app-escrow.teal

#pragma version 5
        // This application accepts payments in algo, and holds them
        // until the requester asks for them back. Depositors invoke
        // the app with "deposit" as arg[0], and make a pay
        // transaction to the app account in the following txn slot.
        // The app records the deposit in the user's local state (so
        // the user must be opted-in), though they may do so in their
        // initial call.

        // To withdraw, users call with "withdraw" in arg[0], and a
        // big-endian integer amount in arg[1].  If the withdrawal
        // amount is less than the amount deposited, the app pays out
        // the request, and decrements the user's balance.

        // ApplicationID is zero in inital creation txn
        txn ApplicationID
        bz handle_createapp

        // Handle possible OnCompletion type. We don't have to
        // worry about handling ClearState, because the
        // ClearStateProgram will execute in that case, not the
        // ApprovalProgram.

        txn OnCompletion
        int NoOp
        ==
        bnz handle_noop

        txn OnCompletion
        int OptIn
        ==
        bnz handle_optin

        txn OnCompletion
        int CloseOut
        ==
        bnz handle_closeout

        txn OnCompletion
        int UpdateApplication
        ==
        bnz handle_updateapp

        txn OnCompletion
        int DeleteApplication
        ==
        bnz handle_deleteapp
        // Unexpected OnCompletion value. Should be unreachable.
        err

handle_createapp:
        int 1
        return

handle_optin:
        // Let anyone optin with a single txn, with no arguments.  If
        // it's not a single txn, fall through to handle_noop, so that
        // a deposit can be made while opting in.
        // We should standardize a behaviour like this in ABI.
        global GroupSize
        int 1
        ==
        bz handle_noop
        int 1
        return


handle_noop:
        txn ApplicationArgs 0
        byte "deposit():void"
        ==
        bz not_deposit


        byte "deposit"
        callsub debug

        // Handle a deposit.  Next txn slot must pay our app account
        txn GroupIndex
        int 1
        +
        dup
        dup

        gtxns TypeEnum
        int pay                 // axfer if we want an ASA escrower
        ==
        assert

        gtxns Receiver
        global CurrentApplicationAddress
        ==
        assert

        gtxns Amount           // For ASA escrow, use AssetAmount


        // Track the amount this sender deposited in their local state
        int 0
        byte "balance"
        dup2
        app_local_get
        uncover 3             // pull up the Amount
        +
        app_local_put

        int 1
        return

not_deposit:
        txn ApplicationArgs 0
        byte "withdraw(uint64):void"
        ==
        bz not_withdraw

        // Handle withdraw.

        int 0
        byte "balance"
        dup2
        app_local_get

        // Subtract the request and replace. Rejects on underflow
        txn ApplicationArgs 1
        btoi
        -
        app_local_put

        tx_begin
         int pay
         tx_field TypeEnum

         txn ApplicationArgs 1
         btoi
         tx_field Amount

         txn Sender
         tx_field Receiver
        tx_submit

        int 1
        return
not_withdraw:
        // Unknown call "method"
        err

handle_closeout:
        int 1
        return

handle_updateapp:
handle_deleteapp:
        txn Sender
        global CreatorAddress
        ==
        return


bad:
        err

debug:
        byte "debug"
        swap
        app_global_put
        retsub