package reporting

import (
	"context"
	"fmt"
	"io"
	"reflect"
	"sort"
	"strconv"
	"strings"

	"github.com/google/uuid"
	"github.com/hay-kot/homebox/backend/internal/data/repo"
	"github.com/hay-kot/homebox/backend/internal/data/types"
	"github.com/rs/zerolog/log"
)

// IOSheet is the representation of a CSV/TSV sheet that is used for importing/exporting
// items from homebox. It is used to read/write the data from/to a CSV/TSV file given
// the standard format of the file.
//
// See ExportTSVRow for the format of the data in the sheet.
type IOSheet struct {
	headers []string
	custom  []int
	index   map[string]int
	Rows    []ExportTSVRow
}

func (s *IOSheet) indexHeaders() {
	s.index = make(map[string]int)

	for i, h := range s.headers {
		if strings.HasPrefix(h, "HB.field") {
			s.custom = append(s.custom, i)
		}

		if strings.HasPrefix(h, "HB.") {
			s.index[h] = i
		}
	}
}

func (s *IOSheet) GetColumn(str string) (col int, ok bool) {
	if s.index == nil {
		s.indexHeaders()
	}

	col, ok = s.index[str]
	return
}

// Read reads a CSV/TSV and populates the "Rows" field with the data from the sheet
// Custom Fields are supported via the `HB.field.*` headers. The `HB.field.*` the "Name"
// of the field is the part after the `HB.field.` prefix. Additionally, Custom Fields with
// no value are excluded from the row.Fields slice, this includes empty strings.
//
// Note That
//   - the first row is assumed to be the header
//   - at least 1 row of data is required
//   - rows and columns must be rectangular (i.e. all rows must have the same number of columns)
func (s *IOSheet) Read(data io.Reader) error {
	sheet, err := readRawCsv(data)
	if err != nil {
		return err
	}

	if len(sheet) < 2 {
		return fmt.Errorf("sheet must have at least 1 row of data (header + 1)")
	}

	s.headers = sheet[0]
	s.Rows = make([]ExportTSVRow, len(sheet)-1)

	for i, row := range sheet[1:] {
		if len(row) != len(s.headers) {
			return fmt.Errorf("row has %d columns, expected %d", len(row), len(s.headers))
		}

		rowData := ExportTSVRow{}

		st := reflect.TypeOf(ExportTSVRow{})

		for i := 0; i < st.NumField(); i++ {
			field := st.Field(i)
			tag := field.Tag.Get("csv")
			if tag == "" || tag == "-" {
				continue
			}

			col, ok := s.GetColumn(tag)
			if !ok {
				continue
			}

			val := row[col]

			var v interface{}

			switch field.Type {
			case reflect.TypeOf(""):
				v = val
			case reflect.TypeOf(int(0)):
				v = parseInt(val)
			case reflect.TypeOf(bool(false)):
				v = parseBool(val)
			case reflect.TypeOf(float64(0)):
				v = parseFloat(val)

			// Custom Types
			case reflect.TypeOf(types.Date{}):
				v = types.DateFromString(val)
			case reflect.TypeOf(repo.AssetID(0)):
				v, _ = repo.ParseAssetID(val)
			case reflect.TypeOf(LocationString{}):
				v = parseLocationString(val)
			case reflect.TypeOf(LabelString{}):
				v = parseLabelString(val)
			}

			log.Debug().
				Str("tag", tag).
				Interface("val", v).
				Str("type", fmt.Sprintf("%T", v)).
				Msg("parsed value")

			// Nil values are not allowed at the moment. This may change.
			if v == nil {
				return fmt.Errorf("could not convert %q to %s", val, field.Type)
			}

			ptrField := reflect.ValueOf(&rowData).Elem().Field(i)
			ptrField.Set(reflect.ValueOf(v))
		}

		for _, col := range s.custom {
			colName := strings.TrimPrefix(s.headers[col], "HB.field.")
			customVal := row[col]
			if customVal == "" {
				continue
			}

			rowData.Fields = append(rowData.Fields, ExportItemFields{
				Name:  colName,
				Value: customVal,
			})
		}

		s.Rows[i] = rowData
	}

	return nil
}

// ReadItems writes the sheet to a writer.
func (s *IOSheet) ReadItems(ctx context.Context, items []repo.ItemOut, GID uuid.UUID, repos *repo.AllRepos) error {
	s.Rows = make([]ExportTSVRow, len(items))

	extraHeaders := map[string]struct{}{}

	for i := range items {
		item := items[i]

		// TODO: Support fetching nested locations
		locID := item.Location.ID

		locPaths, err := repos.Locations.PathForLoc(context.Background(), GID, locID)
		if err != nil {
			log.Error().Err(err).Msg("could not get location path")
			return err
		}

		locString := fromPathSlice(locPaths)

		labelString := make([]string, len(item.Labels))

		for i, l := range item.Labels {
			labelString[i] = l.Name
		}

		customFields := make([]ExportItemFields, len(item.Fields))

		for i, f := range item.Fields {
			extraHeaders[f.Name] = struct{}{}

			customFields[i] = ExportItemFields{
				Name:  f.Name,
				Value: f.TextValue,
			}
		}

		s.Rows[i] = ExportTSVRow{
			// fill struct
			Location: locString,
			LabelStr: labelString,

			ImportRef:   item.ImportRef,
			AssetID:     item.AssetID,
			Name:        item.Name,
			Quantity:    item.Quantity,
			Description: item.Description,
			Insured:     item.Insured,
			Archived:    item.Archived,

			PurchasePrice: item.PurchasePrice,
			PurchaseFrom:  item.PurchaseFrom,
			PurchaseTime:  item.PurchaseTime,

			Manufacturer: item.Manufacturer,
			ModelNumber:  item.ModelNumber,
			SerialNumber: item.SerialNumber,

			LifetimeWarranty: item.LifetimeWarranty,
			WarrantyExpires:  item.WarrantyExpires,
			WarrantyDetails:  item.WarrantyDetails,

			SoldTo:    item.SoldTo,
			SoldTime:  item.SoldTime,
			SoldPrice: item.SoldPrice,
			SoldNotes: item.SoldNotes,

			Fields: customFields,
		}
	}

	// Extract and sort additional headers for deterministic output
	customHeaders := make([]string, 0, len(extraHeaders))

	for k := range extraHeaders {
		customHeaders = append(customHeaders, k)
	}

	sort.Strings(customHeaders)

	st := reflect.TypeOf(ExportTSVRow{})

	// Write headers
	for i := 0; i < st.NumField(); i++ {
		field := st.Field(i)
		tag := field.Tag.Get("csv")
		if tag == "" || tag == "-" {
			continue
		}

		s.headers = append(s.headers, tag)
	}

	for _, h := range customHeaders {
		s.headers = append(s.headers, "HB.field."+h)
	}

	return nil
}

// TSV writes the current sheet to a writer in TSV format.
func (s *IOSheet) TSV() ([][]string, error) {
	memcsv := make([][]string, len(s.Rows)+1)

	memcsv[0] = s.headers

	// use struct tags in rows to dertmine column order
	for i, row := range s.Rows {
		rowIdx := i + 1

		memcsv[rowIdx] = make([]string, len(s.headers))

		st := reflect.TypeOf(row)

		for i := 0; i < st.NumField(); i++ {
			field := st.Field(i)
			tag := field.Tag.Get("csv")
			if tag == "" || tag == "-" {
				continue
			}

			col, ok := s.GetColumn(tag)
			if !ok {
				continue
			}

			val := reflect.ValueOf(row).Field(i)

			var v string

			switch field.Type {
			case reflect.TypeOf(""):
				v = val.String()
			case reflect.TypeOf(int(0)):
				v = strconv.Itoa(int(val.Int()))
			case reflect.TypeOf(bool(false)):
				v = strconv.FormatBool(val.Bool())
			case reflect.TypeOf(float64(0)):
				v = strconv.FormatFloat(val.Float(), 'f', -1, 64)

			// Custom Types
			case reflect.TypeOf(types.Date{}):
				v = val.Interface().(types.Date).String()
			case reflect.TypeOf(repo.AssetID(0)):
				v = val.Interface().(repo.AssetID).String()
			case reflect.TypeOf(LocationString{}):
				v = val.Interface().(LocationString).String()
			case reflect.TypeOf(LabelString{}):
				v = val.Interface().(LabelString).String()
			default:
				log.Debug().Str("type", field.Type.String()).Msg("unknown type")
			}

			memcsv[rowIdx][col] = v
		}

		for _, f := range row.Fields {
			col, ok := s.GetColumn("HB.field." + f.Name)
			if !ok {
				continue
			}

			memcsv[i+1][col] = f.Value
		}
	}

	return memcsv, nil
}