Implement discounted card purchases

Implement purchase logic for a gem-based card game. There are five gem colors: `BLUE`, `WHITE`, `GREEN`, `RED`, and `YELLOW`. Each `Card` has: - a `color` representing the permanent discount it grants after purchase - a `cost` map from gem color to required quantity Each `Player` has: - a `gems` map from gem color to current quantity owned - a `hand` containing purchased cards - a `discountMap` where `discountMap[c]` equals the number of previously purchased cards of color `c` Rules: 1. When buying a card, the player gets a discount on each gem color equal to the number of owned cards of that same color. - Example: if the player owns 2 white cards and 1 red card, then a card costing 4 white and 1 red has discounted cost 2 white and 0 red. 2. A discounted cost for any color cannot go below 0. 3. `canPurchase(card)` should return `true` if the player can afford the card after applying discounts, otherwise `false`. 4. `purchase(card)` should: - return `false` and change nothing if the card is not affordable - otherwise deduct the discounted gem cost from the player's gems - add the card to the player's hand - increase the discount count for the purchased card's `color` by 1 - return `true` Write the logic for `canPurchase` and `purchase` correctly.