package nameserver

import (
	"bytes"
	"encoding/gob"
	"fmt"
	"sort"
	"time"

	"github.com/weaveworks/weave/net/address"
	"github.com/weaveworks/weave/router"
)

var now = func() int64 { return time.Now().Unix() }

type Entry struct {
	ContainerID string
	Origin      router.PeerName
	Addr        address.Address
	Hostname    string
	Version     int
	Tombstone   int64 // timestamp of when it was deleted
}

type Entries []Entry

func (e1 *Entry) equal(e2 *Entry) bool {
	return e1.ContainerID == e2.ContainerID &&
		e1.Origin == e2.Origin &&
		e1.Addr == e2.Addr &&
		e1.Hostname == e2.Hostname
}

func (e1 *Entry) less(e2 *Entry) bool {
	// Entries are kept sorted by Hostname, Origin, ContainerID then address
	switch {
	case e1.Hostname != e2.Hostname:
		return e1.Hostname < e2.Hostname

	case e1.Origin != e2.Origin:
		return e1.Origin < e2.Origin

	case e1.ContainerID != e2.ContainerID:
		return e1.ContainerID < e2.ContainerID

	default:
		return e1.Addr < e2.Addr
	}
}

// returns true to indicate a change
func (e1 *Entry) merge(e2 *Entry) bool {
	// we know container id, origin, add and hostname are equal
	if e2.Version > e1.Version {
		e1.Version = e2.Version
		e1.Tombstone = e2.Tombstone
		return true
	}
	return false
}

func (e1 *Entry) String() string {
	return fmt.Sprintf("%s -> %s", e1.Hostname, e1.Addr.String())
}

func (es Entries) Len() int           { return len(es) }
func (es Entries) Swap(i, j int)      { panic("Swap") }
func (es Entries) Less(i, j int) bool { return es[i].less(&es[j]) }

func (es Entries) check() error {
	if !sort.IsSorted(es) {
		return fmt.Errorf("Not sorted!")
	}
	for i := 1; i < len(es); i++ {
		if es[i].equal(&es[i-1]) {
			return fmt.Errorf("Duplicate entry: %d:%v and %d:%v", i-1, es[i-1], i, es[i])
		}
	}
	return nil
}

func (es *Entries) checkAndPanic() {
	if err := es.check(); err != nil {
		panic(err)
	}
}

func (es *Entries) add(hostname, containerid string, origin router.PeerName, addr address.Address) Entry {
	es.checkAndPanic()
	defer es.checkAndPanic()

	entry := Entry{Hostname: hostname, Origin: origin, ContainerID: containerid, Addr: addr}
	i := sort.Search(len(*es), func(i int) bool {
		return !(*es)[i].less(&entry)
	})
	if i < len(*es) && (*es)[i].equal(&entry) {
		if (*es)[i].Tombstone > 0 {
			(*es)[i].Tombstone = 0
			(*es)[i].Version++
		}
	} else {
		*es = append(*es, Entry{})
		copy((*es)[i+1:], (*es)[i:])
		(*es)[i] = entry
	}
	return (*es)[i]
}

func (es *Entries) merge(incoming Entries) Entries {
	es.checkAndPanic()
	defer es.checkAndPanic()
	newEntries := Entries{}
	i := 0

	for _, entry := range incoming {
		for i < len(*es) && (*es)[i].less(&entry) {
			i++
		}
		if i < len(*es) && (*es)[i].equal(&entry) {
			if (*es)[i].merge(&entry) {
				newEntries = append(newEntries, entry)
			}
		} else {
			*es = append(*es, Entry{})
			copy((*es)[i+1:], (*es)[i:])
			(*es)[i] = entry
			newEntries = append(newEntries, entry)
		}
	}

	return newEntries
}

// f returning true means keep the entry.
func (es *Entries) tombstone(ourname router.PeerName, f func(*Entry) bool) Entries {
	es.checkAndPanic()
	defer es.checkAndPanic()
	tombstoned := Entries{}
	for i, e := range *es {
		if f(&e) && e.Origin == ourname {
			e.Version++
			e.Tombstone = now()
			(*es)[i] = e
			tombstoned = append(tombstoned, e)
		}
	}
	return tombstoned
}

func (es *Entries) filter(f func(*Entry) bool) {
	es.checkAndPanic()
	defer es.checkAndPanic()
	i := 0
	for _, e := range *es {
		if !f(&e) {
			continue
		}
		(*es)[i] = e
		i++
	}
	*es = (*es)[:i]
}

func (es Entries) lookup(hostname string) Entries {
	es.checkAndPanic()
	i := sort.Search(len(es), func(i int) bool {
		return es[i].Hostname >= hostname
	})
	if i >= len(es) || es[i].Hostname != hostname {
		return Entries{}
	}

	j := sort.Search(len(es)-i, func(j int) bool {
		return es[i+j].Hostname > hostname
	})

	return es[i : i+j]
}

func (es *Entries) first(f func(*Entry) bool) (*Entry, error) {
	es.checkAndPanic()
	for _, e := range *es {
		if f(&e) {
			return &e, nil
		}
	}
	return nil, fmt.Errorf("Not found")
}

type GossipData struct {
	Timestamp int64
	Entries
}

func (g *GossipData) Merge(o router.GossipData) {
	other := o.(*GossipData)
	g.Entries.merge(other.Entries)
	if g.Timestamp < other.Timestamp {
		g.Timestamp = other.Timestamp
	}
}

func (g *GossipData) Encode() [][]byte {
	buf := &bytes.Buffer{}
	if err := gob.NewEncoder(buf).Encode(g); err != nil {
		panic(err)
	}
	return [][]byte{buf.Bytes()}
}