// Copyright © 2021-2022 Ettore Di Giacinto <mudler@mocaccino.org>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, see <http://www.gnu.org/licenses/>.

package service

import (
	"context"
	"embed"
	"encoding/base64"
	"fmt"
	"io"
	"io/fs"
	"io/ioutil"
	"os"
	"path"
	"path/filepath"
	"time"

	"github.com/ipfs/go-log"
	"gopkg.in/yaml.v2"

	edgeVPNClient "github.com/mudler/edgevpn/api/client"
	edgevpn "github.com/mudler/edgevpn/pkg/node"
)

// Node is the service Node.
// It have a set of defined available roles which nodes
// in a network can take. It takes a network token or either generates one
type Node struct {
	stateDir                                 string
	tokenFile                                string
	uuid                                     string
	networkToken                             string
	apiAddress                               string
	defaultRoles, persistentRoles, stopRoles string
	minNode                                  int

	assets []string
	fs     embed.FS
	client *Client
	roles  map[Role]func(c *RoleConfig) error

	logger log.StandardLogger
}

// WithRoles defines a set of role keys
func WithRoles(k ...RoleKey) Option {
	return func(mm *Node) error {
		m := map[Role]func(c *RoleConfig) error{}
		for _, kk := range k {
			m[kk.Role] = kk.RoleHandler
		}
		mm.roles = m
		return nil
	}
}

func WithMinNodes(i int) Option {
	return func(k *Node) error {
		k.minNode = i
		return nil
	}
}

// WithFS accepts an embed.FS file system where to copy binaries from
func WithFS(fs embed.FS) Option {
	return func(k *Node) error {
		k.fs = fs
		return nil
	}
}

// WithAssets is a list of assets to copy to a temporary state dir from the embedded FS
// It is used in conjunction with WithFS to ease out binary embedding
func WithAssets(assets ...string) Option {
	return func(k *Node) error {
		k.assets = assets
		return nil
	}
}

// WithLogger defines a logger to be used across the whole execution
func WithLogger(l log.StandardLogger) Option {
	return func(k *Node) error {
		k.logger = l
		return nil
	}
}

// WithStopRoles allows to set a list of comma separated roles that can be applied during cleanup
func WithStopRoles(roles string) Option {
	return func(k *Node) error {
		k.stopRoles = roles
		return nil
	}
}

// WithPersistentRoles allows to set a list of comma separated roles that can is applied persistently
func WithPersistentRoles(roles string) Option {
	return func(k *Node) error {
		k.persistentRoles = roles
		return nil
	}
}

// WithDefaultRoles allows to set a list of comma separated roles prefixed for the node.
// Note, by setting this the node will refuse any assigned role
func WithDefaultRoles(roles string) Option {
	return func(k *Node) error {
		k.defaultRoles = roles
		return nil
	}
}

// WithNetworkToken allows to set a network token.
// If not set, it is automatically generated
func WithNetworkToken(token string) Option {
	return func(k *Node) error {
		k.networkToken = token
		return nil
	}
}

// WithAPIAddress sets the EdgeVPN API address
func WithAPIAddress(s string) Option {
	return func(k *Node) error {
		k.apiAddress = s
		return nil
	}
}

// WithStateDir sets the node state directory.
// It will contain the unpacked assets (if any) and the
// process states generated by the roles.
func WithStateDir(s string) Option {
	return func(k *Node) error {
		k.stateDir = s
		return nil
	}
}

// WithUUID sets a node UUID
func WithUUID(s string) Option {
	return func(k *Node) error {
		k.uuid = s
		return nil
	}
}

// WithTokenfile sets a token file.
// If a token file and a network token is not found it is written
// to such file
func WithTokenfile(s string) Option {
	return func(k *Node) error {
		k.tokenFile = s
		return nil
	}
}

// WithClient sets a service client
func WithClient(e *Client) Option {
	return func(o *Node) error {
		o.client = e
		return nil
	}
}

// Option is a Node option
type Option func(k *Node) error

// NewNode returns a new service Node
// The service Node can have role applied which are
// polled by the API.
// This allows to bootstrap services using the API to coordinate nodes
// and apply roles afterwards (e.g. start vpn with a dynamically received IP, etc. )
func NewNode(o ...Option) (*Node, error) {
	k := &Node{
		stateDir:   "/tmp/Node",
		apiAddress: "localhost:7070",
	}
	for _, oo := range o {
		err := oo(k)
		if err != nil {
			return nil, err
		}
	}
	return k, nil
}

func (k *Node) copyBinary() {
	for _, a := range k.assets {
		b := path.Base(a)
		aa := NewProcessController(k.stateDir)
		p := aa.BinaryPath(b)
		if _, err := os.Stat(p); err != nil {
			os.MkdirAll(filepath.Join(k.stateDir, "bin"), os.ModePerm)
			f, err := k.fs.Open(a)
			if err != nil {
				panic(err)
			}
			if err := copyFileContents(f, p); err != nil {
				panic(err)
			}
		}
	}
}

func copyFileContents(in fs.File, dst string) (err error) {
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return
	}
	defer func() {
		cerr := out.Close()
		if err == nil {
			err = cerr
		}
	}()
	if _, err = io.Copy(out, in); err != nil {
		return
	}
	err = out.Sync()

	os.Chmod(dst, 0755)
	return
}

// Stop stops a node by calling the stop roles
func (k *Node) Stop() {
	k.execRoles(k.stopRoles)
}

// Clean stops and cleanup a node
func (k *Node) Clean() {
	k.client.Clean()
	k.Stop()
	if k.stateDir != "" {
		os.RemoveAll(k.stateDir)
	}
}

func (k *Node) prepare() error {
	k.copyBinary()

	if k.tokenFile != "" {
		f, err := ioutil.ReadFile(k.tokenFile)
		if err == nil {
			k.networkToken = string(f)
		}
	}

	if k.networkToken == "" {

		newData := edgevpn.GenerateNewConnectionData()
		bytesData, err := yaml.Marshal(newData)
		if err != nil {
			return err
		}

		token := base64.StdEncoding.EncodeToString(bytesData)

		k.logger.Infof("Token generated, writing to '%s'", k.tokenFile)
		ioutil.WriteFile(k.tokenFile, []byte(token), os.ModePerm)
		k.networkToken = token
	}

	k.execRoles(k.persistentRoles)

	if k.client == nil {
		k.client = NewClient("Node",
			edgeVPNClient.NewClient(edgeVPNClient.WithHost(fmt.Sprintf("http://%s", k.apiAddress))))
	}
	return nil
}

type roleMessage struct {
	Role Role
}

func (k *Node) options() (r []RoleOption) {
	r = []RoleOption{
		WithRoleLogger(k.logger),
		WithRole(k.roles),
		WithRoleClient(k.client),
		WithRoleUUID(k.uuid),
		WithRoleStateDir(k.stateDir),
		WithRoleAPIAddress(k.apiAddress),
		WithRoleToken(k.networkToken),
	}
	return
}

func (k *Node) execRoles(s string) {
	r := Role(s)
	k.logger.Infof("Applying role '%s'", r)

	r.Apply(k.options()...)
}

// Start starts the node with the context
func (k *Node) Start(ctx context.Context) error {
	// prepare binaries and start the default roles
	if err := k.prepare(); err != nil {
		return err
	}

	k.client.Advertize(k.uuid)

	minNode := 2
	if k.minNode != 0 {
		minNode = k.minNode
	}

	i := 0
	for {
		select {
		case <-ctx.Done():
			return nil
		default:
			i++
			time.Sleep(10 * time.Second)
			if i%2 == 0 {
				k.client.Advertize(k.uuid)
			}

			uuids, _ := k.client.ActiveNodes()

			for _, n := range uuids {
				k.logger.Infof("Active: '%s'", n)
			}

			if k.persistentRoles != "" {
				k.execRoles(k.persistentRoles)
			}

			// If we have default roles, executes them and continue
			if k.defaultRoles != "" {
				k.execRoles(k.defaultRoles)
				continue
			}

			// Not enough nodes
			if len(uuids) < minNode {
				k.logger.Infof("not enough nodes available, sleeping... needed: %d, available: %d", minNode, len(uuids))
				continue
			}

			// Enough active nodes.
			d, err := k.client.Get("role", k.uuid)
			if err == nil {
				k.logger.Info("Roles assigned")
				k.execRoles(d)
			} else {
				// we don't have a role yet, sleeping
				k.logger.Info("No role assigned, sleeping")
			}

		}
	}
}