package charger

/*
MIT License

Copyright (c) 2023-2025 pulsatrix gmbh
Copyright (c) 2019-2025 andig

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/*
This module integrates the pulsatrix Supply Equipment Charge Controller (SECC)
with evcc.io enabling dynamic PV surplus charging. Communication is handled via
a bidirectional WebSocket connection, exchanging state data (e.g. vehicle
status, voltages, currents, energy counters) and sending control commands (e.g.
start/stop charging, current limits, phase switching) to the controller.

Robust operation is ensured by automatic detection and handling of connection
losses, with reconnection based on exponential backoff strategies. In addition
to real-time data exchange, periodic heartbeats maintain connectivity.

For further details, see: https://docs.pulsatrix.com or https://pulsatrix.de
*/

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"sync"
	"sync/atomic"
	"time"

	"github.com/cenkalti/backoff/v4"
	"github.com/coder/websocket"
	"github.com/evcc-io/evcc/api"
	"github.com/evcc-io/evcc/util"
	"github.com/evcc-io/evcc/util/request"
	"github.com/evcc-io/evcc/util/sponsor"
)

const (
	dataTimeout       = 15 * time.Second
	heartbeatInterval = 3 * time.Minute
	maxRetries        = 3
	syncRetries       = 3
	backoffInitial    = 2 * time.Second
	backoffMax        = 30 * time.Second
	backoffMultiplier = 1.5
	errorLogInterval  = 15 * time.Minute
)

// pulsatrix charger implementation
type Pulsatrix struct {
	log                        *util.Logger
	mu                         sync.RWMutex
	conn                       *websocket.Conn
	hostname                   string
	uri                        string
	enabled                    int32 // atomic for thread-safe access
	data                       *util.Monitor[pulsatrixData]
	cancel                     context.CancelFunc // for graceful shutdown
	wg                         sync.WaitGroup     // for goroutine synchronization
	consecutiveReadErrors      int32              // atomic counter
	consecutiveHeartbeatErrors int32              // atomic counter
}

type pulsatrixData struct {
	VehicleStatus   string     `json:"vehicleStatus"`
	LastActivePower float64    `json:"lastActivePower"`
	PhaseVoltage    [3]float64 `json:"voltage"`
	PhaseAmperage   [3]float64 `json:"amperage"`
	AmperageLimit   float64    `json:"amperageLimit"`
	EnergyImported  float64    `json:"energyImported"`
}

func init() {
	registry.Add("pulsatrix", NewPulsatrixFromConfig)
}

// NewPulsatrixFromConfig creates a pulsatrix charger from generic config
func NewPulsatrixFromConfig(other map[string]any) (api.Charger, error) {
	var cc struct {
		Host string
	}

	if err := util.DecodeOther(other, &cc); err != nil {
		return nil, err
	}

	return NewPulsatrix(cc.Host)
}

// NewPulsatrix creates pulsatrix charger
func NewPulsatrix(hostname string) (*Pulsatrix, error) {
	// check sponsor authorization early (fail fast)
	if !sponsor.IsAuthorized() {
		return nil, api.ErrSponsorRequired
	}

	wb := &Pulsatrix{
		log:      util.NewLogger("pulsatrix"),
		hostname: hostname,
		uri:      fmt.Sprintf("ws://%s/api/ws", hostname),
		data:     util.NewMonitor[pulsatrixData](dataTimeout),
	}

	if err := wb.connect(); err != nil {
		return nil, fmt.Errorf("initial connection failed: %w", err)
	}

	return wb, nil
}

// connect connects to a pulsatrix SECC via websocket
func (c *Pulsatrix) connect() error {
	ctx, cancel := context.WithTimeout(context.Background(), request.Timeout)
	defer cancel()

	conn, _, err := websocket.Dial(ctx, c.uri, &websocket.DialOptions{
		CompressionMode: websocket.CompressionDisabled,
	})
	if err != nil {
		return fmt.Errorf("websocket dial to pulsatrix SECC at %s failed: %w", c.hostname, err)
	}

	c.mu.Lock()
	// close existing connection if present
	if c.conn != nil {
		c.conn.Close(websocket.StatusNormalClosure, "replacing connection")
	}
	c.conn = conn

	// create context for shutdown handling
	ctx, c.cancel = context.WithCancel(context.Background())
	c.mu.Unlock()

	// sync with retry mechanism
	if err := c.sync(); err != nil {
		conn.Close(websocket.StatusInternalError, "sync failed")
		return fmt.Errorf("sync failed: %w", err)
	}

	// start background routines
	c.wg.Add(2)
	go c.reader(ctx)
	go c.heartbeat(ctx)

	// reset error counters on successful connection
	atomic.StoreInt32(&c.consecutiveReadErrors, 0)
	atomic.StoreInt32(&c.consecutiveHeartbeatErrors, 0)

	c.log.INFO.Printf("connected to pulsatrix SECC at %s", c.hostname)
	return nil
}

// sync attempts synchronization with retry mechanism
func (c *Pulsatrix) sync() error {
	for i := range syncRetries {
		if err := c.Enable(false); err == nil {
			return nil
		}
		if i < syncRetries-1 {
			time.Sleep(time.Second)
		}
	}
	return fmt.Errorf("sync with pulsatrix SECC at %s failed after %d attempts", c.hostname, syncRetries)
}

// reconnect reconnects to a pulsatrix SECC websocket
func (c *Pulsatrix) reconnect() {
	bo := backoff.NewExponentialBackOff(
		backoff.WithInitialInterval(backoffInitial),
		backoff.WithMaxInterval(backoffMax),
		backoff.WithMultiplier(backoffMultiplier),
	)
	bo.MaxElapsedTime = 0 // 0 means no time limit - retry indefinitely

	var lastErrorLog time.Time
	operation := func() error {
		err := c.connect()
		if err != nil {
			// log error every errorLogInterval
			if time.Since(lastErrorLog) >= errorLogInterval {
				c.log.ERROR.Printf("reconnect to pulsatrix SECC at %s still failing: %v", c.hostname, err)
				lastErrorLog = time.Now()
			}
		}
		return err
	}

	if err := backoff.Retry(operation, bo); err != nil {
		// should never be reached with MaxElapsedTime = 0
		c.log.ERROR.Printf("unexpected backoff failure: %v", err)
	}
}

// reader runs a loop that reads messages from the websocket
func (c *Pulsatrix) reader(ctx context.Context) {
	defer c.wg.Done()
	defer func() {
		c.mu.Lock()
		if c.conn != nil {
			c.conn.Close(websocket.StatusNormalClosure, "websocket reader shutting down")
			c.conn = nil
		}
		c.mu.Unlock()

		// only reconnect if not explicitly stopped
		select {
		case <-ctx.Done():
			return // shutdown requested
		default:
			time.Sleep(time.Second)
			go c.reconnect()
		}
	}()

	for {
		// check for context cancellation
		select {
		case <-ctx.Done():
			return
		default:
		}

		readCtx, cancel := context.WithTimeout(ctx, request.Timeout)
		messageType, message, err := c.getConn().Read(readCtx)
		cancel()

		if err != nil {
			// check if context was cancelled (graceful shutdown)
			if ctx.Err() != nil {
				return
			}

			atomic.AddInt32(&c.consecutiveReadErrors, 1)
			consecutiveErrors := atomic.LoadInt32(&c.consecutiveReadErrors)

			// warn only after consecutive errors
			if consecutiveErrors >= maxRetries {
				c.log.WARN.Printf("websocket read on pulsatrix SECC at %s failed %d times consecutively: %v",
					c.hostname, consecutiveErrors, err)
			} else {
				c.log.TRACE.Printf("websocket read error on pulsatrix SECC at %s (attempt %d of %d): %v",
					c.hostname, consecutiveErrors, maxRetries, err)
			}
			return // trigger defer reconnect
		}

		// reset error counter after successful read
		atomic.StoreInt32(&c.consecutiveReadErrors, 0)

		c.parseMessage(messageType, message)
	}
}

// getConn returns the current connection in a thread-safe manner
func (c *Pulsatrix) getConn() *websocket.Conn {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.conn
}

// write writes a message to the websocket
func (c *Pulsatrix) write(message string) error {
	conn := c.getConn()
	if conn == nil {
		return fmt.Errorf("websocket not connected to pulsatrix SECC at %s", c.hostname)
	}

	ctx, cancel := context.WithTimeout(context.Background(), request.Timeout)
	defer cancel()

	if err := conn.Write(ctx, websocket.MessageText, []byte(message)); err != nil {
		c.log.WARN.Printf("write to pulsatrix SECC at %s failed: %v - trying reconnect", c.hostname, err)
		go c.reconnect() // async reconnect
		return err
	}
	return nil
}

// parseMessage parses a message from the websocket
func (c *Pulsatrix) parseMessage(messageType websocket.MessageType, message []byte) {
	if messageType != websocket.MessageText {
		return
	}

	if bytes.Contains(message, []byte(":NaN")) {
		message = bytes.ReplaceAll(message, []byte(":NaN"), []byte(":null"))
	}

	var parsedMessage struct {
		Message json.RawMessage `json:"message"`
	}

	if err := json.Unmarshal(message, &parsedMessage); err != nil {
		c.log.DEBUG.Printf("failed to unmarshal websocket message: %v", err)
		return
	}

	val, _ := c.data.Get()
	if err := json.Unmarshal(parsedMessage.Message, &val); err != nil {
		c.log.DEBUG.Printf("failed to unmarshal message content: %v", err)
	} else {
		c.data.Set(val)
	}
}

// heartbeat sends a heartbeat to the pulsatrix SECC to keep remote control active
func (c *Pulsatrix) heartbeat(ctx context.Context) {
	defer c.wg.Done()

	for tick := time.NewTicker(heartbeatInterval); ; {
		select {
		case <-ctx.Done():
			return
		case <-tick.C:
			enabled := atomic.LoadInt32(&c.enabled) != 0
			if err := c.Enable(enabled); err != nil {
				atomic.AddInt32(&c.consecutiveHeartbeatErrors, 1)
				consecutiveErrors := atomic.LoadInt32(&c.consecutiveHeartbeatErrors)

				// warn only after consecutive failures
				if consecutiveErrors >= maxRetries {
					c.log.WARN.Printf("heartbeat with pulsatrix SECC at %s failed %d times consecutively: %v",
						c.hostname, consecutiveErrors, err)
				}
			} else {
				// reset error counter after successful heartbeat
				atomic.StoreInt32(&c.consecutiveHeartbeatErrors, 0)
			}
		}
	}
}

// Shutdown gracefully closes the connection and stops all goroutines
func (c *Pulsatrix) Shutdown() error {
	if c.cancel != nil {
		c.cancel()
	}

	// wait for all goroutines to finish
	done := make(chan struct{})
	go func() {
		c.wg.Wait()
		close(done)
	}()

	select {
	case <-done:
		return nil
	case <-time.After(30 * time.Second):
		return fmt.Errorf("shutdown timeout")
	}
}

// evcc.io API functions

// Status implements the api.Charger interface
func (c *Pulsatrix) Status() (api.ChargeStatus, error) {
	res, err := c.data.Get()
	if err != nil {
		return api.StatusNone, err
	}
	return api.ChargeStatusString(res.VehicleStatus)
}

// Enabled implements the api.Charger interface
func (c *Pulsatrix) Enabled() (bool, error) {
	enabled := atomic.LoadInt32(&c.enabled) != 0
	return verifyEnabled(c, enabled)
}

// Enable implements the api.Charger interface
func (c *Pulsatrix) Enable(enable bool) error {
	message := fmt.Sprintf("setEnabled\n%t", enable)
	if err := c.write(message); err != nil {
		return err
	}

	var enabledVal int32
	if enable {
		enabledVal = 1
	}
	atomic.StoreInt32(&c.enabled, enabledVal)
	return nil
}

// MaxCurrent implements the api.CurrentLimiter interface
func (c *Pulsatrix) MaxCurrent(current int64) error {
	return c.MaxCurrentMillis(float64(current))
}

// MaxCurrentMillis implements the api.ChargerEx interface
func (c *Pulsatrix) MaxCurrentMillis(current float64) error {
	message := fmt.Sprintf("setCurrentLimit\n%g", current)
	return c.write(message)
}

var _ api.CurrentGetter = (*Pulsatrix)(nil)

// GetMaxCurrent implements the api.CurrentGetter interface
func (c *Pulsatrix) GetMaxCurrent() (float64, error) {
	res, err := c.data.Get()
	return res.AmperageLimit, err
}

// CurrentPower implements the api.Meter interface
func (c *Pulsatrix) CurrentPower() (float64, error) {
	res, err := c.data.Get()
	return res.LastActivePower, err
}

var _ api.MeterEnergy = (*Pulsatrix)(nil)

// TotalEnergy implements the api.MeterEnergy interface
func (c *Pulsatrix) TotalEnergy() (float64, error) {
	res, err := c.data.Get()
	return res.EnergyImported, err
}

// Phases1p3p implements the api.PhaseSwitcher interface
func (c *Pulsatrix) Phases1p3p(phases int) error {
	message := fmt.Sprintf("set1p3p\n%t", phases == 1)
	return c.write(message)
}

var _ api.PhaseCurrents = (*Pulsatrix)(nil)

// Currents implements the api.PhaseCurrents interface
func (c *Pulsatrix) Currents() (float64, float64, float64, error) {
	res, err := c.data.Get()
	if err != nil {
		return 0, 0, 0, err
	}
	return res.PhaseAmperage[0], res.PhaseAmperage[1], res.PhaseAmperage[2], nil
}

var _ api.PhaseVoltages = (*Pulsatrix)(nil)

// Voltages implements the api.PhaseVoltages interface
func (c *Pulsatrix) Voltages() (float64, float64, float64, error) {
	res, err := c.data.Get()
	if err != nil {
		return 0, 0, 0, err
	}
	return res.PhaseVoltage[0], res.PhaseVoltage[1], res.PhaseVoltage[2], nil
}