# Oracle Module for External Data Feeds

This tutorial will guide you through building an Oracle module using Ignite CLI, which fetches external data feeds for blockchain applications. We'll focus on backend development, laying the foundation for a robust oracle system.

## Overview

Oracles are essential for blockchains to interact with external data. They enable smart contracts to access off-chain data like weather, prices, real-world information or data from other IBC enabled blockchains.

## Prerequisites

- Basic understanding of blockchain and smart contracts.
- Ignite CLI installed on your machine.
- Familiarity with Go programming language.

## Steps to Create an Oracle Module

### Step 1: Scaffold a New Blockchain:

Create a new blockchain project using Ignite CLI:

ignite scaffold chain oraclechain && cd oraclechain

### Step 2: Scaffold the Oracle Module

Generate the Oracle module:

ignite scaffold module oracle --ibc

This command creates a new module with IBC capabilities, ideal for building an oracle that can interact with other blockchains.

### Step 3: Define Data Structures

Scaffold the necessary types for your oracle. For example, to create a data structure for storing external data:

ignite scaffold map externalData key value --module oracle

Here, `externalData` stores key-value pairs representing data fetched from external sources.

### Step 4: Implement Oracle Functionality

**Create Oracle Handler**

In your `x/oracle/handler.go`, define the logic to process oracle-related transactions. For instance, adding a function to handle data submission:

package oracle

import (
    "context"
    "oracle/x/oracle/keeper"
    "oracle/x/oracle/types"
)

func handleMsgSubmitData(ctx sdk.Context, k keeper.Keeper, msg *types.MsgSubmitData) (*sdk.Result, error) {
    // Logic to process data submission
    // ...
    return &sdk.Result{}, nil
}

**Update Module Configuration**

In `x/oracle/module.go`, register your message handlers:

// ...
func (am AppModule) RegisterServices(cfg module.Configurator) {
    types.RegisterMsgServer(cfg.MsgServer(), keeper.NewMsgServerImpl(&am.keeper))
    // ...
}

### Step 5: Implement Data Fetching Logic

Create a new Go file `x/oracle/external_data.go` to handle external data fetching:

package oracle

// Function to fetch external data
func FetchExternalData() (string, error) {
    // Implement logic to fetch and return external data
    // For instance, making an HTTP request to an API
}

Call this function within your message handlers or other appropriate places in your module to fetch and store data.

### Step 6: Register and Handle Oracle Queries

Define queries to retrieve stored data in `x/oracle/keeper/grpc_query.go`:

func (k Keeper) ExternalData(c context.Context, req *types.QueryExternalDataRequest) (*types.QueryExternalDataResponse, error) {
    // Implement logic to return the requested external data
    // ...
}

### Step 7: Add Necessary CLI and gRPC Configurations

Ensure that your module's CLI commands and gRPC endpoints are properly configured to interact with the oracle functionality.

### Conclusion

With these steps, you have laid the foundation for an Oracle module that can fetch and handle external data feeds. This module can be expanded with more complex data handling, authentication mechanisms for data sources, and integration with smart contracts or other blockchain functionalities.