/*
   Copyright 2023 Josh Deprez

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

	   http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package main

import (
	"encoding/binary"
	"errors"
	"fmt"
)

type register struct {
	name string
	conv func([]byte) (float64, error)
	mult float64
	unit string
}

func (r *register) read(data []byte) (float64, error) {
	n, err := r.conv(data)
	return n * r.mult, err
}

var sungrowInputRegs = map[uint16]*register{
	// 4990 - 4999: serial number in ASCII
	5001: {"nominal_power", u16req, 0.1, "kW"},
	5003: {"daily_power_yield", u16req, 0.1, "kWh"},
	5004: {"total_power_yield", u32req, 1, "kWh"},
	5006: {"total_running_time", u32req, 1, "h"},
	5008: {"internal_temperature", u16req, 0.1, "°C"},
	5011: {"pv1_potential", u16req, 0.1, "V"},
	5012: {"pv1_current", u16req, 0.1, "A"},
	5013: {"pv2_potential", u16req, 0.1, "V"},
	5014: {"pv2_current", u16req, 0.1, "A"},
	5015: {"pv3_potential", u16opt, 0.1, "V"},
	5016: {"pv3_current", u16opt, 0.1, "A"},
	5017: {"total_dc_power", u32req, 1, "W"},
	5019: {"phase_a_potential", u16req, 0.1, "V"},
	5020: {"phase_b_potential", u16opt, 0.1, "V"},
	5021: {"phase_c_potential", u16opt, 0.1, "V"},
	5022: {"phase_a_current", u16req, 0.1, "A"},
	5023: {"phase_b_current", u16opt, 0.1, "A"},
	5024: {"phase_c_current", u16opt, 0.1, "A"},
	5031: {"output_real_power", u32req, 1, "VA"},
	5033: {"output_reactive_power", s32opt, 1, "VAr"},
	5035: {"power_factor", s16opt, 0.001, ""},
	5036: {"frequency", u16req, 0.1, "Hz"},
	5049: {"nominal_reactive_power", s16opt, 0.1, "kVA"},

	5083: {"meter_power", s32req, 1, "W"},
	5085: {"meter_a_phase_power", s32opt, 1, "W"},
	5087: {"meter_b_phase_power", s32opt, 1, "W"},
	5089: {"meter_c_phase_power", s32opt, 1, "W"},
	5091: {"usage_power", s32req, 1, "W"},
	5093: {"daily_export_energy", u32req, 0.1, "kWh"},
	5095: {"total_export_energy", u32req, 0.1, "kWh"},
	5097: {"daily_import_energy", u32req, 0.1, "kWh"},
	5099: {"total_import_energy", u32req, 0.1, "kWh"},

	5113: {"daily_running_time", u16req, 1, "m"},
	5144: {"total_power_yield_2", u32req, 0.1, "kWh"},
	5148: {"frequency_2", frequency2, 0.01, "Hz"},
}

var errSkippableRead = errors.New("skip read")

func frequency2(data []byte) (float64, error) {
	n := binary.BigEndian.Uint16(data)
	if n == 0xFFFF {
		// probably a misread
		return 0, fmt.Errorf("likely misread: frequency_2 read %v", n)
	}
	if n == 100 {
		// this translates as 1 Hz, which is unlikely
		return 0, fmt.Errorf("%w: frequency_2 is 1.00Hz", errSkippableRead)
	}
	return float64(n), nil
}

func u16opt(data []byte) (float64, error) {
	return float64(binary.BigEndian.Uint16(data)), nil
}

func u16req(data []byte) (float64, error) {
	n := binary.BigEndian.Uint16(data)
	if n == 0xFFFF {
		// probably a misread
		return 0, fmt.Errorf("likely misread: u16req read %v", n)
	}
	return float64(n), nil
}

func s16opt(data []byte) (float64, error) {
	return float64(int16(binary.BigEndian.Uint16(data))), nil
}

// func s16req(data []byte) (float64, error) {
// 	n := binary.BigEndian.Uint16(data)
// 	if n == 0x7FFF {
// 		// probably a misread
// 		return 0, fmt.Errorf("likely misread: s16req read %v", n)
// 	}
// 	return float64(int16(n)), nil
// }

// func u32opt(data []byte) (float64, error) {
// 	// Little-endian big-endian :#
// 	return float64(uint32(binary.BigEndian.Uint16(data)) + uint32(binary.BigEndian.Uint16(data[2:]))<<16), nil
// }

func u32req(data []byte) (float64, error) {
	// Little-endian big-endian :#
	n := uint32(binary.BigEndian.Uint16(data)) + uint32(binary.BigEndian.Uint16(data[2:]))<<16
	if n == 0xFFFFFFFF {
		// probably a misread
		return 0, fmt.Errorf("likely misread: u32req read %v", n)
	}
	return float64(n), nil
}

func s32opt(data []byte) (float64, error) {
	// Little-endian big-endian :#
	return float64(int32(binary.BigEndian.Uint16(data)) + int32(binary.BigEndian.Uint16(data[2:]))<<16), nil
}

func s32req(data []byte) (float64, error) {
	// Little-endian big-endian :#
	n := uint32(binary.BigEndian.Uint16(data)) + uint32(binary.BigEndian.Uint16(data[2:]))<<16
	if n == 0x7FFFFFFF {
		// probably a misread
		return 0, fmt.Errorf("likely misread: s32req read %v", n)
	}
	return float64(int32(n)), nil
}