// Package httpserver is the emulator's own control surface: a web UI (the
// "controller board") plus the JSON/SSE API it talks to. This is separate
// from the MQTT side — the browser never speaks MQTT directly, it asks this
// server to do so.
package httpserver

import (
	"embed"
	"encoding/json"
	"fmt"
	"io/fs"
	"log/slog"
	"net/http"

	"git.cactoz.su/cacto/home_automation_emulator/internal/mqttclient"
	"git.cactoz.su/cacto/home_automation_emulator/internal/state"
)

//go:embed web
var webFS embed.FS

type Server struct {
	store  *state.Store
	mqtt   *mqttclient.Client
	logger *slog.Logger
	mux    *http.ServeMux
}

func New(store *state.Store, mqtt *mqttclient.Client, logger *slog.Logger) *Server {
	s := &Server{store: store, mqtt: mqtt, logger: logger, mux: http.NewServeMux()}
	s.routes()
	return s
}

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) { s.mux.ServeHTTP(w, r) }

func (s *Server) routes() {
	static, err := fs.Sub(webFS, "web")
	if err != nil {
		panic(err) // embedded FS is compiled in — can only fail if the embed directive itself is wrong
	}
	s.mux.Handle("GET /", http.FileServerFS(static))

	s.mux.HandleFunc("GET /api/snapshot", s.handleSnapshot)
	s.mux.HandleFunc("GET /api/events", s.handleEvents)
	s.mux.HandleFunc("POST /api/devices", s.handleAddDevice)
	s.mux.HandleFunc("DELETE /api/devices/{slot}", s.handleRemoveDevice)
	s.mux.HandleFunc("POST /api/devices/{slot}/identity", s.handleSetIdentity)
	s.mux.HandleFunc("POST /api/devices/{slot}/telemetry", s.handlePublishTelemetry)
}

// handleAddDevice creates a new standalone sensor (input) or actuator
// (output) device — a separate MQTT device_id, not another sensor_type or
// a manual override tacked onto an existing device. Mirrors how you'd
// actually add a second physical device to the platform (a new Device row
// with its own external_id).
func (s *Server) handleAddDevice(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Kind          string `json:"kind"` // "sensor" | "actuator"
		SignalName    string `json:"signal_name"`
		ExternalID    string `json:"external_id"`
		ZoneID        string `json:"zone_id"`
		Pin           string `json:"pin"`
		Discrete      bool   `json:"discrete"`
		SupportsLevel bool   `json:"supports_level"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.ExternalID == "" || req.ZoneID == "" {
		http.Error(w, "external_id and zone_id are required", http.StatusBadRequest)
		return
	}

	var slot string
	switch req.Kind {
	case "sensor":
		if req.SignalName == "" {
			http.Error(w, "signal_name is required for a sensor device", http.StatusBadRequest)
			return
		}
		slot = s.store.AddSensorDevice(req.SignalName, req.ExternalID, req.ZoneID, req.Pin, req.Discrete)
	case "actuator":
		slot = s.store.AddActuatorDevice(req.ExternalID, req.ZoneID, req.Pin, req.SupportsLevel)
	default:
		http.Error(w, `kind must be "sensor" or "actuator"`, http.StatusBadRequest)
		return
	}

	writeJSON(w, http.StatusCreated, s.store.Snapshot())
	s.logger.Info("extra device added", "slot", slot, "kind", req.Kind, "device_id", req.ExternalID)
}

func (s *Server) handleRemoveDevice(w http.ResponseWriter, r *http.Request) {
	slot := r.PathValue("slot")
	if !s.store.RemoveDevice(slot) {
		http.Error(w, "unknown or non-removable slot", http.StatusBadRequest)
		return
	}
	writeJSON(w, http.StatusOK, s.store.Snapshot())
}

func (s *Server) handleSnapshot(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, s.store.Snapshot())
}

func (s *Server) handleEvents(w http.ResponseWriter, r *http.Request) {
	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming unsupported", http.StatusInternalServerError)
		return
	}

	ch, unsubscribe := s.store.Subscribe()
	defer unsubscribe()

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")

	writeEvent(w, s.store.Snapshot())
	flusher.Flush()

	for {
		select {
		case <-r.Context().Done():
			return
		case snap, ok := <-ch:
			if !ok {
				return
			}
			writeEvent(w, snap)
			flusher.Flush()
		}
	}
}

func writeEvent(w http.ResponseWriter, snap state.Snapshot) {
	body, err := json.Marshal(snap)
	if err != nil {
		return
	}
	fmt.Fprintf(w, "data: %s\n\n", body)
}

func (s *Server) handleSetIdentity(w http.ResponseWriter, r *http.Request) {
	slot := r.PathValue("slot")
	if _, ok := s.store.Device(slot); !ok {
		http.Error(w, "unknown slot", http.StatusNotFound)
		return
	}

	var req struct {
		ExternalID string `json:"external_id"`
		ZoneID     string `json:"zone_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.ExternalID == "" || req.ZoneID == "" {
		http.Error(w, "external_id and zone_id are required", http.StatusBadRequest)
		return
	}

	s.store.SetIdentity(slot, req.ExternalID, req.ZoneID)
	writeJSON(w, http.StatusOK, s.store.Snapshot())
}

func (s *Server) handlePublishTelemetry(w http.ResponseWriter, r *http.Request) {
	slot := r.PathValue("slot")
	device, ok := s.store.Device(slot)
	if !ok {
		http.Error(w, "unknown slot", http.StatusNotFound)
		return
	}
	if device.Kind != state.KindSensor {
		http.Error(w, "slot is not a sensor", http.StatusBadRequest)
		return
	}

	var req struct {
		SensorType string  `json:"sensor_type"`
		Value      float64 `json:"value"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil || req.SensorType == "" {
		http.Error(w, "sensor_type is required", http.StatusBadRequest)
		return
	}

	s.store.SetReading(slot, req.SensorType, req.Value)

	if err := s.mqtt.PublishTelemetry(device.ExternalID, device.ZoneID, req.SensorType, req.Value); err != nil {
		s.logger.Error("publish telemetry failed", "slot", slot, "error", err)
		http.Error(w, "failed to publish to mqtt", http.StatusBadGateway)
		return
	}

	writeJSON(w, http.StatusOK, s.store.Snapshot())
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}