package main

/*

Locking
=======

The model has read and write locks. These must be acquired as appropriate by
public methods. To prevent deadlock situations, private methods should never
acquire locks, but document what locks they require.

*/

import (
	"fmt"
	"io"
	"os"
	"path"
	"sync"
	"time"

	"github.com/calmh/syncthing/buffers"
	"github.com/calmh/syncthing/protocol"
)

type Model struct {
	sync.RWMutex
	dir string

	global  map[string]File // the latest version of each file as it exists in the cluster
	local   map[string]File // the files we currently have locally on disk
	remote  map[string]map[string]File
	need    map[string]bool // the files we need to update
	nodes   map[string]*protocol.Connection
	rawConn map[string]io.ReadWriteCloser

	updatedLocal int64 // timestamp of last update to local
	updateGlobal int64 // timestamp of last update to remote

	lastIdxBcast        time.Time
	lastIdxBcastRequest time.Time
}

const (
	FlagDeleted = 1 << 12

	idxBcastHoldtime = 15 * time.Second  // Wait at least this long after the last index modification
	idxBcastMaxDelay = 120 * time.Second // Unless we've already waited this long
)

func NewModel(dir string) *Model {
	m := &Model{
		dir:          dir,
		global:       make(map[string]File),
		local:        make(map[string]File),
		remote:       make(map[string]map[string]File),
		need:         make(map[string]bool),
		nodes:        make(map[string]*protocol.Connection),
		rawConn:      make(map[string]io.ReadWriteCloser),
		lastIdxBcast: time.Now(),
	}

	go m.broadcastIndexLoop()
	return m
}

func (m *Model) Start() {
	go m.puller()
}

func (m *Model) Generation() int64 {
	m.RLock()
	defer m.RUnlock()

	return m.updatedLocal + m.updateGlobal
}

func (m *Model) ConnectionStats() map[string]protocol.Statistics {
	m.RLock()
	defer m.RUnlock()

	var res = make(map[string]protocol.Statistics)
	for node, conn := range m.nodes {
		res[node] = conn.Statistics()
	}
	return res
}

func (m *Model) GlobalSize() (files, bytes int) {
	m.RLock()
	defer m.RUnlock()

	files = len(m.global)
	for _, f := range m.global {
		bytes += f.Size()
	}
	return
}

func (m *Model) LocalSize() (files, bytes int) {
	m.RLock()
	defer m.RUnlock()

	files = len(m.local)
	for _, f := range m.local {
		bytes += f.Size()
	}
	return
}

func (m *Model) NeedSize() (files, bytes int) {
	m.RLock()
	defer m.RUnlock()

	files = len(m.need)
	for n := range m.need {
		bytes += m.global[n].Size()
	}
	return
}

// Index is called when a new node is connected and we receive their full index.
func (m *Model) Index(nodeID string, fs []protocol.FileInfo) {
	m.Lock()
	defer m.Unlock()

	if opts.Debug.TraceNet {
		debugf("NET IDX(in): %s: %d files", nodeID, len(fs))
	}

	m.remote[nodeID] = make(map[string]File)
	for _, f := range fs {
		if f.Flags&FlagDeleted != 0 && !opts.Delete {
			// Files marked as deleted do not even enter the model
			continue
		}
		m.remote[nodeID][f.Name] = fileFromFileInfo(f)
	}

	m.recomputeGlobal()
	m.recomputeNeed()
}

// IndexUpdate is called for incremental updates to connected nodes' indexes.
func (m *Model) IndexUpdate(nodeID string, fs []protocol.FileInfo) {
	m.Lock()
	defer m.Unlock()

	if opts.Debug.TraceNet {
		debugf("NET IDXUP(in): %s: %d files", nodeID, len(fs))
	}

	repo, ok := m.remote[nodeID]
	if !ok {
		return
	}

	for _, f := range fs {
		if f.Flags&FlagDeleted != 0 && !opts.Delete {
			// Files marked as deleted do not even enter the model
			continue
		}
		repo[f.Name] = fileFromFileInfo(f)
	}

	m.recomputeGlobal()
	m.recomputeNeed()
}

// SeedIndex is called when our previously cached index is loaded from disk at startup.
func (m *Model) SeedIndex(fs []protocol.FileInfo) {
	m.Lock()
	defer m.Unlock()

	m.local = make(map[string]File)
	for _, f := range fs {
		m.local[f.Name] = fileFromFileInfo(f)
	}

	m.recomputeGlobal()
	m.recomputeNeed()
}

func (m *Model) Close(node string, err error) {
	m.Lock()
	defer m.Unlock()

	conn, ok := m.rawConn[node]
	if ok {
		conn.Close()
	} else {
		warnln("Close on unknown connection for node", node)
	}

	if err != nil {
		warnf("Disconnected from node %s: %v", node, err)
	} else {
		infoln("Disconnected from node", node)
	}

	delete(m.remote, node)
	delete(m.nodes, node)
	delete(m.rawConn, node)

	m.recomputeGlobal()
	m.recomputeNeed()
}

func (m *Model) Request(nodeID, name string, offset uint64, size uint32, hash []byte) ([]byte, error) {
	if opts.Debug.TraceNet && nodeID != "<local>" {
		debugf("NET REQ(in): %s: %q o=%d s=%d h=%x", nodeID, name, offset, size, hash)
	}
	fn := path.Join(m.dir, name)
	fd, err := os.Open(fn) // XXX: Inefficient, should cache fd?
	if err != nil {
		return nil, err
	}
	defer fd.Close()

	buf := buffers.Get(int(size))
	_, err = fd.ReadAt(buf, int64(offset))
	if err != nil {
		return nil, err
	}

	return buf, nil
}

func (m *Model) RequestGlobal(nodeID, name string, offset uint64, size uint32, hash []byte) ([]byte, error) {
	m.RLock()
	nc, ok := m.nodes[nodeID]
	m.RUnlock()
	if !ok {
		return nil, fmt.Errorf("RequestGlobal: no such node: %s", nodeID)
	}

	if opts.Debug.TraceNet {
		debugf("NET REQ(out): %s: %q o=%d s=%d h=%x", nodeID, name, offset, size, hash)
	}

	return nc.Request(name, offset, size, hash)
}

func (m *Model) ReplaceLocal(fs []File) {
	m.Lock()
	defer m.Unlock()

	var updated bool
	var newLocal = make(map[string]File)

	for _, f := range fs {
		newLocal[f.Name] = f
		if ef := m.local[f.Name]; ef.Modified != f.Modified {
			updated = true
		}
	}

	if m.markDeletedLocals(newLocal) {
		updated = true
	}

	if len(newLocal) != len(m.local) {
		updated = true
	}

	if updated {
		m.local = newLocal
		m.recomputeGlobal()
		m.recomputeNeed()
		m.updatedLocal = time.Now().Unix()
		m.lastIdxBcastRequest = time.Now()
	}
}

func (m *Model) broadcastIndexLoop() {
	for {
		m.RLock()
		bcastRequested := m.lastIdxBcastRequest.After(m.lastIdxBcast)
		holdtimeExceeded := time.Since(m.lastIdxBcastRequest) > idxBcastHoldtime
		m.RUnlock()

		maxDelayExceeded := time.Since(m.lastIdxBcast) > idxBcastMaxDelay
		if bcastRequested && (holdtimeExceeded || maxDelayExceeded) {
			m.Lock()
			var indexWg sync.WaitGroup
			indexWg.Add(len(m.nodes))
			idx := m.protocolIndex()
			m.lastIdxBcast = time.Now()
			for _, node := range m.nodes {
				node := node
				if opts.Debug.TraceNet {
					debugf("NET IDX(out/loop): %s: %d files", node.ID, len(idx))
				}
				go func() {
					node.Index(idx)
					indexWg.Done()
				}()
			}
			m.Unlock()
			indexWg.Wait()
		}
		time.Sleep(idxBcastHoldtime)
	}
}

// markDeletedLocals sets the deleted flag on files that have gone missing locally.
// Must be called with the write lock held.
func (m *Model) markDeletedLocals(newLocal map[string]File) bool {
	// For every file in the existing local table, check if they are also
	// present in the new local table. If they are not, check that we already
	// had the newest version available according to the global table and if so
	// note the file as having been deleted.
	var updated bool
	for n, f := range m.local {
		if _, ok := newLocal[n]; !ok {
			if gf := m.global[n]; gf.Modified <= f.Modified {
				if f.Flags&FlagDeleted == 0 {
					f.Flags = FlagDeleted
					f.Modified = f.Modified + 1
					f.Blocks = nil
					updated = true
				}
				newLocal[n] = f
			}
		}
	}
	return updated
}

func (m *Model) UpdateLocal(f File) {
	m.Lock()
	defer m.Unlock()

	if ef, ok := m.local[f.Name]; !ok || ef.Modified != f.Modified {
		m.local[f.Name] = f
		m.recomputeGlobal()
		m.recomputeNeed()
		m.updatedLocal = time.Now().Unix()
		m.lastIdxBcastRequest = time.Now()
	}
}

func (m *Model) Dir() string {
	m.RLock()
	defer m.RUnlock()
	return m.dir
}

func (m *Model) HaveFiles() []File {
	m.RLock()
	defer m.RUnlock()
	var files []File
	for _, file := range m.local {
		files = append(files, file)
	}
	return files
}

func (m *Model) LocalFile(name string) (File, bool) {
	m.RLock()
	defer m.RUnlock()
	f, ok := m.local[name]
	return f, ok
}

func (m *Model) GlobalFile(name string) (File, bool) {
	m.RLock()
	defer m.RUnlock()
	f, ok := m.global[name]
	return f, ok
}

// Must be called with the write lock held.
func (m *Model) recomputeGlobal() {
	var newGlobal = make(map[string]File)

	for n, f := range m.local {
		newGlobal[n] = f
	}

	for _, fs := range m.remote {
		for n, f := range fs {
			if cf, ok := newGlobal[n]; !ok || cf.Modified < f.Modified {
				newGlobal[n] = f
			}
		}
	}

	// Figure out if anything actually changed

	var updated bool
	if len(newGlobal) != len(m.global) {
		updated = true
	} else {
		for n, f0 := range newGlobal {
			if f1, ok := m.global[n]; !ok || f0.Modified != f1.Modified {
				updated = true
				break
			}
		}
	}

	if updated {
		m.updateGlobal = time.Now().Unix()
		m.global = newGlobal
	}
}

// Must be called with the write lock held.
func (m *Model) recomputeNeed() {
	m.need = make(map[string]bool)
	for n, f := range m.global {
		hf, ok := m.local[n]
		if !ok || f.Modified > hf.Modified {
			m.need[n] = true
		}
	}
}

// Must be called with the read lock held.
func (m *Model) whoHas(name string) []string {
	var remote []string

	gf := m.global[name]
	for node, files := range m.remote {
		if file, ok := files[name]; ok && file.Modified == gf.Modified {
			remote = append(remote, node)
		}
	}

	return remote
}

func (m *Model) ConnectedTo(nodeID string) bool {
	m.RLock()
	defer m.RUnlock()
	_, ok := m.nodes[nodeID]
	return ok
}

func (m *Model) ProtocolIndex() []protocol.FileInfo {
	m.RLock()
	defer m.RUnlock()
	return m.protocolIndex()
}

// Must be called with the read lock held.
func (m *Model) protocolIndex() []protocol.FileInfo {
	var index []protocol.FileInfo
	for _, f := range m.local {
		mf := fileInfoFromFile(f)
		if opts.Debug.TraceIdx {
			var flagComment string
			if mf.Flags&FlagDeleted != 0 {
				flagComment = " (deleted)"
			}
			debugf("IDX: %q m=%d f=%o%s (%d blocks)", mf.Name, mf.Modified, mf.Flags, flagComment, len(mf.Blocks))
		}
		index = append(index, mf)
	}
	return index
}

func (m *Model) AddConnection(conn io.ReadWriteCloser, nodeID string) {
	node := protocol.NewConnection(nodeID, conn, conn, m)

	m.Lock()
	m.nodes[nodeID] = node
	m.rawConn[nodeID] = conn
	m.Unlock()

	infoln("Connected to node", nodeID)

	m.RLock()
	idx := m.protocolIndex()
	m.RUnlock()

	go func() {
		node.Index(idx)
		infoln("Sent initial index to node", nodeID)
	}()
}

func fileFromFileInfo(f protocol.FileInfo) File {
	var blocks []Block
	var offset uint64
	for _, b := range f.Blocks {
		blocks = append(blocks, Block{
			Offset: offset,
			Length: b.Length,
			Hash:   b.Hash,
		})
		offset += uint64(b.Length)
	}
	return File{
		Name:     f.Name,
		Flags:    f.Flags,
		Modified: int64(f.Modified),
		Blocks:   blocks,
	}
}

func fileInfoFromFile(f File) protocol.FileInfo {
	var blocks []protocol.BlockInfo
	for _, b := range f.Blocks {
		blocks = append(blocks, protocol.BlockInfo{
			Length: b.Length,
			Hash:   b.Hash,
		})
	}
	return protocol.FileInfo{
		Name:     f.Name,
		Flags:    f.Flags,
		Modified: int64(f.Modified),
		Blocks:   blocks,
	}
}