Different Volume based discount function app on cart line items

[Tripathi]

I am building a Shopify app functions which apply different discounts on based of quantity of a product added to the cart. 
When 10 or more products of a particular variant is added then 2.5% volume discount must apply and when 25 or more products are added to the cart then 5% volume discount must apply. 
The problem is when the second product is added then the discount applied to that product applies on all cart lines irrespective of their quantity .
Below is the code of run.js file of my volume based discount function app. 

import { DiscountApplicationStrategy } from "../generated/api";

// Use JSDoc annotations for type safety
/**
* @typedef {import("../generated/api").RunInput} RunInput
* @typedef {import("../generated/api").FunctionRunResult} FunctionRunResult
* @typedef {import("../generated/api").Target} Target
* @typedef {import("../generated/api").ProductVariant} ProductVariant
*/

/**
* @type {FunctionRunResult}
*/
const EMPTY_DISCOUNT = {
discountApplicationStrategy: DiscountApplicationStrategy.First,
discounts: [],
};

/**
* @param {RunInput} input
* @returns {FunctionRunResult}
*/
export function run(input) {
let discountValue = 0;
const targets = input.cart.lines
.filter((line) => {
if(line.merchandise.__typename === "ProductVariant"){
if (line.quantity >= 50) {
discountValue = 7.5;
return true;
} else if (line.quantity >= 25) {
discountValue = 5;
return true;
} else if (line.quantity >= 10) {
discountValue = 2.5;
return true;
}
return false;
}

})

.map((line) => {
return {
productVariant : {
id: line.merchandise.id,
}
};
});

if (!targets.length) {
console.error("No cart lines qualify for volume discount.");
return EMPTY_DISCOUNT;
}

if (discountValue === 2.5) {
return {
discounts: [
{
targets: targets,
value: {
percentage: {
value: "2.5",
},
},
message: "2.5% off when buying at least 10",
},
],
discountApplicationStrategy: DiscountApplicationStrategy.First,
};
}
else if(discountValue === 5){
return {
discounts: [
{
targets,
value: {
percentage: {
value: "5.0",
},
},
message: "5% off when buying at least 25",
},
],
discountApplicationStrategy: DiscountApplicationStrategy.First,
};
}
else if(discountValue === 7.5){
return {
discounts: [
{
targets,
value: {
percentage: {
value: "7.5",
},
},
message: "7.5% off when buying at least 50",
},
],
discountApplicationStrategy: DiscountApplicationStrategy.First,
};
}
}

Below is the graphql query :

Help me fix this.

[tobebuilds]

It sounds like there's a significant difference between the code you've written and the actual logic for when you want the discount to apply.

Your code targets every line item with a quantity of 10 or greater and gives them all the same discount.

Also, I recommend using `CartLineTarget` instead of `ProductVariantTarget`.