package main

import (
	"log"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"time"
)

// trashStamp is the timestamp moveToTrash appends: 20060102-150405.
var trashStamp = regexp.MustCompile(`^\d{8}-\d{6}$`)

// trashItem is one recoverable post in content/.trash/, grouping the image and
// its sidecar that were trashed together (same slug, same timestamp).
type trashItem struct {
	ID        string `json:"id"`   // "<slug>.<stamp>", the restore/empty handle
	Slug      string `json:"slug"` // original slug it would restore to
	DeletedAt string `json:"deletedAt"`
	Image     string `json:"image"`   // trash filename of the image, "" if only a sidecar
	HasMeta   bool   `json:"hasMeta"` // whether a sidecar is present
}

func (s *Server) trashDir() string { return filepath.Join(s.contentDir, ".trash") }

// parseTrashName splits a trash filename "<slug>.<stamp><ext>" into its parts.
// slug is a bare sanitised name (no dots) and stamp is a fixed timestamp, so
// the extension and the stamp peel off unambiguously from the right.
func parseTrashName(name string) (slug, stamp, ext string, ok bool) {
	ext = filepath.Ext(name)
	rest := strings.TrimSuffix(name, ext) // "<slug>.<stamp>"
	i := strings.LastIndex(rest, ".")
	if i < 0 {
		return "", "", "", false
	}
	slug, stamp = rest[:i], rest[i+1:]
	if slug == "" || slug != filepath.Base(slug) || strings.Contains(slug, ".") {
		return "", "", "", false
	}
	if !trashStamp.MatchString(stamp) {
		return "", "", "", false
	}
	return slug, stamp, ext, true
}

func isImageExt(ext string) bool {
	for _, e := range contentExts {
		if ext == e {
			return true
		}
	}
	return false
}

// handleListTrash returns trashed items, newest first.
func (s *Server) handleListTrash(w http.ResponseWriter, r *http.Request) {
	entries, err := os.ReadDir(s.trashDir())
	if err != nil {
		// No trash dir yet → empty list, not an error.
		writeJSON(w, []trashItem{})
		return
	}

	byID := make(map[string]*trashItem)
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		slug, stamp, ext, ok := parseTrashName(e.Name())
		if !ok {
			continue
		}
		id := slug + "." + stamp
		it := byID[id]
		if it == nil {
			when := stamp
			if t, err := time.ParseInLocation("20060102-150405", stamp, time.Local); err == nil {
				when = t.Format("2006-01-02 15:04")
			}
			it = &trashItem{ID: id, Slug: slug, DeletedAt: when}
			byID[id] = it
		}
		if ext == ".toml" {
			it.HasMeta = true
		} else if isImageExt(ext) {
			it.Image = e.Name()
		}
	}

	items := make([]trashItem, 0, len(byID))
	for _, it := range byID {
		items = append(items, *it)
	}
	// Newest first: the stamp sorts lexically in time order, and it is the tail
	// of the ID.
	sort.Slice(items, func(i, j int) bool { return items[i].ID > items[j].ID })
	writeJSON(w, items)
}

// splitTrashID validates a "<slug>.<stamp>" handle and returns its parts.
func splitTrashID(id string) (slug, stamp string, ok bool) {
	i := strings.LastIndex(id, ".")
	if i < 0 {
		return "", "", false
	}
	slug, stamp = id[:i], id[i+1:]
	if slug == "" || slug != filepath.Base(slug) || strings.Contains(slug, ".") {
		return "", "", false
	}
	if !trashStamp.MatchString(stamp) {
		return "", "", false
	}
	return slug, stamp, true
}

// trashFiles returns the files in .trash belonging to one id (image + sidecar).
func (s *Server) trashFiles(slug, stamp string) []string {
	var out []string
	prefix := slug + "." + stamp
	for _, ext := range append(append([]string{}, contentExts...), ".toml") {
		p := filepath.Join(s.trashDir(), prefix+ext)
		if _, err := os.Stat(p); err == nil {
			out = append(out, p)
		}
	}
	return out
}

// handleRestore moves a trashed post back into content/, stripping the
// timestamp. It refuses to overwrite a live post with the same slug.
func (s *Server) handleRestore(w http.ResponseWriter, r *http.Request) {
	if s.rejectCrossSite(w, r) {
		return
	}
	if err := parseForm(r); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}
	slug, stamp, ok := splitTrashID(r.FormValue("id"))
	if !ok {
		http.Error(w, "bad id", http.StatusBadRequest)
		return
	}
	if _, live := s.resolveSlug(slug); live {
		http.Error(w, "a post with that slug already exists", http.StatusConflict)
		return
	}

	files := s.trashFiles(slug, stamp)
	if len(files) == 0 {
		http.Error(w, "not in trash", http.StatusNotFound)
		return
	}
	for _, src := range files {
		name := filepath.Base(src)
		trashPrefix := slug + "." + stamp // "<slug>.<stamp>"
		// "<slug>.<stamp>.png" → "<slug>.png"; "<slug>.<stamp>.toml" → "<slug>.toml"
		dstName := slug + strings.TrimPrefix(name, trashPrefix)
		if err := os.Rename(src, filepath.Join(s.contentDir, dstName)); err != nil {
			log.Printf("restore %s: %v", name, err)
			http.Error(w, "could not restore", http.StatusInternalServerError)
			return
		}
	}
	s.rebuild()
	w.WriteHeader(http.StatusOK)
}

// handleEmptyTrash permanently deletes trashed items — specific ids (repeated
// `id` fields), or everything with `all=1`. This is the only hard delete.
func (s *Server) handleEmptyTrash(w http.ResponseWriter, r *http.Request) {
	if s.rejectCrossSite(w, r) {
		return
	}
	if err := parseForm(r); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}

	if r.FormValue("all") == "1" {
		if err := os.RemoveAll(s.trashDir()); err != nil {
			log.Printf("empty trash: %v", err)
			http.Error(w, "could not empty trash", http.StatusInternalServerError)
			return
		}
		writeJSON(w, map[string]string{"emptied": "all"})
		return
	}

	removed := 0
	for _, id := range r.Form["id"] {
		slug, stamp, ok := splitTrashID(id)
		if !ok {
			continue
		}
		for _, p := range s.trashFiles(slug, stamp) {
			if err := os.Remove(p); err == nil {
				removed++
			}
		}
	}
	writeJSON(w, map[string]int{"removed": removed})
}