package webapi

import (
	"bytes"
	"io/ioutil"
	"net/http"
	"strings"

	"github.com/decred/dcrd/blockchain/stake/v3"
	"github.com/decred/dcrd/chaincfg/chainhash"
	"github.com/decred/vspd/rpc"
	"github.com/gin-gonic/gin"
	"github.com/gin-gonic/gin/binding"
	"github.com/gorilla/sessions"
)

type ticketHashRequest struct {
	TicketHash string `json:"tickethash" binding:"required"`
}

// withSession middleware adds a gorilla session to the request context for
// downstream handlers to make use of. Sessions are used by admin pages to
// maintain authentication status.
func withSession(store *sessions.CookieStore) gin.HandlerFunc {
	return func(c *gin.Context) {
		session, err := store.Get(c.Request, "vspd-session")
		if err != nil {
			// "value is not valid" occurs if the cookie secret changes. This is
			// common during development (eg. when using the test harness) but
			// it should not occur in production.
			if strings.Contains(err.Error(), "securecookie: the value is not valid") {
				log.Warn("Cookie secret has changed. Generating new session.")

				// Persist the newly generated session.
				err = store.Save(c.Request, c.Writer, session)
				if err != nil {
					log.Errorf("Error saving session: %v", err)
					c.String(http.StatusInternalServerError, "Error saving session")
					c.Abort()
					return
				}
			} else {
				log.Errorf("Session error: %v", err)
				c.String(http.StatusInternalServerError, "Error getting session")
				c.Abort()
				return
			}
		}

		c.Set("session", session)
	}
}

// requireAdmin will only allow the request to proceed if the current session is
// authenticated as an admin, otherwise it will render the login template.
func requireAdmin() gin.HandlerFunc {
	return func(c *gin.Context) {
		session := c.MustGet("session").(*sessions.Session)
		admin := session.Values["admin"]

		if admin == nil {
			c.HTML(http.StatusUnauthorized, "login.html", gin.H{
				"VspStats": getVSPStats(),
			})
			c.Abort()
			return
		}
	}
}

// withDcrdClient middleware adds a dcrd client to the request context for
// downstream handlers to make use of.
func withDcrdClient(dcrd rpc.DcrdConnect) gin.HandlerFunc {
	return func(c *gin.Context) {
		client, err := dcrd.Client(c, cfg.NetParams)
		if err != nil {
			log.Error(err)
			sendError(errInternalError, c)
			return
		}

		c.Set("DcrdClient", client)
	}
}

// withWalletClients middleware adds a voting wallet clients to the request
// context for downstream handlers to make use of.
func withWalletClients(wallets rpc.WalletConnect) gin.HandlerFunc {
	return func(c *gin.Context) {
		clients, failedConnections := wallets.Clients(c, cfg.NetParams)
		if len(clients) == 0 {
			log.Error("Could not connect to any wallets")
			sendError(errInternalError, c)
			return
		}
		if failedConnections > 0 {
			log.Errorf("Failed to connect to %d wallet(s), proceeding with only %d",
				failedConnections, len(clients))
		}
		c.Set("WalletClients", clients)
	}
}

// vspAuth middleware reads the request body and extracts the ticket hash. The
// commitment address for the ticket is retrieved from the database if it is
// known, or it is retrieved from the chain if not.
// The middleware errors out if the VSP-Client-Signature header of the request
// does not contain the request body signed with the commitment address.
// Ticket information is added to the request context for downstream handlers to
// use.
func vspAuth() gin.HandlerFunc {
	return func(c *gin.Context) {
		// Read request bytes and then replace the request reader for
		// downstream handlers to use.
		reqBytes, err := ioutil.ReadAll(c.Request.Body)
		if err != nil {
			log.Warnf("Error reading request from %s: %v", c.ClientIP(), err)
			sendErrorWithMsg(err.Error(), errBadRequest, c)
			return
		}
		c.Request.Body.Close()
		c.Request.Body = ioutil.NopCloser(bytes.NewBuffer(reqBytes))

		// Parse request and ensure there is a ticket hash included.
		var request ticketHashRequest
		if err := binding.JSON.BindBody(reqBytes, &request); err != nil {
			log.Warnf("Bad request from %s: %v", c.ClientIP(), err)
			sendErrorWithMsg(err.Error(), errBadRequest, c)
			return
		}
		hash := request.TicketHash

		// Before hitting the db or any RPC, ensure this is a valid ticket hash.
		// A ticket hash should be 64 chars (MaxHashStringSize) and should parse
		// into a chainhash.Hash without error.
		if len(hash) != chainhash.MaxHashStringSize {
			log.Errorf("Invalid hash from %s: incorrect length", c.ClientIP())
			sendErrorWithMsg("invalid ticket hash", errBadRequest, c)
			return
		}
		_, err = chainhash.NewHashFromStr(hash)
		if err != nil {
			log.Errorf("Invalid hash from %s: %v", c.ClientIP(), err)
			sendErrorWithMsg("invalid ticket hash", errBadRequest, c)
			return
		}

		// Check if this ticket already appears in the database.
		ticket, ticketFound, err := db.GetTicketByHash(hash)
		if err != nil {
			log.Errorf("GetTicketByHash error: %v", err)
			sendError(errInternalError, c)
			return
		}

		// If the ticket was found in the database, we already know its
		// commitment address. Otherwise we need to get it from the chain.
		var commitmentAddress string
		if ticketFound {
			commitmentAddress = ticket.CommitmentAddress
		} else {
			dcrdClient := c.MustGet("DcrdClient").(*rpc.DcrdRPC)

			resp, err := dcrdClient.GetRawTransaction(hash)
			if err != nil {
				log.Errorf("GetRawTransaction error: %v", err)
				sendError(errInternalError, c)
				return
			}

			msgTx, err := decodeTransaction(resp.Hex)
			if err != nil {
				log.Errorf("decodeTransaction error: %v", err)
				sendError(errInternalError, c)
				return
			}

			err = isValidTicket(msgTx)
			if err != nil {
				log.Warnf("Invalid ticket from %s: %v", c.ClientIP(), err)
				sendError(errInvalidTicket, c)
				return
			}

			addr, err := stake.AddrFromSStxPkScrCommitment(msgTx.TxOut[1].PkScript, cfg.NetParams)
			if err != nil {
				log.Errorf("AddrFromSStxPkScrCommitment error: %v", err)
				sendError(errInternalError, c)
				return
			}

			commitmentAddress = addr.Address()
		}

		// Validate request signature to ensure ticket ownership.
		err = validateSignature(reqBytes, commitmentAddress, c)
		if err != nil {
			log.Warnf("Bad signature from %s: %v", c.ClientIP(), err)
			sendError(errBadSignature, c)
			return
		}

		// Add ticket information to context so downstream handlers don't need
		// to access the db for it.
		c.Set("Ticket", ticket)
		c.Set("KnownTicket", ticketFound)
		c.Set("CommitmentAddress", commitmentAddress)
	}

}