package logfile

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"time"

	"github.com/volker-raschek/flucky/pkg/types"
)

// Define the entry size for each logfile
var templeratureSplitBy = 10000

// CompressTemperature compresses the temperatures from an array. It is checked
// whether the measured temperature of a value corresponds to that of the
// predecessor. If this is the case, the current value is discarded and the
// validity date of the predecessor value is set to that of the current value.
// No information is lost as a result. The validity period of the measured value
// is thereby exclusively increased.
func CompressTemperature(temperatures []*types.Temperature) []*types.Temperature {
	compressedTemperatures := make([]*types.Temperature, 0)
	lastTemperatureBySensors := make(map[string]*types.Temperature, 0)

	// Sort all measured temperatures beforehand by the starting validity date to
	// avoid errors when compressing the temperatures.
	SortTemperatures(temperatures)

	for _, temperature := range temperatures {
		if lastTemperatureBySensor, ok := lastTemperatureBySensors[temperature.SensorID]; ok {
			if lastTemperatureBySensor.TemperatureValue == temperature.TemperatureValue {

				lastTemperatureBySensors[temperature.SensorID].TemperatureTillDate = temperature.TemperatureTillDate

				now := time.Now()
				lastTemperatureBySensors[temperature.SensorID].UpdateDate = &now
			} else {
				compressedTemperatures = append(compressedTemperatures, lastTemperatureBySensors[temperature.SensorID])
				lastTemperatureBySensors[temperature.SensorID] = temperature
			}
		} else {
			lastTemperatureBySensors[temperature.SensorID] = temperature
		}
	}

	// Copy all remaining entries from the map into the array
	for _, lastTemperatureBySensor := range lastTemperatureBySensors {
		compressedTemperatures = append(compressedTemperatures, lastTemperatureBySensor)
	}

	return compressedTemperatures
}

func ReadTemperatures(temperatureLogfile string) ([]*types.Temperature, error) {

	if _, err := os.Stat(temperatureLogfile); os.IsNotExist(err) {
		return nil, fmt.Errorf("Can not find temperature logfile %v", temperatureLogfile)
	}

	temperatures := make([]*types.Temperature, 0)

	f, err := os.Open(temperatureLogfile)
	if err != nil {
		return nil, fmt.Errorf("Can not open temperature logfile %v", temperatureLogfile)
	}
	defer f.Close()

	temperatures, err = ReadTemperaturesCustom(f)
	if err != nil {
		return nil, fmt.Errorf("Can not read temperatures from logfile %v", temperatureLogfile)
	}

	return temperatures, nil
}

func ReadTemperaturesCustom(r io.Reader) ([]*types.Temperature, error) {

	temperatures := make([]*types.Temperature, 0)

	decoder := json.NewDecoder(r)
	err := decoder.Decode(&temperatures)
	if err != nil {
		return nil, fmt.Errorf("Can not decode temperatures from reader: %v", err)
	}

	return temperatures, nil
}

func SplittTemperatures(temperatures []*types.Temperature) [][]*types.Temperature {
	splittedTemperatures := make([][]*types.Temperature, 0)
	newTemperatures := make([]*types.Temperature, 0)
	for _, temperature := range temperatures {
		if len(newTemperatures) == templeratureSplitBy {
			splittedTemperatures = append(splittedTemperatures, newTemperatures)
			newTemperatures = make([]*types.Temperature, 0)
		}
		newTemperatures = append(newTemperatures, temperature)
	}
	splittedTemperatures = append(splittedTemperatures, newTemperatures)
	return splittedTemperatures
}

func SortTemperatures(temperatures []*types.Temperature) {
	sort.SliceStable(temperatures, func(i int, j int) bool {
		return temperatures[i].TemperatureFromDate.Before(temperatures[j].TemperatureFromDate)
	})
}

func WriteTemperatures(temperatures []*types.Temperature, temperatureLogfile string, compression bool) error {

	allTemperatures := make([]*types.Temperature, 0)

	if _, err := os.Stat(temperatureLogfile); os.IsNotExist(err) {
		err := os.MkdirAll(filepath.Dir(temperatureLogfile), 0755)
		if err != nil {
			return fmt.Errorf("Can not create directory %v to write temperatures into the logfile", filepath.Dir(temperatureLogfile))
		}

		f, err := os.Create(temperatureLogfile)
		if err != nil {
			return fmt.Errorf("Can not create file %v: %v", temperatureLogfile, err)
		}
		defer f.Close()

	} else {
		f, err := os.Open(temperatureLogfile)
		if err != nil {
			return fmt.Errorf("Can not open file %v: %v", temperatureLogfile, err)
		}
		defer f.Close()

		savedTemperatures, err := ReadTemperaturesCustom(f)
		if err != nil {
			return fmt.Errorf("Can not read temperatures from logfile %v: %v", temperatureLogfile, err)
		}

		allTemperatures = append(allTemperatures, savedTemperatures...)
	}

	f, err := os.Create(temperatureLogfile)
	if err != nil {
		return fmt.Errorf("Can not create file %v: %v", temperatureLogfile, err)
	}
	defer f.Close()

	allTemperatures = append(allTemperatures, temperatures...)

	err = WriteTemperaturesCustom(allTemperatures, f, compression)
	if err != nil {
		return fmt.Errorf("Can not write temperatures to logfile %v: %v", temperatureLogfile, err)
	}

	return nil
}

func WriteTemperaturesCustom(temperatures []*types.Temperature, w io.Writer, compression bool) error {

	if compression {
		temperatures = CompressTemperature(temperatures)
	}

	writeCreationDate(temperatures)

	jsonEncoder := json.NewEncoder(w)
	jsonEncoder.SetIndent("", " ")
	err := jsonEncoder.Encode(temperatures)
	if err != nil {
		return fmt.Errorf("Can not encode temperatures: %v", err)
	}
	return nil
}

func writeCreationDate(temperatures []*types.Temperature) {
	now := time.Now()
	for _, temperature := range temperatures {
		temperature.CreationDate = &now
	}
}