CoTA Fungible Token Protocol Extension (WIP)

There are four predefined smt_type enum for fungible token operations.

type name	1st byte	2nd byte	description
cota-FT-define	0x82 (FT)	0x00	FT issuance definition
cota-FT-hold	0x82 (FT)	0x01	current hold FT
cota-FT-withdrawal	0x82 (FT)	0x02	FT withdrawal record
cota-FT-claim	0x82 (FT)	0x03	FT claim record

Here are the detailed k-v definitions.

# cota-FT-define data structure
key:        
    smt_type:  uint16       # type byte for cota-FT-define
    token_id:  Byte[20]     # same rules as the cota-nft 
    reserved:  Byte[10] 
value:
blake2b_hash of {
    total:     uint128      # 0 for infinity
    issued:    uint128
    decimal:   uint8
}

# cota-FT-hold data structure
key:
    smt_type:  uint16       # type byte for cota-FT-hold
    token_id:  Byte[20]    
    reserved:  Byte[10] 
value:
    amount:   uint128
    reserved: Byte[16]

CoTA fungible token standard uses the input's outpoint as the unique withdrawal identifier.

# cota-FT-withdraw data structure
key:
    smt_type:  uint16             # type byte for cota-FT-withdraw
    token_id:  Byte[20]
    reserved:  Byte[10] 
value:
blake2b_hash of {
    amount:    uint128
    to_lock:   lock_script
    out_point: OutPoint[12..36]   # outpoint of previous input cell with SMT
}

# cota-FT-claim data structure
key: 
blake2b_hash of {
    smt_type:  uint16             # type byte for cota-FT-claim
    token_id:  Byte[20]
    out_point: OutPoint[12..36]   # copy from the withdrawal record
}
value:
    0x00...00 for nonclaimed
    0xFF...FF for claimed

Where token_id (also written as cota_id in the early designs) is an UUID for all fungible and non-fungible tokens. Its value is set according to the token definition transaction data.

token_id = hash(tx.inputs[0].out_point | tx.outputs.get_first(cota_type).index)[0..20]