package main

import (
    "bufio"
    "context"
    "crypto/rand"
    "crypto/sha256"
    "encoding/hex"
    "encoding/json"
    "flag"
    "fmt"
    "io"
    "log"
    mrand "math/rand"
    "os"
    "strconv"
    "strings"
    "sync"
    "time"

           "github.com/davecgh/go-spew/spew"
    //golog  "go.uber.org/zap/zapcore"
    libp2p "github.com/libp2p/go-libp2p"
    crypto "github.com/libp2p/go-libp2p-crypto"
    host   "github.com/libp2p/go-libp2p-host"
    net    "github.com/libp2p/go-libp2p-core/network"
    peer   "github.com/libp2p/go-libp2p-peer"
    pstore "github.com/libp2p/go-libp2p-peerstore"
    ma     "github.com/multiformats/go-multiaddr"
    //gologging "go.uber.org/zap/zapcore"
)

// Block represents each 'item' in the blockchain
type Block struct {
    Index     int
    Timestamp string
    BPM       int
    Hash      string
    PrevHash  string
}

// Blockchain is a series of validated Blocks
var Blockchain []Block

var mutex = &sync.Mutex{}

// makeBasicHost creates a LibP2P host with a random peer ID listening on the
// given multiaddress. It will use secio if secio is true.
func makeBasicHost(listenPort int, secio bool, randseed int64) (host.Host, error) {

    // If the seed is zero, use real cryptographic randomness. Otherwise, use a
    // deterministic randomness source to make generated keys stay the same
    // across multiple runs
    var r io.Reader
    if randseed == 0 {
        r = rand.Reader
    } else {
        r = mrand.New(mrand.NewSource(randseed))
    }

    // Generate a key pair for this host. We will use it
    // to obtain a valid host ID.
    priv, _, err := crypto.GenerateKeyPairWithReader(crypto.RSA, 2048, r)
    if err != nil {
        return nil, err
    }

    opts := []libp2p.Option{
        libp2p.ListenAddrStrings(fmt.Sprintf("/ip4/127.0.0.1/tcp/%d", listenPort)),
        libp2p.Identity(priv),
    }

    basicHost, err := libp2p.New(context.Background(), opts...)
    if err != nil {
        return nil, err
    }

    // Build host multiaddress
    hostAddr, _ := ma.NewMultiaddr(fmt.Sprintf("/ipfs/%s", basicHost.ID().Pretty()))

    // Now we can build a full multiaddress to reach this host
    // by encapsulating both addresses:
    addrs := basicHost.Addrs()
    var addr ma.Multiaddr
    // select the address starting with "ip4"
    for _, i := range addrs {
        if strings.HasPrefix(i.String(), "/ip4") {
            addr = i
            break
        }
    }
    fullAddr := addr.Encapsulate(hostAddr)
    log.Printf("I am %s\n", fullAddr)
    if secio {
        log.Printf("Now run \"go run p2pblock.go -l %d -d %s -secio\" on a different terminal\n", listenPort+1, fullAddr)
    } else {
        log.Printf("Now run \"go run p2pblock.go -l %d -d %s\" on a different terminal\n", listenPort+1, fullAddr)
    }

    return basicHost, nil
}

func handleStream(s net.Stream) {

    log.Println("Got a new stream!")

    // Create a buffer stream for non blocking read and write.
    rw := bufio.NewReadWriter(bufio.NewReader(s), bufio.NewWriter(s))

    go readData(rw)
    go writeData(rw)

    // stream 's' will stay open until you close it (or the other side closes it).
}

func readData(rw *bufio.ReadWriter) {

    for {
        str, err := rw.ReadString('\n')
        if err != nil {
            log.Fatal(err)
        }

        if str == "" {
            return
        }
        if str != "\n" {

            chain := make([]Block, 0)
            if err := json.Unmarshal([]byte(str), &chain); err != nil {
                log.Fatal(err)
            }

            mutex.Lock()
            if len(chain) > len(Blockchain) {
                Blockchain = chain
                bytes, err := json.MarshalIndent(Blockchain, "", "  ")
                if err != nil {

                    log.Fatal(err)
                }
                // Green console color:     \x1b[32m
                // Reset console color:     \x1b[0m
                fmt.Printf("\x1b[32m%s\x1b[0m> ", string(bytes))
            }
            mutex.Unlock()
        }
    }
}

func writeData(rw *bufio.ReadWriter) {

    go func() {
        for {
            time.Sleep(5 * time.Second)
            mutex.Lock()
            bytes, err := json.Marshal(Blockchain)
            if err != nil {
                log.Println(err)
            }
            mutex.Unlock()

            mutex.Lock()
            rw.WriteString(fmt.Sprintf("%s\n", string(bytes)))
            rw.Flush()
            mutex.Unlock()

        }
    }()

    stdReader := bufio.NewReader(os.Stdin)

    for {
        fmt.Print("> ")
        sendData, err := stdReader.ReadString('\n')
        if err != nil {
            log.Fatal(err)
        }

        sendData = strings.Replace(sendData, "\n", "", -1)
        bpm, err := strconv.Atoi(sendData)
        if err != nil {
            log.Fatal(err)
        }
        newBlock := generateBlock(Blockchain[len(Blockchain)-1], bpm)

        if isBlockValid(newBlock, Blockchain[len(Blockchain)-1]) {
            mutex.Lock()
            Blockchain = append(Blockchain, newBlock)
            mutex.Unlock()
        }

        bytes, err := json.Marshal(Blockchain)
        if err != nil {
            log.Println(err)
        }

        spew.Dump(Blockchain)

        mutex.Lock()
        rw.WriteString(fmt.Sprintf("%s\n", string(bytes)))
        rw.Flush()
        mutex.Unlock()
    }

}

func main() {
    t := time.Now()
    genesisBlock := Block{}
    genesisBlock = Block{0, t.String(), 0, calculateHash(genesisBlock), ""}

    Blockchain = append(Blockchain, genesisBlock)

    // LibP2P code uses golog to log messages. They log with different
    // string IDs (i.e. "swarm"). We can control the verbosity level for
    // all loggers with:
    //golog.SetAllLoggers(gologging.INFO)Change to DEBUG for extra info


    // Parse options from the command line
    listenF := flag.Int("l", 0, "wait for incoming connections")
    target := flag.String("d", "", "target peer to dial")
    secio := flag.Bool("secio", false, "enable secio")
    seed := flag.Int64("seed", 0, "set random seed for id generation")
    flag.Parse()

    if *listenF == 0 {
        log.Fatal("Please provide a port to bind on with -l")
    }

    // Make a host that listens on the given multiaddress
    ha, err := makeBasicHost(*listenF, *secio, *seed)
    if err != nil {
        log.Fatal(err)
    }

    if *target == "" {
        log.Println("listening for connections")
        // Set a stream handler on host A. /p2p/1.0.0 is
        // a user-defined protocol name.
        ha.SetStreamHandler("/p2p/1.0.0", handleStream)

        select {} // hang forever
        /**** This is where the listener code ends ****/
    } else {
        ha.SetStreamHandler("/p2p/1.0.0", handleStream)

        // The following code extracts target's peer ID from the
        // given multiaddress
        ipfsaddr, err := ma.NewMultiaddr(*target)
        if err != nil {
            log.Fatalln(err)
        }

        pid, err := ipfsaddr.ValueForProtocol(ma.P_IPFS)
        if err != nil {
            log.Fatalln(err)
        }

        peerid, err := peer.IDB58Decode(pid)
        if err != nil {
            log.Fatalln(err)
        }

        // Decapsulate the /ipfs/<peerID> part from the target
        // /ip4/<a.b.c.d>/ipfs/<peer> becomes /ip4/<a.b.c.d>
        targetPeerAddr, _ := ma.NewMultiaddr(
            fmt.Sprintf("/ipfs/%s", peer.IDB58Encode(peerid)))
        targetAddr := ipfsaddr.Decapsulate(targetPeerAddr)

        // We have a peer ID and a targetAddr so we add it to the peerstore
        // so LibP2P knows how to contact it
        ha.Peerstore().AddAddr(peerid, targetAddr, pstore.PermanentAddrTTL)

        log.Println("opening stream")
        // make a new stream from host B to host A
        // it should be handled on host A by the handler we set above because
        // we use the same /p2p/1.0.0 protocol
        s, err := ha.NewStream(context.Background(), peerid, "/p2p/1.0.0")
        if err != nil {
            log.Fatalln(err)
        }
        // Create a buffered stream so that read and writes are non blocking.
        rw := bufio.NewReadWriter(bufio.NewReader(s), bufio.NewWriter(s))

        // Create a thread to read and write data.
        go writeData(rw)
        go readData(rw)

        select {} // hang forever

    }
}

// make sure block is valid by checking index, and comparing the hash of the previous block
func isBlockValid(newBlock, oldBlock Block) bool {
    if oldBlock.Index+1 != newBlock.Index {
        return false
    }

    if oldBlock.Hash != newBlock.PrevHash {
        return false
    }

    if calculateHash(newBlock) != newBlock.Hash {
        return false
    }

    return true
}

// SHA256 hashing
func calculateHash(block Block) string {
    record := strconv.Itoa(block.Index) + block.Timestamp + strconv.Itoa(block.BPM) + block.PrevHash
    h := sha256.New()
    h.Write([]byte(record))
    hashed := h.Sum(nil)
    return hex.EncodeToString(hashed)
}

// create a new block using previous block's hash
func generateBlock(oldBlock Block, BPM int) Block {

    var newBlock Block

    t := time.Now()

    newBlock.Index = oldBlock.Index + 1
    newBlock.Timestamp = t.String()
    newBlock.BPM = BPM
    newBlock.PrevHash = oldBlock.Hash
    newBlock.Hash = calculateHash(newBlock)

    return newBlock
}