package main

import (
	"bytes"
	"fmt"
	"html/template"
	"log"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"time"
)

func init() {
	pageTypeHandlers = append(pageTypeHandlers, &diaryHandler{})
}

type diaryHandler struct{}

func (d *diaryHandler) handle(root, fsPath, urlPath string) *specialPage {
	depth, ok := findDiaryContext(root, fsPath)
	if !ok || depth == 0 {
		return nil
	}
	var content template.HTML
	switch depth {
	case 1:
		content = renderDiaryYear(fsPath, urlPath)
	case 2:
		content = renderDiaryMonth(fsPath, urlPath)
	case 3:
		content = renderDiaryDay(fsPath, urlPath)
	}
	return &specialPage{Content: content, SuppressListing: true}
}

// findDiaryContext walks up from fsPath toward root looking for a
// .page-settings file with type=diary. Returns the depth of fsPath
// relative to the diary root, and whether one was found.
// depth=0 means fsPath itself is the diary root.
func findDiaryContext(root, fsPath string) (int, bool) {
	current := fsPath
	for depth := 0; ; depth++ {
		s := readPageSettings(current)
		if s != nil && s.Type == "diary" {
			return depth, true
		}
		if current == root {
			break
		}
		parent := filepath.Dir(current)
		if parent == current {
			break
		}
		current = parent
	}
	return 0, false
}

// diaryPhoto is a photo file whose name starts with a YYYY-MM-DD date prefix.
type diaryPhoto struct {
	Date time.Time
	Name string
	URL  string
}

type diaryMonthSummary struct {
	Name       string
	URL        string
	PhotoCount int
}

type diaryDaySection struct {
	Heading string
	URL     string
	EditURL string
	Content template.HTML
	Photos  []diaryPhoto
}

type diaryYearData struct{ Months []diaryMonthSummary }
type diaryMonthData struct{ Days []diaryDaySection }
type diaryDayData struct{ Photos []diaryPhoto }

var diaryYearTmpl = newTemplate("diary-year.html", "assets/diary/diary-year.html")
var diaryMonthTmpl = newTemplate("diary-month.html", "assets/diary/diary-month.html")
var diaryDayTmpl = newTemplate("diary-day.html", "assets/diary/diary-day.html")

var germanWeekdays = map[time.Weekday]string{
	time.Sunday:    "Sonntag",
	time.Monday:    "Montag",
	time.Tuesday:   "Dienstag",
	time.Wednesday: "Mittwoch",
	time.Thursday:  "Donnerstag",
	time.Friday:    "Freitag",
	time.Saturday:  "Samstag",
}

var germanMonths = map[time.Month]string{
	time.January:   "Januar",
	time.February:  "Februar",
	time.March:     "März",
	time.April:     "April",
	time.May:       "Mai",
	time.June:      "Juni",
	time.July:      "Juli",
	time.August:    "August",
	time.September: "September",
	time.October:   "Oktober",
	time.November:  "November",
	time.December:  "Dezember",
}

func formatGermanDate(t time.Time) string {
	return fmt.Sprintf("%s, %d. %s %d",
		germanWeekdays[t.Weekday()],
		t.Day(),
		germanMonths[t.Month()],
		t.Year(),
	)
}

var photoExts = map[string]bool{
	".jpg": true, ".jpeg": true, ".png": true, ".gif": true, ".webp": true,
}

// yearPhotos returns all photos in yearFsPath whose filename starts with
// a YYYY-MM-DD date prefix.
func yearPhotos(yearFsPath, yearURLPath string) []diaryPhoto {
	entries, err := os.ReadDir(yearFsPath)
	if err != nil {
		return nil
	}
	var photos []diaryPhoto
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		name := e.Name()
		if !photoExts[strings.ToLower(filepath.Ext(name))] {
			continue
		}
		if len(name) < 10 {
			continue
		}
		t, err := time.Parse("2006-01-02", name[:10])
		if err != nil {
			continue
		}
		photos = append(photos, diaryPhoto{
			Date: t,
			Name: name,
			URL:  path.Join(yearURLPath, url.PathEscape(name)),
		})
	}
	return photos
}

// renderDiaryYear renders month sections with photo counts for a year folder.
func renderDiaryYear(fsPath, urlPath string) template.HTML {
	year, err := strconv.Atoi(filepath.Base(fsPath))
	if err != nil {
		return ""
	}

	photos := yearPhotos(fsPath, urlPath)

	entries, err := os.ReadDir(fsPath)
	if err != nil {
		return ""
	}

	var months []diaryMonthSummary
	for _, e := range entries {
		if !e.IsDir() {
			continue
		}
		monthNum, err := strconv.Atoi(e.Name())
		if err != nil || monthNum < 1 || monthNum > 12 {
			continue
		}
		count := 0
		for _, p := range photos {
			if p.Date.Year() == year && int(p.Date.Month()) == monthNum {
				count++
			}
		}
		monthDate := time.Date(year, time.Month(monthNum), 1, 0, 0, 0, 0, time.UTC)
		months = append(months, diaryMonthSummary{
			Name:       monthDate.Format("January 2006"),
			URL:        path.Join(urlPath, e.Name()) + "/",
			PhotoCount: count,
		})
	}

	var buf bytes.Buffer
	if err := diaryYearTmpl.get().Execute(&buf, diaryYearData{Months: months}); err != nil {
		log.Printf("diary year template: %v", err)
		return ""
	}
	return template.HTML(buf.String())
}

// renderDiaryMonth renders a section per day, each with its markdown content
// and photos sourced from the parent year folder.
func renderDiaryMonth(fsPath, urlPath string) template.HTML {
	yearFsPath := filepath.Dir(fsPath)
	yearURLPath := parentURL(urlPath)

	year, err := strconv.Atoi(filepath.Base(yearFsPath))
	if err != nil {
		return ""
	}
	monthNum, err := strconv.Atoi(filepath.Base(fsPath))
	if err != nil || monthNum < 1 || monthNum > 12 {
		return ""
	}

	allPhotos := yearPhotos(yearFsPath, yearURLPath)
	var monthPhotos []diaryPhoto
	for _, p := range allPhotos {
		if p.Date.Year() == year && int(p.Date.Month()) == monthNum {
			monthPhotos = append(monthPhotos, p)
		}
	}

	// Collect day numbers from subdirectories and from photo filenames.
	daySet := map[int]bool{}
	dayDirs := map[int]string{} // day number → actual directory name
	entries, _ := os.ReadDir(fsPath)
	for _, e := range entries {
		if !e.IsDir() {
			continue
		}
		d, err := strconv.Atoi(e.Name())
		if err != nil || d < 1 || d > 31 {
			continue
		}
		daySet[d] = true
		dayDirs[d] = e.Name()
	}
	for _, p := range monthPhotos {
		daySet[p.Date.Day()] = true
	}

	days := make([]int, 0, len(daySet))
	for d := range daySet {
		days = append(days, d)
	}
	sort.Ints(days)

	var sections []diaryDaySection
	for _, dayNum := range days {
		date := time.Date(year, time.Month(monthNum), dayNum, 0, 0, 0, 0, time.UTC)

		heading := formatGermanDate(date)
		dayURL := path.Join(urlPath, fmt.Sprintf("%02d", dayNum)) + "/"
		var content template.HTML
		if dirName, ok := dayDirs[dayNum]; ok {
			dayURL = path.Join(urlPath, dirName) + "/"
			dayFsPath := filepath.Join(fsPath, dirName)
			if raw, err := os.ReadFile(filepath.Join(dayFsPath, "index.md")); err == nil && len(raw) > 0 {
				if h := extractFirstHeading(raw); h != "" {
					heading = h
					raw = stripFirstHeading(raw)
				}
				content = renderMarkdown(raw)
			}
		}

		var photos []diaryPhoto
		for _, p := range monthPhotos {
			if p.Date.Day() == dayNum {
				photos = append(photos, p)
			}
		}

		sections = append(sections, diaryDaySection{
			Heading: heading,
			URL:     dayURL,
			EditURL: dayURL + "?edit",
			Content: content,
			Photos:  photos,
		})
	}

	var buf bytes.Buffer
	if err := diaryMonthTmpl.get().Execute(&buf, diaryMonthData{Days: sections}); err != nil {
		log.Printf("diary month template: %v", err)
		return ""
	}
	return template.HTML(buf.String())
}

// renderDiaryDay renders the photo grid for a single day, sourcing photos
// from the grandparent year folder.
func renderDiaryDay(fsPath, urlPath string) template.HTML {
	monthFsPath := filepath.Dir(fsPath)
	yearFsPath := filepath.Dir(monthFsPath)
	yearURLPath := parentURL(parentURL(urlPath))

	year, err := strconv.Atoi(filepath.Base(yearFsPath))
	if err != nil {
		return ""
	}
	monthNum, err := strconv.Atoi(filepath.Base(monthFsPath))
	if err != nil {
		return ""
	}
	dayNum, err := strconv.Atoi(filepath.Base(fsPath))
	if err != nil {
		return ""
	}

	allPhotos := yearPhotos(yearFsPath, yearURLPath)
	var photos []diaryPhoto
	for _, p := range allPhotos {
		if p.Date.Year() == year && int(p.Date.Month()) == monthNum && p.Date.Day() == dayNum {
			photos = append(photos, p)
		}
	}

	if len(photos) == 0 {
		return ""
	}

	var buf bytes.Buffer
	if err := diaryDayTmpl.get().Execute(&buf, diaryDayData{Photos: photos}); err != nil {
		log.Printf("diary day template: %v", err)
		return ""
	}
	return template.HTML(buf.String())
}