package meteo

import (
	"encoding/csv"
	"fmt"
	"io"
	"pkg"
	"strconv"
	"strings"
	"time"
)

func (mt *MeteoData) validate() error {
	if mt.MaxTemp > 60 {
		return ErrMaxTempOutOfRange
	}

	if mt.MinTemp < -20 {
		return ErrMinTempOutOfRange
	}

	if mt.Rainfall < 0 || mt.Rainfall > 80 {
		return ErrRainfallOutOfRange
	}

	if mt.Cloudiness < 0 || mt.Cloudiness > 100 {
		return ErrCloudinessOutOfRange
	}

	return nil
}

type FileIngest interface {
	Parse(io io.Reader) ([]MeteoData, []RejectedMeteoData, error)
}

type CSV struct{}

var _ FileIngest = (*CSV)(nil)

func (c *CSV) Parse(r io.Reader) ([]MeteoData, []RejectedMeteoData, error) {
	reader := csv.NewReader(r)
	reader.Comma = ';'
	reader.TrimLeadingSpace = true

	header, err := reader.Read()
	if err != nil {
		return nil, nil, fmt.Errorf("%w: %v", ErrReadingCSVHeader, err)
	}

	if len(header) == 1 {
		return nil, nil, fmt.Errorf("%w: invalid separator detected, expected semicolon (;)", ErrCannotParseFile)
	}

	for i := range header {
		header[i] = strings.TrimSpace(header[i])
	}

	var meteoDataList []MeteoData
	var rejectedDataList []RejectedMeteoData

	for {
		row, err := reader.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, nil, fmt.Errorf("%w: %v", ErrReadingCSVRow, err)
		}

		if len(row) == 0 || (len(row) == 1 && row[0] == "") {
			continue
		}

		rowValue := strings.Join(row, ";")

		record := make(pkg.H)
		for i, value := range row {
			if i < len(header) {
				record[header[i]] = value
			}
		}

		meteoData, err := normalize(record)
		if err != nil {
			rejectedDataList = append(rejectedDataList, RejectedMeteoData{
				RowValue: rowValue,
				Reason:   err.Error(),
			})
			continue
		}

		if err := meteoData.validate(); err != nil {
			rejectedDataList = append(rejectedDataList, RejectedMeteoData{
				RowValue: rowValue,
				Reason:   err.Error(),
			})
			continue
		}

		meteoDataList = append(meteoDataList, *meteoData)
	}

	return meteoDataList, rejectedDataList, nil
}

func normalize(record pkg.H) (*MeteoData, error) {
	meteoData := &MeteoData{}

	var err error

	meteoData.Timestamp, err = parseDate(record, "Fecha", ErrMissingOrInvalidDate)
	if err != nil {
		return nil, err
	}

	meteoData.Location, err = parseString(record, "Ciudad", ErrMissingOrInvalidLocation)
	if err != nil {
		return nil, err
	}

	meteoData.MaxTemp, err = parseFloatField(record, "Temperatura Máxima (C)", ErrMissingOrInvalidMaxTemp)
	if err != nil {
		return nil, err
	}

	meteoData.MinTemp, err = parseFloatField(record, "Temperatura Mínima (C)", ErrMissingOrInvalidMinTemp)
	if err != nil {
		return nil, err
	}

	meteoData.Rainfall, err = parseFloatField(record, "Precipitación (mm)", ErrMissingOrInvalidRainfall)
	if err != nil {
		return nil, err
	}

	meteoData.Cloudiness, err = parseIntField(record, "Nubosidad (%)", ErrMissingOrInvalidCloudiness)
	if err != nil {
		return nil, err
	}

	return meteoData, nil
}

func parseDate(record pkg.H, key string, errMissing error) (time.Time, error) {
	if str, ok := record[key].(string); ok && str != "" {
		t, err := time.Parse("2006/01/02", str)
		if err != nil {
			return time.Time{}, errMissing
		}
		return t, nil
	}
	return time.Time{}, errMissing
}

func parseString(record pkg.H, key string, errMissing error) (string, error) {
	if str, ok := record[key].(string); ok && str != "" {
		return str, nil
	}
	return "", errMissing
}

func parseFloatField(record pkg.H, key string, errMissing error) (float32, error) {
	if str, ok := record[key].(string); ok && str != "" {
		str = strings.Replace(str, ",", ".", 1)
		f, err := strconv.ParseFloat(str, 32)
		if err != nil {
			return 0, errMissing
		}
		return float32(f), nil
	}
	return 0, errMissing
}

func parseIntField(record pkg.H, key string, errMissing error) (int, error) {
	if str, ok := record[key].(string); ok && str != "" {
		str = strings.TrimSpace(str)
		i, err := strconv.Atoi(str)
		if err != nil {
			return 0, errMissing
		}
		return i, nil
	}
	return 0, errMissing
}