package bot

import (
	"fmt"
	"time"

	"github.com/xuri/excelize/v2"

	"worktimeBot/internal/db"
)

func GenerateMonthlyReport(store *db.Store, year int, month time.Month) ([]byte, error) {
	f := excelize.NewFile()
	defer f.Close()

	sheet := "Report"
	index, err := f.NewSheet(sheet)
	if err != nil {
		return nil, err
	}
	f.SetActiveSheet(index)
	f.DeleteSheet("Sheet1")

	titleStyle, _ := f.NewStyle(&excelize.Style{
		Font:      &excelize.Font{Bold: true, Size: 14, Color: "FFFFFF"},
		Fill:      excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{"4472C4"}},
		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
	})
	headerStyle, _ := f.NewStyle(&excelize.Style{
		Font: &excelize.Font{Bold: true, Color: "FFFFFF"},
		Fill: excelize.Fill{Type: "pattern", Pattern: 1, Color: []string{"4472C4"}},
		Border: []excelize.Border{
			{Type: "left", Color: "FFFFFF", Style: 1},
			{Type: "right", Color: "FFFFFF", Style: 1},
			{Type: "top", Color: "FFFFFF", Style: 1},
			{Type: "bottom", Color: "FFFFFF", Style: 1},
		},
		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
	})
	dataStyle, _ := f.NewStyle(&excelize.Style{
		Border: []excelize.Border{
			{Type: "left", Color: "D9D9D9", Style: 1},
			{Type: "right", Color: "D9D9D9", Style: 1},
			{Type: "top", Color: "D9D9D9", Style: 1},
			{Type: "bottom", Color: "D9D9D9", Style: 1},
		},
		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
	})

	monthName := time.Date(year, month, 1, 0, 0, 0, 0, time.UTC).Format("January 2006")

	f.SetCellValue(sheet, "A1", fmt.Sprintf("Work Time Report — %s", monthName))
	f.MergeCell(sheet, "A1", "E1")
	f.SetCellStyle(sheet, "A1", "E1", titleStyle)
	f.SetRowHeight(sheet, 1, 30)

	headers := []string{"Date", "Clock In", "Clock Out", "Work (h)", "Break (m)"}
	for i, h := range headers {
		cell, _ := excelize.CoordinatesToCellName(i+1, 2)
		f.SetCellValue(sheet, cell, h)
		f.SetCellStyle(sheet, cell, cell, headerStyle)
	}
	f.SetRowHeight(sheet, 2, 22)

	f.SetColWidth(sheet, "A", "A", 14)
	f.SetColWidth(sheet, "B", "B", 10)
	f.SetColWidth(sheet, "C", "C", 10)
	f.SetColWidth(sheet, "D", "D", 10)
	f.SetColWidth(sheet, "E", "E", 10)

	row := 3
	loc := time.Now().Location()
	firstDay := time.Date(year, month, 1, 0, 0, 0, 0, loc)
	lastDay := firstDay.AddDate(0, 1, -1)

	for d := firstDay; !d.After(lastDay); d = d.AddDate(0, 0, 1) {
		dateStr := d.Format("2006-01-02")

		isOff, err := store.IsDayOff(dateStr)
		if err != nil {
			return nil, err
		}
		if isOff {
			continue
		}

		events, err := store.EventsForDay(dateStr)
		if err != nil {
			return nil, err
		}
		totals := ComputeDailyTotals(events)

		cellDate, _ := excelize.CoordinatesToCellName(1, row)
		f.SetCellValue(sheet, cellDate, dateStr)
		f.SetCellStyle(sheet, cellDate, cellDate, dataStyle)

		if len(events) > 0 {
			cellIn, _ := excelize.CoordinatesToCellName(2, row)
			cellOut, _ := excelize.CoordinatesToCellName(3, row)
			f.SetCellValue(sheet, cellIn, time.Unix(events[0].OccurredAt, 0).Format("15:04"))
			f.SetCellStyle(sheet, cellIn, cellIn, dataStyle)
			if len(events) > 1 && events[len(events)-1].EventType == "out" {
				f.SetCellValue(sheet, cellOut, time.Unix(events[len(events)-1].OccurredAt, 0).Format("15:04"))
			}
			f.SetCellStyle(sheet, cellOut, cellOut, dataStyle)
		}

		cellWork, _ := excelize.CoordinatesToCellName(4, row)
		hours := float64(totals.TotalSeconds) / 3600.0
		f.SetCellValue(sheet, cellWork, fmt.Sprintf("%.2f", hours))
		f.SetCellStyle(sheet, cellWork, cellWork, dataStyle)

		cellBreak, _ := excelize.CoordinatesToCellName(5, row)
		breakMin := totals.BreakSeconds / 60
		f.SetCellValue(sheet, cellBreak, breakMin)
		f.SetCellStyle(sheet, cellBreak, cellBreak, dataStyle)

		row++
	}

	buf, err := f.WriteToBuffer()
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}