package node

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

	"go-blockchain/blockchain"
	"go-blockchain/economy"
	"go-blockchain/wallet"
)

type txListEntry struct {
	ID         string               `json:"id"`
	Type       blockchain.EventType `json:"type"`
	Memo       string               `json:"memo,omitempty"`
	From       string               `json:"from"`
	FromAddr   string               `json:"from_addr,omitempty"`
	To         string               `json:"to,omitempty"`
	ToAddr     string               `json:"to_addr,omitempty"`
	Amount     uint64               `json:"amount_ut"`
	AmountDisp string               `json:"amount"`
	Fee        uint64               `json:"fee_ut"`
	FeeDisp    string               `json:"fee"`
	Time       string               `json:"time"`
	BlockIndex uint64               `json:"block_index"`
	BlockHash  string               `json:"block_hash,omitempty"`
}

func asTxListEntry(rec *blockchain.TxRecord) txListEntry {
	tx := rec.Tx
	out := txListEntry{
		ID:         tx.ID,
		Type:       tx.Type,
		Memo:       txMemo(tx),
		From:       tx.From,
		To:         tx.To,
		Amount:     tx.Amount,
		AmountDisp: economy.FormatTokens(tx.Amount),
		Fee:        tx.Fee,
		FeeDisp:    economy.FormatTokens(tx.Fee),
		Time:       tx.Timestamp.UTC().Format("2006-01-02T15:04:05Z"),
		BlockIndex: rec.BlockIndex,
		BlockHash:  rec.BlockHash,
	}
	if tx.From != "" {
		out.FromAddr = wallet.PubKeyToAddress(tx.From)
	}
	if tx.To != "" {
		out.ToAddr = wallet.PubKeyToAddress(tx.To)
	}
	return out
}

func apiNetStats(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		stats, err := q.NetStats()
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		jsonOK(w, stats)
	}
}

func apiRecentBlocks(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		limit := queryInt(r, "limit", 20)
		blocks, err := q.RecentBlocks(limit)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		type blockSummary struct {
			Index     uint64 `json:"index"`
			Hash      string `json:"hash"`
			Time      string `json:"time"`
			Validator string `json:"validator"`
			TxCount   int    `json:"tx_count"`
			TotalFees uint64 `json:"total_fees_ut"`
		}
		out := make([]blockSummary, len(blocks))
		for i, b := range blocks {
			out[i] = blockSummary{
				Index:     b.Index,
				Hash:      b.HashHex(),
				Time:      b.Timestamp.UTC().Format("2006-01-02T15:04:05Z"),
				Validator: wallet.PubKeyToAddress(b.Validator),
				TxCount:   len(b.Transactions),
				TotalFees: b.TotalFees,
			}
		}
		jsonOK(w, out)
	}
}

func apiRecentTxs(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		limit := queryInt(r, "limit", 20)
		recs, err := q.RecentTxs(limit)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		out := make([]txListEntry, len(recs))
		for i := range recs {
			out[i] = asTxListEntry(recs[i])
		}
		jsonOK(w, out)
	}
}

func apiBlock(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		idxStr := strings.TrimPrefix(r.URL.Path, "/api/block/")
		idx, err := strconv.ParseUint(idxStr, 10, 64)
		if err != nil {
			jsonErr(w, fmt.Errorf("invalid block index: %s", idxStr), 400)
			return
		}
		b, err := q.GetBlock(idx)
		if err != nil {
			jsonErr(w, err, 404)
			return
		}
		type txSummary struct {
			ID     string               `json:"id"`
			Type   blockchain.EventType `json:"type"`
			Memo   string               `json:"memo,omitempty"`
			From   string               `json:"from"`
			To     string               `json:"to,omitempty"`
			Amount uint64               `json:"amount_ut,omitempty"`
			Fee    uint64               `json:"fee_ut"`
		}
		type blockDetail struct {
			Index         uint64      `json:"index"`
			Hash          string      `json:"hash"`
			PrevHash      string      `json:"prev_hash"`
			Time          string      `json:"time"`
			Validator     string      `json:"validator"`
			ValidatorAddr string      `json:"validator_addr"`
			TxCount       int         `json:"tx_count"`
			TotalFees     uint64      `json:"total_fees_ut"`
			Transactions  []txSummary `json:"transactions"`
		}
		txs := make([]txSummary, len(b.Transactions))
		for i, tx := range b.Transactions {
			txs[i] = txSummary{
				ID:     tx.ID,
				Type:   tx.Type,
				Memo:   txMemo(tx),
				From:   tx.From,
				To:     tx.To,
				Amount: tx.Amount,
				Fee:    tx.Fee,
			}
		}
		jsonOK(w, blockDetail{
			Index:         b.Index,
			Hash:          b.HashHex(),
			PrevHash:      fmt.Sprintf("%x", b.PrevHash),
			Time:          b.Timestamp.UTC().Format("2006-01-02T15:04:05Z"),
			Validator:     b.Validator,
			ValidatorAddr: wallet.PubKeyToAddress(b.Validator),
			TxCount:       len(b.Transactions),
			TotalFees:     b.TotalFees,
			Transactions:  txs,
		})
	}
}

func apiTxByID(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		txID := strings.TrimPrefix(r.URL.Path, "/api/tx/")
		if txID == "" {
			jsonErr(w, fmt.Errorf("tx id required"), 400)
			return
		}
		rec, err := q.GetTx(txID)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		if rec == nil {
			jsonErr(w, fmt.Errorf("transaction not found"), 404)
			return
		}
		type txDetail struct {
			ID           string               `json:"id"`
			Type         blockchain.EventType `json:"type"`
			Memo         string               `json:"memo,omitempty"`
			From         string               `json:"from"`
			FromAddr     string               `json:"from_addr,omitempty"`
			To           string               `json:"to,omitempty"`
			ToAddr       string               `json:"to_addr,omitempty"`
			Amount       uint64               `json:"amount_ut"`
			AmountDisp   string               `json:"amount"`
			Fee          uint64               `json:"fee_ut"`
			FeeDisp      string               `json:"fee"`
			Time         string               `json:"time"`
			BlockIndex   uint64               `json:"block_index"`
			BlockHash    string               `json:"block_hash"`
			BlockTime    string               `json:"block_time"`
			GasUsed      uint64               `json:"gas_used,omitempty"`
			Payload      any                  `json:"payload,omitempty"`
			PayloadHex   string               `json:"payload_hex,omitempty"`
			SignatureHex string               `json:"signature_hex,omitempty"`
		}
		tx := rec.Tx
		payload, payloadHex := decodeTxPayload(tx.Payload)
		out := txDetail{
			ID:           tx.ID,
			Type:         tx.Type,
			Memo:         txMemo(tx),
			From:         tx.From,
			To:           tx.To,
			Amount:       tx.Amount,
			AmountDisp:   economy.FormatTokens(tx.Amount),
			Fee:          tx.Fee,
			FeeDisp:      economy.FormatTokens(tx.Fee),
			Time:         tx.Timestamp.UTC().Format("2006-01-02T15:04:05Z"),
			BlockIndex:   rec.BlockIndex,
			BlockHash:    rec.BlockHash,
			BlockTime:    rec.BlockTime.UTC().Format("2006-01-02T15:04:05Z"),
			GasUsed:      rec.GasUsed,
			Payload:      payload,
			PayloadHex:   payloadHex,
			SignatureHex: hex.EncodeToString(tx.Signature),
		}
		if tx.From != "" {
			out.FromAddr = wallet.PubKeyToAddress(tx.From)
		}
		if tx.To != "" {
			out.ToAddr = wallet.PubKeyToAddress(tx.To)
		}
		jsonOK(w, out)
	}
}

func apiAddress(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		addr := strings.TrimPrefix(r.URL.Path, "/api/address/")
		if addr == "" {
			jsonErr(w, fmt.Errorf("address required"), 400)
			return
		}

		pubKey, err := resolveAccountID(q, addr)
		if err != nil {
			jsonErr(w, err, 404)
			return
		}

		limit := queryInt(r, "limit", 50)
		offset := queryIntMin0(r, "offset")
		bal, err := q.Balance(pubKey)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		txs, err := q.TxsByAddress(pubKey, limit, offset)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}

		type txEntry struct {
			ID         string               `json:"id"`
			Type       blockchain.EventType `json:"type"`
			Memo       string               `json:"memo,omitempty"`
			From       string               `json:"from"`
			FromAddr   string               `json:"from_addr,omitempty"`
			To         string               `json:"to,omitempty"`
			ToAddr     string               `json:"to_addr,omitempty"`
			Amount     uint64               `json:"amount_ut"`
			AmountDisp string               `json:"amount"`
			Fee        uint64               `json:"fee_ut"`
			Time       string               `json:"time"`
			BlockIndex uint64               `json:"block_index"`
		}
		entries := make([]txEntry, len(txs))
		for i, rec := range txs {
			tx := rec.Tx
			entries[i] = txEntry{
				ID:         tx.ID,
				Type:       tx.Type,
				Memo:       txMemo(tx),
				From:       tx.From,
				To:         tx.To,
				Amount:     tx.Amount,
				AmountDisp: economy.FormatTokens(tx.Amount),
				Fee:        tx.Fee,
				Time:       tx.Timestamp.UTC().Format("2006-01-02T15:04:05Z"),
				BlockIndex: rec.BlockIndex,
			}
			if tx.From != "" {
				entries[i].FromAddr = wallet.PubKeyToAddress(tx.From)
			}
			if tx.To != "" {
				entries[i].ToAddr = wallet.PubKeyToAddress(tx.To)
			}
		}
		type addrResp struct {
			Address       string    `json:"address"`
			PubKey        string    `json:"pub_key"`
			BalanceMicroT uint64    `json:"balance_ut"`
			Balance       string    `json:"balance"`
			TxCount       int       `json:"tx_count"`
			Offset        int       `json:"offset"`
			Limit         int       `json:"limit"`
			HasMore       bool      `json:"has_more"`
			NextOffset    int       `json:"next_offset"`
			Transactions  []txEntry `json:"transactions"`
		}
		hasMore := len(entries) == limit
		jsonOK(w, addrResp{
			Address:       wallet.PubKeyToAddress(pubKey),
			PubKey:        pubKey,
			BalanceMicroT: bal,
			Balance:       economy.FormatTokens(bal),
			TxCount:       len(entries),
			Offset:        offset,
			Limit:         limit,
			HasMore:       hasMore,
			NextOffset:    offset + len(entries),
			Transactions:  entries,
		})
	}
}

func apiNode(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		input := strings.TrimPrefix(r.URL.Path, "/api/node/")
		if input == "" {
			jsonErr(w, fmt.Errorf("node id required"), 400)
			return
		}

		pubKey, err := resolveAccountID(q, input)
		if err != nil {
			jsonErr(w, err, 404)
			return
		}

		rep, err := q.Reputation(pubKey)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		nodeBal, err := q.Balance(pubKey)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		walletPubKey, err := q.WalletBinding(pubKey)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}

		var walletAddr string
		var walletBalance uint64
		if walletPubKey != "" {
			walletAddr = wallet.PubKeyToAddress(walletPubKey)
			walletBalance, _ = q.Balance(walletPubKey)
		}

		window := queryInt(r, "window", 200)
		recentBlocks, err := q.RecentBlocks(window)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}

		recentProduced := 0
		var recentRewardsUT uint64
		for _, b := range recentBlocks {
			if b.Validator != pubKey {
				continue
			}
			recentProduced++
			recentRewardsUT += b.TotalFees
		}

		type nodeResp struct {
			QueryInput             string `json:"query_input"`
			PubKey                 string `json:"pub_key"`
			Address                string `json:"address"`
			NodeBalanceUT          uint64 `json:"node_balance_ut"`
			NodeBalance            string `json:"node_balance"`
			WalletBindingPubKey    string `json:"wallet_binding_pub_key,omitempty"`
			WalletBindingAddress   string `json:"wallet_binding_address,omitempty"`
			WalletBindingBalanceUT uint64 `json:"wallet_binding_balance_ut,omitempty"`
			WalletBindingBalance   string `json:"wallet_binding_balance,omitempty"`
			ReputationScore        int64  `json:"reputation_score"`
			ReputationRank         string `json:"reputation_rank"`
			BlocksProduced         uint64 `json:"blocks_produced"`
			RelayProofs            uint64 `json:"relay_proofs"`
			SlashCount             uint64 `json:"slash_count"`
			Heartbeats             uint64 `json:"heartbeats"`
			LifetimeBaseRewardUT   uint64 `json:"lifetime_base_reward_ut"`
			LifetimeBaseReward     string `json:"lifetime_base_reward"`
			RecentWindowBlocks     int    `json:"recent_window_blocks"`
			RecentBlocksProduced   int    `json:"recent_blocks_produced"`
			RecentRewardsUT        uint64 `json:"recent_rewards_ut"`
			RecentRewards          string `json:"recent_rewards"`
		}

		jsonOK(w, nodeResp{
			QueryInput:             input,
			PubKey:                 pubKey,
			Address:                wallet.PubKeyToAddress(pubKey),
			NodeBalanceUT:          nodeBal,
			NodeBalance:            economy.FormatTokens(nodeBal),
			WalletBindingPubKey:    walletPubKey,
			WalletBindingAddress:   walletAddr,
			WalletBindingBalanceUT: walletBalance,
			WalletBindingBalance:   economy.FormatTokens(walletBalance),
			ReputationScore:        rep.Score,
			ReputationRank:         rep.Rank(),
			BlocksProduced:         rep.BlocksProduced,
			RelayProofs:            rep.RelayProofs,
			SlashCount:             rep.SlashCount,
			Heartbeats:             rep.Heartbeats,
			LifetimeBaseRewardUT:   0,
			LifetimeBaseReward:     economy.FormatTokens(0),
			RecentWindowBlocks:     len(recentBlocks),
			RecentBlocksProduced:   recentProduced,
			RecentRewardsUT:        recentRewardsUT,
			RecentRewards:          economy.FormatTokens(recentRewardsUT),
		})
	}
}

func apiRelays(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if q.RegisteredRelays == nil {
			jsonOK(w, []any{})
			return
		}
		relays, err := q.RegisteredRelays()
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		if relays == nil {
			relays = []blockchain.RegisteredRelayInfo{}
		}
		jsonOK(w, relays)
	}
}

func apiValidators(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if q.ValidatorSet == nil {
			jsonOK(w, []any{})
			return
		}
		validators, err := q.ValidatorSet()
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		type validatorEntry struct {
			PubKey  string `json:"pub_key"`
			Address string `json:"address"`
			Staked  uint64 `json:"staked_ut,omitempty"`
		}
		out := make([]validatorEntry, len(validators))
		for i, pk := range validators {
			var staked uint64
			if q.Stake != nil {
				staked, _ = q.Stake(pk)
			}
			out[i] = validatorEntry{
				PubKey:  pk,
				Address: wallet.PubKeyToAddress(pk),
				Staked:  staked,
			}
		}
		jsonOK(w, map[string]any{
			"count":      len(out),
			"validators": out,
		})
	}
}

func apiIdentity(q ExplorerQuery) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		input := strings.TrimPrefix(r.URL.Path, "/api/identity/")
		if input == "" {
			jsonErr(w, fmt.Errorf("pubkey or address required"), 400)
			return
		}
		if q.IdentityInfo == nil {
			jsonErr(w, fmt.Errorf("identity lookup not available"), 503)
			return
		}
		// Resolve DC address → pubkey if needed.
		pubKey, err := resolveAccountID(q, input)
		if err != nil {
			jsonErr(w, err, 404)
			return
		}
		info, err := q.IdentityInfo(pubKey)
		if err != nil {
			jsonErr(w, err, 500)
			return
		}
		jsonOK(w, info)
	}
}

func apiSubmitTx(q ExplorerQuery) http.HandlerFunc {
	// The returned handler is wrapped in withSubmitTxGuards() by the caller:
	// body size is capped at MaxTxRequestBytes and per-IP rate limiting is
	// applied upstream (see api_guards.go). This function therefore only
	// handles the semantics — shape, signature, timestamp window, dispatch.
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			jsonErr(w, fmt.Errorf("method not allowed"), 405)
			return
		}
		var tx blockchain.Transaction
		if err := json.NewDecoder(r.Body).Decode(&tx); err != nil {
			jsonErr(w, fmt.Errorf("invalid JSON: %w", err), 400)
			return
		}
		// Reject txs with an obviously-bad clock value before we even verify
		// the signature — cheaper failure, and cuts a replay window against
		// long-rotated dedup caches.
		if err := ValidateTxTimestamp(&tx); err != nil {
			MetricTxSubmitRejected.Inc()
			jsonErr(w, fmt.Errorf("bad timestamp: %w", err), 400)
			return
		}
		if err := verifyTransactionSignature(&tx); err != nil {
			MetricTxSubmitRejected.Inc()
			jsonErr(w, err, 400)
			return
		}
		if err := q.SubmitTx(&tx); err != nil {
			MetricTxSubmitRejected.Inc()
			jsonErr(w, err, 500)
			return
		}
		MetricTxSubmitAccepted.Inc()
		jsonOK(w, map[string]string{"id": tx.ID, "status": "accepted"})
	}
}