# Price Feed on AO using 0rbit By [0rbit](https://paragraph.com/@0rbit) · 2024-05-13 --- gm gm!! When it comes to interacting with the external world via blockchain, it's often seen as an impossible task. That's where **_0rbit_** comes into play. 0rbit allows you to bring _ANY DATA from both the on-chain and off-chain world_ to the `ao` process through a decentralized network of 0rbit Nodes. 0rbit is a decentralized, permissionless, and censorship-resistant oracle network built on top of Arweave using `ao`. It's designed to make accessing and utilizing data on the blockchain easier and more efficient. Your mission is to create a bot that responds to user queries for token prices, fetching the data using _0rbit's ao process and the CoinGecko API_. Meanwhile, you can meet other builders working on this quest and get help in the [0rbit’s Discord Channel!](https://discord.gg/abUkA59exC) **Pre-Requisites:** ------------------- * Understanding of the [ao](https://staging-docs.0rbit.co/concepts/what-is-ao) and [aos](https://staging-docs.0rbit.co/concepts/what-is-aos). * aos installed on your system. * Some $0RBT. _Learn how to get $0RBT_ [_here_](https://staging-docs.0rbit.co/protocol/token#how-to-get-0rbt) * Any Code Editor (VSCode, Sublime Text, etc) Let's jump into the quest tutorial and finish each step one by one Checkpoint 0:**📦 Initialize The Project** ------------------------------------------ Create a new file named 0rbit-Price-Feed.lua in your project directory. `touch 0rbit-Price-Feed.lua` Che**ckpoint 1: 📝 Initialize the CONSTANTS** --------------------------------------------- `local json = require("json") _0RBIT = "WSXUI2JjYUldJ7CKq9wE1MGwXs-ldzlUlHOQszwQe0s" _0RBT_TOKEN = "BUhZLMwQ6yZHguLtJYA5lLUa9LQzLXMXRfaq9FVcPJc" BASE_URL = "https://api.coingecko.com/api/v3/simple/price" FEE_AMOUNT = "1000000000000" -- 1 $0RBT` Breakdown of the above code: * `json`: This module is required to destruct the stringified JSON data. In this case, you interact with an API (api.coingecko.com) to fetch cryptocurrency prices. The data returned by this API is typically in JSON format. Therefore, you must parse this JSON data to extract the required information.. * `_0RBIT`: The processId of the 0rbit process. * `_0RBT_TOKEN`: The processId of the $0RBT process. * `BASE_URL`: The API URL you want to fetch data from. In this case, we are fetching cryptocurrency prices from the CoinGecko API. * `FEE_AMOUNT`: The amount of $0RBT you want to send to the 0rbit process for the request. > _For more detailed information on how to use the JSON module, you can visit the documentation_ [_here_](https://cookbook_ao.arweave.dev/guides/aos/modules/json.html) **Checkpoint 2: 🛠 Initialize the Variables** --------------------------------------------- `TOKEN_PRICES = TOKEN_PRICES or { BTC = { coingecko_id = "bitcoin", price = 0, last_update_timestamp = 0 }, ETH = { coingecko_id = "ethereum", price = 0, last_update_timestamp = 0 }, SOL = { coingecko_id = "solana", price = 0, last_update_timestamp = 0 } } ID_TOKEN = ID_TOKEN or { bitcoin = "BTC", ethereum = "ETH", solana = "SOL" } LOGS = LOGS or {}` Breakdown of the above code: * `TOKEN_PRICES`: The table stores the latest prices and other details of the tokens you want to fetch. If the table is not already defined, we initialize it with default values for Bitcoin (BTC), Ethereum (ETH), and Solana (SOL). * `ID_TOKEN`: The table stores the mapping of the token IDs from the CoinGecko API to the token symbols you want to fetch. * `REQUESTED_TOKENS`: The table stores information about tokens requested to be added to the price feed. * `LOGS`: The table stores logs of the process for debugging. > _Yayy! Keep Going and remember, every small step counts towards progress! 🚀_ **Checkpoint 3: 📦 Create Functions** ------------------------------------- ### **Fetch Token Price Function** The `fetchTokenPrice` function fetches the token's price from the CoinGecko API using 0rbit's `Get-Real-Data` handler. `function fetchPrice() local url; local token_ids; for _, v in pairs(TOKEN_PRICES) do token_ids = token_ids .. v.coingecko_id .. "," end url = BASE_URL .. "?ids=" .. token_ids .. "&vs_currencies=usd" Send({ Target = _0RBT_TOKEN, Action = "Transfer", Recipient = _0RBIT, Quantity = FEE_AMOUNT, ["X-Url"] = url, ["X-Action"] = "Get-Real-Data" }) print(Colors.green .. "GET Request sent to the 0rbit process.") end` Breakdown of the above code: * `for _, v in pairs(TOKEN_PRICES)`: Iterate over the `TOKEN_PRICES` table to get a token. * `token_ids`: Concatenate all the tokens coingecko\_id. * `url`: The final URL to fetch the token prices. * `Send`: Transfer 1 $0RBT to the 0rbit process and make a GET request. With this, we initiate a transfer of 1 $0RBT to the 0rbit process and execute a GET request. * `Target`**:** This denotes the process to be pinged with the following `Action`, specifically the 0rbit Token Process. * `Action`**:** This signifies the task to be carried out, in this case, the transfer of 1 0rbit token from the current process to the 0rbit process ID. * `Recipient`**:** This indicates the receiver of the transfer, which, in this context, is the 0rbit oracle's process. * `Quantity`**:** This denotes the amount intended for transfer. Additionally: * The `["X-Url"]` tag specifies the URL from which the data is to be fetched. * The `["X-Action"]` tag specifies the action to be performed. The **_"X-"_** prefix in these tags is a convention used to denote forwarded tags. Forwarded tags refer to additional information included in a message that is passed along to subsequent messages or handlers. ### **Receive Data Function** The `receiveData` function is called when the 0rbit process sends the fetched data to the process. `function receiveData(msg) local res = json.decode(msg.Data) for k, v in pairs(res) do TOKEN_PRICES[ID_TOKEN[k]].price = tonumber(v.usd) TOKEN_PRICES[ID_TOKEN[k]].last_update_timestamp = msg.Timestamp end end` Breakdown of the above code: * `res`: Parse the JSON data received from the 0rbit process. * `for k, v in pairs(res)`: Iterate over the parsed data. * Update the token's price and last\_update\_timestamp in the `TOKEN_PRICES` table. ### **Get Token Price Function** The `getTokenPrice` function returns the token's price from the `TOKEN_PRICES` table. `function getTokenPrice(msg) local token = msg.Tags.Token local price = TOKEN_PRICES[token].price if price == 0 then Handlers.utils.reply("Price not available!!!")(msg) else Handlers.utils.reply(tostring(price))(msg) end end` Breakdown of the above code: * `token`: Extract the token from the incoming message. * `price`: Get the token's price from the `TOKEN_PRICES` table. * If the price is 0, send a message stating that the price is not available. * If the price is not 0, send the price to the sender. > _Remember, just like planets in space, you're moving forward on your own journey. Keep taking steps and you'll reach your destination. 🚀_ **Checkpoint 4: 🔄 Create Handlers** ------------------------------------ ### **Get Token Price Handler** The `GetTokenPrice` handler is called when a process wants to get the latest price of a token. `Handlers.add( "GetTokenPrice", Handlers.utils.hasMatchingTag("Action", "Get-Token-Price"), getTokenPrice )` Breakdown of the above code: * **GetTokenPrice**: The name of the handler. * `Handlers.utils.hasMatchingTag("Action", "Get-Token-Price")`: Checks if the message action tag is `Get-Token-Price` * `getTokenPrice`: The function that sends the latest price of a token from the `TOKEN_PRICES` table. ### **Cron Handler** The `CronTick` handler creates a cron job on the process. This handler will fetch the token prices in the defined period, and update them in the `TOKEN_PRICES` table. `Handlers.add( "CronTick", Handlers.utils.hasMatchingTag("Action", "Cron"), fetchPrice )` Breakdown of the above code: * **CronTick**: The name of the handler. * `Handlers.utils.hasMatchingTag("Action", "Cron")`: Checks if the message action tag is `Cron` * `fetchPrice`: The function that sends a GET Request to 0rbit process to fetch the token prices. ### **Receive Data Handler** The `ReceiveData` handler is called when the 0rbit process sends the fetched data to the process. `Handlers.add( "ReceiveData", Handlers.utils.hasMatchingTag("Action", "Receive-Data-Feed"), receiveData )` Breakdown of the above code: * **ReceivingData**: The name of the handler. * `Handlers.utils.hasMatchingTag("Action", "Receive-Data-Feed")`: Checks if the message action tag is `Receive-Data-Feed` * `receiveData`: The function that updates the token prices in the `TOKEN_PRICES` table. > _You're almost there! Keep up the great work, and let's tackle the next checkpoint together! 🎉_ **Checkpoint 5: 🛠️ Run the Process** ------------------------------------- ### **Open your terminal** Open your terminal in the directory that contains `0rbit-Price-Feed.lua` and enter the following command: `aos 0rbitPriceFeed --cron 30-seconds` The above command will create a new process with the name **0rbitPriceFeed** and set a cron job every 30 seconds. ### **Load your process** Load your script into the process: `aos> .load 0rbit-Price-Feed.lua` ### **Fund your process** Transfer some $0RBT to your processID. ### **Monitor Cron Job** Now you can start monitoring the real-time messaging of the cron: `aos> .monitor` ### **Check the Token Price** `aos> Send({ Target = ao.id, Action="Get-Token-Price", Tags = { Token = "BTC" }})` > **_Voila! You have successfully created a Price Feed Process. 🎉_** I hope you have learned something today with this quite a long blog. Moreover, you can find the complete code [here](https://github.com/0rbit-co/examples/blob/main/Price-Feed.lua). If you have any queries feel free to DM us on [Twitter](https://twitter.com/0rbitco) or [join our Discord community](https://discord.gg/abUkA59exC) to know more about 0rbit. Happy Building!! 🧱💫🚀 --- *Originally published on [0rbit](https://paragraph.com/@0rbit/price-feed-on-ao-using-0rbit)*