// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package network

import (
    "fmt"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/common/hexutil"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/p2p/enode"
    "github.com/ethereum/go-ethereum/swarm/log"
    "github.com/ethereum/go-ethereum/swarm/state"
)

/*
Hive is the logistic manager of the swarm

When the hive is started, a forever loop is launched that
asks the  kademlia nodetable
to suggest peers to bootstrap connectivity
*/

// HiveParams holds the config options to hive
type HiveParams struct {
    Discovery             bool  // if want discovery of not
    PeersBroadcastSetSize uint8 // how many peers to use when relaying
    MaxPeersPerRequest    uint8 // max size for peer address batches
    KeepAliveInterval     time.Duration
}

// NewHiveParams returns hive config with only the
func NewHiveParams() *HiveParams {
    return &HiveParams{
        Discovery:             true,
        PeersBroadcastSetSize: 3,
        MaxPeersPerRequest:    5,
        KeepAliveInterval:     500 * time.Millisecond,
    }
}

// Hive manages network connections of the swarm node
type Hive struct {
    *HiveParams                   // settings
    *Kademlia                     // the overlay connectiviy driver
    Store       state.Store       // storage interface to save peers across sessions
    addPeer     func(*enode.Node) // server callback to connect to a peer
    // bookkeeping
    lock   sync.Mutex
    peers  map[enode.ID]*BzzPeer
    ticker *time.Ticker
}

// NewHive constructs a new hive
// HiveParams: config parameters
// Kademlia: connectivity driver using a network topology
// StateStore: to save peers across sessions
func NewHive(params *HiveParams, kad *Kademlia, store state.Store) *Hive {
    return &Hive{
        HiveParams: params,
        Kademlia:   kad,
        Store:      store,
        peers:      make(map[enode.ID]*BzzPeer),
    }
}

// Start stars the hive, receives p2p.Server only at startup
// server is used to connect to a peer based on its NodeID or enode URL
// these are called on the p2p.Server which runs on the node
func (h *Hive) Start(server *p2p.Server) error {
    log.Info("Starting hive", "baseaddr", fmt.Sprintf("%x", h.BaseAddr()[:4]))
    // if state store is specified, load peers to prepopulate the overlay address book
    if h.Store != nil {
        log.Info("Detected an existing store. trying to load peers")
        if err := h.loadPeers(); err != nil {
            log.Error(fmt.Sprintf("%08x hive encoutered an error trying to load peers", h.BaseAddr()[:4]))
            return err
        }
    }
    // assigns the p2p.Server#AddPeer function to connect to peers
    h.addPeer = server.AddPeer
    // ticker to keep the hive alive
    h.ticker = time.NewTicker(h.KeepAliveInterval)
    // this loop is doing bootstrapping and maintains a healthy table
    go h.connect()
    return nil
}

// Stop terminates the updateloop and saves the peers
func (h *Hive) Stop() error {
    log.Info(fmt.Sprintf("%08x hive stopping, saving peers", h.BaseAddr()[:4]))
    h.ticker.Stop()
    if h.Store != nil {
        if err := h.savePeers(); err != nil {
            return fmt.Errorf("could not save peers to persistence store: %v", err)
        }
        if err := h.Store.Close(); err != nil {
            return fmt.Errorf("could not close file handle to persistence store: %v", err)
        }
    }
    log.Info(fmt.Sprintf("%08x hive stopped, dropping peers", h.BaseAddr()[:4]))
    h.EachConn(nil, 255, func(p *Peer, _ int, _ bool) bool {
        log.Info(fmt.Sprintf("%08x dropping peer %08x", h.BaseAddr()[:4], p.Address()[:4]))
        p.Drop(nil)
        return true
    })

    log.Info(fmt.Sprintf("%08x all peers dropped", h.BaseAddr()[:4]))
    return nil
}

// connect is a forever loop
// at each iteration, ask the overlay driver to suggest the most preferred peer to connect to
// as well as advertises saturation depth if needed
func (h *Hive) connect() {
    for range h.ticker.C {

        addr, depth, changed := h.SuggestPeer()
        if h.Discovery && changed {
            NotifyDepth(uint8(depth), h.Kademlia)
        }
        if addr == nil {
            continue
        }

        log.Trace(fmt.Sprintf("%08x hive connect() suggested %08x", h.BaseAddr()[:4], addr.Address()[:4]))
        under, err := enode.ParseV4(string(addr.Under()))
        if err != nil {
            log.Warn(fmt.Sprintf("%08x unable to connect to bee %08x: invalid node URL: %v", h.BaseAddr()[:4], addr.Address()[:4], err))
            continue
        }
        log.Trace(fmt.Sprintf("%08x attempt to connect to bee %08x", h.BaseAddr()[:4], addr.Address()[:4]))
        h.addPeer(under)
    }
}

// Run protocol run function
func (h *Hive) Run(p *BzzPeer) error {
    h.trackPeer(p)
    defer h.untrackPeer(p)

    dp := NewPeer(p, h.Kademlia)
    depth, changed := h.On(dp)
    // if we want discovery, advertise change of depth
    if h.Discovery {
        if changed {
            // if depth changed, send to all peers
            NotifyDepth(depth, h.Kademlia)
        } else {
            // otherwise just send depth to new peer
            dp.NotifyDepth(depth)
        }
    }
    NotifyPeer(p.BzzAddr, h.Kademlia)
    defer h.Off(dp)
    return dp.Run(dp.HandleMsg)
}

func (h *Hive) trackPeer(p *BzzPeer) {
    h.lock.Lock()
    h.peers[p.ID()] = p
    h.lock.Unlock()
}

func (h *Hive) untrackPeer(p *BzzPeer) {
    h.lock.Lock()
    delete(h.peers, p.ID())
    h.lock.Unlock()
}

// NodeInfo function is used by the p2p.server RPC interface to display
// protocol specific node information
func (h *Hive) NodeInfo() interface{} {
    return h.String()
}

// PeerInfo function is used by the p2p.server RPC interface to display
// protocol specific information any connected peer referred to by their NodeID
func (h *Hive) PeerInfo(id enode.ID) interface{} {
    h.lock.Lock()
    p := h.peers[id]
    h.lock.Unlock()

    if p == nil {
        return nil
    }
    addr := NewAddr(p.Node())
    return struct {
        OAddr hexutil.Bytes
        UAddr hexutil.Bytes
    }{
        OAddr: addr.OAddr,
        UAddr: addr.UAddr,
    }
}

// loadPeers, savePeer implement persistence callback/
func (h *Hive) loadPeers() error {
    var as []*BzzAddr
    err := h.Store.Get("peers", &as)
    if err != nil {
        if err == state.ErrNotFound {
            log.Info(fmt.Sprintf("hive %08x: no persisted peers found", h.BaseAddr()[:4]))
            return nil
        }
        return err
    }
    log.Info(fmt.Sprintf("hive %08x: peers loaded", h.BaseAddr()[:4]))

    return h.Register(as...)
}

// savePeers, savePeer implement persistence callback/
func (h *Hive) savePeers() error {
    var peers []*BzzAddr
    h.Kademlia.EachAddr(nil, 256, func(pa *BzzAddr, i int, _ bool) bool {
        if pa == nil {
            log.Warn(fmt.Sprintf("empty addr: %v", i))
            return true
        }
        log.Trace("saving peer", "peer", pa)
        peers = append(peers, pa)
        return true
    })
    if err := h.Store.Put("peers", peers); err != nil {
        return fmt.Errorf("could not save peers: %v", err)
    }
    return nil
}