apiroutes.go

// Copyright (c) 2018, The Decred developers
// Copyright (c) 2017, The dcrdata developers
// See LICENSE for details.

package api

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"sort"
	"strconv"
	"strings"
	"sync"

	"github.com/decred/dcrd/chaincfg"
	"github.com/decred/dcrd/dcrjson"
	"github.com/decred/dcrd/rpcclient"
	apitypes "github.com/decred/dcrdata/v3/api/types"
	"github.com/decred/dcrdata/v3/db/dbtypes"
	"github.com/decred/dcrdata/v3/explorer"
	m "github.com/decred/dcrdata/v3/middleware"
	notify "github.com/decred/dcrdata/v3/notification"
	"github.com/decred/dcrdata/v3/txhelpers"
	appver "github.com/decred/dcrdata/v3/version"
)

// DataSourceLite specifies an interface for collecting data from the built-in
// databases (i.e. SQLite, badger, ffldb)
type DataSourceLite interface {
	CoinSupply() *apitypes.CoinSupply
	GetHeight() int
	GetBestBlockHash() (string, error)
	GetBlockHash(idx int64) (string, error)
	GetBlockHeight(hash string) (int64, error)
	//Get(idx int) *blockdata.BlockData
	GetHeader(idx int) *dcrjson.GetBlockHeaderVerboseResult
	GetBlockVerbose(idx int, verboseTx bool) *dcrjson.GetBlockVerboseResult
	GetBlockVerboseByHash(hash string, verboseTx bool) *dcrjson.GetBlockVerboseResult
	GetRawTransaction(txid string) *apitypes.Tx
	GetTransactionHex(txid string) string
	GetTrimmedTransaction(txid string) *apitypes.TrimmedTx
	GetRawTransactionWithPrevOutAddresses(txid string) (*apitypes.Tx, [][]string)
	GetVoteInfo(txid string) (*apitypes.VoteInfo, error)
	GetVoteVersionInfo(ver uint32) (*dcrjson.GetVoteInfoResult, error)
	GetStakeVersions(txHash string, count int32) (*dcrjson.GetStakeVersionsResult, error)
	GetStakeVersionsLatest() (*dcrjson.StakeVersions, error)
	GetAllTxIn(txid string) []*apitypes.TxIn
	GetAllTxOut(txid string) []*apitypes.TxOut
	GetTransactionsForBlock(idx int64) *apitypes.BlockTransactions
	GetTransactionsForBlockByHash(hash string) *apitypes.BlockTransactions
	GetFeeInfo(idx int) *dcrjson.FeeInfoBlock
	//GetStakeDiffEstimate(idx int) *dcrjson.EstimateStakeDiffResult
	GetStakeInfoExtended(idx int) *apitypes.StakeInfoExtended
	//needs db update: GetStakeInfoExtendedByHash(hash string) *apitypes.StakeInfoExtended
	GetStakeDiffEstimates() *apitypes.StakeDiff
	//GetBestBlock() *blockdata.BlockData
	GetSummary(idx int) *apitypes.BlockDataBasic
	GetSummaryByHash(hash string) *apitypes.BlockDataBasic
	GetBestBlockSummary() *apitypes.BlockDataBasic
	GetBlockSize(idx int) (int32, error)
	GetBlockSizeRange(idx0, idx1 int) ([]int32, error)
	GetPoolInfo(idx int) *apitypes.TicketPoolInfo
	GetPoolInfoByHash(hash string) *apitypes.TicketPoolInfo
	GetPoolInfoRange(idx0, idx1 int) []apitypes.TicketPoolInfo
	GetPool(idx int64) ([]string, error)
	GetPoolByHash(hash string) ([]string, error)
	GetPoolValAndSizeRange(idx0, idx1 int) ([]float64, []float64)
	GetSDiff(idx int) float64
	GetSDiffRange(idx0, idx1 int) []float64
	GetMempoolSSTxSummary() *apitypes.MempoolTicketFeeInfo
	GetMempoolSSTxFeeRates(N int) *apitypes.MempoolTicketFees
	GetMempoolSSTxDetails(N int) *apitypes.MempoolTicketDetails
	GetAddressTransactions(addr string, count int) *apitypes.Address
	GetAddressTransactionsRaw(addr string, count int) []*apitypes.AddressTxRaw
	GetAddressTransactionsWithSkip(addr string, count, skip int) *apitypes.Address
	GetAddressTransactionsRawWithSkip(addr string, count, skip int) []*apitypes.AddressTxRaw
	SendRawTransaction(txhex string) (string, error)
	GetExplorerAddress(address string, count, offset int64) (*explorer.AddressInfo, error)
}

// DataSourceAux specifies an interface for advanced data collection using the
// auxiliary DB (e.g. PostgreSQL).
type DataSourceAux interface {
	SpendingTransaction(fundingTx string, vout uint32) (string, uint32, int8, error)
	SpendingTransactions(fundingTxID string) ([]string, []uint32, []uint32, error)
	AddressHistory(address string, N, offset int64, txnType dbtypes.AddrTxnType) ([]*dbtypes.AddressRow, *explorer.AddressBalance, error)
	FillAddressTransactions(addrInfo *explorer.AddressInfo) error
	AddressTransactionDetails(addr string, count, skip int64,
		txnType dbtypes.AddrTxnType) (*apitypes.Address, error)
	AddressTotals(address string) (*apitypes.AddressTotals, error)
	VotesInBlock(hash string) (int16, error)
	GetTxHistoryData(address string, addrChart dbtypes.HistoryChart,
		chartGroupings dbtypes.ChartGrouping) (*dbtypes.ChartsData, error)
	TicketPoolVisualization(interval dbtypes.ChartGrouping) (
		[]*dbtypes.PoolTicketsData, *dbtypes.PoolTicketsData, uint64, error)
}

// dcrdata application context used by all route handlers
type appContext struct {
	nodeClient    *rpcclient.Client
	Params        *chaincfg.Params
	BlockData     DataSourceLite
	AuxDataSource DataSourceAux
	LiteMode      bool
	Status        apitypes.Status
	statusMtx     sync.RWMutex
	JSONIndent    string
}

// NewContext constructs a new appContext from the RPC client, primary and
// auxiliary data sources, and JSON indentation string.
func NewContext(client *rpcclient.Client, params *chaincfg.Params, dataSource DataSourceLite, auxDataSource DataSourceAux, JSONIndent string) *appContext {
	conns, _ := client.GetConnectionCount()
	nodeHeight, _ := client.GetBlockCount()

	// explorerDataSource is an interface that could have a value of pointer
	// type, and if either is nil this means lite mode.
	liteMode := auxDataSource == nil || reflect.ValueOf(auxDataSource).IsNil()

	return &appContext{
		nodeClient:    client,
		Params:        params,
		BlockData:     dataSource,
		AuxDataSource: auxDataSource,
		LiteMode:      liteMode,
		Status: apitypes.Status{
			Height:          uint32(nodeHeight),
			NodeConnections: conns,
			APIVersion:      APIVersion,
			DcrdataVersion:  appver.Version(),
		},
		JSONIndent: JSONIndent,
	}
}

// StatusNtfnHandler keeps the appContext's Status up-to-date with changes in
// node and DB status.
func (c *appContext) StatusNtfnHandler(ctx context.Context, wg *sync.WaitGroup) {
	defer wg.Done()
out:
	for {
	keepon:
		select {
		case height, ok := <-notify.NtfnChans.UpdateStatusNodeHeight:
			if !ok {
				log.Warnf("Block connected channel closed.")
				break out
			}

			c.statusMtx.Lock()
			c.Status.Height = height

			// if DB height agrees with node height, then we're ready
			c.Status.Ready = c.Status.Height == c.Status.DBHeight

			var err error
			c.Status.NodeConnections, err = c.nodeClient.GetConnectionCount()
			if err != nil {
				c.Status.Ready = false
				c.statusMtx.Unlock()
				log.Warn("Failed to get connection count: ", err)
				break keepon
			}
			c.statusMtx.Unlock()

		case height, ok := <-notify.NtfnChans.UpdateStatusDBHeight:
			if !ok {
				log.Warnf("Block connected channel closed.")
				break out
			}

			if c.BlockData == nil {
				panic("BlockData DataSourceLite is nil")
			}

			summary := c.BlockData.GetBestBlockSummary()
			if summary == nil {
				log.Errorf("BlockData summary is nil for height %d.", height)
				break keepon
			}

			c.statusMtx.Lock()
			c.Status.DBHeight = height
			c.Status.DBLastBlockTime = summary.Time

			bdHeight := c.BlockData.GetHeight()
			if bdHeight >= 0 && summary.Height == uint32(bdHeight) &&
				height == uint32(bdHeight) {
				// if DB height agrees with node height, then we're ready
				c.Status.Ready = c.Status.Height == c.Status.DBHeight
				c.statusMtx.Unlock()
				break keepon
			}

			c.Status.Ready = false
			c.statusMtx.Unlock()
			log.Errorf("New DB height (%d) and stored block data (%d, %d) not consistent.",
				height, bdHeight, summary.Height)

		case <-ctx.Done():
			log.Debugf("Got quit signal. Exiting block connected handler for STATUS monitor.")
			break out
		}
	}
}

// root is a http.Handler intended for the API root path. This essentially
// provides a heartbeat, and no information about the application status.
func (c *appContext) root(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, "dcrdata api running")
}

func (c *appContext) writeJSONHandlerFunc(thing interface{}) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		writeJSON(w, thing, c.JSONIndent)
	}
}

func writeJSON(w http.ResponseWriter, thing interface{}, indent string) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	encoder := json.NewEncoder(w)
	encoder.SetIndent("", indent)
	if err := encoder.Encode(thing); err != nil {
		apiLog.Infof("JSON encode error: %v", err)
	}
}

func (c *appContext) getIndentQuery(r *http.Request) (indent string) {
	useIndentation := r.URL.Query().Get("indent")
	if useIndentation == "1" || useIndentation == "true" {
		indent = c.JSONIndent
	}
	return
}

func getVoteVersionQuery(r *http.Request) (int32, string, error) {
	verLatest := int64(m.GetLatestVoteVersionCtx(r))
	voteVersion := r.URL.Query().Get("version")
	if voteVersion == "" {
		return int32(verLatest), voteVersion, nil
	}

	ver, err := strconv.ParseInt(voteVersion, 10, 0)
	if err != nil {
		return -1, voteVersion, err
	}
	if ver > verLatest {
		ver = verLatest
	}

	return int32(ver), voteVersion, nil
}

func (c *appContext) status(w http.ResponseWriter, r *http.Request) {
	c.statusMtx.RLock()
	defer c.statusMtx.RUnlock()
	writeJSON(w, c.Status, c.getIndentQuery(r))
}

func (c *appContext) coinSupply(w http.ResponseWriter, r *http.Request) {
	supply := c.BlockData.CoinSupply()
	if supply == nil {
		apiLog.Error("Unable to get coin supply.")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, supply, c.getIndentQuery(r))
}

func (c *appContext) currentHeight(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	if _, err := io.WriteString(w, strconv.Itoa(int(c.Status.Height))); err != nil {
		apiLog.Infof("failed to write height response: %v", err)
	}
}

func (c *appContext) getLatestBlock(w http.ResponseWriter, r *http.Request) {
	latestBlockSummary := c.BlockData.GetBestBlockSummary()
	if latestBlockSummary == nil {
		apiLog.Error("Unable to get latest block summary")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, latestBlockSummary, c.getIndentQuery(r))
}

func (c *appContext) getBlockHeight(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)

	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	if _, err := io.WriteString(w, strconv.Itoa(int(idx))); err != nil {
		apiLog.Infof("failed to write height response: %v", err)
	}
}

func (c *appContext) getBlockHash(w http.ResponseWriter, r *http.Request) {
	hash := c.getBlockHashCtx(r)

	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	if _, err := io.WriteString(w, hash); err != nil {
		apiLog.Infof("failed to write height response: %v", err)
	}
}

func (c *appContext) getBlockSummary(w http.ResponseWriter, r *http.Request) {
	// attempt to get hash of block set by hash or (fallback) height set on path
	hash := c.getBlockHashCtx(r)
	if hash == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockSummary := c.BlockData.GetSummaryByHash(hash)
	if blockSummary == nil {
		apiLog.Errorf("Unable to get block %s summary", hash)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockSummary, c.getIndentQuery(r))
}

func (c *appContext) getBlockTransactions(w http.ResponseWriter, r *http.Request) {
	hash := c.getBlockHashCtx(r)
	if hash == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockTransactions := c.BlockData.GetTransactionsForBlockByHash(hash)
	if blockTransactions == nil {
		apiLog.Errorf("Unable to get block %s transactions", hash)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockTransactions, c.getIndentQuery(r))
}

func (c *appContext) getBlockTransactionsCount(w http.ResponseWriter, r *http.Request) {
	hash := c.getBlockHashCtx(r)
	if hash == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockTransactions := c.BlockData.GetTransactionsForBlockByHash(hash)
	if blockTransactions == nil {
		apiLog.Errorf("Unable to get block %s transactions", hash)
		return
	}

	counts := &apitypes.BlockTransactionCounts{
		Tx:  len(blockTransactions.Tx),
		STx: len(blockTransactions.STx),
	}
	writeJSON(w, counts, c.getIndentQuery(r))
}

func (c *appContext) getBlockHeader(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockHeader := c.BlockData.GetHeader(int(idx))
	if blockHeader == nil {
		apiLog.Errorf("Unable to get block %d header", idx)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockHeader, c.getIndentQuery(r))
}

func (c *appContext) getBlockVerbose(w http.ResponseWriter, r *http.Request) {
	hash := c.getBlockHashCtx(r)
	if hash == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockVerbose := c.BlockData.GetBlockVerboseByHash(hash, false)
	if blockVerbose == nil {
		apiLog.Errorf("Unable to get block %s", hash)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockVerbose, c.getIndentQuery(r))
}

func (c *appContext) getVoteInfo(w http.ResponseWriter, r *http.Request) {
	ver, verStr, err := getVoteVersionQuery(r)
	if err != nil || ver < 0 {
		apiLog.Errorf("Unable to get vote info for stake version %s", verStr)
		http.Error(w, "Unable to get vote info for stake version "+verStr, 422)
		return
	}
	voteVersionInfo, err := c.BlockData.GetVoteVersionInfo(uint32(ver))
	if err != nil || voteVersionInfo == nil {
		apiLog.Errorf("Unable to get vote version %d info: %v", ver, err)
		http.Error(w, "Unable to get vote info for stake version "+verStr, 422)
		return
	}
	writeJSON(w, voteVersionInfo, c.getIndentQuery(r))
}

// setOutputSpends retrieves spending transaction information for each output of
// the specified transaction. This sets the vouts[i].Spend fields for each
// output that is spent. For unspent outputs, the Spend field remains a nil
// pointer.
func (c *appContext) setOutputSpends(txid string, vouts []apitypes.Vout) error {
	if c.LiteMode {
		apiLog.Warnf("Not setting spending transaction data in lite mode.")
		return nil
	}

	// For each output of this transaction, look up any spending transactions,
	// and the index of the spending transaction input.
	spendHashes, spendVinInds, voutInds, err := c.AuxDataSource.SpendingTransactions(txid)
	if err != nil && err != sql.ErrNoRows {
		return fmt.Errorf("unable to get spending transaction info for outputs of %s", txid)
	}
	if len(voutInds) > len(vouts) {
		return fmt.Errorf("invalid spending transaction data for %s", txid)
	}
	for i, vout := range voutInds {
		if int(vout) >= len(vouts) {
			return fmt.Errorf("invalid spending transaction data (%s:%d)", txid, vout)
		}
		vouts[vout].Spend = &apitypes.TxInputID{
			Hash:  spendHashes[i],
			Index: spendVinInds[i],
		}
	}
	return nil
}

// setTxSpends retrieves spending transaction information for each output of the
// given transaction. This sets the tx.Vout[i].Spend fields for each output that
// is spent. For unspent outputs, the Spend field remains a nil pointer.
func (c *appContext) setTxSpends(tx *apitypes.Tx) error {
	return c.setOutputSpends(tx.TxID, tx.Vout)
}

// setTrimmedTxSpends is like setTxSpends except that it operates on a TrimmedTx
// instead of a Tx.
func (c *appContext) setTrimmedTxSpends(tx *apitypes.TrimmedTx) error {
	return c.setOutputSpends(tx.TxID, tx.Vout)
}

func (c *appContext) getTransaction(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	tx := c.BlockData.GetRawTransaction(txid)
	if tx == nil {
		apiLog.Errorf("Unable to get transaction %s", txid)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	// Look up any spending transactions for each output of this transaction.
	// This is only done in full mode, and when the client requests spends with
	// the URL query ?spends=true.
	spendParam := r.URL.Query().Get("spends")
	withSpends := spendParam == "1" || strings.EqualFold(spendParam, "true")

	if withSpends && !c.LiteMode {
		if err := c.setTxSpends(tx); err != nil {
			apiLog.Errorf("Unable to get spending transaction info for outputs of %s: %v", txid, err)
			http.Error(w, http.StatusText(http.StatusInternalServerError),
				http.StatusInternalServerError)
			return
		}
	}

	writeJSON(w, tx, c.getIndentQuery(r))
}

func (c *appContext) getTransactionHex(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	hex := c.BlockData.GetTransactionHex(txid)

	fmt.Fprintf(w, hex)
}

func (c *appContext) getDecodedTx(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	tx := c.BlockData.GetTrimmedTransaction(txid)
	if tx == nil {
		apiLog.Errorf("Unable to get transaction %s", txid)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	// Look up any spending transactions for each output of this transaction.
	// This is only done in full mode, and when the client requests spends with
	// the URL query ?spends=true.
	spendParam := r.URL.Query().Get("spends")
	withSpends := spendParam == "1" || strings.EqualFold(spendParam, "true")

	if withSpends && !c.LiteMode {
		if err := c.setTrimmedTxSpends(tx); err != nil {
			apiLog.Errorf("Unable to get spending transaction info for outputs of %s: %v", txid, err)
			http.Error(w, http.StatusText(http.StatusInternalServerError),
				http.StatusInternalServerError)
			return
		}
	}

	writeJSON(w, tx, c.getIndentQuery(r))
}

func (c *appContext) getTransactions(w http.ResponseWriter, r *http.Request) {
	txids := m.GetTxnsCtx(r)
	if txids == nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	// Look up any spending transactions for each output of this transaction.
	// This is only done in full mode, and when the client requests spends with
	// the URL query ?spends=true.
	spendParam := r.URL.Query().Get("spends")
	withSpends := spendParam == "1" || strings.EqualFold(spendParam, "true")

	txns := make([]*apitypes.Tx, 0, len(txids))
	for i := range txids {
		tx := c.BlockData.GetRawTransaction(txids[i])
		if tx == nil {
			apiLog.Errorf("Unable to get transaction %s", txids[i])
			http.Error(w, http.StatusText(422), 422)
			return
		}

		if withSpends && !c.LiteMode {
			if err := c.setTxSpends(tx); err != nil {
				apiLog.Errorf("Unable to get spending transaction info for outputs of %s: %v",
					txids[i], err)
				http.Error(w, http.StatusText(http.StatusInternalServerError),
					http.StatusInternalServerError)
				return
			}
		}

		txns = append(txns, tx)
	}

	writeJSON(w, txns, c.getIndentQuery(r))
}

func (c *appContext) getDecodedTransactions(w http.ResponseWriter, r *http.Request) {
	txids := m.GetTxnsCtx(r)
	if txids == nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	txns := make([]*apitypes.TrimmedTx, 0, len(txids))
	for i := range txids {
		tx := c.BlockData.GetTrimmedTransaction(txids[i])
		if tx == nil {
			apiLog.Errorf("Unable to get transaction %v", tx)
			http.Error(w, http.StatusText(422), 422)
			return
		}
		txns = append(txns, tx)
	}

	writeJSON(w, txns, c.getIndentQuery(r))
}

func (c *appContext) getTxVoteInfo(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}
	vinfo, err := c.BlockData.GetVoteInfo(txid)
	if err != nil {
		apiLog.Errorf("Unable to get vote info for transaction %s", txid)
		http.Error(w, "Unable to get vote info. Is tx "+txid+" a vote?", 422)
		return
	}
	writeJSON(w, vinfo, c.getIndentQuery(r))
}

// getTransactionInputs serves []TxIn
func (c *appContext) getTransactionInputs(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	allTxIn := c.BlockData.GetAllTxIn(txid)
	// allTxIn may be empty, but not a nil slice
	if allTxIn == nil {
		apiLog.Errorf("Unable to get all TxIn for transaction %s", txid)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, allTxIn, c.getIndentQuery(r))
}

// getTransactionInput serves TxIn[i]
func (c *appContext) getTransactionInput(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	index := m.GetTxIOIndexCtx(r)
	if index < 0 {
		http.NotFound(w, r)
		//http.Error(w, http.StatusText(422), 422)
		return
	}

	allTxIn := c.BlockData.GetAllTxIn(txid)
	// allTxIn may be empty, but not a nil slice
	if allTxIn == nil {
		apiLog.Warnf("Unable to get all TxIn for transaction %s", txid)
		http.NotFound(w, r)
		return
	}

	if len(allTxIn) <= index {
		apiLog.Debugf("Index %d larger than []TxIn length %d", index, len(allTxIn))
		http.NotFound(w, r)
		return
	}

	writeJSON(w, *allTxIn[index], c.getIndentQuery(r))
}

// getTransactionOutputs serves []TxOut
func (c *appContext) getTransactionOutputs(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	allTxOut := c.BlockData.GetAllTxOut(txid)
	// allTxOut may be empty, but not a nil slice
	if allTxOut == nil {
		apiLog.Errorf("Unable to get all TxOut for transaction %s", txid)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, allTxOut, c.getIndentQuery(r))
}

// getTransactionOutput serves TxOut[i]
func (c *appContext) getTransactionOutput(w http.ResponseWriter, r *http.Request) {
	txid := m.GetTxIDCtx(r)
	if txid == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	index := m.GetTxIOIndexCtx(r)
	if index < 0 {
		http.NotFound(w, r)
		return
	}

	allTxOut := c.BlockData.GetAllTxOut(txid)
	// allTxOut may be empty, but not a nil slice
	if allTxOut == nil {
		apiLog.Errorf("Unable to get all TxOut for transaction %s", txid)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	if len(allTxOut) <= index {
		apiLog.Debugf("Index %d larger than []TxOut length %d", index, len(allTxOut))
		http.NotFound(w, r)
		return
	}

	writeJSON(w, *allTxOut[index], c.getIndentQuery(r))
}

func (c *appContext) getBlockFeeInfo(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockFeeInfo := c.BlockData.GetFeeInfo(int(idx))
	if blockFeeInfo == nil {
		apiLog.Errorf("Unable to get block %d fee info", idx)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockFeeInfo, c.getIndentQuery(r))
}

func (c *appContext) getBlockStakeInfoExtended(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	stakeinfo := c.BlockData.GetStakeInfoExtended(int(idx))
	if stakeinfo == nil {
		apiLog.Errorf("Unable to get block %d fee info", idx)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, stakeinfo, c.getIndentQuery(r))
}

func (c *appContext) getStakeDiffSummary(w http.ResponseWriter, r *http.Request) {
	stakeDiff := c.BlockData.GetStakeDiffEstimates()
	if stakeDiff == nil {
		apiLog.Errorf("Unable to get stake diff info")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, stakeDiff, c.getIndentQuery(r))
}

func (c *appContext) getStakeDiffCurrent(w http.ResponseWriter, r *http.Request) {
	stakeDiff := c.BlockData.GetStakeDiffEstimates()
	if stakeDiff == nil {
		apiLog.Errorf("Unable to get stake diff info")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	stakeDiffCurrent := dcrjson.GetStakeDifficultyResult{
		CurrentStakeDifficulty: stakeDiff.CurrentStakeDifficulty,
		NextStakeDifficulty:    stakeDiff.NextStakeDifficulty,
	}

	writeJSON(w, stakeDiffCurrent, c.getIndentQuery(r))
}

func (c *appContext) getStakeDiffEstimates(w http.ResponseWriter, r *http.Request) {
	stakeDiff := c.BlockData.GetStakeDiffEstimates()
	if stakeDiff == nil {
		apiLog.Errorf("Unable to get stake diff info")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, stakeDiff.Estimates, c.getIndentQuery(r))
}

func (c *appContext) getSSTxSummary(w http.ResponseWriter, r *http.Request) {
	sstxSummary := c.BlockData.GetMempoolSSTxSummary()
	if sstxSummary == nil {
		apiLog.Errorf("Unable to get SSTx info from mempool")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, sstxSummary, c.getIndentQuery(r))
}

func (c *appContext) getSSTxFees(w http.ResponseWriter, r *http.Request) {
	N := m.GetNCtx(r)
	sstxFees := c.BlockData.GetMempoolSSTxFeeRates(N)
	if sstxFees == nil {
		apiLog.Errorf("Unable to get SSTx fees from mempool")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, sstxFees, c.getIndentQuery(r))
}

func (c *appContext) getSSTxDetails(w http.ResponseWriter, r *http.Request) {
	N := m.GetNCtx(r)
	sstxDetails := c.BlockData.GetMempoolSSTxDetails(N)
	if sstxDetails == nil {
		apiLog.Errorf("Unable to get SSTx details from mempool")
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, sstxDetails, c.getIndentQuery(r))
}

func (c *appContext) getTicketPoolByDate(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		// not available in lite mode
		http.Error(w, "not available in lite mode", 422)
		return
	}

	tp := m.GetTpCtx(r)
	// default to day if no grouping was sent
	if tp == "" {
		tp = "day"
	}

	// The db queries are fast enough that it makes sense to call
	// TicketPoolVisualization here even though it returns a lot of data not
	// needed by this request.
	interval := dbtypes.ChartGroupingFromStr(tp)
	barCharts, _, height, err := c.AuxDataSource.TicketPoolVisualization(interval)
	if err != nil {
		apiLog.Errorf("Unable to get ticket pool by date: %v", err)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	tpResponse := struct {
		Height     uint64                   `json:"height"`
		PoolByDate *dbtypes.PoolTicketsData `json:"ticket_pool_data"`
	}{
		height,
		barCharts[0], // purchase time distribution
	}

	writeJSON(w, tpResponse, c.getIndentQuery(r))
}

func (c *appContext) getBlockSize(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockSize, err := c.BlockData.GetBlockSize(int(idx))
	if err != nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockSize, "")
}

func (c *appContext) blockSubsidies(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		// not available in lite mode
		http.Error(w, "not available in lite mode", 422)
		return
	}

	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}
	hash := c.getBlockHashCtx(r)

	// Unless this is a mined block, assume all votes.
	numVotes := int16(c.Params.TicketsPerBlock)
	if hash != "" {
		var err error
		numVotes, err = c.AuxDataSource.VotesInBlock(hash)
		if err != nil {
			http.NotFound(w, r)
			return
		}
	}

	work, stake, tax := txhelpers.RewardsAtBlock(idx, uint16(numVotes), c.Params)
	rewards := apitypes.BlockSubsidies{
		BlockNum:   idx,
		BlockHash:  hash,
		Work:       work,
		Stake:      stake,
		NumVotes:   numVotes,
		TotalStake: stake * int64(numVotes),
		Tax:        tax,
		Total:      work + stake*int64(numVotes) + tax,
	}

	writeJSON(w, rewards, c.getIndentQuery(r))
}

func (c *appContext) getBlockRangeSize(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 || idx < idx0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	blockSizes, err := c.BlockData.GetBlockSizeRange(idx0, idx)
	if err != nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, blockSizes, "")
}

func (c *appContext) getBlockRangeSteppedSize(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 || idx < idx0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	step := m.GetBlockStepCtx(r)
	if step <= 0 {
		http.Error(w, "Yeaaah, that step's not gonna work with me.", 422)
		return
	}

	blockSizesFull, err := c.BlockData.GetBlockSizeRange(idx0, idx)
	if err != nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	var blockSizes []int32
	if step == 1 {
		blockSizes = blockSizesFull
	} else {
		numValues := (idx - idx0 + 1) / step
		blockSizes = make([]int32, 0, numValues)
		for i := idx0; i <= idx; i += step {
			blockSizes = append(blockSizes, blockSizesFull[i-idx0])
		}
		// it's the client's problem if i doesn't go all the way to idx
	}

	writeJSON(w, blockSizes, "")
}

func (c *appContext) getBlockRangeSummary(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	// TODO: check that we have all in range

	// N := idx - idx0 + 1
	// summaries := make([]*apitypes.BlockDataBasic, 0, N)
	// for i := idx0; i <= idx; i++ {
	// 	summaries = append(summaries, c.BlockData.GetSummary(i))
	// }

	// writeJSON(w, summaries, c.getIndentQuery(r))

	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	encoder := json.NewEncoder(w)
	indent := c.getIndentQuery(r)
	prefix, newline := indent, ""
	encoder.SetIndent(prefix, indent)
	if indent != "" {
		newline = "\n"
	}
	fmt.Fprintf(w, "[%s%s", newline, prefix)
	for i := idx0; i <= idx; i++ {
		summary := c.BlockData.GetSummary(i)
		if summary == nil {
			apiLog.Debugf("Unknown block %d", i)
			http.Error(w, fmt.Sprintf("I don't know block %d", i), http.StatusNotFound)
			return
		}
		// TODO: deal with the extra newline from Encode, if needed
		if err := encoder.Encode(summary); err != nil {
			apiLog.Infof("JSON encode error: %v", err)
			http.Error(w, http.StatusText(422), 422)
			return
		}
		if i != idx {
			fmt.Fprintf(w, ",%s%s", newline, prefix)
		}
	}
	fmt.Fprintf(w, "]")
}

func (c *appContext) getBlockRangeSteppedSummary(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	step := m.GetBlockStepCtx(r)
	if step <= 0 {
		http.Error(w, "Yeaaah, that step's not gonna work with me.", 422)
		return
	}

	// Compute the last block in the range
	numSteps := (idx - idx0) / step
	last := idx0 + step*numSteps
	// Support reverse list (e.g. 10/0/5 counts down from 10 to 0 in steps of 5)
	if idx0 > idx {
		step = -step
		// TODO: support reverse in other endpoints
	}

	// Prepare JSON encode for streaming response
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	encoder := json.NewEncoder(w)
	indent := c.getIndentQuery(r)
	prefix, newline := indent, ""
	encoder.SetIndent(prefix, indent)
	if indent != "" {
		newline = "\n"
	}

	// Manually structure outer JSON array
	fmt.Fprintf(w, "[%s%s", newline, prefix)
	// Go through blocks in list, stop after last (i.e. on last+step)
	for i := idx0; i != last+step; i += step {
		summary := c.BlockData.GetSummary(i)
		if summary == nil {
			apiLog.Debugf("Unknown block %d", i)
			http.Error(w, fmt.Sprintf("I don't know block %d", i), http.StatusNotFound)
			return
		}
		// TODO: deal with the extra newline from Encode, if needed
		if err := encoder.Encode(summary); err != nil {
			apiLog.Infof("JSON encode error: %v", err)
			http.Error(w, http.StatusText(422), 422)
			return
		}
		// After last block, do not print comma+newline+prefix
		if i != last {
			fmt.Fprintf(w, ",%s%s", newline, prefix)
		}
	}
	fmt.Fprintf(w, "]")
}

func (c *appContext) getTicketPool(w http.ResponseWriter, r *http.Request) {
	// getBlockHeightCtx falls back to try hash if height fails
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	tp, err := c.BlockData.GetPool(idx)
	if err != nil {
		apiLog.Errorf("Unable to fetch ticket pool: %v", err)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	sortPool := r.URL.Query().Get("sort")
	if sortPool == "1" || sortPool == "true" {
		sort.Strings(tp)
	}

	writeJSON(w, tp, c.getIndentQuery(r))
}

func (c *appContext) getTicketPoolInfo(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	tpi := c.BlockData.GetPoolInfo(int(idx))
	writeJSON(w, tpi, c.getIndentQuery(r))
}

func (c *appContext) getTicketPoolInfoRange(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	useArray := r.URL.Query().Get("arrays")
	if useArray == "1" || useArray == "true" {
		c.getTicketPoolValAndSizeRange(w, r)
		return
	}

	tpis := c.BlockData.GetPoolInfoRange(idx0, idx)
	if tpis == nil {
		http.Error(w, "invalid range", http.StatusUnprocessableEntity)
		return
	}
	writeJSON(w, tpis, c.getIndentQuery(r))
}

func (c *appContext) getTicketPoolValAndSizeRange(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	pvs, pss := c.BlockData.GetPoolValAndSizeRange(idx0, idx)
	if pvs == nil || pss == nil {
		http.Error(w, "invalid range", http.StatusUnprocessableEntity)
		return
	}

	tPVS := apitypes.TicketPoolValsAndSizes{
		StartHeight: uint32(idx0),
		EndHeight:   uint32(idx),
		Value:       pvs,
		Size:        pss,
	}
	writeJSON(w, tPVS, c.getIndentQuery(r))
}

func (c *appContext) getStakeDiff(w http.ResponseWriter, r *http.Request) {
	idx := c.getBlockHeightCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	sdiff := c.BlockData.GetSDiff(int(idx))
	writeJSON(w, []float64{sdiff}, c.getIndentQuery(r))
}

func (c *appContext) getStakeDiffRange(w http.ResponseWriter, r *http.Request) {
	idx0 := m.GetBlockIndex0Ctx(r)
	if idx0 < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	idx := m.GetBlockIndexCtx(r)
	if idx < 0 {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	sdiffs := c.BlockData.GetSDiffRange(idx0, idx)
	writeJSON(w, sdiffs, c.getIndentQuery(r))
}

func (c *appContext) addressTotals(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		// not available in lite mode
		http.Error(w, "not available in lite mode", 422)
		return
	}

	address := m.GetAddressCtx(r)
	if address == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	totals, err := c.AuxDataSource.AddressTotals(address)
	if err != nil {
		log.Warnf("failed to get address totals (%s): %v", address, err)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, totals, c.getIndentQuery(r))
}

func (c *appContext) getAddressTxTypesData(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		http.Error(w, "not available in lite mode", 422)
		return
	}

	address := m.GetAddressCtx(r)
	chartGrouping := m.GetChartGroupingCtx(r)
	if address == "" || chartGrouping == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	data, err := c.AuxDataSource.GetTxHistoryData(address, dbtypes.TxsType,
		dbtypes.ChartGroupingFromStr(chartGrouping))
	if err != nil {
		log.Warnf("failed to get address (%s) history by tx type : %v", address, err)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, data, c.getIndentQuery(r))
}

func (c *appContext) getAddressTxAmountFlowData(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		http.Error(w, "not available in lite mode", 422)
		return
	}

	address := m.GetAddressCtx(r)
	chartGrouping := m.GetChartGroupingCtx(r)
	if address == "" || chartGrouping == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	data, err := c.AuxDataSource.GetTxHistoryData(address, dbtypes.AmountFlow,
		dbtypes.ChartGroupingFromStr(chartGrouping))
	if err != nil {
		log.Warnf("failed to get address (%s) history by amount flow: %v", address, err)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, data, c.getIndentQuery(r))
}

func (c *appContext) getAddressTxUnspentAmountData(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		http.Error(w, "not available in lite mode", 422)
		return
	}

	address := m.GetAddressCtx(r)
	chartGrouping := m.GetChartGroupingCtx(r)
	if address == "" || chartGrouping == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	data, err := c.AuxDataSource.GetTxHistoryData(address, dbtypes.TotalUnspent,
		dbtypes.ChartGroupingFromStr(chartGrouping))
	if err != nil {
		log.Warnf("failed to get address (%s) history by unspent amount flow: %v", address, err)
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, data, c.getIndentQuery(r))
}

func (c *appContext) getTicketPriceChartData(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		http.Error(w, "not available in lite mode", 422)
		return
	}

	chartData, ok := explorer.ChartTypeData("ticket-price")
	if !ok {
		http.NotFound(w, r)
		log.Warnf(`No data matching "ticket-price" chart Type was found`)
		return
	}
	writeJSON(w, chartData, c.getIndentQuery(r))
}

func (c *appContext) ChartTypeData(w http.ResponseWriter, r *http.Request) {
	if c.LiteMode {
		http.Error(w, "not available in lite mode", 422)
		return
	}

	chartType := m.GetChartTypeCtx(r)
	chartData, ok := explorer.ChartTypeData(chartType)
	if !ok {
		http.NotFound(w, r)
		log.Warnf(`No data matching "%s" chart Type was found`, chartType)
		return
	}
	writeJSON(w, chartData, c.getIndentQuery(r))
}

func (c *appContext) getAddressTransactions(w http.ResponseWriter, r *http.Request) {
	address := m.GetAddressCtx(r)
	if address == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	count := int64(m.GetNCtx(r))
	skip := int64(m.GetMCtx(r))
	if count <= 0 {
		count = 10
	} else if c.LiteMode && count > 2000 {
		count = 2000
	} else if count > 8000 {
		count = 8000
	}
	if skip <= 0 {
		skip = 0
	}

	var err error
	var txs *apitypes.Address
	if c.LiteMode {
		txs = c.BlockData.GetAddressTransactionsWithSkip(address, int(count), int(skip))
	} else {
		txs, err = c.AuxDataSource.AddressTransactionDetails(address, count, skip, dbtypes.AddrTxnAll)
	}

	if txs == nil || err != nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}
	writeJSON(w, txs, c.getIndentQuery(r))
}

func (c *appContext) getAddressTransactionsRaw(w http.ResponseWriter, r *http.Request) {
	address := m.GetAddressCtx(r)
	if address == "" {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	count := int64(m.GetNCtx(r))
	skip := int64(m.GetMCtx(r))
	if count <= 0 {
		count = 10
	} else if c.LiteMode && count > 2000 {
		count = 2000
	} else if count > 8000 {
		count = 8000
	}
	if skip <= 0 {
		skip = 0
	}

	//var txs []*apitypes.AddressTxRaw
	// TODO: add postgresql powered method
	//if c.LiteMode {
	txs := c.BlockData.GetAddressTransactionsRawWithSkip(address, int(count), int(skip))
	// } else {
	// 	txs, err = c.AuxDataSource.AddressTransactionRawDetails(address, count, skip, dbtypes.AddrTxnAll)
	// }
	if txs == nil {
		http.Error(w, http.StatusText(422), 422)
		return
	}

	writeJSON(w, txs, c.getIndentQuery(r))
}

func (c *appContext) StakeVersionLatestCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx := m.StakeVersionLatestCtx(r, c.BlockData.GetStakeVersionsLatest)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func (c *appContext) BlockHashPathAndIndexCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx := m.BlockHashPathAndIndexCtx(r, c.BlockData)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func (c *appContext) BlockIndexLatestCtx(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ctx := m.BlockIndexLatestCtx(r, c.BlockData)
		next.ServeHTTP(w, r.WithContext(ctx))
	})
}

func (c *appContext) getBlockHeightCtx(r *http.Request) int64 {
	idx := m.GetBlockHeightCtx(r, c.BlockData)
	return idx
}

func (c *appContext) getBlockHashCtx(r *http.Request) string {
	hash := m.GetBlockHashCtx(r)
	if hash == "" {
		idx := int64(m.GetBlockIndexCtx(r))
		var err error
		hash, err = c.BlockData.GetBlockHash(idx)
		if err != nil {
			apiLog.Errorf("Unable to GetBlockHash(%d): %v", idx, err)
		}
	}
	return hash
}