initial release

internal/fetcher/alchemy.go

@@ -0,0 +1,74 @@
+package fetcher
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+type AlchemyClient struct {
+	apiKey string
+	http  *http.Client
+}
+
+func NewAlchemyClient(apiKey string) *AlchemyClient {
+	return &AlchemyClient{apiKey: apiKey, http: &http.Client{}}
+}
+
+// FetchOwnerTokens returns tokenIDs (as strings) for the owner for a single contract.
+// network: e.g. "arb" (arbitrum one) -> uses arb-mainnet endpoint.
+func (c *AlchemyClient) FetchOwnerTokens(network, contract, owner string) ([]string, error) {
+	if c.apiKey == "" {
+		return nil, errors.New("missing ALCHEMY_API_KEY")
+	}
+	base := networkBase(network)
+	if base == "" {
+		return nil, fmt.Errorf("unsupported network: %s", network)
+	}
+	endpoint := fmt.Sprintf("%s/nft/v3/%s/getNFTsForOwner", base, c.apiKey)
+	q := url.Values{}
+	q.Set("owner", owner)
+	q.Add("contractAddresses[]", contract)
+	q.Set("withMetadata", "false")
+	url := endpoint + "?" + q.Encode()
+
+	resp, err := c.http.Get(url)
+	if err != nil { return nil, err }
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("alchemy error: %s", resp.Status)
+	}
+	var parsed struct {
+		OwnedNfts []struct {
+			Id struct { TokenId string `json:"tokenId"` } `json:"id"`
+		} `json:"ownedNfts"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&parsed); err != nil { return nil, err }
+	ids := make([]string, 0, len(parsed.OwnedNfts))
+	for _, n := range parsed.OwnedNfts {
+		ids = append(ids, stripHexPrefix(n.Id.TokenId))
+	}
+	return ids, nil
+}
+
+func stripHexPrefix(s string) string {
+	s = strings.TrimPrefix(s, "0x")
+	// Alchemy may return hex with leading zeros; keep as-is (frontend can parse)
+	return s
+}
+
+func networkBase(network string) string {
+	switch strings.ToLower(network) {
+	case "arb", "arbitrum", "arbitrum-one":
+		return "https://arb-mainnet.g.alchemy.com"
+	case "arb-sepolia", "arbitrum-sepolia":
+		return "https://arb-sepolia.g.alchemy.com"
+	case "eth", "mainnet", "ethereum":
+		return "https://eth-mainnet.g.alchemy.com"
+	default:
+		return ""
+	}
+}