package admin

import (
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"net/url"
	"os"

	"strings"
	"time"

	"github.com/gologme/log"

	"github.com/yggdrasil-network/yggdrasil-go/src/config"
	"github.com/yggdrasil-network/yggdrasil-go/src/core"
)

// TODO: Add authentication

type AdminSocket struct {
	core       *core.Core
	log        *log.Logger
	listenaddr string
	listener   net.Listener
	handlers   map[string]handler
	done       chan struct{}
}

type AdminSocketResponse struct {
	Status  string `json:"status"`
	Request struct {
		Name      string `json:"request"`
		KeepAlive bool   `json:"keepalive"`
	} `json:"request"`
	Response interface{} `json:"response"`
}

type handler struct {
	args    []string            // List of human-readable argument names
	handler core.AddHandlerFunc // First is input map, second is output
}

type ListResponse struct {
	List map[string]ListEntry `json:"list"`
}

type ListEntry struct {
	Fields []string `json:"fields"`
}

// AddHandler is called for each admin function to add the handler and help documentation to the API.
func (a *AdminSocket) AddHandler(name string, args []string, handlerfunc core.AddHandlerFunc) error {
	if _, ok := a.handlers[strings.ToLower(name)]; ok {
		return errors.New("handler already exists")
	}
	a.handlers[strings.ToLower(name)] = handler{
		args:    args,
		handler: handlerfunc,
	}
	return nil
}

// Init runs the initial admin setup.
func (a *AdminSocket) Init(c *core.Core, nc *config.NodeConfig, log *log.Logger, options interface{}) error {
	a.core = c
	a.log = log
	a.handlers = make(map[string]handler)
	nc.RLock()
	a.listenaddr = nc.AdminListen
	nc.RUnlock()
	a.done = make(chan struct{})
	close(a.done) // Start in a done / not-started state
	_ = a.AddHandler("list", []string{}, func(_ json.RawMessage) (interface{}, error) {
		res := &ListResponse{
			List: map[string]ListEntry{},
		}
		for name, handler := range a.handlers {
			res.List[name] = ListEntry{
				Fields: handler.args,
			}
		}
		return res, nil
	})
	return a.core.SetAdmin(a)
}

func (a *AdminSocket) SetupAdminHandlers() {
	_ = a.AddHandler("getSelf", []string{}, func(in json.RawMessage) (interface{}, error) {
		req := &GetSelfRequest{}
		res := &GetSelfResponse{}
		if err := json.Unmarshal(in, &req); err != nil {
			return nil, err
		}
		if err := a.getSelfHandler(req, res); err != nil {
			return nil, err
		}
		return res, nil
	})
	_ = a.AddHandler("getPeers", []string{}, func(in json.RawMessage) (interface{}, error) {
		req := &GetPeersRequest{}
		res := &GetPeersResponse{}
		if err := json.Unmarshal(in, &req); err != nil {
			return nil, err
		}
		if err := a.getPeersHandler(req, res); err != nil {
			return nil, err
		}
		return res, nil
	})
	_ = a.AddHandler("getDHT", []string{}, func(in json.RawMessage) (interface{}, error) {
		req := &GetDHTRequest{}
		res := &GetDHTResponse{}
		if err := json.Unmarshal(in, &req); err != nil {
			return nil, err
		}
		if err := a.getDHTHandler(req, res); err != nil {
			return nil, err
		}
		return res, nil
	})
	_ = a.AddHandler("getPaths", []string{}, func(in json.RawMessage) (interface{}, error) {
		req := &GetPathsRequest{}
		res := &GetPathsResponse{}
		if err := json.Unmarshal(in, &req); err != nil {
			return nil, err
		}
		if err := a.getPathsHandler(req, res); err != nil {
			return nil, err
		}
		return res, nil
	})
	_ = a.AddHandler("getSessions", []string{}, func(in json.RawMessage) (interface{}, error) {
		req := &GetSessionsRequest{}
		res := &GetSessionsResponse{}
		if err := json.Unmarshal(in, &req); err != nil {
			return nil, err
		}
		if err := a.getSessionsHandler(req, res); err != nil {
			return nil, err
		}
		return res, nil
	})
	//_ = a.AddHandler("getNodeInfo", []string{"key"}, t.proto.nodeinfo.nodeInfoAdminHandler)
	//_ = a.AddHandler("debug_remoteGetSelf", []string{"key"}, t.proto.getSelfHandler)
	//_ = a.AddHandler("debug_remoteGetPeers", []string{"key"}, t.proto.getPeersHandler)
	//_ = a.AddHandler("debug_remoteGetDHT", []string{"key"}, t.proto.getDHTHandler)
}

// Start runs the admin API socket to listen for / respond to admin API calls.
func (a *AdminSocket) Start() error {
	if a.listenaddr != "none" && a.listenaddr != "" {
		a.done = make(chan struct{})
		go a.listen()
	}
	return nil
}

// IsStarted returns true if the module has been started.
func (a *AdminSocket) IsStarted() bool {
	select {
	case <-a.done:
		// Not blocking, so we're not currently running
		return false
	default:
		// Blocked, so we must have started
		return true
	}
}

// Stop will stop the admin API and close the socket.
func (a *AdminSocket) Stop() error {
	if a.listener != nil {
		select {
		case <-a.done:
		default:
			close(a.done)
		}
		return a.listener.Close()
	}
	return nil
}

// listen is run by start and manages API connections.
func (a *AdminSocket) listen() {
	u, err := url.Parse(a.listenaddr)
	if err == nil {
		switch strings.ToLower(u.Scheme) {
		case "unix":
			if _, err := os.Stat(a.listenaddr[7:]); err == nil {
				a.log.Debugln("Admin socket", a.listenaddr[7:], "already exists, trying to clean up")
				if _, err := net.DialTimeout("unix", a.listenaddr[7:], time.Second*2); err == nil || err.(net.Error).Timeout() {
					a.log.Errorln("Admin socket", a.listenaddr[7:], "already exists and is in use by another process")
					os.Exit(1)
				} else {
					if err := os.Remove(a.listenaddr[7:]); err == nil {
						a.log.Debugln(a.listenaddr[7:], "was cleaned up")
					} else {
						a.log.Errorln(a.listenaddr[7:], "already exists and was not cleaned up:", err)
						os.Exit(1)
					}
				}
			}
			a.listener, err = net.Listen("unix", a.listenaddr[7:])
			if err == nil {
				switch a.listenaddr[7:8] {
				case "@": // maybe abstract namespace
				default:
					if err := os.Chmod(a.listenaddr[7:], 0660); err != nil {
						a.log.Warnln("WARNING:", a.listenaddr[:7], "may have unsafe permissions!")
					}
				}
			}
		case "tcp":
			a.listener, err = net.Listen("tcp", u.Host)
		default:
			// err = errors.New(fmt.Sprint("protocol not supported: ", u.Scheme))
			a.listener, err = net.Listen("tcp", a.listenaddr)
		}
	} else {
		a.listener, err = net.Listen("tcp", a.listenaddr)
	}
	if err != nil {
		a.log.Errorf("Admin socket failed to listen: %v", err)
		os.Exit(1)
	}
	a.log.Infof("%s admin socket listening on %s",
		strings.ToUpper(a.listener.Addr().Network()),
		a.listener.Addr().String())
	defer a.listener.Close()
	for {
		conn, err := a.listener.Accept()
		if err == nil {
			go a.handleRequest(conn)
		} else {
			select {
			case <-a.done:
				// Not blocked, so we havent started or already stopped
				return
			default:
				// Blocked, so we're supposed to keep running
			}
		}
	}
}

// handleRequest calls the request handler for each request sent to the admin API.
func (a *AdminSocket) handleRequest(conn net.Conn) {
	decoder := json.NewDecoder(conn)
	decoder.DisallowUnknownFields()

	encoder := json.NewEncoder(conn)
	encoder.SetIndent("", "  ")

	defer conn.Close()

	defer func() {
		r := recover()
		if r != nil {
			a.log.Debugln("Admin socket error:", r)
			if err := encoder.Encode(&ErrorResponse{
				Error: "Check your syntax and input types",
			}); err != nil {
				a.log.Debugln("Admin socket JSON encode error:", err)
			}
			conn.Close()
		}
	}()

	for {
		var err error
		var buf json.RawMessage
		_ = decoder.Decode(&buf)
		var resp AdminSocketResponse
		resp.Status = "success"
		if err = json.Unmarshal(buf, &resp.Request); err == nil {
			if resp.Request.Name == "" {
				resp.Status = "error"
				resp.Response = &ErrorResponse{
					Error: "No request specified",
				}
			} else if h, ok := a.handlers[strings.ToLower(resp.Request.Name)]; ok {
				resp.Response, err = h.handler(buf)
				if err != nil {
					resp.Status = "error"
					resp.Response = &ErrorResponse{
						Error: err.Error(),
					}
				}
			} else {
				resp.Status = "error"
				resp.Response = &ErrorResponse{
					Error: fmt.Sprintf("Unknown action '%s', try 'list' for help", resp.Request.Name),
				}
			}
		}
		if err = encoder.Encode(resp); err != nil {
			a.log.Debugln("Encode error:", err)
		}
		if !resp.Request.KeepAlive {
			break
		} else {
			continue
		}
	}
}