package runtime

import (
	"encoding/json"
	"log"
	"os"
	"sync"
	"time"

	"github.com/FreifunkBremen/yanic/data"
	"github.com/FreifunkBremen/yanic/jsontime"
)

// Nodes struct: cache DB of Node's structs
type Nodes struct {
	List   map[string]*Node `json:"nodes"` // the current nodemap, indexed by node ID
	config *Config
	sync.RWMutex
}

// NewNodes create Nodes structs
func NewNodes(config *Config) *Nodes {
	nodes := &Nodes{
		List:   make(map[string]*Node),
		config: config,
	}

	if config.Nodes.StatePath != "" {
		nodes.load()
	}

	return nodes
}

// Start all services to manage Nodes
func (nodes *Nodes) Start() {
	go nodes.worker()
}

// Update a Node
func (nodes *Nodes) Update(nodeID string, res *data.ResponseData) *Node {
	now := jsontime.Now()

	nodes.Lock()
	node, _ := nodes.List[nodeID]

	if node == nil {
		node = &Node{
			Firstseen: now,
		}
		nodes.List[nodeID] = node
	}
	nodes.Unlock()

	node.Lastseen = now
	node.Online = true

	// Update neighbours
	if val := res.Neighbours; val != nil {
		node.Neighbours = val
	}

	// Update nodeinfo
	if val := res.NodeInfo; val != nil {
		node.Nodeinfo = val
		node.Gateway = val.VPN
	}

	// Update statistics
	if val := res.Statistics; val != nil {

		// Update channel utilization if previous statistics are present
		if node.Statistics != nil && node.Statistics.Wireless != nil && val.Wireless != nil {
			val.Wireless.SetUtilization(node.Statistics.Wireless)
		}

		node.Statistics = val
	}

	return node
}

// Select selects a list of nodes to be returned
func (nodes *Nodes) Select(f func(*Node) bool) []*Node {
	nodes.RLock()
	defer nodes.RUnlock()

	result := make([]*Node, 0, len(nodes.List))
	for _, node := range nodes.List {
		if f(node) {
			result = append(result, node)
		}
	}
	return result
}

// Periodically saves the cached DB to json file
func (nodes *Nodes) worker() {
	c := time.Tick(nodes.config.Nodes.SaveInterval.Duration)

	for range c {
		nodes.expire()
		nodes.save()
	}
}

// Expires nodes and set nodes offline
func (nodes *Nodes) expire() {
	now := jsontime.Now()

	// Nodes last seen before expireAfter will be removed
	prunePeriod := nodes.config.Nodes.PruneAfter.Duration
	if prunePeriod == 0 {
		prunePeriod = time.Hour * 24 * 7 // our default
	}
	pruneAfter := now.Add(-prunePeriod)

	// Nodes last seen within OfflineAfter are changed to 'offline'
	offlineAfter := now.Add(-nodes.config.Nodes.OfflineAfter.Duration)

	// Locking foo
	nodes.Lock()
	defer nodes.Unlock()

	for id, node := range nodes.List {
		if node.Lastseen.Before(pruneAfter) {
			// expire
			delete(nodes.List, id)
		} else if node.Lastseen.Before(offlineAfter) {
			// set to offline
			node.Online = false
		}
	}
}

func (nodes *Nodes) load() {
	path := nodes.config.Nodes.StatePath

	if f, err := os.Open(path); err == nil { // transform data to legacy meshviewer
		if err = json.NewDecoder(f).Decode(nodes); err == nil {
			log.Println("loaded", len(nodes.List), "nodes")
		} else {
			log.Println("failed to unmarshal nodes:", err)
		}
	} else {
		log.Println("failed to load cached nodes:", err)
	}
}

func (nodes *Nodes) save() {
	// Locking foo
	nodes.RLock()
	defer nodes.RUnlock()

	// serialize nodes
	SaveJSON(nodes, nodes.config.Nodes.StatePath)
}

// SaveJSON to path
func SaveJSON(input interface{}, outputFile string) {
	tmpFile := outputFile + ".tmp"

	f, err := os.OpenFile(tmpFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
	if err != nil {
		log.Panic(err)
	}

	err = json.NewEncoder(f).Encode(input)
	if err != nil {
		log.Panic(err)
	}

	f.Close()
	if err := os.Rename(tmpFile, outputFile); err != nil {
		log.Panic(err)
	}
}