帮我用solidity写一个200行的食品溯源智能合约的例子，其中包括食品，中间商和买方

很高兴能够为您提供帮助。下面是一个示例智能合约，它可以用来实现食品溯源：pragma solidity ^0.5.0;//定义一个Food结构
struct Food {
string name;
string origin;
uint quantity;
uint price;
}//定义一个中间商结构
struct Middleman {
string name;
uint price;
uint quantity;
}//定义买方结构
struct Buyer {
string name;
uint price;
uint quantity;
}//定义智能合约
contract FoodTraceability {
Food[] public foods;
Middleman[] public middlemen;
Buyer[] public buyers; //添加食品
function addFood(string memory _name, string memory _origin, uint _quantity, uint _price) public {
Food memory food = Food(_name, _origin, _quantity, _price);
foods.push(food);
} //添加中间商
function addMiddleman(string memory _name, uint _price, uint _quantity) public {
Middleman memory middleman = Middleman(_name, _price, _quantity);
middlemen.push(middleman);
} //添加买方
function addBuyer(string memory _name, uint _price, uint _quantity) public {
Buyer memory buyer = Buyer(_name, _price, _quantity);
buyers.push(buyer);
} //获取食品详情
function getFood(uint _index) public view returns (string memory, string memory, uint, uint) {
Food memory food = foods[_index];
return (food.name, food.origin, food.quantity, food.price);
} //获取中间商详情
function getMiddleman(uint _index) public view returns (string memory, uint, uint) {
Middleman memory middleman = middlemen[_index];
return (middleman.name, middleman.price, middleman.quantity);
} //获取买方详情
function getBuyer(uint _index) public view returns (string memory, uint, uint) {
Buyer memory buyer = buyers[_index];
return (buyer.name, buyer.price, buyer.quantity);
}
}