package charger

// LICENSE

// Copyright (c) evcc.io (andig, naltatis, premultiply)

// This module is NOT covered by the MIT license. All rights reserved.

// 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.

import (
	"context"
	"encoding/binary"
	"fmt"

	"github.com/evcc-io/evcc/api"
	"github.com/evcc-io/evcc/api/implement"
	"github.com/evcc-io/evcc/util"
	"github.com/evcc-io/evcc/util/modbus"
)

// https://www.etek-electric.com/epc-ev-charge-controller/ekepc2-cs-ev-charging-station-controller
// https://www.etek-electric.com/ev-charging-station-knowledge/how-to-setting-rs485-communication-for-ekepc2-c-s-epc-controller

// ETEK EKEPC2 charger implementation
type Etek struct {
	implement.Caps
	log  *util.Logger
	conn *modbus.Connection
}

const (
	etekRegInvalidMeterAddr = 0xffff // Indicates no external meter configured

	// Meter configuration registers
	etekRegMeterVoltagesAddr = 90 // Meter voltages address
	etekRegMeterCurrentAddr  = 93 // Meter total current address
	etekRegMeterPowerAddr    = 94 // Meter total power address
	etekRegMeterEnergyAddr   = 95 // Meter total energy address

	// Write registers
	etekRegRemoteControl = 89  // Remote start/stop (0=invalid, 1=start, 2=stop)
	etekRegMaxCurrent    = 109 // Max Output Current PWM Duty cycle (*100)

	// Read registers
	etekRegStatus    = 141 // Current working status (0-19)
	etekRegCPVoltage = 153 // CP positive voltage
	etekRegPWMDuty   = 152 // Current output PWM duty cycle

	// Metering registers
	etekRegVoltages = 159 // Meter voltages
	etekRegCurrent  = 162 // Meter average phase current
	etekRegPower    = 163 // Total power of the meter (W)
	etekRegEnergy   = 164 // Total energy (2 registers, 32-bit, Wh)
)

func init() {
	registry.AddCtx("etek", NewEtekFromConfig)
}

// NewEtekFromConfig creates an ETEK EKEPC2 charger from generic config
func NewEtekFromConfig(ctx context.Context, other map[string]any) (api.Charger, error) {
	cc := modbus.Settings{
		ID: 255,
	}

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

	wb, err := NewEtek(ctx, cc)
	if err != nil {
		return nil, err
	}

	// Check if external meter is configured
	// If register value is 65535 (0xffff), no external meter is configured

	// Check power register (94)
	if b, err := wb.conn.ReadHoldingRegisters(etekRegMeterPowerAddr, 1); err == nil {
		if binary.BigEndian.Uint16(b) != etekRegInvalidMeterAddr {
			implement.Has(wb, implement.Meter(wb.currentPower))
		}
	}

	// Check energy register (95)
	if b, err := wb.conn.ReadHoldingRegisters(etekRegMeterEnergyAddr, 1); err == nil {
		if binary.BigEndian.Uint16(b) != etekRegInvalidMeterAddr {
			implement.Has(wb, implement.MeterEnergy(wb.totalEnergy))
		}
	}

	// Check voltage registers (90, 91, 92) - if any is configured, enable voltages
	if b, err := wb.conn.ReadHoldingRegisters(etekRegMeterVoltagesAddr, 3); err == nil {
		l1 := binary.BigEndian.Uint16(b[0:2])
		l2 := binary.BigEndian.Uint16(b[2:4])
		l3 := binary.BigEndian.Uint16(b[4:6])
		if l1 != etekRegInvalidMeterAddr && l2 != etekRegInvalidMeterAddr && l3 != etekRegInvalidMeterAddr {
			implement.Has(wb, implement.PhaseVoltages(wb.voltages))
		}
	}

	return wb, nil
}

// NewEtek creates an ETEK EKEPC2 charger
func NewEtek(ctx context.Context, settings modbus.Settings) (*Etek, error) {
	conn, err := settings.Connection(ctx)
	if err != nil {
		return nil, err
	}

	log := util.NewLogger("etek")
	conn.Logger(log.TRACE)

	wb := &Etek{
		Caps: implement.New(),
		log:  log,
		conn: conn,
	}

	return wb, nil
}

// getStatus reads the current working status from register 141
func (wb *Etek) getStatus() (uint16, error) {
	b, err := wb.conn.ReadHoldingRegisters(etekRegStatus, 1)
	if err != nil {
		return 0, err
	}

	return binary.BigEndian.Uint16(b), nil
}

// getCPVoltage reads the CP positive voltage from register 153
func (wb *Etek) getCPVoltage() (uint16, error) {
	b, err := wb.conn.ReadHoldingRegisters(etekRegCPVoltage, 1)
	if err != nil {
		return 0, err
	}

	return binary.BigEndian.Uint16(b), nil
}

// Status implements the api.Charger interface
func (wb *Etek) Status() (api.ChargeStatus, error) {
	status, err := wb.getStatus()
	if err != nil {
		return api.StatusNone, err
	}

	// Status mapping based on EKEPC2 documentation and user feedback:
	// 0: Initialization
	// 1: Ready (no vehicle connected)
	// 2: Fault
	// 3,4: Connected (vehicle connected, not charging)
	// 5: Charging
	// 19: Emergency stop (when disabled via register 89)
	//
	// When status is 19 (emergency stop), we need to check CP voltage
	// to determine if a vehicle is connected (voltage > 300 means connected)

	switch status {
	case 1:
		// Ready - no vehicle connected
		return api.StatusA, nil
	case 3, 4:
		// Vehicle connected, not charging
		return api.StatusB, nil
	case 5:
		// Charging
		return api.StatusC, nil
	case 19:
		// Emergency stop - check CP voltage to determine actual status
		voltage, err := wb.getCPVoltage()
		if err != nil {
			return api.StatusNone, err
		}
		if voltage < 300 {
			// No vehicle connected
			return api.StatusA, nil
		}
		// Vehicle connected but not charging (disabled)
		return api.StatusB, nil
	default:
		return api.StatusNone, fmt.Errorf("unknown status: %d", status)
	}
}

// Enabled implements the api.Charger interface
func (wb *Etek) Enabled() (bool, error) {
	b, err := wb.conn.ReadHoldingRegisters(etekRegRemoteControl, 1)
	if err != nil {
		return false, err
	}

	// Register 89: 0=invalid/disabled, 1=start/enabled, 2=stop/disabled
	return binary.BigEndian.Uint16(b) == 1, nil
}

// Enable implements the api.Charger interface
func (wb *Etek) Enable(enable bool) error {
	value := uint16(2) // Stop charging
	if enable {
		value = 1 // Start charging
	}

	_, err := wb.conn.WriteSingleRegister(etekRegRemoteControl, value)
	return err
}

// MaxCurrent implements the api.Charger interface
func (wb *Etek) MaxCurrent(current int64) error {
	return wb.MaxCurrentMillis(float64(current))
}

var _ api.ChargerEx = (*Etek)(nil)

// MaxCurrentMillis implements the api.ChargerEx interface
func (wb *Etek) MaxCurrentMillis(current float64) error {
	// The PWM value is calculated as: current (A) * 167
	if current < 6 {
		return fmt.Errorf("current %.1fA is below minimum of 6A", current)
	}

	_, err := wb.conn.WriteSingleRegister(etekRegMaxCurrent, uint16(current*167))
	return err
}

// currentPower implements the api.Meter interface
func (wb *Etek) currentPower() (float64, error) {
	b, err := wb.conn.ReadHoldingRegisters(etekRegPower, 1)
	if err != nil {
		return 0, err
	}

	return float64(binary.BigEndian.Uint16(b)), nil
}

// totalEnergy implements the api.MeterEnergy interface
func (wb *Etek) totalEnergy() (float64, error) {
	b, err := wb.conn.ReadHoldingRegisters(etekRegEnergy, 2)
	if err != nil {
		return 0, err
	}

	return float64(binary.BigEndian.Uint32(b)) / 1e3, nil // Convert to kWh
}

// voltages implements the api.PhaseVoltages interface
func (wb *Etek) voltages() (float64, float64, float64, error) {
	b, err := wb.conn.ReadHoldingRegisters(etekRegVoltages, 3)
	if err != nil {
		return 0, 0, 0, err
	}

	l1 := float64(binary.BigEndian.Uint16(b[0:2]))
	l2 := float64(binary.BigEndian.Uint16(b[2:4]))
	l3 := float64(binary.BigEndian.Uint16(b[4:6]))

	return l1, l2, l3, nil
}