Module 12: REST API - Part 2

First read this page then start the module with the GitHub classroom link below.
Github Classroom Link: https://classroom.github.com/a/LJqMiP3v

Resources

Exercise 1:

Review the code in the GitHub repository. Take note of the changes since module 11, including the relocation of the toppings handler functions to the toppingFunctions.cpp file. Also take note of a new class file PizzaSize.h.

Notice the new map in the pizzaAPI.cpp that will store the size of the pizza.

 // Creating a map to store pizza sizes
 map<string, PizzaSize> pizzaSizesMap;

Create a new endpoint to read this new resource. The endpoint should return all of the available pizza sizes and should use the HTTP method: GET. Add your code in the pizzaAPI.cpp where it says: ` // Exercise 1: Add new end points here…`
Test your new endpoint.
Create a new endpoint to read a single instance of the resource. The endpoint should return one of the available pizza sizes based on an id and should use the HTTP method: GET.
Test your new endpoint.
Create a new endpoint to update a single instance of the resource. The endpoint should modify one of the available pizza sizes based on an id and should use the HTTP method: PUT. A JSON body should be provided in the request.
```
 {"id":"1","size":"Mini"}
```
Test your new endpoint.
Create a new endpoint to create a single instance of the resource. The endpoint should create a new pizza sizes and should use the HTTP method: POST.A JSON body should be provided in the request.
```
 {"id":"4","size":"Mega-Large"}
```
Test your new endpoint
Create a new endpoint to delete a single instance of the resource. The endpoint should return one of the available pizza sizes based on an id and should use the HTTP method: DELETE.
Test your new endpoint.

Exercise 2:

Add a new function to pizzaAPI.cpp that will save the PizzaSize map to a file.

 void saveToFile(std::map<std::string, PizzaSize> data, std::string filename)

Implement the save to file function.
Call the function where it says: // Exercise 2: Add code here to save the resources to a file.
Test this function by starting and stopping the pizzaAPI program.

Hint:

json::wvalue convertPizzaSizeToJson(PizzaSize pizzaSize) 
{
    json::wvalue writeValueJson;
    writeValueJson["id"] = pizzaSize.getId();
    writeValueJson["size"] = pizzaSize.getSize();
    return writeValueJson;
}


void saveToFile(map<string, PizzaSize> data, string filename)  
{
    // Open the file for writing
    ofstream file(filename);

    if (file.is_open()) 
    {
        // Create a new JSON write value use to write to the file.
        json::wvalue jsonWriteValue;
        
        // For each object in the map, convert the object to JSON and add to the write value.
        int index = 0;
        for (pair<string, PizzaSize> keyValuePair : data)
        {
            // first: gives you access to the first item in the pair.
            // second: gives you access to the second item in the pair.
            jsonWriteValue[index] = convertPizzaSizeToJson(keyValuePair.second);
            index++;
        }

        // Write the JSON to the file.
        file << jsonWriteValue.dump();
        file.close();
    }
}

Exercise 3:

Add a new function to pizzaAPI.cpp that will load the PizzaSize map from a file.
```
 map<string, PizzaSize> loadFromFile(string filename)
```
Implement the load from file function.
Call the function where it says: // Exercise 3: Add code here to read data from a file....
Test this function by starting and stopping the pizzaAPI program.

Hint:

map<string, PizzaSize> loadFromFile(string filename) 
{
    map<string, PizzaSize> data;
    
    // Open the file for reading.
    ifstream file(filename);

    // If the file is open. 
    if (file.is_open()) 
    {      
        // Create a stream for reading in the file.
        ostringstream stringStreamJson;

        // Read the entire JSON string.
        stringStreamJson << file.rdbuf();

        // Load the string into a JSON read value object.
        json::rvalue jsonReadValue = json::load(stringStreamJson.str());

        // Close the file.
        file.close();

        // For each item in the JSON convert it to an object, 
        // and add it to the data map.
        for (json::rvalue item : jsonReadValue) 
        {
            PizzaSize pizzaSize{item["id"].s(), item["size"].s()};
            data[pizzaSize.getId()] = pizzaSize;
        }
    }
    
    return data;
}