================================== Example: Essay Store ================================== The main page of the essay store shows links to essays of the form `/essay?name=:essayname`. The `/essay` URL takes the following query parameters: * `name`: mandatory, name of the essay * `tid`: optional, transaction ID generated by the merchant for the contract that was used to purchase an instance of the article These are the steps for showing `/essay`. Note that checks for wallet presence are omitted, it the wallet is not present in steps 2 and 3, the user agent should be redirected to a mock credit card payment page. 1. The server checks the status of the the essay with the name `name` in the server-side session state * If the essay is marked as payed for the client, display the essay. * Otherwise proceed with step 2 2. The server checks if the `tid` parameter is present * If `tid` is present, restore the contract to pay for the essay and emit the `taler-execute-contract` DOM event in the user agent. * Otherwise proceed with step 3 3. The server generates a new contract and emits the `taler-confirm-contract` DOM event in the user agent, with the essay name as repurchase correlation identifier and `/essay?name=:name?tid=:tid` as fulfillment url. In step 2, the `taler-execute-contract` event has the following parameters: * `H_contract`: hash of the contract that was restored * `payment_url`: The internal URL `/pay?H_contract=...` of the essay store, will set the server-side session state for the article associated with the contract hash on successful coin deposit * `offer_url`: Link to a teaser page (`/teaser?name=...`), which also contains a link to the article page, without the `tid` parameter.