package resolver

import (
	"errors"
	"fmt"

	"git.frostfs.info/TrueCloudLab/frostfs-contract/nns"
	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
	"github.com/nspcc-dev/neo-go/pkg/rpcclient/invoker"
	"github.com/nspcc-dev/neo-go/pkg/rpcclient/unwrap"
	"github.com/nspcc-dev/neo-go/pkg/util"
	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
)

// ResolveHash resolves contract hash.
func ResolveHash(cli *rpcclient.Client, domain string) (util.Uint160, error) {
	nnsCs, err := cli.GetContractStateByID(1)
	if err != nil {
		return util.Uint160{}, fmt.Errorf("get NNS contract by id: %w", err)
	}

	item, err := nnsResolve(invoker.New(cli, nil), nnsCs.Hash, domain)
	if err != nil {
		return util.Uint160{}, err
	}
	return parseNNSResolveResult(item)
}

func nnsResolve(inv *invoker.Invoker, nnsHash util.Uint160, domain string) (stackitem.Item, error) {
	return unwrap.Item(inv.Call(nnsHash, "resolve", domain, int64(nns.TXT)))
}

// parseNNSResolveResult parses the result of resolving NNS record.
// It works with multiple formats (corresponding to multiple NNS versions).
// If array of hashes is provided, it returns only the first one.
func parseNNSResolveResult(res stackitem.Item) (util.Uint160, error) {
	arr, ok := res.Value().([]stackitem.Item)
	if !ok {
		arr = []stackitem.Item{res}
	}
	if _, ok := res.Value().(stackitem.Null); ok || len(arr) == 0 {
		return util.Uint160{}, errors.New("NNS record is missing")
	}
	for i := range arr {
		bs, err := arr[i].TryBytes()
		if err != nil {
			continue
		}

		h, err := address.StringToUint160(string(bs))
		if err == nil {
			return h, nil
		}

		h, err = util.Uint160DecodeStringLE(string(bs))
		if err == nil {
			return h, nil
		}
	}
	return util.Uint160{}, errors.New("no valid hashes are found")
}