package app

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"strings"
	"time"

	"github.com/xuri/excelize/v2"
)

const maxAuditExportRows = 1_048_572

func (s *Server) handleAuditExport(w http.ResponseWriter, r *http.Request) {
	tech, err := s.currentTechnician(r)
	if err != nil {
		http.Redirect(w, r, "/", http.StatusSeeOther)
		return
	}

	filters := auditFiltersFromRequest(r)
	records, err := s.listAuditEvents(r, filters, maxAuditExportRows+1)
	if err != nil {
		http.Error(w, "unable to export audit events", http.StatusInternalServerError)
		return
	}
	if len(records) > maxAuditExportRows {
		http.Error(
			w,
			"audit export is too large for a single Excel worksheet; narrow the filters and try again",
			http.StatusRequestEntityTooLarge,
		)
		return
	}

	_ = s.audit(
		r.Context(),
		"audit_exported",
		tech.Login,
		nil,
		"",
		"",
		s.clientIP(r),
		fmt.Sprintf("format=xlsx rows=%d range=%s", len(records), filters.TimeRange),
	)

	exportedAt := time.Now()
	filename := "tapm-audit-" + exportedAt.In(s.displayTimeZone()).Format("20060102-150405") + ".xlsx"
	w.Header().Set("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
	w.Header().Set("Content-Disposition", `attachment; filename="`+filename+`"`)
	w.Header().Set("Cache-Control", "no-store")

	if err := writeAuditWorkbook(w, records, filters, exportedAt, s.displayTimeZone()); err != nil {
		log.Printf("write audit Excel export: %v", err)
	}
}

func (s *Server) displayTimeZone() *time.Location {
	if s.cfg.DisplayTimeZone != nil {
		return s.cfg.DisplayTimeZone
	}
	return time.UTC
}

func writeAuditWorkbook(
	output io.Writer,
	records []auditRecord,
	filters auditFilters,
	exportedAt time.Time,
	displayTimeZone *time.Location,
) error {
	if displayTimeZone == nil {
		displayTimeZone = time.UTC
	}

	workbook := excelize.NewFile()
	defer func() {
		if err := workbook.Close(); err != nil {
			log.Printf("close audit Excel workbook: %v", err)
		}
	}()

	const sheet = "Audit Log"
	if err := workbook.SetSheetName("Sheet1", sheet); err != nil {
		return err
	}
	if err := workbook.SetDocProps(&excelize.DocProperties{
		Title:          "TAPM Audit Log",
		Creator:        "TAPM Broker",
		LastModifiedBy: "TAPM Broker",
		Created:        exportedAt.UTC().Format(time.RFC3339),
		Modified:       exportedAt.UTC().Format(time.RFC3339),
	}); err != nil {
		return err
	}

	styles, err := newAuditWorkbookStyles(workbook)
	if err != nil {
		return err
	}
	stream, err := workbook.NewStreamWriter(sheet)
	if err != nil {
		return err
	}
	if err := configureAuditWorksheet(stream); err != nil {
		return err
	}

	if err := stream.SetRow(
		"A1",
		styledAuditRow(styles.title, "TAPM Audit Log"),
		excelize.RowOpts{Height: 30},
	); err != nil {
		return err
	}
	if err := stream.MergeCell("A1", "H1"); err != nil {
		return err
	}

	metadata := fmt.Sprintf(
		"Exported %s · %s · %d event(s)",
		exportedAt.In(displayTimeZone).Format("Jan 2, 2006 3:04 PM MST"),
		auditFilterDescription(filters),
		len(records),
	)
	if err := stream.SetRow(
		"A2",
		styledAuditRow(styles.metadata, metadata),
		excelize.RowOpts{Height: 24},
	); err != nil {
		return err
	}
	if err := stream.MergeCell("A2", "H2"); err != nil {
		return err
	}
	if err := stream.SetRow("A3", []interface{}{nil}, excelize.RowOpts{Height: 8}); err != nil {
		return err
	}

	headers := []string{
		"Timestamp",
		"Event",
		"Customer / Deployment",
		"User",
		"Hostname",
		"Package ID",
		"Source IP",
		"Details",
	}
	headerRow := make([]interface{}, len(headers))
	for index, header := range headers {
		headerRow[index] = excelize.Cell{StyleID: styles.header, Value: header}
	}
	if err := stream.SetRow("A4", headerRow, excelize.RowOpts{Height: 24}); err != nil {
		return err
	}

	for index, record := range records {
		rowNumber := index + 5
		local := record.CreatedAt.In(displayTimeZone)
		displayedTime := time.Date(
			local.Year(),
			local.Month(),
			local.Day(),
			local.Hour(),
			local.Minute(),
			local.Second(),
			local.Nanosecond(),
			time.UTC,
		)
		row := []interface{}{
			excelize.Cell{StyleID: styles.timestamp, Value: displayedTime},
			excelize.Cell{StyleID: styles.body, Value: record.EventType},
			excelize.Cell{StyleID: styles.body, Value: record.CustomerLabel},
			excelize.Cell{StyleID: styles.body, Value: record.User},
			excelize.Cell{StyleID: styles.body, Value: record.Hostname},
			excelize.Cell{StyleID: styles.body, Value: record.PackageSlug},
			excelize.Cell{StyleID: styles.body, Value: record.SourceIP},
			excelize.Cell{StyleID: styles.details, Value: record.Details},
		}
		if err := stream.SetRow(fmt.Sprintf("A%d", rowNumber), row); err != nil {
			return err
		}
	}

	if len(records) > 0 {
		lastRow := len(records) + 4
		showStripes := false
		if err := stream.AddTable(&excelize.Table{
			Range:           fmt.Sprintf("A4:H%d", lastRow),
			Name:            "AuditLog",
			StyleName:       "TableStyleMedium2",
			ShowRowStripes:  &showStripes,
			ShowFirstColumn: false,
			ShowLastColumn:  false,
		}); err != nil {
			return err
		}
	}
	if err := stream.Flush(); err != nil {
		return err
	}
	return workbook.Write(output)
}

type auditWorkbookStyles struct {
	title     int
	metadata  int
	header    int
	body      int
	timestamp int
	details   int
}

func newAuditWorkbookStyles(workbook *excelize.File) (auditWorkbookStyles, error) {
	var styles auditWorkbookStyles
	var err error

	styles.title, err = workbook.NewStyle(&excelize.Style{
		Font: &excelize.Font{
			Bold:   true,
			Family: "Aptos Display",
			Size:   18,
			Color:  "FFFFFF",
		},
		Fill:      excelize.Fill{Type: "pattern", Color: []string{"33404A"}, Pattern: 1},
		Alignment: &excelize.Alignment{Vertical: "center"},
	})
	if err != nil {
		return styles, err
	}
	styles.metadata, err = workbook.NewStyle(&excelize.Style{
		Font: &excelize.Font{Family: "Aptos", Size: 11, Color: "33404A"},
		Fill: excelize.Fill{Type: "pattern", Color: []string{"F4F7ED"}, Pattern: 1},
		Alignment: &excelize.Alignment{
			Vertical: "center",
		},
	})
	if err != nil {
		return styles, err
	}
	styles.header, err = workbook.NewStyle(&excelize.Style{
		Font: &excelize.Font{
			Bold:   true,
			Family: "Aptos",
			Size:   11,
			Color:  "FFFFFF",
		},
		Fill:      excelize.Fill{Type: "pattern", Color: []string{"33404A"}, Pattern: 1},
		Alignment: &excelize.Alignment{Vertical: "center"},
	})
	if err != nil {
		return styles, err
	}
	bodyStyle := excelize.Style{
		Font:      &excelize.Font{Family: "Aptos", Size: 11, Color: "33404A"},
		Border:    []excelize.Border{{Type: "bottom", Color: "D9DED4", Style: 1}},
		Alignment: &excelize.Alignment{Vertical: "top"},
	}
	styles.body, err = workbook.NewStyle(&bodyStyle)
	if err != nil {
		return styles, err
	}
	numberFormat := "yyyy-mm-dd hh:mm:ss"
	timestampStyle := bodyStyle
	timestampStyle.CustomNumFmt = &numberFormat
	styles.timestamp, err = workbook.NewStyle(&timestampStyle)
	if err != nil {
		return styles, err
	}
	detailsStyle := bodyStyle
	detailsStyle.Alignment = &excelize.Alignment{Vertical: "top", WrapText: true}
	styles.details, err = workbook.NewStyle(&detailsStyle)
	return styles, err
}

func configureAuditWorksheet(stream *excelize.StreamWriter) error {
	widths := []float64{22, 28, 30, 22, 24, 24, 18, 54}
	for index, width := range widths {
		if err := stream.SetColWidth(index+1, index+1, width); err != nil {
			return err
		}
	}
	return stream.SetPanes(&excelize.Panes{
		Freeze:      true,
		YSplit:      4,
		TopLeftCell: "A5",
		ActivePane:  "bottomLeft",
		Selection: []excelize.Selection{{
			SQRef:      "A5",
			ActiveCell: "A5",
			Pane:       "bottomLeft",
		}},
	})
}

func styledAuditRow(style int, firstValue string) []interface{} {
	row := make([]interface{}, 8)
	for index := range row {
		value := ""
		if index == 0 {
			value = firstValue
		}
		row[index] = excelize.Cell{StyleID: style, Value: value}
	}
	return row
}

func auditFilterDescription(filters auditFilters) string {
	rangeLabels := map[string]string{
		"24h": "Past 24 hours",
		"7d":  "Past 7 days",
		"30d": "Past 30 days",
		"90d": "Past 90 days",
		"all": "All retained events",
	}
	parts := []string{rangeLabels[filters.TimeRange]}
	filterValues := []struct {
		label string
		value string
	}{
		{"event", filters.EventType},
		{"customer", filters.CustomerLabel},
		{"user", filters.User},
		{"hostname", filters.Hostname},
		{"package", filters.PackageSlug},
		{"IP", filters.SourceIP},
		{"details", filters.Details},
	}
	for _, filter := range filterValues {
		if filter.value != "" {
			parts = append(parts, filter.label+": "+filter.value)
		}
	}
	return strings.Join(parts, " · ")
}