AENSWrappingCustomTTL.aes

@compiler >= 7

include "../interfaces/IAEX141.aes"
include "../interfaces/IAEX141NFTReceiver.aes"
include "../interfaces/IAENSWrapping.aes"

include "Pair.aes"

main contract AENSWrappingCustomTTL : IAEX141, IAENSWrapping =

    datatype metadata_type = URL | OBJECT_ID | MAP
    datatype metadata = MetadataIdentifier(string) | MetadataMap(map(string, string))

    record meta_info =
        { name: string
        , symbol: string
        , base_url: option(string)
        , metadata_type : metadata_type }

    record nft_data =
        { id: int
        , owner: address
        , owner_config: option(config)
        , names: list(string)
        , expiration_height: int }

    record config =
        { reward: int
        , reward_block_window: int
        , emergency_reward: int
        , emergency_reward_block_window: int
        , can_receive_from_others: bool
        , burnable_if_expired_or_empty: bool }

    record state =
        { owner: address
        , meta_info: meta_info
        , token_to_owner: map(int, address)
        , owner_to_tokens: map(address, Set.set(int))
        , name_to_token: map(string, int)
        , token_to_name_expiration: map(int, Chain.ttl)
        , token_to_config: map(int, config)
        , account_to_config: map(address, config)
        , account_to_reward_pool: map(address, int)
        , name_limit: int
        , max_name_ttl: Chain.ttl
        , balances: map(address, int)
        , approvals: map(int, address)
        , operators: map(address, map(address, bool))
        , metadata: map(int, metadata)
        , total_supply: int
        , counter: int }

    datatype event
        = Transfer(address, address, int)
        | Approval(address, address, int, string)
        | ApprovalForAll(address, address, string)
        // extension "mintable"
        | Mint(address, int)
        // extension "burnable"
        | Burn(address, int)
        // AENS Wrapping
        // name, nft_id, owner, new_ttl
        | NameWrap(string, int, address, int)
        // name, nft_id, current_owner, recipient
        | NameUnwrap(string, int, address, address)
        // name, nft_id, new_ttl, caller
        | NameExtend(string, int, int, address)
        // name, nft_id_old, nft_id_new
        | NameTransfer(string, int, int)
        // name, nft_id
        | NameRevoke(string, int)
        // nft_id, caller, reward
        | Reward(int, address, int)

    stateful entrypoint init(ttl: int) =
        { owner = Contract.creator, // TODO owner related actions (e.g. update max_name_ttl, name_limit or migration related actions)
          meta_info = { name = "Wrapped AENS", symbol = "WAENS", base_url = None, metadata_type = MAP },
          token_to_owner = {},
          owner_to_tokens = {},
          name_to_token = {},
          token_to_name_expiration = {},
          token_to_config = {},
          account_to_config = {},
          account_to_reward_pool = {},
          name_limit = 100,
          max_name_ttl = RelativeTTL(ttl),
          balances = {},
          approvals = {},
          operators = {},
          metadata = {},
          total_supply = 0,
          counter = 1 }

    entrypoint aex141_extensions() : list(string) =
        ["mintable", "burnable"]

    entrypoint meta_info() : meta_info =
        state.meta_info

    entrypoint metadata(token_id: int) : option(metadata) =
        Map.lookup(token_id, state.metadata)

    entrypoint total_supply() : int =
        state.total_supply

    entrypoint balance(owner: address) : option(int) =
        Map.lookup(owner, state.balances)

    entrypoint owner(token_id: int) : option(address) =
        Map.lookup(token_id, state.token_to_owner)

    stateful entrypoint transfer(to: address, token_id: int, data: option(string)) =
        __transfer_single_nft(to, token_id, data)

    stateful entrypoint transfer_to_contract(token_id: int) =
        let to = Call.caller
        require(Address.is_contract(to), "CALLER_MUST_BE_A_CONTRACT")
        let from = require_authorized(token_id)
        require(from != to, "SENDER_MUST_NOT_BE_RECEIVER")
        __remove_approval(token_id)
        put(state{ balances[from] @balance1 = balance1 - 1
            , balances[to = 0] @balance2 = balance2 + 1
            , token_to_owner[token_id] = to
            , owner_to_tokens[from] @from_tokens = Set.delete(token_id, from_tokens)
            , owner_to_tokens[to = Set.new()] @to_tokens = Set.insert(token_id, to_tokens)
            , token_to_config @token_config = Map.delete(token_id, token_config) })
        Chain.event(Transfer(from, to, token_id))

    stateful entrypoint approve(approved: address, token_id: int, enabled: bool) =
        require_authorized(token_id)
        if(enabled)
            put(state{approvals[token_id] = approved})
        else
            __remove_approval(token_id)
        Chain.event(Approval(Call.caller, approved, token_id, bool_to_string(enabled)))

    stateful entrypoint approve_all(operator: address, enabled: bool) =
        put(state{operators @ ops = ops{[Call.caller = {}] @ op = op{[operator] = enabled}}})
        Chain.event(ApprovalForAll(Call.caller, operator, bool_to_string(enabled)))

    entrypoint get_approved(token_id: int) : option(address) =
        Map.lookup(token_id, state.approvals)

    entrypoint is_approved(token_id: int, a: address) : bool =
        switch(Map.lookup(token_id, state.approvals))
            None => false
            Some(o) => o == a

    entrypoint is_approved_for_all(owner: address, operator: address) : bool =
        switch(Map.lookup(owner, state.operators))
            None => false
            Some(ops) =>
                switch(Map.lookup(operator, ops))
                    None => false
                    Some(v) => v

    // mintable extension

    stateful entrypoint mint(to: address, metadata: option(metadata), data: option(string)) : int =
        switch(metadata)
            None =>
                let token_id = __mint(to, data)
                // init the name expiration to sync for the NFT
                let name_expiration_height = to_fixed_ttl(state.max_name_ttl)
                put(state{ token_to_name_expiration[token_id] @name_expiration = FixedTTL(name_expiration_height) })
                put(state{ metadata[token_id] @nft_metadata = MetadataMap({}) })
                token_id
            Some(_) => abort("MINTING_WITH_METADATA_NOT_ALLOWED")

    // burnable extension

    stateful entrypoint burn(token_id: int) =
        __burn_single(token_id)

    // AENSWrapping

    /// @notice returns the account address of the real owner
    /// @param name the name to lookup
    /// @return real owner
    entrypoint resolve_owner(name: string) : option(address) =
        switch(Map.lookup(name, state.name_to_token))
            Some(nft_id) =>
                Map.lookup(nft_id, state.token_to_owner)
            None => None

    /// @notice returns the nft id where the AENS name is wrapped into
    /// @param name the name to lookup
    /// @return nft_id
    entrypoint resolve_nft_id(name: string) : option(int) =
        Map.lookup(name, state.name_to_token)

    /// @notice returns the nft id where the AENS name is wrapped into as well as the real owner of the name
    /// @param name the name to lookup
    /// @return nft_id and owner
    entrypoint resolve_nft_id_and_owner(name: string) : option(int * address) =
        switch(resolve_nft_id(name))
            Some(nft_id) =>
                let Some(owner) = Map.lookup(nft_id, state.token_to_owner)
                Some((nft_id, owner))
            None => None

    /// @notice returns nft data (id, owner and the list of names wrapped into the nft and the expiration_height)
    /// @param nft_id the NFT id
    /// @return nft_data
    entrypoint get_nft_data(nft_id: int) : option(nft_data) =
        switch(owner(nft_id))
            None => None
            Some(owner) =>
                let Some(MetadataMap(nft_metadata_map)) = Map.lookup(nft_id, state.metadata)
                let names = List.map(Pair.fst, Map.to_list(nft_metadata_map))
                let Some(FixedTTL(expiration_height)) = Map.lookup(nft_id, state.token_to_name_expiration)
                let config = get_nft_config(nft_id, owner)
                Some({ id = nft_id, owner = owner, owner_config = config, names = names, expiration_height = expiration_height })

    /// @notice returns the expiration height of names that are wrapped into the provided nft id
    /// @param nft_id the NFT id
    /// @return the (fixed) height where all names wrapped into the NFT will expire OR None if the NFT does not exist
    entrypoint get_expiration_by_nft_id(nft_id: int) : option(int) =
        switch(Map.lookup(nft_id, state.token_to_name_expiration))
            None => None
            Some(v) =>
                let FixedTTL(height) = v
                Some(height)

    /// @notice returns the global config for an account
    /// @param account the account address to lookup the config for
    /// @return the global config for an account OR None if not set
    entrypoint get_global_config(account: address) : option(config) =
        Map.lookup(account, state.account_to_config)

    /// @notice returns the balance included in the reward pool
    /// @param account the account where the reward pool balance should be looked up for
    /// @return the reward pool balance
    entrypoint get_reward_pool(account: address) : int =
        state.account_to_reward_pool[account = 0]

    /// @notice wraps AENS names into a fresh minted NFT, adds NFT metadata, extends all names
    /// @param names_delegation_sigs a map (key = AENS name, value = delegation signature)
    /// @return the NFT id
    stateful entrypoint wrap_and_mint(names_delegation_sigs: map(string, signature)) : int =
        require_name_limit_not_exceeded(0, Map.size(names_delegation_sigs))
        let token_id = __mint(Call.caller, None)
        let names_delegation_sigs_list: list(string * signature) = Map.to_list(names_delegation_sigs)
        let name_expiration_height = to_fixed_ttl(state.max_name_ttl)
        List.foreach(names_delegation_sigs_list, (val) => __claim_and_assign(val, token_id, name_expiration_height))
        put(state{ token_to_name_expiration[token_id] @name_expiration = FixedTTL(name_expiration_height) })
        token_id

    /// @notice wraps a single AENS name into an existing NFT, adds NFT metadata, updates expiry of name to match expiry of already wrapped names
    /// @param nft_id the id of the NFT to wrap the AENS name into
    /// @param name the AENS name to wrap
    /// @param delegation_sig the delegation signature for the name
    stateful entrypoint wrap_single(nft_id: int, name: string, delegation_sig: signature) =
        require_authorized(nft_id)
        let expiration_height = require_not_expired(nft_id)
        require_name_limit_not_exceeded(get_wrap_count(nft_id), 1)
        __claim_and_assign((name, delegation_sig), nft_id, expiration_height)

    /// @notice wraps multiple AENS names into an existing NFT, adds NFT metadata, updates expiry of names to match expiry of already wrapped names
    /// @param nft_id the id of the NFT to wrap the AENS name into
    /// @param names_delegation_sigs a map (key = AENS name, value = delegation signature)
    stateful entrypoint wrap_multiple(nft_id: int, names_delegation_sigs: map(string, signature)) =
      require_authorized(nft_id)
      let expiration_height = require_not_expired(nft_id)
      require_name_limit_not_exceeded(get_wrap_count(nft_id), Map.size(names_delegation_sigs))
      let names_delegation_sigs_list: list(string * signature) = Map.to_list(names_delegation_sigs)
      List.foreach(names_delegation_sigs_list, (val) => __claim_and_assign(val, nft_id, expiration_height))

    /// @notice adds / replaces a pointer of the AENS name while keeping existing pointers
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param name the AENS name where the pointer will be added / replaced
    /// @param key the key of the pointer
    /// @param pt the object to point to (account, channel, contract, oracle)
    stateful entrypoint add_or_replace_pointer(nft_id: int, name: string, key: string, pt: AENS.pointee) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        require_name_wrapped(nft_id, name)
        let Some(AENS.Name(_, _, ptrs)) = AENS.lookup(name)
        let updated_pointers = ptrs{[key] = pt}
        require_matching_pointer_limit(updated_pointers)
        AENS.update(Contract.address, name, None, None, Some(updated_pointers))

    /// @notice adds / replaces a set of pointers of the AENS name
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param name the AENS name where the pointer will be added / replaced
    /// @param pointers a map of pointers to set
    /// @param keep_existing a bool indicating whether to keep existing pointers or not
    stateful entrypoint add_or_replace_pointers(nft_id: int, name: string, pointers: map(string, AENS.pointee), keep_existing: bool) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        require_name_wrapped(nft_id, name)
        if(keep_existing)
            let Some(AENS.Name(_, _, old_ptrs)) = AENS.lookup(name)
            let merged_ptrs = merge_maps(old_ptrs, pointers)
            require_matching_pointer_limit(merged_ptrs)
            AENS.update(Contract.address, name, None, None, Some(pointers))
        else
            require_matching_pointer_limit(pointers)
            AENS.update(Contract.address, name, None, None, Some(pointers))

    /// @notice removes a pointer of the AENS name
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param name the AENS name where the pointer will be removed
    /// @param key the key of the pointer
    stateful entrypoint remove_pointer(nft_id: int, name: string, key: string) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        require_name_wrapped(nft_id, name)
        let Some(AENS.Name(_, _, ptrs)) = AENS.lookup(name)
        AENS.update(Contract.address, name, None, None, Some(Map.delete(key, ptrs)))

    /// @notice removes multiple pointers of the AENS name
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param name the AENS name where the pointers will be removed
    /// @param keys a set of pointer keys
    stateful entrypoint remove_pointers(nft_id: int, name: string, keys: Set.set(string)) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        require_name_wrapped(nft_id, name)
        let Some(AENS.Name(_, _, ptrs)) = AENS.lookup(name)
        let updated_ptrs = delete_keys(ptrs, keys)
        AENS.update(Contract.address, name, None, None, Some(updated_ptrs))


    /// @notice removes all pointers of the AENS name
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param name the AENS name where the pointers will be removed
    stateful entrypoint remove_all_pointers(nft_id: int, name: string) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        require_name_wrapped(nft_id, name)
        AENS.update(Contract.address, name, None, None, Some({}))

    /// @notice revokes a single AENS name wrapped in the NFT, removes metadata
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param name the AENS name to revoke
    stateful entrypoint revoke_single(nft_id: int, name: string) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        __revoke(nft_id, name)

    /// @notice revokes multiple AENS names wrapped in the NFT, removes metadata
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    /// @param names the AENS names to revoke
    stateful entrypoint revoke_multiple(nft_id: int, names: Set.set(string)) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        List.foreach(Set.to_list(names), (n) => __revoke(nft_id, n))

    /// @notice revokes all AENS names wrapped in the NFT, removes metadata
    /// @param nft_id the id of the NFT where the AENS name is wrapped into
    stateful entrypoint revoke_all(nft_id: int) =
        require_authorized(nft_id)
        require_not_expired(nft_id)
        let nft_metadata_map = require_names_wrapped(nft_id)
        List.foreach(Map.to_list(nft_metadata_map), (val) => __revoke(nft_id, Pair.fst(val)))

    /// @notice transfers a single AENS name to another NFT by updating metadata of both NFTs, updates expiry of name to match expiry of already wrapped names
    /// @param nft_id_old the id of the NFT that currently wraps the AENS name
    /// @param nft_id_new the id of the NFT that will wrap the AENS name in the future
    /// @param name the AENS name to transfer
    stateful entrypoint transfer_single(nft_id_old: int, nft_id_new: int, name: string) =
        let current_owner = require_authorized(nft_id_old)
        let target_owner = require_exists(nft_id_new)
        require_not_expired(nft_id_old)
        let new_expiration_height = require_not_expired(nft_id_new)
        require_name_limit_not_exceeded(get_wrap_count(nft_id_new), 1)
        if(current_owner != target_owner)
            require_can_receive_name(nft_id_new, target_owner)
        __transfer_single_common(nft_id_old, nft_id_new, name, new_expiration_height)

    /// @notice transfers multiple AENS names to another NFT by updating metadata of both NFTs, updates expiry of names to match expiry of already wrapped names
    /// @param nft_id_old the id of the NFT that currently wraps the AENS name
    /// @param nft_id_new the id of the NFT that will wrap the AENS name in the future
    /// @param names the AENS names to transfer
    stateful entrypoint transfer_multiple(nft_id_old: int, nft_id_new: int, names: Set.set(string)) =
        let current_owner = require_authorized(nft_id_old)
        let target_owner = require_exists(nft_id_new)
        require_not_expired(nft_id_old)
        let new_expiration_height = require_not_expired(nft_id_new)
        require_name_limit_not_exceeded(get_wrap_count(nft_id_new), Set.size(names))
        if(current_owner != target_owner)
            require_can_receive_name(nft_id_new, target_owner)
        List.foreach(Set.to_list(names), (n) => __transfer_single_common(nft_id_old, nft_id_new, n, new_expiration_height))

    /// @notice transfers a single AENS name to another NFT by updating metadata of both NFTs, updates expiry of names to match expiry of already wrapped names
    /// @param nft_id_old the id of the NFT that currently wraps the AENS name
    /// @param nft_id_new the id of the NFT that will wrap the AENS name in the future
    stateful entrypoint transfer_all(nft_id_old: int, nft_id_new: int) =
        let current_owner = require_authorized(nft_id_old)
        let target_owner = require_exists(nft_id_new)
        require_not_expired(nft_id_old)
        let new_expiration_height = require_not_expired(nft_id_new)
        let nft_metadata_map = require_names_wrapped(nft_id_old)
        require_name_limit_not_exceeded(get_wrap_count(nft_id_new), Map.size(nft_metadata_map))
        if(current_owner != target_owner)
            require_can_receive_name(nft_id_new, target_owner)
        List.foreach(Map.to_list(nft_metadata_map), (val) => __transfer_single_common(nft_id_old, nft_id_new, Pair.fst(val), new_expiration_height))

    /// @notice transfers the AENS name back to the owner or to another defined recipient, updates metadata
    /// @param nft_id the id of the NFT that currently wraps the AENS name
    /// @param name the AENS name to transfer
    /// @param recipient the address that should receive the AENS name
    stateful entrypoint unwrap_single(nft_id: int, name: string, recipient: option(address)) =
        let current_owner = require_authorized(nft_id)
        require_not_expired(nft_id)
        __unwrap(nft_id, name, current_owner, recipient)

    /// @notice transfers the AENS names back to the owner or to another defined recipient, updates metadata
    /// @param nft_id the id of the NFT that currently wraps the AENS name
    /// @param names the AENS names to transfer
    /// @param recipient the address that should receive the AENS name
    stateful entrypoint unwrap_multiple(nft_id: int, names: Set.set(string), recipient: option(address)) =
        let current_owner = require_authorized(nft_id)
        require_not_expired(nft_id)
        List.foreach(Set.to_list(names), (val) => __unwrap(nft_id, val, current_owner, recipient))

    /// @notice transfers all AENS names back to the owner or to another defined recipient, updates metadata
    /// @param nft_id the id of the NFT that currently wraps the AENS name
    /// @param recipient the address that should receive the AENS name
    stateful entrypoint unwrap_all(nft_id: int, recipient: option(address)) =
        let current_owner = require_authorized(nft_id)
        require_not_expired(nft_id)
        let nft_metadata_map = require_names_wrapped(nft_id)
        List.foreach(Map.to_list(nft_metadata_map), (val) => __unwrap(nft_id, Pair.fst(val), current_owner, recipient))

    /// @notice caller sets global config for NFTs owned by the caller
    /// @param config the global config
    stateful entrypoint set_global_config(config: config) =
        put(state{ account_to_config[Call.caller] @cfg = config })

    /// @notice caller removes global config for NFTs owned by the caller
    stateful entrypoint remove_global_config() =
        put(state{ account_to_config @ val = Map.delete(Call.caller, val) })

    /// @notice caller sets NFT specific config
    /// @param nft_id the id of the NFT to set the config
    /// @param config the nft specific config
    stateful entrypoint set_nft_config(nft_id: int, config: config) =
        require_authorized(nft_id)
        put(state{ token_to_config[nft_id] @cfg = config })

    /// @notice caller removes NFT specific config
    /// @param nft_id the id of the NFT to remove the config from
    stateful entrypoint remove_nft_config(nft_id: int) =
        require_authorized(nft_id)
        put(state{ token_to_config @val = Map.delete(nft_id, val) })

    /// @notice caller deposits AE to his reward pool
    stateful payable entrypoint deposit_to_reward_pool() =
        require(Call.value > 0, "DEPOSIT_VALUE_MISSING")
        put(state{ account_to_reward_pool[Call.caller = 0] @reward_pool = reward_pool + Call.value })

    /// @notice caller withdraws all AE or a specific amount from his reward pool
    /// @param amount the optional amount of AE to withdraw
    stateful entrypoint withdraw_from_reward_pool(amount: option(int)) =
        let reward_pool = require_ae_in_reward_pool()
        switch(amount)
            None =>
                put(state{ account_to_reward_pool @val = Map.delete(Call.caller, val) })
                Chain.spend(Call.caller, reward_pool)
            Some(value) =>
                require(reward_pool >= value, "INSUFFICIENT_BALANCE_IN_POOL")
                put(state{ account_to_reward_pool[Call.caller] @reward_pool = reward_pool - value })
                Chain.spend(Call.caller, value)

    /// @notice calculates the reward based on the expiration date of the names wrapped in an NFT, considering the global config (or the NFT specific config if set) and the amount of Æ deposited by the NFT owner
    /// @param nft_id the id of the NFT to extend
    /// @return the estimated reward
    entrypoint estimate_reward(nft_id: int) =
        let owner = require_exists(nft_id)
        let expiration_height = require_not_expired(nft_id)
        switch(get_nft_config(nft_id, owner))
            None => 0
            Some(config) => get_possible_reward(owner, config, expiration_height)

    /// @notice extends all AENS names wrapped in the NFT without getting a reward
    /// @param nft_id the id of the NFT that wraps the AENS names to extend
    stateful entrypoint extend_all(nft_id: int) =
        require_exists(nft_id)
        require_not_expired(nft_id)
        let nft_metadata_map = require_names_wrapped(nft_id)
        let new_expiration_height = to_fixed_ttl(state.max_name_ttl)
        List.foreach(Map.to_list(nft_metadata_map), (val) => __extend(nft_id, Pair.fst(val), new_expiration_height))
        put(state{ token_to_name_expiration[nft_id] @name_expiration = FixedTTL(new_expiration_height) })

    /// @notice extends all AENS names wrapped in the NFT and distributes a reward to the caller
    /// @param nft_id the id of the NFT that wraps the AENS names to extend
    stateful entrypoint extend_all_for_reward(nft_id: int) =
        let owner = require_exists(nft_id)
        let expiration_height = require_not_expired(nft_id)
        let nft_metadata_map = require_names_wrapped(nft_id)
        let reward =
            switch(get_nft_config(nft_id, owner))
                None => 0
                Some(config) => get_possible_reward(owner, config, expiration_height)
        // TODO => shall we allow 0 reward?!
        let new_expiration_height = to_fixed_ttl(state.max_name_ttl)
        List.foreach(Map.to_list(nft_metadata_map), (val) => __extend(nft_id, Pair.fst(val), new_expiration_height))
        put(state{ token_to_name_expiration[nft_id] @name_expiration = FixedTTL(new_expiration_height) })
        put(state{ account_to_reward_pool[owner = 0] @reward_pool = reward_pool - reward })
        Chain.spend(Call.caller, reward)
        Chain.event(Reward(nft_id, Call.caller, reward))

    /// @notice transfers a set of NFTs to the desired recipient
    /// @param recipient the address to become new owner of the NFTs
    /// @param nft_ids the ids of the NFTs to transfer
    /// @param data optional data to be provided to a contract receiver
    stateful entrypoint transfer_multiple_nfts(recipient: address, nft_ids: Set.set(int), data: option(string)) =
        List.foreach(Set.to_list(nft_ids), (id) => __transfer_single_nft(recipient, id, data))

    stateful function __revoke(nft_id: int, name: string) =
        let nft_metadata_map = require_name_wrapped(nft_id, name)
        AENS.revoke(Contract.address, name)
        put(state{ metadata[nft_id] @nft_metadata = MetadataMap(Map.delete(name, nft_metadata_map)) })
        put(state{ name_to_token @ val = Map.delete(name, val) })
        Chain.event(NameRevoke(name, nft_id))

    stateful function __transfer_single_nft(to: address, token_id: int, data: option(string)) =
        let from = require_authorized(token_id)
        require(from != to, "SENDER_MUST_NOT_BE_RECEIVER")
        __remove_approval(token_id)
        put(state{ balances[from] @balance1 = balance1 - 1
            , balances[to = 0] @balance2 = balance2 + 1
            , token_to_owner[token_id] = to
            , owner_to_tokens[from] @from_tokens = Set.delete(token_id, from_tokens)
            , owner_to_tokens[to = Set.new()] @to_tokens = Set.insert(token_id, to_tokens)
            , token_to_config @token_config = Map.delete(token_id, token_config) })
        switch(invoke_nft_receiver(Some(from), to, token_id, data))
            (true, false) => abort("SAFE_TRANSFER_FAILED")
            _ => Chain.event(Transfer(from, to, token_id))

    /// @notice burns a set of NFTs (only possible if AENS names are expired)
    /// @param nft_ids the ids of the NFTs to burn
    stateful entrypoint burn_multiple_nfts(nft_ids: Set.set(int)) =
        List.foreach(Set.to_list(nft_ids), (id) => __burn_single(id))

    // external helpers for AEX-141

    entrypoint get_owned_tokens(owner: address) : list(int) =
        Set.to_list(Map.lookup_default(owner, state.owner_to_tokens, Set.new()))

    // internal helper functions

    function require_name_limit_not_exceeded(current_wrap_count: int, to_wrap: int) =
        require(current_wrap_count + to_wrap =< state.name_limit, "NAME_LIMIT_EXCEEDED")

    function require_burnable_if_expired_or_empty(nft_id: int, owner: address) =
        switch(get_nft_config(nft_id, owner))
            None => () // allow burning if no config is set
            Some(cfg) => require(cfg.burnable_if_expired_or_empty, "BURNING_NOT_ALLOWED")

    function require_matching_pointer_limit(pointers: map(string, AENS.pointee)) =
        require(Map.size(pointers) =< 32, "POINTER_LIMIT_EXCEEDED")

    function require_expired_if_wrapped(nft_id: int) =
        let Some(MetadataMap(nft_metadata_map)) = Map.lookup(nft_id, state.metadata)
        if(Map.size(nft_metadata_map) > 0)
            let Some(FixedTTL(expiration_height)) = Map.lookup(nft_id, state.token_to_name_expiration)
            require(Chain.block_height > expiration_height, "WRAPPED_NAMES_NOT_EXPIRED")

    function require_can_receive_name(target_nft_id: int, target_owner: address) =
        switch(get_nft_config(target_nft_id, target_owner))
            None => abort("RECEIVING_NAME_NOT_ALLOWED")
            Some(cfg) => require(cfg.can_receive_from_others, "RECEIVING_NAME_NOT_ALLOWED")

    function require_ae_in_reward_pool() : int =
        let reward_pool = Map.lookup_default(Call.caller, state.account_to_reward_pool, 0)
        require(reward_pool > 0, "NO_AE_IN_REWARD_POOL")
        reward_pool

    function require_names_wrapped(nft_id: int) : map(string, string) =
        let Some(MetadataMap(nft_metadata_map)) = Map.lookup(nft_id, state.metadata)
        require(Map.size(nft_metadata_map) > 0, "NO_NAMES_WRAPPED")
        nft_metadata_map

    function require_name_wrapped(nft_id: int, name: string) : map(string, string) =
        let Some(MetadataMap(nft_metadata_map)) = Map.lookup(nft_id, state.metadata)
        require(Map.member(name, nft_metadata_map), "NAME_NOT_WRAPPED")
        nft_metadata_map

    function require_not_expired(nft_id: int) : int =
        let Some(FixedTTL(expiration_height)) = Map.lookup(nft_id, state.token_to_name_expiration)
        require(expiration_height >= Chain.block_height, "NAMES_IN_NFT_EXPIRED")
        expiration_height

    function require_caller_is_receipient(recipient: address) =
        require(Call.caller == recipient, "CALLER_MUST_BE_RECIPIENT")

    function require_exists(token_id: int) : address =
        switch(owner(token_id))
            None => abort("TOKEN_NOT_EXISTS")
            Some(v) => v

    function require_authorized(token_id: int) : address =
        let owner = require_exists(token_id)
        require(Call.caller == owner || is_approved(token_id, Call.caller) || is_approved_for_all(owner, Call.caller), "ONLY_OWNER_APPROVED_OR_OPERATOR_CALL_ALLOWED")
        owner

    stateful function __extend(nft_id: int, name: string, new_expiration_height: int) =
        AENS.update(Contract.address, name, Some(FixedTTL(new_expiration_height)), None, None)
        Chain.event(NameExtend(name, nft_id, new_expiration_height, Call.caller))

    stateful function __transfer_single_common(nft_id_old: int, nft_id_new: int, name: string, new_expiration_height: int) =
        require_name_wrapped(nft_id_old, name)
        // update state of old nft
        let Some(MetadataMap(metadata_map_old_nft)) = Map.lookup(nft_id_old, state.metadata)
        put(state{ metadata[nft_id_old] @nft_metadata = MetadataMap(Map.delete(name, metadata_map_old_nft)) })
        // update state of new nft
        let Some(MetadataMap(metadata_map_new_nft)) = Map.lookup(nft_id_new, state.metadata)
        let updated_map_new_nft = metadata_map_new_nft{[name] @ n = ""}
        put(state{ metadata[nft_id_new] @nft_metadata = MetadataMap(updated_map_new_nft) })
        // update the ttl of the transfered name and keep in sync with expiration height of new nft
        __update_name_ttl(name, FixedTTL(new_expiration_height))
        // update map for name resolving
        put(state{ name_to_token[name] @token_id = nft_id_new })
        Chain.event(NameTransfer(name, nft_id_old, nft_id_new))

    stateful function __unwrap(nft_id: int, name: string, current_owner, recipient: option(address)) =
        let nft_metadata_map = require_name_wrapped(nft_id, name)
        put(state{ metadata[nft_id] @nft_metadata = MetadataMap(Map.delete(name, nft_metadata_map)) })
        put(state{ name_to_token @ val = Map.delete(name, val) })
        let new_owner =
            switch(recipient)
                None => current_owner
                Some(v) => v
        AENS.transfer(Contract.address, new_owner, name)
        Chain.event(NameUnwrap(name, nft_id, current_owner, new_owner))

    stateful function __claim_and_assign(name_delegation_sig: string * signature, token_id: int, expiration_height: int) =
        let name = Pair.fst(name_delegation_sig)
        AENS.transfer(Call.caller, Contract.address, name, signature = Pair.snd(name_delegation_sig))
        let MetadataMap(nft_metadata_map) = Map.lookup_default(token_id, state.metadata, MetadataMap({}))
        // adding name to the MetadataMap (value is irrelevant)
        let updated_map = nft_metadata_map{[name] @ n = ""}
        put(state{ metadata[token_id] @nft_metadata = MetadataMap(updated_map) })
        put(state{ name_to_token[name] @t = token_id })
        __update_name_ttl(name, FixedTTL(expiration_height))
        Chain.event(NameWrap(name, token_id, Call.caller, expiration_height))

    /// @notice updates TTL of an AENS name
    /// @param name the name to update
    /// @param new_ttl the optional ttl to set
    stateful function __update_name_ttl(name: string, new_ttl: Chain.ttl) =
        AENS.update(Contract.address, name, Some(new_ttl), None, None)

    stateful function __mint(to: address, data: option(string)) : int =
        require_caller_is_receipient(to)
        let token_id = state.counter
        put(state{ counter = state.counter + 1
            , total_supply = state.total_supply + 1
            , balances[to = 0] @balance = balance + 1
            , token_to_owner[token_id] = to
            , owner_to_tokens[to = Set.new()] @owners_tokens = Set.insert(token_id, owners_tokens)})
        switch(invoke_nft_receiver(None, to, token_id, data))
            (true, false) => abort("SAFE_TRANSFER_FAILED")
            _ => Chain.event(Mint(to, token_id))
        token_id

    stateful function __remove_approval(token_id: int) =
        if(Map.member(token_id, state.approvals))
            put(state{ approvals = Map.delete(token_id, state.approvals) })

    stateful function __burn_single(token_id: int) =
        let owner = require_exists(token_id)
        require_expired_if_wrapped(token_id)
        require_burnable_if_expired_or_empty(token_id, owner)
        __remove_approval(token_id)
        put(state{ balances[owner] @balance = balance - 1
            , total_supply = state.total_supply - 1
            , token_to_owner = Map.delete(token_id, state.token_to_owner)
            , owner_to_tokens[owner] @owners_tokens = Set.delete(token_id, owners_tokens)
            , token_to_name_expiration = Map.delete(token_id, state.token_to_name_expiration)
            , token_to_config = Map.delete(token_id, state.token_to_config)
            , metadata = Map.delete(token_id, state.metadata) })
        Chain.event(Burn(owner, token_id))

    function get_wrap_count(token_id: int) =
        let Some(MetadataMap(nft_metadata_map)) = Map.lookup(token_id, state.metadata)
        Map.size(nft_metadata_map)

    function get_possible_reward(owner: address, owner_cfg : config, expiration_height: int) : int =
        let delta = expiration_height - Chain.block_height
        if(delta > owner_cfg.reward_block_window)
            0
        else
            let expected_reward =
                switch(delta > owner_cfg.emergency_reward_block_window)
                    true => owner_cfg.reward
                    false => owner_cfg.emergency_reward
            let reward_pool = state.account_to_reward_pool[owner = 0]
            if(reward_pool >= expected_reward)
                expected_reward
            else
                reward_pool

    function get_nft_config(nft_id: int, owner: address) : option(config) =
        switch(Map.lookup(nft_id, state.token_to_config))
            None => get_global_config(owner)
            Some(cfg) => Some(cfg)

    function to_fixed_ttl(relative_ttl: Chain.ttl) : int =
        let RelativeTTL(ttl) = relative_ttl
        Chain.block_height + ttl

    function invoke_nft_receiver(from: option(address), to: address, token_id: int, data: option(string)) : (bool * bool) =
        if(Address.is_contract(to))
            let c = Address.to_contract(to)
            switch(c.on_aex141_received(from, token_id, data, protected = true) : option(bool))
                None => (true, false)
                Some(val) => (true, val)
        else
            (false, false)

    function bool_to_string(v: bool): string =
        switch(v)
            true => "true"
            false => "false"

    function merge_maps(old: map('a, 'b), new: map('a, 'b)) : map('a, 'b) =
        List.foldl(insert, old, Map.to_list(new))

    function delete_keys(m: map('a, 'b), keys: Set.set('a)) =
        List.foldl(remove, m, Set.to_list(keys))
    
    function insert(m: map('a, 'b), (k, v): 'a * 'b) =
        m{[k] = v}

    function remove(m: map('a, 'b), k: 'a) =
        Map.delete(k, m)