package rpc

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"github.com/kaspanet/kaspad/dagconfig"
	"github.com/kaspanet/kaspad/database"
	"github.com/kaspanet/kaspad/rpcmodel"
	"github.com/kaspanet/kaspad/txscript"
	"github.com/kaspanet/kaspad/util"
	"github.com/kaspanet/kaspad/util/daghash"
	"github.com/kaspanet/kaspad/util/pointers"
	"github.com/kaspanet/kaspad/wire"
)

// retrievedTx represents a transaction that was either loaded from the
// transaction memory pool or from the database. When a transaction is loaded
// from the database, it is loaded with the raw serialized bytes while the
// mempool has the fully deserialized structure. This structure therefore will
// have one of the two fields set depending on where is was retrieved from.
// This is mainly done for efficiency to avoid extra serialization steps when
// possible.
type retrievedTx struct {
	txBytes []byte
	blkHash *daghash.Hash // Only set when transaction is in a block.
	tx      *util.Tx
}

// handleSearchRawTransactions implements the searchRawTransactions command.
func handleSearchRawTransactions(s *Server, cmd interface{}, closeChan <-chan struct{}) (interface{}, error) {
	// Respond with an error if the address index is not enabled.
	addrIndex := s.cfg.AddrIndex
	if addrIndex == nil {
		return nil, &rpcmodel.RPCError{
			Code:    rpcmodel.ErrRPCMisc,
			Message: "Address index must be enabled (--addrindex)",
		}
	}

	// Override the flag for including extra previous output information in
	// each input if needed.
	c := cmd.(*rpcmodel.SearchRawTransactionsCmd)
	vinExtra := false
	if c.VinExtra != nil {
		vinExtra = *c.VinExtra
	}

	// Including the extra previous output information requires the
	// transaction index. Currently the address index relies on the
	// transaction index, so this check is redundant, but it's better to be
	// safe in case the address index is ever changed to not rely on it.
	if vinExtra && s.cfg.TxIndex == nil {
		return nil, &rpcmodel.RPCError{
			Code:    rpcmodel.ErrRPCMisc,
			Message: "Transaction index must be enabled (--txindex)",
		}
	}

	// Attempt to decode the supplied address.
	params := s.cfg.DAGParams
	addr, err := util.DecodeAddress(c.Address, params.Prefix)
	if err != nil {
		return nil, &rpcmodel.RPCError{
			Code:    rpcmodel.ErrRPCInvalidAddressOrKey,
			Message: "Invalid address or key: " + err.Error(),
		}
	}

	// Override the default number of requested entries if needed. Also,
	// just return now if the number of requested entries is zero to avoid
	// extra work.
	numRequested := 100
	if c.Count != nil {
		numRequested = *c.Count
		if numRequested < 0 {
			numRequested = 1
		}
	}
	if numRequested == 0 {
		return nil, nil
	}

	// Override the default number of entries to skip if needed.
	var numToSkip int
	if c.Skip != nil {
		numToSkip = *c.Skip
		if numToSkip < 0 {
			numToSkip = 0
		}
	}

	// Override the reverse flag if needed.
	var reverse bool
	if c.Reverse != nil {
		reverse = *c.Reverse
	}

	// Add transactions from mempool first if client asked for reverse
	// order. Otherwise, they will be added last (as needed depending on
	// the requested counts).
	//
	// NOTE: This code doesn't sort by dependency. This might be something
	// to do in the future for the client's convenience, or leave it to the
	// client.
	numSkipped := uint32(0)
	addressTxns := make([]retrievedTx, 0, numRequested)
	if reverse {
		// Transactions in the mempool are not in a block header yet,
		// so the block header field in the retieved transaction struct
		// is left nil.
		mpTxns, mpSkipped := fetchMempoolTxnsForAddress(s, addr,
			uint32(numToSkip), uint32(numRequested))
		numSkipped += mpSkipped
		for _, tx := range mpTxns {
			addressTxns = append(addressTxns, retrievedTx{tx: tx})
		}
	}

	// Fetch transactions from the database in the desired order if more are
	// needed.
	if len(addressTxns) < numRequested {
		err = s.cfg.DB.View(func(dbTx database.Tx) error {
			regions, dbSkipped, err := addrIndex.TxRegionsForAddress(
				dbTx, addr, uint32(numToSkip)-numSkipped,
				uint32(numRequested-len(addressTxns)), reverse)
			if err != nil {
				return err
			}

			// Load the raw transaction bytes from the database.
			serializedTxns, err := dbTx.FetchBlockRegions(regions)
			if err != nil {
				return err
			}

			// Add the transaction and the hash of the block it is
			// contained in to the list. Note that the transaction
			// is left serialized here since the caller might have
			// requested non-verbose output and hence there would be
			// no point in deserializing it just to reserialize it
			// later.
			for i, serializedTx := range serializedTxns {
				addressTxns = append(addressTxns, retrievedTx{
					txBytes: serializedTx,
					blkHash: regions[i].Hash,
				})
			}
			numSkipped += dbSkipped

			return nil
		})
		if err != nil {
			context := "Failed to load address index entries"
			return nil, internalRPCError(err.Error(), context)
		}

	}

	// Add transactions from mempool last if client did not request reverse
	// order and the number of results is still under the number requested.
	if !reverse && len(addressTxns) < numRequested {
		// Transactions in the mempool are not in a block header yet,
		// so the block header field in the retieved transaction struct
		// is left nil.
		mpTxns, mpSkipped := fetchMempoolTxnsForAddress(s, addr,
			uint32(numToSkip)-numSkipped, uint32(numRequested-
				len(addressTxns)))
		numSkipped += mpSkipped
		for _, tx := range mpTxns {
			addressTxns = append(addressTxns, retrievedTx{tx: tx})
		}
	}

	// Address has never been used if neither source yielded any results.
	if len(addressTxns) == 0 {
		return []rpcmodel.SearchRawTransactionsResult{}, nil
	}

	// Serialize all of the transactions to hex.
	hexTxns := make([]string, len(addressTxns))
	for i := range addressTxns {
		// Simply encode the raw bytes to hex when the retrieved
		// transaction is already in serialized form.
		rtx := &addressTxns[i]
		if rtx.txBytes != nil {
			hexTxns[i] = hex.EncodeToString(rtx.txBytes)
			continue
		}

		// Serialize the transaction first and convert to hex when the
		// retrieved transaction is the deserialized structure.
		hexTxns[i], err = messageToHex(rtx.tx.MsgTx())
		if err != nil {
			return nil, err
		}
	}

	// When not in verbose mode, simply return a list of serialized txns.
	if c.Verbose != nil && !*c.Verbose {
		return hexTxns, nil
	}

	// Normalize the provided filter addresses (if any) to ensure there are
	// no duplicates.
	filterAddrMap := make(map[string]struct{})
	if c.FilterAddrs != nil && len(*c.FilterAddrs) > 0 {
		for _, addr := range *c.FilterAddrs {
			filterAddrMap[addr] = struct{}{}
		}
	}

	// The verbose flag is set, so generate the JSON object and return it.
	srtList := make([]rpcmodel.SearchRawTransactionsResult, len(addressTxns))
	for i := range addressTxns {
		// The deserialized transaction is needed, so deserialize the
		// retrieved transaction if it's in serialized form (which will
		// be the case when it was lookup up from the database).
		// Otherwise, use the existing deserialized transaction.
		rtx := &addressTxns[i]
		var mtx *wire.MsgTx
		if rtx.tx == nil {
			// Deserialize the transaction.
			mtx = new(wire.MsgTx)
			err := mtx.Deserialize(bytes.NewReader(rtx.txBytes))
			if err != nil {
				context := "Failed to deserialize transaction"
				return nil, internalRPCError(err.Error(),
					context)
			}
		} else {
			mtx = rtx.tx.MsgTx()
		}

		result := &srtList[i]
		result.Hex = hexTxns[i]
		result.TxID = mtx.TxID().String()
		result.Vin, err = createVinListPrevOut(s, mtx, params, vinExtra,
			filterAddrMap)
		if err != nil {
			return nil, err
		}
		result.Vout = createVoutList(mtx, params, filterAddrMap)
		result.Version = mtx.Version
		result.LockTime = mtx.LockTime

		// Transactions grabbed from the mempool aren't yet in a block,
		// so conditionally fetch block details here. This will be
		// reflected in the final JSON output (mempool won't have
		// confirmations or block information).
		var blkHeader *wire.BlockHeader
		var blkHashStr string
		if blkHash := rtx.blkHash; blkHash != nil {
			// Fetch the header from DAG.
			header, err := s.cfg.DAG.HeaderByHash(blkHash)
			if err != nil {
				return nil, &rpcmodel.RPCError{
					Code:    rpcmodel.ErrRPCBlockNotFound,
					Message: "Block not found",
				}
			}

			blkHeader = header
			blkHashStr = blkHash.String()
		}

		// Add the block information to the result if there is any.
		if blkHeader != nil {
			result.Time = uint64(blkHeader.Timestamp.Unix())
			result.Blocktime = uint64(blkHeader.Timestamp.Unix())
			result.BlockHash = blkHashStr
		}

		// rtx.tx is only set when the transaction was retrieved from the mempool
		result.IsInMempool = rtx.tx != nil

		if s.cfg.TxIndex != nil && !result.IsInMempool {
			confirmations, err := txConfirmations(s, mtx.TxID())
			if err != nil {
				context := "Failed to obtain block confirmations"
				return nil, internalRPCError(err.Error(), context)
			}
			result.Confirmations = &confirmations
		}
	}

	return srtList, nil
}

// createVinListPrevOut returns a slice of JSON objects for the inputs of the
// passed transaction.
func createVinListPrevOut(s *Server, mtx *wire.MsgTx, dagParams *dagconfig.Params, vinExtra bool, filterAddrMap map[string]struct{}) ([]rpcmodel.VinPrevOut, error) {
	// Use a dynamically sized list to accommodate the address filter.
	vinList := make([]rpcmodel.VinPrevOut, 0, len(mtx.TxIn))

	// Lookup all of the referenced transaction outputs needed to populate the
	// previous output information if requested. Coinbase transactions do not contain
	// valid inputs: block hash instead of transaction ID.
	var originOutputs map[wire.Outpoint]wire.TxOut
	if !mtx.IsCoinBase() && (vinExtra || len(filterAddrMap) > 0) {
		var err error
		originOutputs, err = fetchInputTxos(s, mtx)
		if err != nil {
			return nil, err
		}
	}

	for _, txIn := range mtx.TxIn {
		// The disassembled string will contain [error] inline
		// if the script doesn't fully parse, so ignore the
		// error here.
		disbuf, _ := txscript.DisasmString(txIn.SignatureScript)

		// Create the basic input entry without the additional optional
		// previous output details which will be added later if
		// requested and available.
		prevOut := &txIn.PreviousOutpoint
		vinEntry := rpcmodel.VinPrevOut{
			TxID:     prevOut.TxID.String(),
			Vout:     prevOut.Index,
			Sequence: txIn.Sequence,
			ScriptSig: &rpcmodel.ScriptSig{
				Asm: disbuf,
				Hex: hex.EncodeToString(txIn.SignatureScript),
			},
		}

		// Add the entry to the list now if it already passed the filter
		// since the previous output might not be available.
		passesFilter := len(filterAddrMap) == 0
		if passesFilter {
			vinList = append(vinList, vinEntry)
		}

		// Only populate previous output information if requested and
		// available.
		if len(originOutputs) == 0 {
			continue
		}
		originTxOut, ok := originOutputs[*prevOut]
		if !ok {
			continue
		}

		// Ignore the error here since an error means the script
		// couldn't parse and there is no additional information about
		// it anyways.
		_, addr, _ := txscript.ExtractScriptPubKeyAddress(
			originTxOut.ScriptPubKey, dagParams)

		var encodedAddr *string
		if addr != nil {
			// Encode the address while checking if the address passes the
			// filter when needed.
			encodedAddr = pointers.String(addr.EncodeAddress())

			// If the filter doesn't already pass, make it pass if
			// the address exists in the filter.
			if _, exists := filterAddrMap[*encodedAddr]; exists {
				passesFilter = true
			}
		}

		// Ignore the entry if it doesn't pass the filter.
		if !passesFilter {
			continue
		}

		// Add entry to the list if it wasn't already done above.
		if len(filterAddrMap) != 0 {
			vinList = append(vinList, vinEntry)
		}

		// Update the entry with previous output information if
		// requested.
		if vinExtra {
			vinListEntry := &vinList[len(vinList)-1]
			vinListEntry.PrevOut = &rpcmodel.PrevOut{
				Address: encodedAddr,
				Value:   util.Amount(originTxOut.Value).ToKAS(),
			}
		}
	}

	return vinList, nil
}

// fetchInputTxos fetches the outpoints from all transactions referenced by the
// inputs to the passed transaction by checking the transaction mempool first
// then the transaction index for those already mined into blocks.
func fetchInputTxos(s *Server, tx *wire.MsgTx) (map[wire.Outpoint]wire.TxOut, error) {
	mp := s.cfg.TxMemPool
	originOutputs := make(map[wire.Outpoint]wire.TxOut)
	for txInIndex, txIn := range tx.TxIn {
		// Attempt to fetch and use the referenced transaction from the
		// memory pool.
		origin := &txIn.PreviousOutpoint
		originTx, err := mp.FetchTransaction(&origin.TxID)
		if err == nil {
			txOuts := originTx.MsgTx().TxOut
			if origin.Index >= uint32(len(txOuts)) {
				errStr := fmt.Sprintf("unable to find output "+
					"%s referenced from transaction %s:%d",
					origin, tx.TxID(), txInIndex)
				return nil, internalRPCError(errStr, "")
			}

			originOutputs[*origin] = *txOuts[origin.Index]
			continue
		}

		// Look up the location of the transaction.
		blockRegion, err := s.cfg.TxIndex.TxFirstBlockRegion(&origin.TxID)
		if err != nil {
			context := "Failed to retrieve transaction location"
			return nil, internalRPCError(err.Error(), context)
		}
		if blockRegion == nil {
			return nil, rpcNoTxInfoError(&origin.TxID)
		}

		// Load the raw transaction bytes from the database.
		var txBytes []byte
		err = s.cfg.DB.View(func(dbTx database.Tx) error {
			var err error
			txBytes, err = dbTx.FetchBlockRegion(blockRegion)
			return err
		})
		if err != nil {
			return nil, rpcNoTxInfoError(&origin.TxID)
		}

		// Deserialize the transaction
		var msgTx wire.MsgTx
		err = msgTx.Deserialize(bytes.NewReader(txBytes))
		if err != nil {
			context := "Failed to deserialize transaction"
			return nil, internalRPCError(err.Error(), context)
		}

		// Add the referenced output to the map.
		if origin.Index >= uint32(len(msgTx.TxOut)) {
			errStr := fmt.Sprintf("unable to find output %s "+
				"referenced from transaction %s:%d", origin,
				tx.TxID(), txInIndex)
			return nil, internalRPCError(errStr, "")
		}
		originOutputs[*origin] = *msgTx.TxOut[origin.Index]
	}

	return originOutputs, nil
}

// fetchMempoolTxnsForAddress queries the address index for all unconfirmed
// transactions that involve the provided address. The results will be limited
// by the number to skip and the number requested.
func fetchMempoolTxnsForAddress(s *Server, addr util.Address, numToSkip, numRequested uint32) ([]*util.Tx, uint32) {
	// There are no entries to return when there are less available than the
	// number being skipped.
	mpTxns := s.cfg.AddrIndex.UnconfirmedTxnsForAddress(addr)
	numAvailable := uint32(len(mpTxns))
	if numToSkip > numAvailable {
		return nil, numAvailable
	}

	// Filter the available entries based on the number to skip and number
	// requested.
	rangeEnd := numToSkip + numRequested
	if rangeEnd > numAvailable {
		rangeEnd = numAvailable
	}
	return mpTxns[numToSkip:rangeEnd], numToSkip
}