// package Server provides a way to listen for incoming connections
// and manage multiple reactor clients.
package server

import (
	pb "FRMS/internal/pkg/grpc"
	"FRMS/internal/pkg/influxdb"
	"FRMS/internal/pkg/logging"
	"context"
	"fmt"
	"net"
	"sync"

	"github.com/spf13/viper"
	"google.golang.org/grpc"
)

// Database is an interface to interact with the server database.
// Used mainly to find existing credentials for
// incoming reactor client connections.
type Database interface {
	GetReactorClient(int) (string, string, string, string, error) // returns (url, org, bucket, token, err)
}

// NewDatabaseAdmin creates a new database admin that implements the
// Database interface.
// Allows access to the database to find/create reactor credentials.
// Implemented via the influxdb package.
func NewDatabaseAdmin(config *viper.Viper) (Database, error) {
	return influxdb.NewDBAdmin(config)
}

// CentralCoordinator is the main coordinator struct that runs on the server.
// Used to oversee the reactor managers as well as process incoming
// client connections.
// Also interacts with the database and global config.
type CentralCoordinator struct {
	ClientConnections *ClientPacket
	*ReactorCoordinator
	Database
	Config *viper.Viper
	// from config
	Ports map[string]int `mapstructure:"ports"`
	Err   chan error
}

// NewCentralCoordinator creates a central coordinator with the given global
// config and error channel.
// It will create a new reactor coordinator and database admin.
// It will also try to load the existing configuration information.
func NewCentralCoordinator(config *viper.Viper, ch chan error) *CentralCoordinator {
	// create a central coordinator to manage requests
	db, err := NewDatabaseAdmin(config)
	if err != nil {
		ch <- err
	}

	rc, err := NewReactorCoordinator(config, ch)
	if err != nil {
		ch <- err
	}

	config.UnmarshalKey("server.ports", rc)

	c := &CentralCoordinator{
		Err:                ch,
		Config:             config,
		Database:           db,
		ReactorCoordinator: rc,
	}

	// grab config settings
	if err = config.UnmarshalKey("server", c); err != nil {
		ch <- err
	}

	return c
}

// Start activates the central coordinator and ensures it is ready for
// new clients.
// Creates a listener and starts both reactor coordinator and listener.
func (c *CentralCoordinator) Start() {

	clientChan := make(chan *ClientPacket)

	l, err := NewListener(clientChan, c.Err)

	if err != nil {
		c.Err <- err
	}

	c.Config.UnmarshalKey("server.ports", l)

	if err := c.ReactorCoordinator.Start(); err != nil {
		c.Err <- err
	}

	if err := l.Start(); err != nil {
		c.Err <- err
	}

	go c.ClientListener(clientChan)
}

// ClientListener listens on the given channel for clients that are sent
// over from the listener.
// The clients are then passed to the handler before returning the response.
func (c *CentralCoordinator) ClientListener(ch chan *ClientPacket) {

	for client := range ch {
		client.Response <- c.ClientHandler(client.Client) // respond with cred
	}
}

// ClientHandler takes in a client and retrieves the associated
// database credentials.
// Currently only handles reactor type clients, can be modified
// to support others.
func (c *CentralCoordinator) ClientHandler(cl *Client) *ClientResponse {
	// returns reactor db info
	var err error
	cr := &ClientResponse{Port: c.Ports[cl.Type]}

	if cl.Type != "reactor" {
		c.Err <- fmt.Errorf("client type %s not recognized", cl.Type)
	}

	go c.ReactorCoordinator.ClientHandler(cl)

	// db info
	cr.URL, cr.Org, cr.Token, cr.Bucket, err = c.Database.GetReactorClient(cl.Id)

	if err != nil {
		c.Err <- err
	}

	return cr
}

// ReactorCoordinator is a strucutre used to store reactor managers for
// clients that have connected at some point.
type ReactorCoordinator struct {
	Port int `mapstructure:"reactor"`
	*ReactorManagers
	Err chan error
	pb.UnimplementedMonitoringServer
}

// ReactorManagers is a structure that stores a concurrent map of the
// reactor managers as well as the global config.
type ReactorManagers struct {
	Config    *viper.Viper
	Directory map[int]*ReactorManager
	sync.RWMutex
}

// NewReactorCoordinator takes the global config and error channel and returns
// a pointer to a ReactorCoordinator as well as any errors.
func NewReactorCoordinator(config *viper.Viper, errCh chan error) (*ReactorCoordinator, error) {

	rmap := make(map[int]*ReactorManager)

	rm := &ReactorManagers{
		Directory: rmap,
		Config:    config,
	}

	return &ReactorCoordinator{
		Err:             errCh,
		ReactorManagers: rm,
	}, nil
}

// Start starts the reactor coordinator and kicks off
// registering the gRPC service
func (c *ReactorCoordinator) Start() error {

	logging.Debug(logging.DStart, "RCO 01 Starting!")

	return c.Register()
}

// ClientHandler takes in a client and finds or creates the correct
// manager for said client.
func (c *ReactorCoordinator) ClientHandler(cl *Client) {

	if err := c.UpdateReactorManager(cl, c.Err); err != nil {
		c.Err <- err
	}
}

// GetReactorManager attempts to locate a reactor manager for a given id.
// Returns either the associated reactor manager, or an error if
// a manager does not exist for the given id.
func (m *ReactorManagers) GetReactorManager(id int) (*ReactorManager, error) {
	m.RLock()
	defer m.RUnlock()

	rm, exists := m.Directory[id]

	if !exists {
		return &ReactorManager{}, fmt.Errorf("no manager for reactor %d", id)
	}
	return rm, nil
}

// UpdateReactorManager takes in a client and error channel and passes the
// client to the associate reactor manager.
// If the client does not have an existing reactor manager, it will create one
// , start it, and add it to the map for future calls.
// The function then calls UpdateClient on the reactor manager and returns
// any errors generated by this function.
func (m *ReactorManagers) UpdateReactorManager(cl *Client, errCh chan error) error {
	m.RLock()
	defer m.RUnlock()

	var err error

	rm, exists := m.Directory[cl.Id]

	if !exists {
		// reactor manager does not exist, creating new one
		logging.Debug(
			logging.DClient,
			"RCO 01 creating manager for %v",
			cl.Id,
		)

		if rm, err = NewReactorManager(cl, m.Config, errCh); err != nil {
			return err
		}

		if err = rm.Start(); err != nil {
			return err
		}

		m.Directory[cl.Id] = rm
	}

	return rm.UpdateClient(cl)
}

// Register attaches to the servers port and attempts to bind
// a gRPC server to it.
func (r *ReactorCoordinator) Register() error {

	lis, err := net.Listen("tcp", fmt.Sprintf(":%v", r.Port))
	if err != nil {
		return err
	}

	grpcServer := grpc.NewServer()
	pb.RegisterMonitoringServer(grpcServer, r)

	go grpcServer.Serve(lis)

	logging.Debug(logging.DClient, "RCO 01 ready")

	return nil
}

// ReactorStatusHandler is a gRPC handler used to handle incoming
// reactor requests containing information about said reactor.
// It will get the associate reactor manager and pass the
// request device information before returning an acknowledgement.
func (r *ReactorCoordinator) ReactorStatusHandler(ctx context.Context, req *pb.ReactorStatusPing) (*pb.ReactorStatusResponse, error) {

	rm, err := r.GetReactorManager(int(req.GetId()))

	if err != nil {
		return &pb.ReactorStatusResponse{}, err
	}

	go rm.ReactorDeviceHandler(req.GetDevices())

	return &pb.ReactorStatusResponse{Id: int32(rm.Id)}, nil
}