// Package store keeps pages as markdown files, one per page, encrypted at rest (see package vault)
// and exportable as plain markdown. An in-memory index makes listing, searching and linking quick.
package store

import (
	"archive/zip"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"slices"
	"sort"
	"strings"
	"sync"
	"time"
	"unicode"
	"unicode/utf8"

	"git.veillax.com/Veillax/mako/internal/vault"
)

// MaxBody is the longest page, in bytes. MaxTitle is the longest title, in characters.
const (
	MaxBody  = 256 << 10
	MaxTitle = 120
)

var (
	ErrNotFound   = errors.New("page not found")
	ErrBadID      = errors.New("bad page id")
	ErrEmpty      = errors.New("a page needs a title or some text")
	ErrTooLong    = errors.New("that page is too long")
	ErrConflict   = errors.New("this page changed somewhere else")
	ErrBadDate    = errors.New("the date must look like 2026-10-31")
	ErrNotTrash   = errors.New("only a page in the trash can be deleted for good")
	ErrTitleTaken = errors.New("another page already has that title")
	ErrDailyTitle = errors.New("a journal day is named by its date")
	ErrBadParent  = errors.New("a page can only go inside another page, and not inside itself")
)

type Note struct {
	ID      string    `json:"id"`
	Created time.Time `json:"created"`
	Updated time.Time `json:"updated"`
	Pinned  bool      `json:"pinned"`
	Daily   string    `json:"daily,omitempty"` // the date, for a journal day
	Trashed bool      `json:"trashed,omitempty"`
	Title   string    `json:"title"`
	Name    string    `json:"name"` // what to call it: the title, else the first line
	Parent  string    `json:"parent,omitempty"`
	Body    string    `json:"body"`
	Tags    []string  `json:"tags"`

	lower string   // lower-cased title and body, for searching
	links []string // lower-cased titles this page links to with [[...]]
}

type Store struct {
	dir string
	box *vault.Cipher
	mu  sync.RWMutex
	by  map[string]*Note
}

var (
	idRe   = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{0,63}$`)
	dateRe = regexp.MustCompile(`^\d{4}-\d{2}-\d{2}$`)
)

// ValidID says whether s can be used as a page id (and so as a file name).
func ValidID(s string) bool { return idRe.MatchString(s) }

// Open reads every page under dir, creating the folders if needed. Pages are encrypted with box. A
// plain markdown file found there is still read, and is saved again encrypted.
func Open(dir string, box *vault.Cipher) (*Store, error) {
	if box == nil {
		return nil, errors.New("a notebook needs an encryption key")
	}
	s := &Store{dir: dir, box: box, by: map[string]*Note{}}
	var plain []*Note
	for _, sub := range []string{"notes", "trash"} {
		if err := os.MkdirAll(filepath.Join(dir, sub), 0o700); err != nil {
			return nil, err
		}
		entries, err := os.ReadDir(filepath.Join(dir, sub))
		if err != nil {
			return nil, err
		}
		for _, e := range entries {
			id := strings.TrimSuffix(e.Name(), ".md")
			if e.IsDir() || id == e.Name() || !ValidID(id) {
				continue
			}
			path := filepath.Join(dir, sub, e.Name())
			b, err := os.ReadFile(path)
			if err != nil {
				return nil, err
			}
			info, err := e.Info()
			if err != nil {
				return nil, err
			}
			sealed := vault.IsSealed(b)
			if sealed {
				if b, err = box.Open(b, id); err != nil {
					return nil, fmt.Errorf("%s: %w; put the original key back (key in the settings file, or MAKO_KEY)", path, err)
				}
			}
			n := parse(id, string(b), info.ModTime())
			n.Trashed = sub == "trash"
			s.by[id] = n
			if !sealed {
				plain = append(plain, n)
			}
		}
	}
	s.mend()
	for _, n := range plain {
		if err := s.write(n); err != nil {
			return nil, err
		}
	}
	return s, nil
}

// mend drops parents that point nowhere, or in a circle, so a hand-edited file cannot break the tree.
func (s *Store) mend() {
	for _, n := range s.by {
		if n.Parent == "" {
			continue
		}
		p, ok := s.by[n.Parent]
		if !ok || (p.Trashed && !n.Trashed) || n.Daily != "" {
			n.Parent = ""
			continue
		}
		seen := map[string]bool{n.ID: true}
		for cur := p; cur != nil; cur = s.by[cur.Parent] {
			if seen[cur.ID] {
				n.Parent = ""
				break
			}
			seen[cur.ID] = true
		}
	}
}

func (s *Store) path(n *Note) string {
	sub := "notes"
	if n.Trashed {
		sub = "trash"
	}
	return filepath.Join(s.dir, sub, n.ID+".md")
}

// ---- file format ----
//
//	---
//	title: "Trip to Lisbon"
//	parent: 20261031-143205-a1b2c3
//	created: 2026-10-31T14:32:05.123Z
//	updated: 2026-10-31T14:35:00.456Z
//	pinned: true
//	daily: 2026-10-31
//	---
//
//	the page, in markdown

func format(n *Note) []byte {
	var b strings.Builder
	b.WriteString("---\n")
	if n.Title != "" && n.Title != n.Daily {
		t, _ := json.Marshal(n.Title)
		fmt.Fprintf(&b, "title: %s\n", t)
	}
	if n.Parent != "" {
		fmt.Fprintf(&b, "parent: %s\n", n.Parent)
	}
	fmt.Fprintf(&b, "created: %s\n", n.Created.UTC().Format(time.RFC3339Nano))
	fmt.Fprintf(&b, "updated: %s\n", n.Updated.UTC().Format(time.RFC3339Nano))
	if n.Pinned {
		b.WriteString("pinned: true\n")
	}
	if n.Daily != "" {
		fmt.Fprintf(&b, "daily: %s\n", n.Daily)
	}
	b.WriteString("---\n\n")
	b.WriteString(n.Body)
	b.WriteString("\n")
	return []byte(b.String())
}

// parse reads a page file. A file with no header is still a page: it takes its time from the file.
func parse(id, text string, mod time.Time) *Note {
	text = strings.ReplaceAll(text, "\r\n", "\n")
	n := &Note{ID: id, Created: mod.UTC(), Updated: mod.UTC()}
	if rest, ok := strings.CutPrefix(text, "---\n"); ok {
		if head, body, ok := strings.Cut(rest, "\n---\n"); ok || strings.HasSuffix(rest, "\n---") {
			if !ok {
				head, body = strings.TrimSuffix(rest, "\n---"), ""
			}
			for _, line := range strings.Split(head, "\n") {
				k, v, _ := strings.Cut(line, ":")
				v = strings.TrimSpace(v)
				switch strings.TrimSpace(k) {
				case "title":
					var t string
					if strings.HasPrefix(v, `"`) && json.Unmarshal([]byte(v), &t) == nil {
						n.Title = CleanTitle(t)
					} else {
						n.Title = CleanTitle(v)
					}
				case "parent":
					if ValidID(v) {
						n.Parent = v
					}
				case "created":
					if t, err := time.Parse(time.RFC3339Nano, v); err == nil {
						n.Created = t.UTC()
					}
				case "updated":
					if t, err := time.Parse(time.RFC3339Nano, v); err == nil {
						n.Updated = t.UTC()
					}
				case "pinned":
					n.Pinned = v == "true"
				case "daily":
					if _, err := time.Parse("2006-01-02", v); err == nil {
						n.Daily = v
					}
				}
			}
			text = strings.TrimPrefix(body, "\n")
		}
	}
	if n.Daily != "" {
		n.Title = n.Daily
		n.Parent = ""
	}
	n.set(text)
	return n
}

// CleanTitle makes a title safe to link to: one line, no brackets or bars, not too long.
func CleanTitle(s string) string {
	s = strings.Map(func(r rune) rune {
		switch {
		case r == '[' || r == ']' || r == '|':
			return -1
		case unicode.IsControl(r):
			return ' '
		}
		return r
	}, s)
	s = strings.Join(strings.Fields(s), " ")
	if utf8.RuneCountInString(s) > MaxTitle {
		s = strings.TrimSpace(string([]rune(s)[:MaxTitle]))
	}
	return s
}

// set stores the body (without trailing blank space) and works out what is derived from it.
func (n *Note) set(body string) {
	n.Body = strings.TrimRight(strings.ReplaceAll(body, "\r\n", "\n"), " \t\n")
	n.refresh()
}

func (n *Note) refresh() {
	n.lower = strings.ToLower(n.Title + "\n" + n.Body)
	n.Tags = Tags(n.Body)
	n.links = Links(n.Body)
	n.Name = nameOf(n)
}

var leadRe = regexp.MustCompile(`^(?:#{1,6}\s+|>\s*|[-*+]\s+(?:\[[ xX]\]\s+)?|\d+[.)]\s+)+`)

func nameOf(n *Note) string {
	if n.Title != "" {
		return n.Title
	}
	for _, l := range strings.Split(n.Body, "\n") {
		l = strings.TrimSpace(leadRe.ReplaceAllString(strings.TrimSpace(l), ""))
		if l == "" || strings.HasPrefix(l, "```") {
			continue
		}
		l = strings.NewReplacer("[[", "", "]]", "", "**", "", "`", "").Replace(l)
		if r := []rune(l); len(r) > 60 {
			l = strings.TrimSpace(string(r[:60])) + "..."
		}
		return l
	}
	return "Untitled"
}

var (
	tagRe        = regexp.MustCompile(`(?:^|[\s(])#([\p{L}\p{N}_][\p{L}\p{N}_/-]*)`)
	inlineCodeRe = regexp.MustCompile("`[^`\n]*`")
	linkRe       = regexp.MustCompile(`\[\[([^\[\]|\n]+?)(?:\|[^\[\]\n]*)?\]\]`)
)

// withoutCode is the body with fenced and inline code taken out, so tags and links inside code
// are not counted.
func withoutCode(body string) string {
	var lines []string
	fence := false
	for _, l := range strings.Split(body, "\n") {
		if strings.HasPrefix(strings.TrimSpace(l), "```") {
			fence = !fence
			continue
		}
		if !fence {
			lines = append(lines, inlineCodeRe.ReplaceAllString(l, ""))
		}
	}
	return strings.Join(lines, "\n")
}

// Tags returns the #tags in a page, lower-cased and without repeats. Code is skipped, and so are
// numbers such as #12.
func Tags(body string) []string {
	seen := map[string]bool{}
	out := []string{}
	for _, m := range tagRe.FindAllStringSubmatch(withoutCode(body), -1) {
		t := strings.ToLower(strings.TrimRight(m[1], "/-"))
		if t == "" || len(t) > 40 || isNumber(t) || seen[t] {
			continue
		}
		seen[t] = true
		out = append(out, t)
	}
	return out
}

// Links returns the titles a page links to with [[Title]] or [[Title|text]], lower-cased and
// without repeats.
func Links(body string) []string {
	var out []string
	for _, m := range linkRe.FindAllStringSubmatch(withoutCode(body), -1) {
		t := strings.ToLower(strings.TrimSpace(m[1]))
		if t != "" && !slices.Contains(out, t) {
			out = append(out, t)
		}
	}
	return out
}

func isNumber(s string) bool {
	for _, r := range s {
		if r < '0' || r > '9' {
			return false
		}
	}
	return true
}

func (s *Store) write(n *Note) error {
	path := s.path(n)
	tmp := filepath.Join(filepath.Dir(path), "."+n.ID+".tmp")
	if err := os.WriteFile(tmp, s.box.Seal(format(n), n.ID), 0o600); err != nil {
		return err
	}
	return os.Rename(tmp, path)
}

func newID(t time.Time) string {
	b := make([]byte, 3)
	rand.Read(b)
	return t.UTC().Format("20060102-150405") + "-" + hex.EncodeToString(b)
}

func (n *Note) copy() Note {
	c := *n
	c.Tags = append([]string{}, n.Tags...)
	return c
}

func checkBody(body string) error {
	if len(body) > MaxBody {
		return ErrTooLong
	}
	return nil
}

// moved keeps updated moving forward, so a stale tab is always noticed.
func moved(prev time.Time) time.Time {
	now := time.Now().UTC()
	if !now.After(prev) {
		return prev.Add(time.Microsecond)
	}
	return now
}

// ---- changes ----

// titleTaken says whether another live page has this title. Dates belong to the journal.
func (s *Store) titleTaken(title, except string) bool {
	l := strings.ToLower(title)
	if dateRe.MatchString(title) && !strings.HasPrefix(except, "daily-") {
		return true
	}
	for id, n := range s.by {
		if id != except && !n.Trashed && n.Title != "" && strings.ToLower(n.Title) == l {
			return true
		}
	}
	return false
}

// underneath says whether id is parent or lies somewhere below it.
func (s *Store) underneath(id, parent string) bool {
	for cur, hops := parent, 0; cur != "" && hops < 200; hops++ {
		if cur == id {
			return true
		}
		n, ok := s.by[cur]
		if !ok {
			return false
		}
		cur = n.Parent
	}
	return false
}

func (s *Store) checkParent(id, parent string) error {
	if parent == "" {
		return nil
	}
	p, ok := s.by[parent]
	if !ok || p.Trashed || p.Daily != "" || s.underneath(id, parent) {
		return ErrBadParent
	}
	return nil
}

type NewNote struct {
	Title, Body, Parent string
}

// Create saves a new page.
func (s *Store) Create(in NewNote) (Note, error) {
	if err := checkBody(in.Body); err != nil {
		return Note{}, err
	}
	title := CleanTitle(in.Title)
	if title == "" && strings.TrimSpace(in.Body) == "" {
		return Note{}, ErrEmpty
	}
	now := time.Now().UTC()
	n := &Note{ID: newID(now), Created: now, Updated: now, Title: title, Parent: in.Parent}
	n.set(in.Body)
	s.mu.Lock()
	defer s.mu.Unlock()
	if title != "" && s.titleTaken(title, n.ID) {
		return Note{}, ErrTitleTaken
	}
	if err := s.checkParent(n.ID, n.Parent); err != nil {
		return Note{}, err
	}
	if err := s.write(n); err != nil {
		return Note{}, err
	}
	s.by[n.ID] = n
	return n.copy(), nil
}

// Daily returns the page for a date (like 2026-10-31), making it if it is not there yet.
func (s *Store) Daily(date string) (Note, error) {
	if _, err := time.Parse("2006-01-02", date); err != nil {
		return Note{}, ErrBadDate
	}
	id := "daily-" + date
	s.mu.Lock()
	defer s.mu.Unlock()
	if n, ok := s.by[id]; ok {
		if n.Trashed { // asking for the day brings it back
			old := s.path(n)
			n.Trashed = false
			if err := s.write(n); err != nil {
				n.Trashed = true
				return Note{}, err
			}
			os.Remove(old)
		}
		return n.copy(), nil
	}
	now := time.Now().UTC()
	n := &Note{ID: id, Created: now, Updated: now, Daily: date, Title: date}
	n.refresh()
	if err := s.write(n); err != nil {
		return Note{}, err
	}
	s.by[id] = n
	return n.copy(), nil
}

func (s *Store) Get(id string) (Note, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	n, ok := s.by[id]
	if !ok {
		return Note{}, ErrNotFound
	}
	return n.copy(), nil
}

// Change is an update; fields that are nil stay as they are.
type Change struct {
	Title, Body, Parent *string
	Pinned              *bool
}

// Update changes a page. When base is given, the title and text are only replaced if the page has
// not been changed since then; otherwise the current page comes back with ErrConflict. Everything is
// checked before anything is written.
func (s *Store) Update(id string, ch Change, base time.Time) (Note, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.by[id]
	if !ok {
		return Note{}, ErrNotFound
	}
	next := n.copy()
	content := false
	if ch.Body != nil {
		if err := checkBody(*ch.Body); err != nil {
			return Note{}, err
		}
		content = true
	}
	if ch.Title != nil {
		t := CleanTitle(*ch.Title)
		if t != n.Title {
			if n.Daily != "" {
				return Note{}, ErrDailyTitle
			}
			if t != "" && s.titleTaken(t, id) {
				return Note{}, ErrTitleTaken
			}
			next.Title = t
			content = true
		}
	}
	if content && !base.IsZero() && !n.Updated.Equal(base) {
		return n.copy(), ErrConflict
	}
	if ch.Parent != nil {
		if n.Daily != "" && *ch.Parent != "" {
			return Note{}, ErrBadParent
		}
		if err := s.checkParent(id, *ch.Parent); err != nil {
			return Note{}, err
		}
		next.Parent = *ch.Parent
	}
	if ch.Pinned != nil {
		next.Pinned = *ch.Pinned
	}
	if ch.Body != nil {
		next.set(*ch.Body)
	} else {
		next.refresh()
	}
	if content {
		next.Updated = moved(n.Updated)
	}
	if err := s.write(&next); err != nil {
		return Note{}, err
	}
	old := n.Title
	*n = next
	if old != "" && n.Title != old {
		if err := s.relink(old, n.Title, id); err != nil {
			return n.copy(), err
		}
	}
	return n.copy(), nil
}

// relink points the [[old]] links of other pages at a renamed page. It rewrites nothing inside code.
func (s *Store) relink(oldTitle, newTitle, except string) error {
	if newTitle == "" {
		return nil
	}
	old := strings.ToLower(oldTitle)
	for _, m := range s.by {
		if m.ID == except || m.Trashed || !slices.Contains(m.links, old) {
			continue
		}
		body := rewriteLinks(m.Body, old, newTitle)
		if body == m.Body {
			continue
		}
		next := m.copy()
		next.set(body)
		next.Updated = moved(m.Updated)
		if err := s.write(&next); err != nil {
			return err
		}
		*m = next
	}
	return nil
}

func rewriteLinks(body, old, newTitle string) string {
	lines := strings.Split(body, "\n")
	fence := false
	for i, l := range lines {
		if strings.HasPrefix(strings.TrimSpace(l), "```") {
			fence = !fence
			continue
		}
		if fence {
			continue
		}
		lines[i] = linkRe.ReplaceAllStringFunc(l, func(x string) string {
			sub := linkRe.FindStringSubmatch(x)
			if strings.ToLower(strings.TrimSpace(sub[1])) != old {
				return x
			}
			alias := ""
			if k := strings.Index(x, "|"); k >= 0 {
				alias = x[k : len(x)-2]
			}
			return "[[" + newTitle + alias + "]]"
		})
	}
	return strings.Join(lines, "\n")
}

// free finds a title that no live page has, by adding a number if it must.
func (s *Store) free(title, except string) string {
	if title == "" || !s.titleTaken(title, except) {
		return title
	}
	for i := 2; ; i++ {
		t := fmt.Sprintf("%s %d", title, i)
		if !s.titleTaken(t, except) {
			return t
		}
	}
}

func (s *Store) move(id string, toTrash bool) (Note, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.by[id]
	if !ok {
		return Note{}, ErrNotFound
	}
	if n.Trashed == toTrash {
		return n.copy(), nil
	}
	old := s.path(n)
	prev := n.copy()
	n.Trashed = toTrash
	if toTrash {
		// Pages inside it move up a level, so nothing is lost with it.
		for _, c := range s.by {
			if c.Parent == id && !c.Trashed {
				next := c.copy()
				next.Parent = n.Parent
				if err := s.write(&next); err != nil {
					*n = prev
					return Note{}, err
				}
				*c = next
			}
		}
	} else {
		if p, ok := s.by[n.Parent]; n.Parent != "" && (!ok || p.Trashed) {
			n.Parent = ""
		}
		n.Title = s.free(n.Title, id)
		if n.Daily != "" {
			n.Title = n.Daily
		}
		n.refresh()
	}
	if err := s.write(n); err != nil {
		*n = prev
		return Note{}, err
	}
	os.Remove(old)
	return n.copy(), nil
}

// Trash moves a page to the trash. Restore brings it back.
func (s *Store) Trash(id string) (Note, error)   { return s.move(id, true) }
func (s *Store) Restore(id string) (Note, error) { return s.move(id, false) }

// Purge deletes a page that is already in the trash, for good.
func (s *Store) Purge(id string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.by[id]
	if !ok {
		return ErrNotFound
	}
	if !n.Trashed {
		return ErrNotTrash
	}
	if err := os.Remove(s.path(n)); err != nil && !errors.Is(err, os.ErrNotExist) {
		return err
	}
	delete(s.by, id)
	return nil
}

// EmptyTrash deletes everything in the trash for good and says how many pages that was.
func (s *Store) EmptyTrash() (int, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	count := 0
	for id, n := range s.by {
		if !n.Trashed {
			continue
		}
		if err := os.Remove(s.path(n)); err != nil && !errors.Is(err, os.ErrNotExist) {
			return count, err
		}
		delete(s.by, id)
		count++
	}
	return count, nil
}

// ---- reading ----

type Query struct {
	Text   string // words that must all appear; #tag words must be tags
	Tag    string
	View   string // "" or "all", "pinned", "daily", "trash"
	Offset int
	Limit  int
}

// List returns one page of matching pages, newest first, and how many matched in all.
func (s *Store) List(q Query) ([]Note, int) {
	words, tags := splitQuery(q.Text)
	if t := strings.ToLower(strings.TrimPrefix(q.Tag, "#")); t != "" {
		tags = append(tags, t)
	}

	s.mu.RLock()
	var hits []*Note
	for _, n := range s.by {
		if n.Trashed != (q.View == "trash") || (q.View == "pinned" && !n.Pinned) || (q.View == "daily" && n.Daily == "") {
			continue
		}
		if matches(n, words, tags) {
			hits = append(hits, n)
		}
	}
	sort.Slice(hits, func(i, j int) bool {
		a, b := hits[i], hits[j]
		if q.View == "daily" && a.Daily != b.Daily {
			return a.Daily > b.Daily
		}
		if !a.Created.Equal(b.Created) {
			return a.Created.After(b.Created)
		}
		return a.ID > b.ID
	})
	total := len(hits)
	if q.Offset > 0 {
		hits = hits[min(q.Offset, len(hits)):]
	}
	if q.Limit > 0 && len(hits) > q.Limit {
		hits = hits[:q.Limit]
	}
	out := make([]Note, len(hits))
	for i, n := range hits {
		out[i] = n.copy()
	}
	s.mu.RUnlock()
	return out, total
}

func splitQuery(text string) (words, tags []string) {
	for _, w := range strings.Fields(strings.ToLower(text)) {
		if t := strings.TrimPrefix(w, "#"); t != w && t != "" {
			tags = append(tags, t)
		} else {
			words = append(words, w)
		}
	}
	return
}

func matches(n *Note, words, tags []string) bool {
	for _, w := range words {
		if !strings.Contains(n.lower, w) {
			return false
		}
	}
	for _, want := range tags {
		found := false
		for _, have := range n.Tags {
			if have == want || strings.HasPrefix(have, want+"/") {
				found = true
				break
			}
		}
		if !found {
			return false
		}
	}
	return true
}

// Ref is a page as the sidebar and link pickers see it: no text.
type Ref struct {
	ID     string `json:"id"`
	Title  string `json:"title"`
	Name   string `json:"name"`
	Parent string `json:"parent,omitempty"`
	Daily  string `json:"daily,omitempty"`
	Pinned bool   `json:"pinned,omitempty"`
}

func ref(n *Note) Ref {
	return Ref{ID: n.ID, Title: n.Title, Name: n.Name, Parent: n.Parent, Daily: n.Daily, Pinned: n.Pinned}
}

// Pages lists the pages worth showing in navigation: those with a title, those inside another page or
// holding one, the pinned ones, and journal days with something written. Untitled quick notes are left
// out, so jotting things down never clutters the sidebar.
func (s *Store) Pages() []Ref {
	s.mu.RLock()
	defer s.mu.RUnlock()
	holders := map[string]bool{}
	for _, n := range s.by {
		if !n.Trashed && n.Parent != "" {
			holders[n.Parent] = true
		}
	}
	out := []Ref{}
	for _, n := range s.by {
		switch {
		case n.Trashed:
		case n.Daily != "":
			if n.Body != "" {
				out = append(out, ref(n))
			}
		case n.Title != "" || n.Parent != "" || n.Pinned || holders[n.ID]:
			out = append(out, ref(n))
		}
	}
	sort.Slice(out, func(i, j int) bool {
		a, b := strings.ToLower(out[i].Name), strings.ToLower(out[j].Name)
		if a != b {
			return a < b
		}
		return out[i].ID < out[j].ID
	})
	return out
}

// Backlinks lists the pages that link to this one with [[its title]].
func (s *Store) Backlinks(id string) []Ref {
	s.mu.RLock()
	defer s.mu.RUnlock()
	n, ok := s.by[id]
	out := []Ref{}
	if !ok || n.Title == "" {
		return out
	}
	want := strings.ToLower(n.Title)
	for _, m := range s.by {
		if m.ID != id && !m.Trashed && slices.Contains(m.links, want) {
			out = append(out, ref(m))
		}
	}
	sort.Slice(out, func(i, j int) bool { return strings.ToLower(out[i].Name) < strings.ToLower(out[j].Name) })
	return out
}

// Hit is a search result for the quick switcher.
type Hit struct {
	Ref
	Snippet string `json:"snippet,omitempty"`
}

// Find searches titles and text for the quick switcher and the [[ picker. Title matches come first.
// With no query it returns the pages touched most recently.
func (s *Store) Find(q string, limit int) []Hit {
	words, _ := splitQuery(q)
	whole := strings.ToLower(strings.TrimSpace(q))
	type scored struct {
		n     *Note
		score int
	}
	s.mu.RLock()
	defer s.mu.RUnlock()
	var hits []scored
	for _, n := range s.by {
		if n.Trashed {
			continue
		}
		if len(words) == 0 {
			hits = append(hits, scored{n, 0})
			continue
		}
		if !matches(n, words, nil) {
			continue
		}
		t, score := strings.ToLower(n.Name), 3
		switch {
		case t == whole:
			score = 0
		case strings.HasPrefix(t, whole):
			score = 1
		case strings.Contains(t, whole) || allIn(t, words):
			score = 2
		}
		hits = append(hits, scored{n, score})
	}
	sort.Slice(hits, func(i, j int) bool {
		a, b := hits[i], hits[j]
		if a.score != b.score {
			return a.score < b.score
		}
		if !a.n.Updated.Equal(b.n.Updated) {
			return a.n.Updated.After(b.n.Updated)
		}
		return a.n.ID < b.n.ID
	})
	if limit > 0 && len(hits) > limit {
		hits = hits[:limit]
	}
	out := make([]Hit, len(hits))
	for i, h := range hits {
		out[i] = Hit{Ref: ref(h.n)}
		if h.score == 3 {
			out[i].Snippet = snippet(h.n.Body, words)
		}
	}
	return out
}

func allIn(s string, words []string) bool {
	for _, w := range words {
		if !strings.Contains(s, w) {
			return false
		}
	}
	return true
}

// snippet is the first line that has one of the words in it, cut to a sensible length.
func snippet(body string, words []string) string {
	for _, l := range strings.Split(body, "\n") {
		low := strings.ToLower(l)
		for _, w := range words {
			if strings.Contains(low, w) {
				l = strings.TrimSpace(l)
				if r := []rune(l); len(r) > 100 {
					l = string(r[:100]) + "..."
				}
				return l
			}
		}
	}
	return ""
}

type TagCount struct {
	Tag   string `json:"tag"`
	Count int    `json:"count"`
}

type Counts struct {
	All    int `json:"all"`
	Pinned int `json:"pinned"`
	Daily  int `json:"daily"`
	Trash  int `json:"trash"`
}

// Summary counts the pages and the tags in use (trashed pages do not count towards tags).
func (s *Store) Summary() (Counts, []TagCount) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	var c Counts
	per := map[string]int{}
	for _, n := range s.by {
		if n.Trashed {
			c.Trash++
			continue
		}
		c.All++
		if n.Pinned {
			c.Pinned++
		}
		if n.Daily != "" {
			c.Daily++
		}
		for _, t := range n.Tags {
			per[t]++
		}
	}
	tags := make([]TagCount, 0, len(per))
	for t, k := range per {
		tags = append(tags, TagCount{t, k})
	}
	sort.Slice(tags, func(i, j int) bool {
		if tags[i].Count != tags[j].Count {
			return tags[i].Count > tags[j].Count
		}
		return tags[i].Tag < tags[j].Tag
	})
	return c, tags
}

var badFile = strings.NewReplacer("/", "-", `\`, "-", ":", "-", "*", "-", "?", "-", `"`, "-", "<", "-", ">", "-", "|", "-", "#", "-", "^", "-")

func fileName(n *Note) string {
	name := strings.Trim(badFile.Replace(n.Name), ". ")
	if name == "" {
		name = "Untitled"
	}
	if n.Daily != "" {
		return "Journal/" + n.Daily
	}
	return name
}

// WriteZip writes every page that is not in the trash as a .md file in a zip archive that opens as a
// vault in Obsidian: a page's file name is its title, so [[links]] keep working, and journal days sit
// in a Journal folder.
func (s *Store) WriteZip(w io.Writer) error {
	s.mu.RLock()
	defer s.mu.RUnlock()
	all := make([]*Note, 0, len(s.by))
	for _, n := range s.by {
		if !n.Trashed {
			all = append(all, n)
		}
	}
	sort.Slice(all, func(i, j int) bool { return all[i].ID < all[j].ID })
	used := map[string]bool{}
	zw := zip.NewWriter(w)
	for _, n := range all {
		base := fileName(n)
		name := base
		for i := 2; used[strings.ToLower(name)]; i++ {
			name = fmt.Sprintf("%s %d", base, i)
		}
		used[strings.ToLower(name)] = true
		f, err := zw.CreateHeader(&zip.FileHeader{Name: "mako/" + name + ".md", Method: zip.Deflate, Modified: n.Updated})
		if err != nil {
			return err
		}
		if _, err := f.Write(exportFormat(n)); err != nil {
			return err
		}
	}
	return zw.Close()
}

// exportFormat is the page with a header Obsidian understands.
func exportFormat(n *Note) []byte {
	var b strings.Builder
	b.WriteString("---\n")
	fmt.Fprintf(&b, "created: %s\n", n.Created.UTC().Format(time.RFC3339))
	fmt.Fprintf(&b, "updated: %s\n", n.Updated.UTC().Format(time.RFC3339))
	if n.Pinned {
		b.WriteString("pinned: true\n")
	}
	b.WriteString("---\n\n")
	b.WriteString(n.Body)
	b.WriteString("\n")
	return []byte(b.String())
}