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--- id: dev-rentonzilliqa-procedures title: Procedures keywords: - scilla - procedures - rentonzilliqa description: The Procedures of the Scilla Contract for the RentOnZilliqa Application --- --- We proceed to declare the procedures that we will use in the RentOnZilliqa Smart Contract. We will declare the following types of procedures in this section. [The source code](https://github.com/Quinence/zilliqa-fullstack-app-rentOnZilliqa/blob/main/src/scilla/RentOnZilliqa.scilla). - [General Procedures](#general-procedures) - [`send_message`](#send_message) - [Listing Management Procedures](#listing-management-procedures) - [`set_listing_details`](#set_listing_details) - [`claim_rent_by_id`](#claim_rent_by_id) - [`delete_listing_by_id`](#delete_listing_by_id) - [Listing Booking Procedures](#listing-booking-procedures) - [`check_listing_available`](#check_listing_available) - [`check_amount_and_book`](#check_amount_and_book) - [`book_listing_by_id`](#book_listing_by_id) ## General Procedures Since we will send messages on multiple occasions in the contract, we create the `send_message` procedure to send messages. ### `send_message` This procedure creates a message with the passed arguments. It uses the `one_msg` library function to create a list of messages and then proceeds to send it. Note that the `_recipient` is always the implicit variable `_sender`. | Arguments | Description | Type | | --------- | ------------------------------------------------------------------------------------------ | --------- | | `amount` | The amount to be sent with the message | `Uint128` | | `code` | The [message code](dev-rentonzilliqa-library.md#message-codes) to be sent with the message | `Int32` | ```ocaml procedure send_message (amount: Uint128, code: Int32) msg = { _tag: ""; _recipient: _sender; _amount: amount; code: code }; msgs = one_msg msg; send msgs end ``` ## Listing Management Procedures This group of procedures is used in the transitions that a host account user may use to manage their listings. ### `set_listing_details` This procedure creates or updates the [Listing Details](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) for the given ID. It is used by the `create_listing` and `update_listing` transitions. | Arguments | Description | Type | | ------------- | --------------------------------------------------------------------------------------------- | --------- | | `id` | The ID of the listing | `Uint128` | | `name` | The name of the listing | `String` | | `description` | The description of the listing | `String` | | `price` | The price of the listing | `Uint128` | | `rooms` | The number of rooms in the listing | `Uint32` | | `bathrooms` | The number of bathrooms in the listing | `Uint32` | | `image` | A URL to an image of the listing | `String` | | `location` | A [Google Maps Plus Code](https://maps.google.com/pluscodes/) for the location of the listing | `String` | | `wifi` | The availability of WiFi at the listing | `String` | | `laundry` | The availability of a Landry at the listing | `String` | | `hvac` | The availability of an HVAC at the listing | `String` | | `tv` | The availability of a TV at the listing | `String` | | `kitchen` | The availability of a Kitchen at the listing | `String` | ```ocaml procedure set_listing_details ( id: Uint128, name: String, description: String, price: Uint128, rooms: Uint32, bathrooms: Uint32, image: String, location: String, wifi: String, laundry: String, hvac: String, tv: String, kitchen: String ) listing_name[id] := name; listing_description[id] := description; listing_price[id] := price; listing_rooms[id] := rooms; listing_bathrooms[id] := bathrooms; listing_image[id] := image; listing_location[id] := location; listing_wifi[id] := wifi; listing_laundry[id] := laundry; listing_hvac[id] := hvac; listing_tv[id] := tv; listing_kitchen[id] := kitchen end ``` ### `claim_rent_by_id` This procedure is used in conjunction with the `claim_rent` transition. The accumulated rent is checked for the listing with the given ID, in the [`listing_accumulated_rent`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) field. If the rent is missing or empty, the corresponding messages are sent using the `send_message` procedure. If there is non-zero accumulated rent, it is sent to the `_sender` using the `send_message` procedure. The accumulated rent is passed as an argument to `send_message`, along with the `rent_claimed` message code. A "Rent Claimed" event is also emitted. The accumulated rent in the [`listing_accumulated_rent`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) field is set to zero for that ID, as it is claimed by the host account. | Arguments | Description | Type | | --------- | --------------------- | --------- | | `id` | The ID of the listing | `Uint128` | ```ocaml procedure claim_rent_by_id (id: Uint128) accumulated_rent <- listing_accumulated_rent[id]; match accumulated_rent with | Some accumulated_rent => no_accumulated_rent = builtin eq accumulated_rent zero; match no_accumulated_rent with | True => send_message zero rent_empty | False => listing_accumulated_rent[id] := zero; e = { _eventname: "RentClaimed"; listing_id: id; renter: _sender; amount: accumulated_rent }; event e; send_message accumulated_rent rent_claimed end | None => send_message zero listing_details_missing end end ``` ### `delete_listing_by_id` This procedure is used in conjunction with the `delete_listing` transition. It deletes the [Listing Details](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) entries for the listing with the given ID. | Arguments | Description | Type | | --------- | --------------------- | --------- | | `id` | The ID of the listing | `Uint128` | ```ocaml procedure delete_listing_by_id (id: Uint128) delete listing_name[id]; delete listing_description[id]; delete listing_price[id]; delete listing_rooms[id]; delete listing_image[id]; delete listing_host[id]; delete listing_renter[id]; delete listing_rented_till[id]; delete listing_accumulated_rent[id]; delete listing_bathrooms[id]; delete listing_location[id]; delete listing_wifi[id]; delete listing_laundry[id]; delete listing_hvac[id]; delete listing_tv[id]; delete listing_kitchen[id] end ``` ## Listing Booking Procedures ### `check_listing_available` This procedure is used in conjunction with the `book_listing` transition. It checks if the listing is available by checking the [`listing_rented_till`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) field. If it is not available, the [`listing_unavailable`](dev-rentonzilliqa-library.md#renter-account-codes) message is sent back. When the listing is available, the [`check_amount_and_book`](#check_amount_and_book) procedure is called with the `id`. | Arguments | Description | Type | | --------- | --------------------- | --------- | | `id` | The ID of the listing | `Uint128` | ```ocaml procedure check_listing_available (id: Uint128) current_block_number <- & BLOCKNUMBER; listing_rented_till_value <- listing_rented_till[id]; match listing_rented_till_value with | Some listing_rented_till_value => is_rented_lt = builtin blt current_block_number listing_rented_till_value; is_rented_eq = builtin eq current_block_number listing_rented_till_value; listing_is_rented_check = orb is_rented_lt is_rented_eq; match listing_is_rented_check with | True => send_message zero listing_unavailable | False => check_amount_and_book id end | None => send_message zero listing_details_missing end end ``` ### `check_amount_and_book` This procedure is used in conjunction with the `book_listing` transition. It is called after the listing's availibility is checked by the [`check_listing_available`](#check_listing_available) procedure. It checks if the sent amount is equal to the [`listing_price`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields). If not, the [`wrong_amount_sent`](dev-rentonzilliqa-library.md#renter-account-codes) is sent back. If the correct amount is sent, the [`book_listing_by_id`](#book_listing_by_id) procedure is called with the `id`. | Arguments | Description | Type | | --------- | --------------------- | --------- | | `id` | The ID of the listing | `Uint128` | ```ocaml procedure check_amount_and_book (id: Uint128) listing_price_value <- listing_price[id]; match listing_price_value with | Some listing_price_value => correct_amount_check = builtin eq _amount listing_price_value; match correct_amount_check with | True => book_listing_by_id id | False => send_message zero wrong_amount_sent end | None => send_message zero listing_details_missing end end ``` ### `book_listing_by_id` This procedure is used in conjunction with the `book_listing` transition. In this procedure, the `accept` command is called. The [`night_duration`](dev-rentonzilliqa-mutable-variables.md#owner-fields) is added to the current `BLOCKNUMBER` and assigned to the [`listing_rented_till`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) field. The `_sender` wallet address is assigned to the [`listing_renter`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) field. The rent amount is added to the [`listing_accumulated_rent`](dev-rentonzilliqa-mutable-variables.md#listing-details-fields) field, after subtracting the commission set in the [`owners_commission`](dev-rentonzilliqa-mutable-variables.md#owner-fields) field. A "ListingBooked" event is emitted and a [`listing_booked`](dev-rentonzilliqa-library.md#renter-account-codes) message is sent. As the commission amount is stored in the contract balance, it can be claimed by the contract owner via the `_balance` implicit variable. | Arguments | Description | Type | | --------- | --------------------- | --------- | | `id` | The ID of the listing | `Uint128` | ```ocaml procedure book_listing_by_id (id: Uint128) accumulated_rent <- listing_accumulated_rent[id]; match accumulated_rent with | Some accumulated_rent => accept; current_block_number <- & BLOCKNUMBER; night_duration_value <- night_duration; rented_till = builtin badd current_block_number night_duration_value; listing_rented_till[id] := rented_till; listing_renter[id] := _sender; commission <- owners_commission; rent = builtin sub _amount commission; new_accumulated_rent = builtin add accumulated_rent rent; listing_accumulated_rent[id] := new_accumulated_rent; e = { _eventname: "ListingBooked"; listing_id: id; renter: _sender; amount: _amount }; event e; send_message zero listing_booked | None => send_message zero listing_details_missing end end ```