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.

1. A discounted cost for any color cannot go below 0.
2. canPurchase(card) should return true if the player can afford the card after applying discounts, otherwise false.
3. 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.