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diff --git a/banks.rst b/banks.rst new file mode 100644 index 00000000..c6565261 --- /dev/null +++ b/banks.rst @@ -0,0 +1,131 @@ +=================================== +Interaction with banks Web portals +=================================== + +This section describes the interactions that should occur between +a wallet and a bank which chooses to adapt its Web portal to interact +with the Taler wallet. This interaction is supposed to occur when +the user is sending a SEPA transfer to some mint (i.e. he is creating +a new reserve). + +Through this interaction, the wallet can generate a new reserve's public +key and insert it into the 'subject' field of the transfer without manual +copy&paste. Secondly, the wallet is then able to fetch the amount to be +tranferred to the mint directly from the Web form, in order to poll the mint +to check if the desired amount has been transferred. + +---------------------- +Mutual acknowledgement +---------------------- + +The mutual acknowledgement between a wallet and a bank portal occurs when +the user is on the page which hosts the SEPA form, and is realized by the +mean of JavaScript signals issued on the `body` HTML element. + +When the bank wants to notify to a wallet, it sends the following event: + + .. js:data:: taler-wire-probe + +This event must be sent from a callback for the `onload` event of the +`body` element, otherwise the extension would have not time to +register a listener for this event. It also needs to be sent when +the Taler extension is dynamically loaded, like when the user activates +the extension while he is on the SEPA form page. This is done by +listening for the + + .. js:data:: taler-load + +event. If the Taler extension is present, it will respond with a + + .. js:data:: taler-wallet-present + +event. The handler should then activate its mechanism to trigger the generation +of a new reserve key in the wallet, for example by updating the DOM to enable a +dedicated button. + +If the Taler extension is unloaded while the user is visiting a SEPA form page, +the page should listen for a + + .. js:data:: taler-unload + +event, in order to hide the previously enabled button. + +------------------------- +How to trigger the wallet +------------------------- + +This interaction will make the wallet generate a new reserve public key, +as well as allowing the user to choose his wanted mint. Finally, the wallet +will directly paste this information inside the SEPA form and submit it. +Lastly, it allows the wallet to fetch the desired amount to be transferred +to the mint from the SEPA form. Typically, this trigger is initiated by the +user pushing a button while he is on the page which hosts the SEPA Web form. + +The wallet listens to a + + .. js:data:: taler-create-reserve + +event, through which it expects to receive the following object: + +.. sourcecode:: javascript + + {form_id: sepa-form-id, + input_amount: input-amount-id, + input_pub: input-pub-id, + mint_rcv: receiving-money-mint} + +`input_amount` is the `id` attribute of the HTML `input` element which +hosts the amount to wire to the desired mint. Please note that the wallet will +only accept amounts of the form `n[.x[y]] CUR`, where `CUR` is the ISO code +of the specified currency. So it may be necessary for the bank's webmaster to +preprocess this data to give it to the wallet in the right format. + +`input_pub` must be the `id` attribute of the `input` element within the form +which represents this SEPA transfer's "subject". +`form_id` must be the `id` attribute of the SEPA `form` element (needed by the wallet to +call `submit()` on it). +Finally, `mint_rcv` is the `id` attribute of the `input` element within the form +from which the server side handler of this form will fetch the mint base URL to issue +`/admin/add/incoming` on; see :ref:`add-incoming`. + +The following source code highlights the key steps for adding the Taler button +to trigger the wallet on a SEPA form page: + +.. sourcecode:: javascript + + function has_taler_wallet_callback(aEvent){ + // This function is called if a Taler wallet is available. + // suppose the radio button for the Taler option has + // the DOM ID attribute 'taler-wallet-trigger' + var tbutton = document.getElementById("taler-wallet-trigger"); + tbutton.removeAttribute("disabled"); + }; + + function taler_wallet_load_callback(aEvent){ + // let the Taler wallet know that this is a SEPA form page + // which supports Taler (the extension will have + // missed our initial 'taler-wire-probe' from onload()) + document.body.dispatchEvent(new Event('taler-wire-probe')); + }; + + function taler_wallet_unload_callback(aEvent){ + // suppose the button which triggers the wallet has + // the DOM ID attribute 'taler-wallet-trigger' + var tbutton = document.getElementById("taler-wallet-trigger"); + tbutton.setAttribute("disabled", "true"); + }; + +.. sourcecode:: html + + <body onload="function(){ + // First, we set up the listener to be called if a wallet is present. + document.body.addEventListener("taler-wallet-present", has_taler_wallet_callback, false); + // Detect if a wallet is dynamically added (rarely needed) + document.body.addEventListener("taler-load", taler_wallet_load_callback, false); + // Detect if a wallet is dynamically removed (rarely needed) + document.body.addEventListener("taler-unload", taler_wallet_unload_callback, false); + // Finally, signal the wallet that this is a payment page. + document.body.dispatchEvent(new Event('taler-wire-probe')); + };"> + ... + </body> |