// SPDX-License-Identifier: MIT
pragma solidity >=0.8.4;

import "../ResolverBase.sol";
import "../../dnssec-oracle/RRUtils.sol";
import "./IDNSRecordResolver.sol";
import "./IDNSZoneResolver.sol";

abstract contract DNSResolver is
    IDNSRecordResolver,
    IDNSZoneResolver,
    ResolverBase
{
    using RRUtils for *;
    using BytesUtils for bytes;

    // Zone hashes for the domains.
    // A zone hash is an EIP-1577 content hash in binary format that should point to a
    // resource containing a single zonefile.
    // node => contenthash
    mapping(uint64 => mapping(bytes32 => bytes)) private versionable_zonehashes;

    // The records themselves.  Stored as binary RRSETs
    // node => version => name => resource => data
    mapping(uint64 => mapping(bytes32 => mapping(bytes32 => mapping(uint16 => bytes))))
        private versionable_records;

    // Count of number of entries for a given name.  Required for DNS resolvers
    // when resolving wildcards.
    // node => version => name => number of records
    mapping(uint64 => mapping(bytes32 => mapping(bytes32 => uint16)))
        private versionable_nameEntriesCount;

    /// Set one or more DNS records.  Records are supplied in wire-format.
    /// Records with the same node/name/resource must be supplied one after the
    /// other to ensure the data is updated correctly. For example, if the data
    /// was supplied:
    ///     a.example.com IN A 1.2.3.4
    ///     a.example.com IN A 5.6.7.8
    ///     www.example.com IN CNAME a.example.com.
    /// then this would store the two A records for a.example.com correctly as a
    /// single RRSET, however if the data was supplied:
    ///     a.example.com IN A 1.2.3.4
    ///     www.example.com IN CNAME a.example.com.
    ///     a.example.com IN A 5.6.7.8
    /// then this would store the first A record, the CNAME, then the second A
    /// record which would overwrite the first.
    ///
    /// @param node the namehash of the node for which to set the records
    /// @param data the DNS wire format records to set
    function setDNSRecords(
        bytes32 node,
        bytes calldata data
    ) external virtual authorised(node) {
        uint16 resource = 0;
        uint256 offset = 0;
        bytes memory name;
        bytes memory value;
        bytes32 nameHash;
        uint64 version = recordVersions[node];
        // Iterate over the data to add the resource records
        for (
            RRUtils.RRIterator memory iter = data.iterateRRs(0);
            !iter.done();
            iter.next()
        ) {
            if (resource == 0) {
                resource = iter.dnstype;
                name = iter.name();
                nameHash = keccak256(abi.encodePacked(name));
                value = bytes(iter.rdata());
            } else {
                bytes memory newName = iter.name();
                if (resource != iter.dnstype || !name.equals(newName)) {
                    setDNSRRSet(
                        node,
                        name,
                        resource,
                        data,
                        offset,
                        iter.offset - offset,
                        value.length == 0,
                        version
                    );
                    resource = iter.dnstype;
                    offset = iter.offset;
                    name = newName;
                    nameHash = keccak256(name);
                    value = bytes(iter.rdata());
                }
            }
        }
        if (name.length > 0) {
            setDNSRRSet(
                node,
                name,
                resource,
                data,
                offset,
                data.length - offset,
                value.length == 0,
                version
            );
        }
    }

    /// Obtain a DNS record.
    /// @param node the namehash of the node for which to fetch the record
    /// @param name the keccak-256 hash of the fully-qualified name for which to fetch the record
    /// @param resource the ID of the resource as per https://en.wikipedia.org/wiki/List_of_DNS_record_types
    /// @return the DNS record in wire format if present, otherwise empty
    function dnsRecord(
        bytes32 node,
        bytes32 name,
        uint16 resource
    ) public view virtual override returns (bytes memory) {
        return versionable_records[recordVersions[node]][node][name][resource];
    }

    /// Check if a given node has records.
    /// @param node the namehash of the node for which to check the records
    /// @param name the namehash of the node for which to check the records
    function hasDNSRecords(
        bytes32 node,
        bytes32 name
    ) public view virtual returns (bool) {
        return (versionable_nameEntriesCount[recordVersions[node]][node][
            name
        ] != 0);
    }

    /// setZonehash sets the hash for the zone.
    /// May only be called by the owner of that node in the ENS registry.
    /// @param node The node to update.
    /// @param hash The zonehash to set
    function setZonehash(
        bytes32 node,
        bytes calldata hash
    ) external virtual authorised(node) {
        uint64 currentRecordVersion = recordVersions[node];
        bytes memory oldhash = versionable_zonehashes[currentRecordVersion][
            node
        ];
        versionable_zonehashes[currentRecordVersion][node] = hash;
        emit DNSZonehashChanged(node, oldhash, hash);
    }

    /// zonehash obtains the hash for the zone.
    /// @param node The ENS node to query.
    /// @return The associated contenthash.
    function zonehash(
        bytes32 node
    ) external view virtual override returns (bytes memory) {
        return versionable_zonehashes[recordVersions[node]][node];
    }

    function supportsInterface(
        bytes4 interfaceID
    ) public view virtual override returns (bool) {
        return
            interfaceID == type(IDNSRecordResolver).interfaceId ||
            interfaceID == type(IDNSZoneResolver).interfaceId ||
            super.supportsInterface(interfaceID);
    }

    function setDNSRRSet(
        bytes32 node,
        bytes memory name,
        uint16 resource,
        bytes memory data,
        uint256 offset,
        uint256 size,
        bool deleteRecord,
        uint64 version
    ) private {
        bytes32 nameHash = keccak256(name);
        bytes memory rrData = data.substring(offset, size);
        if (deleteRecord) {
            if (
                versionable_records[version][node][nameHash][resource].length !=
                0
            ) {
                versionable_nameEntriesCount[version][node][nameHash]--;
            }
            delete (versionable_records[version][node][nameHash][resource]);
            emit DNSRecordDeleted(node, name, resource);
        } else {
            if (
                versionable_records[version][node][nameHash][resource].length ==
                0
            ) {
                versionable_nameEntriesCount[version][node][nameHash]++;
            }
            versionable_records[version][node][nameHash][resource] = rrData;
            emit DNSRecordChanged(node, name, resource, rrData);
        }
    }
}