package main

import (
	"encoding/csv"
	"fmt"
	"io"
	"net/http"
	"strings"
)

type ImportResult struct {
	Inserted int      `json:"inserted"`
	Skipped  int      `json:"skipped"`
	Errors   []string `json:"errors"`
}

func (app *App) handleImport(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseMultipartForm(10 << 20); err != nil {
		writeError(w, "invalid form", http.StatusBadRequest)
		return
	}
	file, _, err := r.FormFile("csv")
	if err != nil {
		writeError(w, "csv file required", http.StatusBadRequest)
		return
	}
	defer file.Close()

	result, err := app.importCSV(file)
	if err != nil {
		writeError(w, err.Error(), http.StatusBadRequest)
		return
	}
	if result.Errors == nil {
		result.Errors = []string{}
	}
	writeJSON(w, result)
}

func (app *App) importCSV(r io.Reader) (ImportResult, error) {
	reader := csv.NewReader(r)
	reader.TrimLeadingSpace = true
	reader.LazyQuotes = true

	header, err := reader.Read()
	if err != nil {
		return ImportResult{}, fmt.Errorf("reading header: %w", err)
	}
	if len(header) > 0 {
		header[0] = strings.TrimPrefix(header[0], "\xef\xbb\xbf") // strip BOM
	}

	colIndex := make(map[string]int)
	for i, h := range header {
		colIndex[strings.ToLower(strings.TrimSpace(h))] = i
	}

	var (
		nameIdx, emailIdx, ticketIDIdx, ticketTypeIdx int
		hasEmail, hasTicketID, hasTicketType          bool
		isCrowdWork                                   bool
	)

	if idx, ok := colIndex["patron name"]; ok {
		// CrowdWork / ticketing platform format
		isCrowdWork = true
		nameIdx = idx
		if idx, ok := colIndex["patron email"]; ok {
			emailIdx, hasEmail = idx, true
		}
		if idx, ok := colIndex["tier name"]; ok {
			ticketTypeIdx, hasTicketType = idx, true
		}
		if idx, ok := colIndex["order number"]; ok {
			ticketIDIdx, hasTicketID = idx, true
		}
	} else if idx, ok := colIndex["name"]; ok {
		// Generic format
		nameIdx = idx
		if idx, ok := colIndex["email"]; ok {
			emailIdx, hasEmail = idx, true
		}
		if idx, ok := colIndex["ticket_id"]; ok {
			ticketIDIdx, hasTicketID = idx, true
		}
		if idx, ok := colIndex["ticket_type"]; ok {
			ticketTypeIdx, hasTicketType = idx, true
		}
	} else {
		return ImportResult{}, fmt.Errorf("CSV must have a 'name' or 'patron name' column")
	}

	var result ImportResult
	lineNum := 1

	for {
		record, err := reader.Read()
		if err == io.EOF {
			break
		}
		lineNum++
		if err != nil {
			result.Errors = append(result.Errors, fmt.Sprintf("line %d: %v", lineNum, err))
			continue
		}

		name := strings.TrimSpace(csvGet(record, nameIdx))
		if name == "" {
			continue
		}

		email := ""
		if hasEmail {
			email = strings.TrimSpace(csvGet(record, emailIdx))
		}
		externalID := ""
		if hasTicketID {
			externalID = strings.TrimSpace(csvGet(record, ticketIDIdx))
		}
		ticketType := ""
		if hasTicketType {
			ticketType = strings.TrimSpace(csvGet(record, ticketTypeIdx))
		}

		source := "manual"
		orderID := ""
		if isCrowdWork {
			source = "crowdwork"
			orderID = externalID
		}

		// Find or create participant when email is present.
		var participantID *int
		if email != "" {
			p, _, err := app.upsertParticipant(email, name)
			if err != nil {
				result.Errors = append(result.Errors, fmt.Sprintf("line %d (%s): participant: %v", lineNum, name, err))
				continue
			}
			if p != nil {
				participantID = &p.ID
			}
		}

		_, err = app.createTicket(Ticket{
			ParticipantID: participantID,
			Name:          name,
			TicketType:    ticketType,
			Source:        source,
			ExternalID:    externalID,
			OrderID:       orderID,
		})
		if err != nil {
			if strings.Contains(err.Error(), "UNIQUE constraint failed") {
				result.Skipped++
			} else {
				result.Errors = append(result.Errors, fmt.Sprintf("line %d (%s): %v", lineNum, name, err))
			}
			continue
		}
		result.Inserted++
	}

	return result, nil
}

func csvGet(record []string, idx int) string {
	if idx < len(record) {
		return record[idx]
	}
	return ""
}