NFT1155URI_with_V1_CID.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.8.11;

import "@openzeppelin/contracts/token/ERC1155/extensions/ERC1155Burnable.sol";

contract NFT1155 is ERC1155Burnable {

    /**
     *
     * @dev `uri_` tokens base URI pattern.
     */
    constructor()
        ERC1155("ipfs://b{id}")
    {}

    /**
     *
     * @dev Mint token using external token ID and amount.
     */
    function mint(
        address to,
        uint256 tokenId,
        uint256 amount
    ) public onlyOperator {
        _mint(to, tokenId, amount, "");
    }

    function uri(uint256 _tokenID)
        public
        pure
        override
        returns (string memory)
    {
        string memory cidV1tokenID;
        cidV1tokenID = cidv1encode(_tokenID);

        return string(abi.encodePacked("ipfs://b", cidV1tokenID));
    }

    function cidv1encode(uint256 id) public pure returns (string memory) {
        if (id == 0) return "aa";

        uint8[32] memory alphabet = [
            97,
            98,
            99,
            100,
            101,
            102,
            103,
            104,
            105,
            106,
            107,
            108,
            109,
            110,
            111,
            112,
            113,
            114,
            115,
            116,
            117,
            118,
            119,
            120,
            121,
            122,
            50,
            51,
            52,
            53,
            54,
            55
        ];
        uint256 bits = 0;
        uint256 buffer = 0;

        uint256 header = 0x01551220;
        uint8 _byte = 0;

        bytes memory bstr = new bytes(58);
        uint256 idx = 0;
        uint256 mask = 31;
        for (uint256 i = 0; i < 36; ++i) {
            if (i < 4) {
                _byte = uint8(header >> (32 - (i + 1) * 8));
            } else {
                _byte = uint8(id >> (256 - (i - 3) * 8));
            }

            buffer = (buffer << 8) | _byte;
            bits += 8;

            while (bits > 5) {
                bits -= 5;
                bstr[idx++] = bytes1(alphabet[mask & (buffer >> bits)]);
            }
        }
        if (bits != 0) {
            bstr[idx] = bytes1(alphabet[mask & (buffer << (5 - bits))]);
        }
        return string(bstr);
    }
}