package services

import (
	"archive/zip"
	"bytes"
	"encoding/xml"
	"fmt"
	"io"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"

	"git.mchus.pro/mchus/priceforge/internal/lotmatch"
)

var (
	reISODate = regexp.MustCompile(`\b(20\d{2})-(\d{2})-(\d{2})\b`)
	reRuDate  = regexp.MustCompile(`\b([0-3]\d)\.([01]\d)\.(20\d{2})\b`)
	mxlCellRe = regexp.MustCompile(`(?s)\{16,\d+,\s*\{1,\d+,\s*\{\s*"ru","((?:""|[^"])*)"\s*\}\s*\},0\},(\d+),`)
)

func parseStockRows(filename string, content []byte) ([]stockImportRow, error) {
	switch strings.ToLower(filepath.Ext(filename)) {
	case ".mxl":
		return parseMXLRows(content)
	case ".xlsx":
		return parseXLSXRows(content)
	default:
		return nil, fmt.Errorf("unsupported file format: %s", filepath.Ext(filename))
	}
}

func parseMXLRows(content []byte) ([]stockImportRow, error) {
	text := string(content)
	matches := mxlCellRe.FindAllStringSubmatch(text, -1)
	if len(matches) == 0 {
		return nil, fmt.Errorf("mxl parsing failed: no cells found")
	}

	rows := make([]map[int]string, 0, 128)
	current := map[int]string{}
	for _, m := range matches {
		val := strings.ReplaceAll(m[1], `""`, `"`)
		col, err := strconv.Atoi(m[2])
		if err != nil {
			continue
		}
		if col == 1 && len(current) > 0 {
			rows = append(rows, current)
			current = map[int]string{}
		}
		current[col] = strings.TrimSpace(val)
	}
	if len(current) > 0 {
		rows = append(rows, current)
	}
	return parseGridRows(rows, "mxl")
}

func parseXLSXRows(content []byte) ([]stockImportRow, error) {
	zr, err := zip.NewReader(bytes.NewReader(content), int64(len(content)))
	if err != nil {
		return nil, fmt.Errorf("opening xlsx: %w", err)
	}

	sharedStrings, _ := readSharedStrings(zr)
	sheetPath := firstWorksheetPath(zr)
	if sheetPath == "" {
		return nil, fmt.Errorf("xlsx parsing failed: worksheet not found")
	}
	sheetData, err := readZipFile(zr, sheetPath)
	if err != nil {
		return nil, err
	}

	type xlsxInline struct {
		T string `xml:"t"`
	}
	type xlsxCell struct {
		R  string      `xml:"r,attr"`
		T  string      `xml:"t,attr"`
		V  string      `xml:"v"`
		IS *xlsxInline `xml:"is"`
	}
	type xlsxRow struct {
		C []xlsxCell `xml:"c"`
	}
	type xlsxSheet struct {
		Rows []xlsxRow `xml:"sheetData>row"`
	}

	var ws xlsxSheet
	if err := xml.Unmarshal(sheetData, &ws); err != nil {
		return nil, fmt.Errorf("decode worksheet: %w", err)
	}

	grid := make([]map[int]string, 0, len(ws.Rows))
	for _, r := range ws.Rows {
		rowMap := make(map[int]string, len(r.C))
		for _, c := range r.C {
			colIdx := excelRefColumn(c.R)
			if colIdx < 0 {
				continue
			}
			inlineText := ""
			if c.IS != nil {
				inlineText = c.IS.T
			}
			rowMap[colIdx] = decodeXLSXCell(c.T, c.V, inlineText, sharedStrings)
		}
		grid = append(grid, rowMap)
	}

	return parseGridRows(grid, "xlsx")
}

func parseGridRows(grid []map[int]string, format string) ([]stockImportRow, error) {
	headerRow := -1
	headers := map[string]int{}
	for i, row := range grid {
		rowHeaders := map[string]int{}
		for idx, val := range row {
			norm := normalizeHeader(val)
			switch norm {
			case "папка", "артикул", "описание", "вендор", "стоимость", "свободно":
				rowHeaders[norm] = idx
			}
		}
		if _, hasArticle := rowHeaders["артикул"]; !hasArticle {
			continue
		}
		if _, hasPrice := rowHeaders["стоимость"]; !hasPrice {
			continue
		}
		headers = rowHeaders
		headerRow = i
		break
	}
	if headerRow < 0 {
		return nil, fmt.Errorf("%s parsing failed: header row not found", format)
	}

	result := make([]stockImportRow, 0, len(grid)-headerRow-1)
	idxFolder, hasFolder := headers["папка"]
	idxArticle := headers["артикул"]
	idxDesc, hasDesc := headers["описание"]
	idxVendor, hasVendor := headers["вендор"]
	idxPrice := headers["стоимость"]
	idxQty, hasQty := headers["свободно"]
	if !hasQty {
		return nil, fmt.Errorf("%s parsing failed: qty column 'Свободно' not found", format)
	}
	for i := headerRow + 1; i < len(grid); i++ {
		row := grid[i]
		article := strings.TrimSpace(row[idxArticle])
		if article == "" {
			continue
		}
		price, err := parseLocalizedFloat(row[idxPrice])
		if err != nil {
			continue
		}
		qtyRaw := strings.TrimSpace(row[idxQty])
		qty, err := parseLocalizedQty(qtyRaw)
		qtyInvalid := false
		if err != nil {
			qty = 0
			qtyInvalid = true
		}

		folder := ""
		if hasFolder {
			folder = strings.TrimSpace(row[idxFolder])
		}
		description := ""
		if hasDesc {
			description = strings.TrimSpace(row[idxDesc])
		}
		vendor := ""
		if hasVendor {
			vendor = strings.TrimSpace(row[idxVendor])
		}

		result = append(result, stockImportRow{
			Folder:      folder,
			Article:     article,
			Description: description,
			Vendor:      vendor,
			Price:       price,
			Qty:         qty,
			QtyRaw:      qtyRaw,
			QtyInvalid:  qtyInvalid,
		})
	}
	return result, nil
}

func parseLocalizedFloat(value string) (float64, error) {
	clean := strings.TrimSpace(value)
	clean = strings.ReplaceAll(clean, "\u00a0", "")
	clean = strings.ReplaceAll(clean, " ", "")
	clean = strings.ReplaceAll(clean, ",", ".")
	if clean == "" {
		return 0, fmt.Errorf("empty number")
	}
	return strconv.ParseFloat(clean, 64)
}

func parseLocalizedQty(value string) (float64, error) {
	clean := strings.TrimSpace(value)
	if clean == "" {
		return 0, fmt.Errorf("empty qty")
	}
	if v, err := parseLocalizedFloat(clean); err == nil {
		return v, nil
	}
	// Tolerate strings like "1 200 шт" by extracting the first numeric token.
	re := regexp.MustCompile(`[-+]?\d[\d\s\u00a0]*(?:[.,]\d+)?`)
	match := re.FindString(clean)
	if strings.TrimSpace(match) == "" {
		return 0, fmt.Errorf("invalid qty: %s", value)
	}
	return parseLocalizedFloat(match)
}

func detectImportDate(content []byte, filename string, fileModTime time.Time) time.Time {
	if d, ok := extractDateFromText(string(content)); ok {
		return d
	}
	if d, ok := extractDateFromFilename(filename); ok {
		return d
	}
	if !fileModTime.IsZero() {
		return normalizeDate(fileModTime)
	}
	return normalizeDate(time.Now())
}

func extractDateFromText(text string) (time.Time, bool) {
	if m := reISODate.FindStringSubmatch(text); len(m) == 4 {
		d, err := time.Parse("2006-01-02", m[0])
		if err == nil {
			return normalizeDate(d), true
		}
	}
	if m := reRuDate.FindStringSubmatch(text); len(m) == 4 {
		d, err := time.Parse("02.01.2006", m[0])
		if err == nil {
			return normalizeDate(d), true
		}
	}
	return time.Time{}, false
}

func extractDateFromFilename(filename string) (time.Time, bool) {
	base := filepath.Base(filename)
	if m := reISODate.FindStringSubmatch(base); len(m) == 4 {
		d, err := time.Parse("2006-01-02", m[0])
		if err == nil {
			return normalizeDate(d), true
		}
	}
	if m := reRuDate.FindStringSubmatch(base); len(m) == 4 {
		d, err := time.Parse("02.01.2006", m[0])
		if err == nil {
			return normalizeDate(d), true
		}
	}
	return time.Time{}, false
}

func normalizeDate(t time.Time) time.Time {
	y, m, d := t.Date()
	return time.Date(y, m, d, 0, 0, 0, 0, time.Local)
}

func median(values []float64) float64 {
	if len(values) == 0 {
		return 0
	}
	c := append([]float64(nil), values...)
	sort.Float64s(c)
	n := len(c)
	if n%2 == 0 {
		return (c[n/2-1] + c[n/2]) / 2
	}
	return c[n/2]
}

func weightedMedian(values []weightedPricePoint) float64 {
	if len(values) == 0 {
		return 0
	}

	type pair struct {
		price  float64
		weight float64
	}
	items := make([]pair, 0, len(values))
	totalWeight := 0.0
	prices := make([]float64, 0, len(values))

	for _, v := range values {
		if v.price <= 0 {
			continue
		}
		prices = append(prices, v.price)
		w := v.weight
		if w > 0 {
			items = append(items, pair{price: v.price, weight: w})
			totalWeight += w
		}
	}

	// Fallback for rows without positive weights.
	if totalWeight <= 0 {
		return median(prices)
	}

	sort.Slice(items, func(i, j int) bool {
		if items[i].price == items[j].price {
			return items[i].weight < items[j].weight
		}
		return items[i].price < items[j].price
	})

	threshold := totalWeight / 2.0
	acc := 0.0
	for _, it := range items {
		acc += it.weight
		if acc >= threshold {
			return it.price
		}
	}
	return items[len(items)-1].price
}

func normalizeKey(v string) string {
	return lotmatch.NormalizeKey(v)
}

func readZipFile(zr *zip.Reader, name string) ([]byte, error) {
	for _, f := range zr.File {
		if f.Name != name {
			continue
		}
		rc, err := f.Open()
		if err != nil {
			return nil, err
		}
		defer rc.Close()
		return io.ReadAll(rc)
	}
	return nil, fmt.Errorf("zip entry not found: %s", name)
}

func firstWorksheetPath(zr *zip.Reader) string {
	candidates := make([]string, 0, 4)
	for _, f := range zr.File {
		if strings.HasPrefix(f.Name, "xl/worksheets/") && strings.HasSuffix(f.Name, ".xml") {
			candidates = append(candidates, f.Name)
		}
	}
	if len(candidates) == 0 {
		return ""
	}
	sort.Strings(candidates)
	for _, c := range candidates {
		if strings.HasSuffix(c, "sheet1.xml") {
			return c
		}
	}
	return candidates[0]
}

func readSharedStrings(zr *zip.Reader) ([]string, error) {
	data, err := readZipFile(zr, "xl/sharedStrings.xml")
	if err != nil {
		return nil, err
	}
	type richRun struct {
		Text string `xml:"t"`
	}
	type si struct {
		Text string    `xml:"t"`
		Runs []richRun `xml:"r"`
	}
	type sst struct {
		Items []si `xml:"si"`
	}

	var parsed sst
	if err := xml.Unmarshal(data, &parsed); err != nil {
		return nil, err
	}

	values := make([]string, 0, len(parsed.Items))
	for _, item := range parsed.Items {
		if item.Text != "" {
			values = append(values, item.Text)
			continue
		}
		var b strings.Builder
		for _, run := range item.Runs {
			b.WriteString(run.Text)
		}
		values = append(values, b.String())
	}
	return values, nil
}

func decodeXLSXCell(cellType, value, inlineText string, sharedStrings []string) string {
	switch cellType {
	case "s":
		idx, err := strconv.Atoi(strings.TrimSpace(value))
		if err == nil && idx >= 0 && idx < len(sharedStrings) {
			return strings.TrimSpace(sharedStrings[idx])
		}
	case "inlineStr":
		return strings.TrimSpace(inlineText)
	default:
		return strings.TrimSpace(value)
	}
	return strings.TrimSpace(value)
}

func excelRefColumn(ref string) int {
	if ref == "" {
		return -1
	}
	var letters []rune
	for _, r := range ref {
		if r >= 'A' && r <= 'Z' {
			letters = append(letters, r)
		} else if r >= 'a' && r <= 'z' {
			letters = append(letters, r-'a'+'A')
		} else {
			break
		}
	}
	if len(letters) == 0 {
		return -1
	}
	col := 0
	for _, r := range letters {
		col = col*26 + int(r-'A'+1)
	}
	return col - 1
}

func normalizeHeader(v string) string {
	return strings.ToLower(strings.TrimSpace(strings.ReplaceAll(v, "\u00a0", " ")))
}