell nft_item_code, int index,
         slice collection_address, slice owner_address, slice sender_address, int query_id, slice in_msg_body,
         int fwd_fees, cell domain, cell auction) impure inline {
@@ -171,6 +172,7 @@ slice calculate_nft_item_address(int wc, cell state_init) {
 }
 
 ;; Create a new item
+;; As described in https://ton.org/tblkch.pdf part 1.7, we send a message to the new address with the initial state
 () deploy_nft_item(int item_index, cell nft_item_code, cell nft_content) impure {
     cell state_init = calculate_nft_item_state_init(item_index, nft_item_code);
     slice nft_address = calculate_nft_item_address(workchain(), state_init);
@@ -180,7 +182,7 @@ slice calculate_nft_item_address(int wc, cell state_init) {
             .store_coins(0)
             .store_uint(4 + 2 + 1, 1 + 4 + 4 + 64 + 32 + 1 + 1 + 1)
             .store_ref(state_init)
-            .store_ref(nft_content);
+            .store_ref(nft_content);  ;; the content of the NFT item, will be treated as the parameter of the first incoming message
     send_raw_message(msg.end_cell(), 64); ;; carry all the remaining value of the inbound message, fee deducted from amount
 }
 
@@ -282,6 +284,12 @@ cell get_nft_content(int index, cell individual_nft_content) method_id {
     return individual_nft_content;
 }
 
+;; Resolving the subdomain - the most important part of the contract
+
+;; category is either `sha256("dns_next_resolver")` or `sha256("wallet")` or `sha256("site")`
+;; Returns two values
+;; * The first is `8m`, the length (in bits) of the prefix of the internal representation of the domain that has been resolved, `0 < m <= n`.
+;; * The second is a `Cell` with the TON DNS record for the required domain in the required category, or the root a `Dictionary` with 256-bit unsigned integer keys (categories) and values equal to the serializations of corresponding TON DNS records.
 (int, cell) dnsresolve(slice subdomain, int category) method_id {
     int subdomain_bits = slice_bits(subdomain);
 
@@ -294,12 +302,9 @@ cell get_nft_content(int index, cell individual_nft_content) method_id {
     cell keyvalue_map = cs~load_dict();
 
     int starts_with_zero_byte = subdomain.preload_int(8) == 0;
-    throw_unless(413, starts_with_zero_byte);
-
-    if (subdomain_bits > 8) { ;; more than "." requested
-        category = "dns_next_resolver"H;
-    }
 
+    if (starts_with_zero_byte & (slice_bits(subdomain) == 8)) { ;; "." requested
+        ;; If it's ".", we behave like an item
         if (category == 0) { ;;  all categories are requested
         return (8, keyvalue_map);
         }
@@ -307,3 +312,17 @@ cell get_nft_content(int index, cell individual_nft_content) method_id {
         (cell value, int found) = keyvalue_map.udict_get_ref?(256, category);
         return (8, value);
     }
+    ;; Otherwise, we behave like a collection
+    if (starts_with_zero_byte) {
+        subdomain~load_uint(8);
+    }
+
+    int top_subdomain_bits = get_top_domain_bits(subdomain);
+    slice top_subdomain = subdomain~load_bits(top_subdomain_bits);
+    int item_index = slice_hash(top_subdomain);
+    cell result = begin_cell()
+            .store_uint(dns_next_resolver_prefix, 16)
+            .store_slice(get_nft_address_by_index(item_index))
+            .end_cell();
+    return (top_subdomain_bits + (starts_with_zero_byte ? 8 : 0), result);
+}