Generate NFT metadata and ensure uniqueness

You are implementing an NFT metadata generator. Each NFT is defined by selecting exactly one trait value from each trait category. You must generate a requested number of NFTs, ensure they are unique (no repeated trait combinations), and output JSON metadata.

Input

A single JSON object with:

• collectionName (string)
• traits: an array of trait categories. Each category is:
• name (string)
• values (array of strings, non-empty)
• n (integer): number of NFTs to generate
• seed (integer): seed for deterministic pseudo-random generation

Example:

{
 "collectionName": "MyCollection",
 "traits": [
 {"name": "Background", "values": ["Blue", "Red"]},
 {"name": "Eyes", "values": ["Normal", "Laser"]}
 ],
 "n": 3,
 "seed": 42
}

Required behavior

1. Each generated NFT must have exactly one value for each trait category.
2. Two NFTs are considered the same if they have the same value for every trait category.
3. Use seed to make generation deterministic:

• Using the same input must produce the same outputs in the same order.

1. If n exceeds the number of possible unique combinations, output ERROR.

Output

Output a JSON array of length n. Each element is an object:

• name: "<collectionName> #<index>" where index starts at 1
• attributes: array of { "trait_type": <categoryName>, "value": <selectedValue> }

Example output element:

{
 "name": "MyCollection #1",
 "attributes": [
 {"trait_type": "Background", "value": "Red"},
 {"trait_type": "Eyes", "value": "Laser"}
 ]
}

Constraints

• Up to 10 trait categories.
• Each category has up to 200 values.
• n can be up to 100,000.

Notes

You must define your own approach for generating unique combinations efficiently (not by repeatedly sampling and retrying until unique).