package node

import (
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"net/http"
	"strconv"
	"strings"

	"go-blockchain/blockchain"
	"go-blockchain/identity"
)

func jsonOK(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	_ = json.NewEncoder(w).Encode(v)
}

func jsonErr(w http.ResponseWriter, err error, code int) {
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(map[string]string{"error": err.Error()})
}

func queryInt(r *http.Request, key string, def int) int {
	s := r.URL.Query().Get(key)
	if s == "" {
		return def
	}
	n, err := strconv.Atoi(s)
	if err != nil || n <= 0 {
		return def
	}
	return n
}

// queryIntMin0 parses a query param as a non-negative integer; returns 0 if absent or invalid.
func queryIntMin0(r *http.Request, key string) int {
	s := r.URL.Query().Get(key)
	if s == "" {
		return 0
	}
	n, err := strconv.Atoi(s)
	if err != nil || n < 0 {
		return 0
	}
	return n
}

func queryUint64Optional(r *http.Request, key string) (*uint64, error) {
	raw := strings.TrimSpace(r.URL.Query().Get(key))
	if raw == "" {
		return nil, nil
	}
	n, err := strconv.ParseUint(raw, 10, 64)
	if err != nil {
		return nil, fmt.Errorf("invalid %s: %s", key, raw)
	}
	return &n, nil
}

func resolveAccountID(q ExplorerQuery, accountID string) (string, error) {
	if accountID == "" {
		return "", fmt.Errorf("account id required")
	}
	if strings.HasPrefix(accountID, "DC") {
		pubKey, err := q.AddressToPubKey(accountID)
		if err != nil {
			return "", err
		}
		if pubKey == "" {
			return "", fmt.Errorf("account not found")
		}
		return pubKey, nil
	}
	return accountID, nil
}

func verifyTransactionSignature(tx *blockchain.Transaction) error {
	if tx == nil {
		return fmt.Errorf("transaction is nil")
	}
	return identity.VerifyTx(tx)
}

func decodeTransactionEnvelope(raw string) (*blockchain.Transaction, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return nil, fmt.Errorf("empty transaction envelope")
	}

	tryDecodeJSON := func(data []byte) (*blockchain.Transaction, error) {
		var tx blockchain.Transaction
		if err := json.Unmarshal(data, &tx); err != nil {
			return nil, err
		}
		if tx.ID == "" || tx.From == "" || tx.Type == "" {
			return nil, fmt.Errorf("invalid tx payload")
		}
		return &tx, nil
	}

	if strings.HasPrefix(raw, "{") {
		return tryDecodeJSON([]byte(raw))
	}

	base64Decoders := []*base64.Encoding{
		base64.StdEncoding,
		base64.RawStdEncoding,
		base64.URLEncoding,
		base64.RawURLEncoding,
	}
	for _, enc := range base64Decoders {
		if b, err := enc.DecodeString(raw); err == nil {
			if tx, txErr := tryDecodeJSON(b); txErr == nil {
				return tx, nil
			}
		}
	}

	if b, err := hex.DecodeString(raw); err == nil {
		if tx, txErr := tryDecodeJSON(b); txErr == nil {
			return tx, nil
		}
	}

	return nil, fmt.Errorf("failed to decode transaction envelope")
}

func txMemo(tx *blockchain.Transaction) string {
	if tx == nil {
		return ""
	}
	if memo := strings.TrimSpace(tx.Memo); memo != "" {
		return memo
	}
	switch tx.Type {
	case blockchain.EventTransfer:
		var p blockchain.TransferPayload
		if err := json.Unmarshal(tx.Payload, &p); err == nil {
			return strings.TrimSpace(p.Memo)
		}
	case blockchain.EventBlockReward:
		return blockRewardReason(tx.Payload)
	case blockchain.EventRelayProof:
		return "Relay delivery fee"
	case blockchain.EventHeartbeat:
		return "Liveness heartbeat"
	case blockchain.EventRegisterRelay:
		return "Register relay service"
	case blockchain.EventBindWallet:
		return "Bind payout wallet"
	}
	return ""
}

func blockRewardReason(payload []byte) string {
	var p blockchain.BlockRewardPayload
	if err := json.Unmarshal(payload, &p); err != nil {
		return "Block fees"
	}
	if p.FeeReward == 0 && p.TotalReward > 0 {
		return "Genesis allocation"
	}
	return "Block fees collected"
}

func decodeTxPayload(payload []byte) (any, string) {
	if len(payload) == 0 {
		return nil, ""
	}
	var decoded any
	if err := json.Unmarshal(payload, &decoded); err == nil {
		return decoded, ""
	}
	return nil, hex.EncodeToString(payload)
}