package nomad

import (
	"fmt"
	"math/rand"
	"net"
	"os"
	"path/filepath"
	"strconv"

	memdb "github.com/hashicorp/go-memdb"
	version "github.com/hashicorp/go-version"
	"github.com/hashicorp/nomad/nomad/state"
	"github.com/hashicorp/nomad/nomad/structs"
	"github.com/hashicorp/serf/serf"
)

// MinVersionPlanNormalization is the minimum version to support the
// normalization of Plan in SubmitPlan, and the denormalization raft log entry committed
// in ApplyPlanResultsRequest
var MinVersionPlanNormalization = version.Must(version.NewVersion("0.9.2"))

// ensurePath is used to make sure a path exists
func ensurePath(path string, dir bool) error {
	if !dir {
		path = filepath.Dir(path)
	}
	return os.MkdirAll(path, 0755)
}

// serverParts is used to return the parts of a server role
type serverParts struct {
	Name         string
	ID           string
	Region       string
	Datacenter   string
	Port         int
	Bootstrap    bool
	Expect       int
	MajorVersion int
	MinorVersion int
	Build        version.Version
	RaftVersion  int
	Addr         net.Addr
	RPCAddr      net.Addr
	Status       serf.MemberStatus
	NonVoter     bool
}

func (s *serverParts) String() string {
	return fmt.Sprintf("%s (Addr: %s) (DC: %s)",
		s.Name, s.Addr, s.Datacenter)
}

func (s *serverParts) Copy() *serverParts {
	ns := new(serverParts)
	*ns = *s
	return ns
}

// Returns if a member is a Nomad server. Returns a boolean,
// and a struct with the various important components
func isNomadServer(m serf.Member) (bool, *serverParts) {
	if m.Tags["role"] != "nomad" {
		return false, nil
	}

	id := "unknown"
	if v, ok := m.Tags["id"]; ok {
		id = v
	}
	region := m.Tags["region"]
	datacenter := m.Tags["dc"]
	_, bootstrap := m.Tags["bootstrap"]

	expect := 0
	expectStr, ok := m.Tags["expect"]
	var err error
	if ok {
		expect, err = strconv.Atoi(expectStr)
		if err != nil {
			return false, nil
		}
	}

	// If the server is missing the rpc_addr tag, default to the serf advertise addr
	rpcIP := net.ParseIP(m.Tags["rpc_addr"])
	if rpcIP == nil {
		rpcIP = m.Addr
	}

	portStr := m.Tags["port"]
	port, err := strconv.Atoi(portStr)
	if err != nil {
		return false, nil
	}

	buildVersion, err := version.NewVersion(m.Tags["build"])
	if err != nil {
		return false, nil
	}

	// The "vsn" tag was Version, which is now the MajorVersion number.
	majorVersionStr := m.Tags["vsn"]
	majorVersion, err := strconv.Atoi(majorVersionStr)
	if err != nil {
		return false, nil
	}

	// To keep some semblance of convention, "mvn" is now the "Minor
	// Version Number."
	minorVersionStr := m.Tags["mvn"]
	minorVersion, err := strconv.Atoi(minorVersionStr)
	if err != nil {
		minorVersion = 0
	}

	raftVsn := 0
	raftVsnString, ok := m.Tags["raft_vsn"]
	if ok {
		raftVsn, err = strconv.Atoi(raftVsnString)
		if err != nil {
			return false, nil
		}
	}

	// Check if the server is a non voter
	_, nonVoter := m.Tags["nonvoter"]

	addr := &net.TCPAddr{IP: m.Addr, Port: port}
	rpcAddr := &net.TCPAddr{IP: rpcIP, Port: port}
	parts := &serverParts{
		Name:         m.Name,
		ID:           id,
		Region:       region,
		Datacenter:   datacenter,
		Port:         port,
		Bootstrap:    bootstrap,
		Expect:       expect,
		Addr:         addr,
		RPCAddr:      rpcAddr,
		MajorVersion: majorVersion,
		MinorVersion: minorVersion,
		Build:        *buildVersion,
		RaftVersion:  raftVsn,
		Status:       m.Status,
		NonVoter:     nonVoter,
	}
	return true, parts
}

// ServersMeetMinimumVersion returns whether the Nomad servers are at least on the
// given Nomad version. The checkFailedServers parameter specifies whether version
// for the failed servers should be verified.
func ServersMeetMinimumVersion(members []serf.Member, minVersion *version.Version, checkFailedServers bool) bool {
	for _, member := range members {
		if valid, parts := isNomadServer(member); valid && (parts.Status == serf.StatusAlive || (checkFailedServers && parts.Status == serf.StatusFailed)) {
			// Check if the versions match - version.LessThan will return true for
			// 0.8.0-rc1 < 0.8.0, so we want to ignore the metadata
			versionsMatch := slicesMatch(minVersion.Segments(), parts.Build.Segments())
			if parts.Build.LessThan(minVersion) && !versionsMatch {
				return false
			}
		}
	}

	return true
}

func slicesMatch(a, b []int) bool {
	if a == nil && b == nil {
		return true
	}

	if a == nil || b == nil {
		return false
	}

	if len(a) != len(b) {
		return false
	}

	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}

	return true
}

// shuffleStrings randomly shuffles the list of strings
func shuffleStrings(list []string) {
	for i := range list {
		j := rand.Intn(i + 1)
		list[i], list[j] = list[j], list[i]
	}
}

// partitionAll splits a slice of strings into a slice of slices of strings, each with a max
// size of `size`. All entries from the original slice are preserved. The last slice may be
// smaller than `size`. The input slice is unmodified
func partitionAll(size int, xs []string) [][]string {
	if size < 1 {
		return [][]string{xs}
	}

	out := [][]string{}

	for i := 0; i < len(xs); i += size {
		j := i + size
		if j > len(xs) {
			j = len(xs)
		}
		out = append(out, xs[i:j])
	}

	return out
}

// maxUint64 returns the maximum value
func maxUint64(inputs ...uint64) uint64 {
	l := len(inputs)
	if l == 0 {
		return 0
	} else if l == 1 {
		return inputs[0]
	}

	max := inputs[0]
	for i := 1; i < l; i++ {
		cur := inputs[i]
		if cur > max {
			max = cur
		}
	}
	return max
}

// getNodeForRpc returns a Node struct if the Node supports Node RPC. Otherwise
// an error is returned.
func getNodeForRpc(snap *state.StateSnapshot, nodeID string) (*structs.Node, error) {
	node, err := snap.NodeByID(nil, nodeID)
	if err != nil {
		return nil, err
	}

	if node == nil {
		return nil, fmt.Errorf("Unknown node %q", nodeID)
	}

	if err := nodeSupportsRpc(node); err != nil {
		return nil, err
	}

	return node, nil
}

var minNodeVersionSupportingRPC = version.Must(version.NewVersion("0.8.0-rc1"))

// nodeSupportsRpc returns a non-nil error if a Node does not support RPC.
func nodeSupportsRpc(node *structs.Node) error {
	rawNodeVer, ok := node.Attributes["nomad.version"]
	if !ok {
		return structs.ErrUnknownNomadVersion
	}

	nodeVer, err := version.NewVersion(rawNodeVer)
	if err != nil {
		return structs.ErrUnknownNomadVersion
	}

	if nodeVer.LessThan(minNodeVersionSupportingRPC) {
		return structs.ErrNodeLacksRpc
	}

	return nil
}

// AllocGetter is an interface for retrieving allocations by ID. It is
// satisfied by *state.StateStore and *state.StateSnapshot.
type AllocGetter interface {
	AllocByID(ws memdb.WatchSet, id string) (*structs.Allocation, error)
}

// getAlloc retrieves an allocation by ID and namespace. If the allocation is
// nil, an error is returned.
func getAlloc(state AllocGetter, allocID string) (*structs.Allocation, error) {
	if allocID == "" {
		return nil, structs.ErrMissingAllocID
	}

	alloc, err := state.AllocByID(nil, allocID)
	if err != nil {
		return nil, err
	}

	if alloc == nil {
		return nil, structs.NewErrUnknownAllocation(allocID)
	}

	return alloc, nil
}

// dropButLastChannel returns a channel that drops all but last value from sourceCh.
//
// Useful for aggressively consuming sourceCh when intermediate values aren't relevant.
//
// This function propagates values to result quickly and drops intermediate messages
// in best effort basis.  Golang scheduler may delay delivery or result in extra
// deliveries.
//
// Consider this function for example:
//
// ```
// src := make(chan bool)
// dst := dropButLastChannel(src, nil)
//
// go func() {
//   src <- true
//   src <- false
// }()
//
// // v can be `true` here but is very unlikely
// v := <-dst
// ```
//
func dropButLastChannel(sourceCh <-chan bool, shutdownCh <-chan struct{}) chan bool {
	// buffer the most recent result
	dst := make(chan bool)

	go func() {
		// last value received
		lv := false
		// ok source was closed
		ok := false
		// received message since last delivery to destination
		messageReceived := false

	DEQUE_SOURCE:
		// wait for first message
		select {
		case lv, ok = <-sourceCh:
			if !ok {
				goto SOURCE_CLOSED
			}
			messageReceived = true
			goto ENQUEUE_DST
		case <-shutdownCh:
			return
		}

	ENQUEUE_DST:
		// prioritize draining source first dequeue without blocking
		for {
			select {
			case lv, ok = <-sourceCh:
				if !ok {
					goto SOURCE_CLOSED
				}
				messageReceived = true
			default:
				break ENQUEUE_DST
			}
		}

		// attempt to enqueue but keep monitoring source channel
		select {
		case lv, ok = <-sourceCh:
			if !ok {
				goto SOURCE_CLOSED
			}
			messageReceived = true
			goto ENQUEUE_DST
		case dst <- lv:
			messageReceived = false
			// enqueued value; back to dequeing from source
			goto DEQUE_SOURCE
		case <-shutdownCh:
			return
		}

	SOURCE_CLOSED:
		if messageReceived {
			select {
			case dst <- lv:
			case <-shutdownCh:
				return
			}
		}
		close(dst)
	}()

	return dst

}