/*
Copyright (c) 2015, 2017 Hendrik van Wyk
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.

* Neither the name of invertergui nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package webui

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"sync"
	"time"

	"invertergui/mk2driver"
	"invertergui/websocket"
	"github.com/sirupsen/logrus"
)

var log = logrus.WithField("ctx", "inverter-gui-webgui")

const (
	LedOff     = "dot-off"
	LedRed     = "dot-red"
	BlinkRed   = "blink-red"
	LedGreen   = "dot-green"
	BlinkGreen = "blink-green"
)

const (
	modeChargerOnly  = "charger_only"
	modeInverterOnly = "inverter_only"
	modeOn           = "on"
	modeOff          = "off"
	modeUnknown      = "unknown"
)

type WebGui struct {
	mk2driver.Mk2
	writer   mk2driver.SettingsWriter
	stopChan chan struct{}

	wg  sync.WaitGroup
	hub *websocket.Hub

	stateMu sync.RWMutex
	latest  *templateInput
	remote  remotePanelState
}

func NewWebGui(source mk2driver.Mk2, writer mk2driver.SettingsWriter) *WebGui {
	w := &WebGui{
		stopChan: make(chan struct{}),
		Mk2:      source,
		writer:   writer,
		hub:      websocket.NewHub(),
		remote: remotePanelState{
			Writable: writer != nil,
			Mode:     modeUnknown,
		},
	}
	w.wg.Add(1)
	go w.dataPoll()
	return w
}

type remotePanelState struct {
	Writable     bool     `json:"writable"`
	Mode         string   `json:"mode"`
	CurrentLimit *float64 `json:"current_limit,omitempty"`
	Standby      *bool    `json:"standby,omitempty"`
	LastCommand  string   `json:"last_command,omitempty"`
	LastError    string   `json:"last_error,omitempty"`
	LastUpdated  string   `json:"last_updated,omitempty"`
}

type templateInput struct {
	Error []error `json:"errors"`

	Date string `json:"date"`

	OutCurrent string `json:"output_current"`
	OutVoltage string `json:"output_voltage"`
	OutPower   string `json:"output_power"`

	InCurrent string `json:"input_current"`
	InVoltage string `json:"input_voltage"`
	InPower   string `json:"input_power"`

	InMinOut string

	BatVoltage string `json:"battery_voltage"`
	BatCurrent string `json:"battery_current"`
	BatPower   string `json:"battery_power"`
	BatCharge  string `json:"battery_charge"`

	InFreq  string `json:"input_frequency"`
	OutFreq string `json:"output_frequency"`

	LedMap map[string]string `json:"led_map"`

	RemotePanel remotePanelState `json:"remote_panel"`
}

type setRemotePanelStateRequest struct {
	Mode         string   `json:"mode"`
	CurrentLimit *float64 `json:"current_limit"`
}

type setRemotePanelStandbyRequest struct {
	Standby bool `json:"standby"`
}

func (w *WebGui) ServeHub(rw http.ResponseWriter, r *http.Request) {
	w.hub.ServeHTTP(rw, r)
}

func (w *WebGui) ServeRemotePanelState(rw http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		writeJSON(rw, http.StatusOK, w.getRemotePanelState())
	case http.MethodPost:
		w.handleSetRemotePanelState(rw, r)
	default:
		http.Error(rw, "method not allowed", http.StatusMethodNotAllowed)
	}
}

func (w *WebGui) ServeRemotePanelStandby(rw http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		writeJSON(rw, http.StatusOK, w.getRemotePanelState())
	case http.MethodPost:
		w.handleSetRemotePanelStandby(rw, r)
	default:
		http.Error(rw, "method not allowed", http.StatusMethodNotAllowed)
	}
}

func (w *WebGui) handleSetRemotePanelState(rw http.ResponseWriter, r *http.Request) {
	if w.writer == nil {
		http.Error(rw, "remote control is not supported by this data source", http.StatusNotImplemented)
		return
	}

	req := setRemotePanelStateRequest{}
	if err := decodeJSONBody(r, &req); err != nil {
		http.Error(rw, err.Error(), http.StatusBadRequest)
		return
	}

	switchState, normalizedMode, err := parsePanelMode(req.Mode)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusBadRequest)
		return
	}

	if err := w.writer.SetPanelState(switchState, req.CurrentLimit); err != nil {
		w.updateRemotePanelState(func(state *remotePanelState) {
			state.LastCommand = "set_remote_panel_state"
			state.LastError = err.Error()
		})
		http.Error(rw, err.Error(), http.StatusBadGateway)
		return
	}

	w.updateRemotePanelState(func(state *remotePanelState) {
		state.Mode = normalizedMode
		state.CurrentLimit = copyFloat64Ptr(req.CurrentLimit)
		state.LastCommand = "set_remote_panel_state"
		state.LastError = ""
	})
	writeJSON(rw, http.StatusOK, w.getRemotePanelState())
}

func (w *WebGui) handleSetRemotePanelStandby(rw http.ResponseWriter, r *http.Request) {
	if w.writer == nil {
		http.Error(rw, "remote control is not supported by this data source", http.StatusNotImplemented)
		return
	}

	req := setRemotePanelStandbyRequest{}
	if err := decodeJSONBody(r, &req); err != nil {
		http.Error(rw, err.Error(), http.StatusBadRequest)
		return
	}

	if err := w.writer.SetStandby(req.Standby); err != nil {
		w.updateRemotePanelState(func(state *remotePanelState) {
			state.LastCommand = "set_remote_panel_standby"
			state.LastError = err.Error()
		})
		http.Error(rw, err.Error(), http.StatusBadGateway)
		return
	}

	w.updateRemotePanelState(func(state *remotePanelState) {
		state.Standby = copyBoolPtr(&req.Standby)
		state.LastCommand = "set_remote_panel_standby"
		state.LastError = ""
	})
	writeJSON(rw, http.StatusOK, w.getRemotePanelState())
}

func parsePanelMode(raw string) (mk2driver.PanelSwitchState, string, error) {
	switch strings.TrimSpace(strings.ToLower(raw)) {
	case modeChargerOnly:
		return mk2driver.PanelSwitchChargerOnly, modeChargerOnly, nil
	case modeInverterOnly:
		return mk2driver.PanelSwitchInverterOnly, modeInverterOnly, nil
	case modeOn:
		return mk2driver.PanelSwitchOn, modeOn, nil
	case modeOff:
		return mk2driver.PanelSwitchOff, modeOff, nil
	default:
		return 0, "", fmt.Errorf("unsupported panel mode %q", raw)
	}
}

func ledName(led mk2driver.Led) string {
	name, ok := mk2driver.LedNames[led]
	if !ok {
		return "Unknown led"
	}
	return name
}

func buildTemplateInput(status *mk2driver.Mk2Info) *templateInput {
	outPower := status.OutVoltage * status.OutCurrent
	inPower := status.InCurrent * status.InVoltage

	tmpInput := &templateInput{
		Error:      status.Errors,
		Date:       status.Timestamp.Format(time.RFC1123Z),
		OutCurrent: fmt.Sprintf("%.2f", status.OutCurrent),
		OutVoltage: fmt.Sprintf("%.2f", status.OutVoltage),
		OutPower:   fmt.Sprintf("%.2f", outPower),
		InCurrent:  fmt.Sprintf("%.2f", status.InCurrent),
		InVoltage:  fmt.Sprintf("%.2f", status.InVoltage),
		InFreq:     fmt.Sprintf("%.2f", status.InFrequency),
		OutFreq:    fmt.Sprintf("%.2f", status.OutFrequency),
		InPower:    fmt.Sprintf("%.2f", inPower),

		InMinOut: fmt.Sprintf("%.2f", inPower-outPower),

		BatCurrent: fmt.Sprintf("%.2f", status.BatCurrent),
		BatVoltage: fmt.Sprintf("%.2f", status.BatVoltage),
		BatPower:   fmt.Sprintf("%.2f", status.BatVoltage*status.BatCurrent),
		BatCharge:  fmt.Sprintf("%.2f", status.ChargeState*100),

		LedMap: map[string]string{},
	}
	for k, v := range status.LEDs {
		if k == mk2driver.LedOverload || k == mk2driver.LedTemperature || k == mk2driver.LedLowBattery {
			switch v {
			case mk2driver.LedOn:
				tmpInput.LedMap[ledName(k)] = LedRed
			case mk2driver.LedBlink:
				tmpInput.LedMap[ledName(k)] = BlinkRed
			default:
				tmpInput.LedMap[ledName(k)] = LedOff
			}
		} else {
			switch v {
			case mk2driver.LedOn:
				tmpInput.LedMap[ledName(k)] = LedGreen
			case mk2driver.LedBlink:
				tmpInput.LedMap[ledName(k)] = BlinkGreen
			default:
				tmpInput.LedMap[ledName(k)] = LedOff
			}
		}
	}
	return tmpInput
}

func (w *WebGui) Stop() {
	close(w.stopChan)
	w.wg.Wait()
}

func (w *WebGui) dataPoll() {
	for {
		select {
		case s := <-w.C():
			if s.Valid {
				payload := buildTemplateInput(s)
				w.stateMu.Lock()
				payload.RemotePanel = w.remote
				w.latest = payload
				w.stateMu.Unlock()
				if err := w.hub.Broadcast(payload); err != nil {
					log.Errorf("Could not send update to clients: %v", err)
				}
			}
		case <-w.stopChan:
			w.wg.Done()
			return
		}
	}
}

func (w *WebGui) getRemotePanelState() remotePanelState {
	w.stateMu.RLock()
	defer w.stateMu.RUnlock()
	return copyRemotePanelState(w.remote)
}

func (w *WebGui) updateRemotePanelState(update func(state *remotePanelState)) {
	w.stateMu.Lock()
	update(&w.remote)
	w.remote.LastUpdated = time.Now().UTC().Format(time.RFC3339)
	snapshot := w.snapshotLocked()
	w.stateMu.Unlock()

	if snapshot != nil {
		if err := w.hub.Broadcast(snapshot); err != nil {
			log.Errorf("Could not send control update to clients: %v", err)
		}
	}
}

func (w *WebGui) snapshotLocked() *templateInput {
	if w.latest == nil {
		return nil
	}

	snapshot := cloneTemplateInput(w.latest)
	snapshot.RemotePanel = copyRemotePanelState(w.remote)
	return snapshot
}

func cloneTemplateInput(in *templateInput) *templateInput {
	if in == nil {
		return nil
	}
	out := *in

	if in.Error != nil {
		out.Error = append([]error(nil), in.Error...)
	}
	if in.LedMap != nil {
		out.LedMap = make(map[string]string, len(in.LedMap))
		for k, v := range in.LedMap {
			out.LedMap[k] = v
		}
	}

	out.RemotePanel = copyRemotePanelState(in.RemotePanel)
	return &out
}

func copyRemotePanelState(in remotePanelState) remotePanelState {
	in.CurrentLimit = copyFloat64Ptr(in.CurrentLimit)
	in.Standby = copyBoolPtr(in.Standby)
	return in
}

func copyFloat64Ptr(in *float64) *float64 {
	if in == nil {
		return nil
	}
	value := *in
	return &value
}

func copyBoolPtr(in *bool) *bool {
	if in == nil {
		return nil
	}
	value := *in
	return &value
}

func decodeJSONBody(r *http.Request, destination any) error {
	defer r.Body.Close()
	decoder := json.NewDecoder(r.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(destination); err != nil {
		return fmt.Errorf("invalid request body: %w", err)
	}
	return nil
}

func writeJSON(rw http.ResponseWriter, statusCode int, payload any) {
	rw.Header().Set("Content-Type", "application/json")
	rw.WriteHeader(statusCode)
	if err := json.NewEncoder(rw).Encode(payload); err != nil {
		log.Errorf("Could not encode webui API response: %v", err)
	}
}