package main

import (
	"encoding/csv"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
	"time"
)

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Usage: flitsmeister <filename.csv>")
		return
	}

	file, err := os.Open(os.Args[1])
	if err != nil {
		panic(err)
	}
	defer file.Close()

	reader := csv.NewReader(file)
	reader.Comma = ','
	records, err := reader.ReadAll()
	if err != nil {
		panic(err)
	}

	// Dutch to English month translation
	dutchMonths := map[string]string{
		"januari": "January", "februari": "February", "maart": "March",
		"april": "April", "mei": "May", "juni": "June", "juli": "July",
		"augustus": "August", "september": "September", "oktober": "October",
		"november": "November", "december": "December",
	}

	monthlyTotals := make(map[string]float64)
	monthlyCounts := make(map[string]int)
	monthlyLongest := make(map[string]float64)
	monthlyShortest := make(map[string]float64)

	// Skip header row
	for _, record := range records[1:] {
		if len(record) < 8 {
			continue
		}

		// Parse date with Dutch month names
		dateParts := strings.Split(record[1], " ")
		if len(dateParts) < 4 {
			continue
		}

		// Translate Dutch month to English
		dutchMonth := strings.ToLower(dateParts[1])
		engMonth, ok := dutchMonths[dutchMonth]
		if !ok {
			fmt.Printf("Unknown month: %s\n", dutchMonth)
			continue
		}

		// Rebuild date string with English month
		dateStr := fmt.Sprintf("%s %s %s %s",
			dateParts[0], engMonth, dateParts[2], dateParts[3])

		// Parse date (single-digit days allowed)
		tripDate, err := time.Parse("2 January 2006 15:04", dateStr)
		if err != nil {
			fmt.Printf("Error parsing date: %v\n", err)
			continue
		}

		// Create month key (format: YYYY-MM)
		monthKey := fmt.Sprintf("%d-%02d", tripDate.Year(), tripDate.Month())

		// Parse distance
		distance, err := strconv.ParseFloat(record[7], 64)
		if err != nil {
			fmt.Printf("Error parsing distance: %v\n", err)
			continue
		}

		monthlyTotals[monthKey] += distance
		monthlyCounts[monthKey]++

		// Track longest and shortest trip
		if _, exists := monthlyLongest[monthKey]; !exists {
			monthlyLongest[monthKey] = distance
			monthlyShortest[monthKey] = distance
		} else {
			if distance > monthlyLongest[monthKey] {
				monthlyLongest[monthKey] = distance
			}
			if distance < monthlyShortest[monthKey] {
				monthlyShortest[monthKey] = distance
			}
		}
	}

	// Sort months chronologically
	var months []string
	for k := range monthlyTotals {
		months = append(months, k)
	}
	sort.Strings(months)

	// Print table header
	fmt.Printf("%-10s | %-12s | %-7s | %-12s | %-12s | %-12s\n", "Month", "Total KM", "Trips", "Avg KM/Trip", "Longest", "Shortest")
	fmt.Println(strings.Repeat("-", 77))

	// Print stats per month
	for _, month := range months {
		total := monthlyTotals[month]
		trips := monthlyCounts[month]
		avg := 0.0
		if trips > 0 {
			avg = total / float64(trips)
		}
		longest := monthlyLongest[month]
		shortest := monthlyShortest[month]
		fmt.Printf("%-10s | %-12.2f | %-7d | %-12.2f | %-12.2f | %-12.2f\n",
			month, total, trips, avg, longest, shortest)
	}
}