package useCases

import (
	"RenewCMS/internal/domain/audit"
	"encoding/csv"
	"io"
	"strings"
	"time"
)

const exportBatchSize = 500

const formulaGuard = "'"
const formulaStarts = "=+-@"

var exportHeader = []string{"when", "actor", "action", "target", "outcome", "source", "ip"}

type ExportActivityUseCase struct {
	events audit.Repository
	now    func() time.Time
}

type ActivityExport struct {
	events audit.Repository
	filter audit.Filter
}

func NewExportActivityUseCase(events audit.Repository, now func() time.Time) *ExportActivityUseCase {
	return &ExportActivityUseCase{events, now}
}

func (e *ExportActivityUseCase) Prepare(query ActivityQuery) (*ActivityExport, error) {
	filter, err := buildActivityFilter(query, e.now())
	if err != nil {
		return nil, err
	}
	return &ActivityExport{events: e.events, filter: filter}, nil
}

func (a *ActivityExport) WriteCSV(w io.Writer) error {
	writer := csv.NewWriter(w)
	if err := writer.Write(exportHeader); err != nil {
		return err
	}
	for page := 1; ; page++ {
		filter := a.filter
		filter.Page, filter.Size = page, exportBatchSize
		found, err := a.events.List(filter)
		if err != nil {
			return err
		}
		for _, event := range found.Items {
			if err := writer.Write(exportRow(event)); err != nil {
				return err
			}
		}
		writer.Flush()
		if err := writer.Error(); err != nil {
			return err
		}
		if len(found.Items) < exportBatchSize || page*exportBatchSize >= found.Total {
			return nil
		}
	}
}

func exportRow(event audit.Event) []string {
	ip := ""
	if event.IP != nil {
		ip = *event.IP
	}
	return []string{
		event.CreatedAt.UTC().Format(time.RFC3339),
		guardCell(event.Actor.Name),
		guardCell(event.Action),
		guardCell(event.Target.Name),
		string(event.Outcome),
		string(event.Source),
		guardCell(ip),
	}
}

func guardCell(value string) string {
	if value != "" && strings.ContainsRune(formulaStarts, rune(value[0])) {
		return formulaGuard + value
	}
	return value
}