// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

package notify

import "sync"

// Popup is one notification as the renderers see it. The JSON tags are the
// file contract in the spec.
type Popup struct {
	ID      uint32      `json:"id"`
	App     string      `json:"app"`
	Summary string      `json:"summary"`
	Body    string      `json:"body"`
	Urgency Urgency     `json:"urgency"`
	Icon    string      `json:"icon"`
	Image   string      `json:"image"`
	Actions [][2]string `json:"actions"`
	Created int64       `json:"created"`
	Expires int64       `json:"expires"`
}

// live rounds out a Popup with the state the renderers do not need: the stack
// tag it replaces on, and whether the D-Bus client has already been closed.
type live struct {
	Popup
	Stack  string
	Closed bool
}

const (
	liveCap    = 20
	historyCap = 20
)

// Store holds the live queue and the history ring. Time, signals and file
// writes are injected, so the whole thing is tested without a bus or a clock.
type Store struct {
	mu          sync.Mutex
	nextID      uint32
	order       []uint32
	entries     map[uint32]*live
	history     []*live
	emit        func(id, reason uint32)
	publish     func(live, history []Popup)
	removeImage func(string)
}

func NewStore(emit func(id, reason uint32), publish func(live, history []Popup), removeImage func(string)) *Store {
	return &Store{
		nextID:      1,
		entries:     map[uint32]*live{},
		emit:        emit,
		publish:     publish,
		removeImage: removeImage,
	}
}

// Add inserts n, replacing the entry named by replacesID or stack when one
// matches. A replace reuses the id and emits nothing: the old client is told
// nothing because a new client owns the id now.
func (s *Store) Add(n *Popup, stack string, replacesID uint32) (uint32, bool) {
	s.mu.Lock()
	defer s.mu.Unlock()

	var old *live
	if replacesID != 0 {
		old = s.entries[replacesID]
	}
	if old == nil && stack != "" {
		for _, id := range s.order {
			if s.entries[id].Stack == stack {
				old = s.entries[id]
				break
			}
		}
	}
	add := &live{Popup: *n, Stack: stack}
	if old != nil {
		if s.removeImage != nil {
			s.removeImage(old.Image)
		}
		add.ID = old.ID
		s.entries[add.ID] = add
		s.moveToFrontLocked(add.ID)
		s.evictLocked()
		s.publishLocked()
		return add.ID, true
	}
	add.ID = s.nextID
	s.nextID++
	s.entries[add.ID] = add
	s.order = append([]uint32{add.ID}, s.order...)
	s.evictLocked()
	s.publishLocked()
	return add.ID, false
}

// Expire is the balloon timeout: tell the client, keep the entry as inert.
func (s *Store) Expire(id uint32) {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.entries[id]
	if !ok || n.Closed {
		return
	}
	n.Closed = true
	if s.removeImage != nil {
		s.removeImage(n.Image)
	}
	s.emit(id, 1)
}

// SetImage attaches a materialised image path to a live entry and republishes.
func (s *Store) SetImage(id uint32, path string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.entries[id]
	if !ok {
		return
	}
	n.Image = path
	s.publishLocked()
}

// Dismiss is an explicit close from either renderer. The client is told only
// if expiry has not already told it, then the entry is filed.
func (s *Store) Dismiss(id, reason uint32) {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.entries[id]
	if !ok {
		return
	}
	s.removeLocked(id)
	s.fileLocked(n, reason)
	s.publishLocked()
}

// DismissAll dismisses every live entry.
func (s *Store) DismissAll() {
	s.mu.Lock()
	defer s.mu.Unlock()
	for _, id := range append([]uint32(nil), s.order...) {
		n := s.entries[id]
		if n == nil {
			continue
		}
		s.removeLocked(id)
		s.fileLocked(n, 2)
	}
	s.publishLocked()
}

// ClearHistory empties the history ring.
func (s *Store) ClearHistory() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.history = nil
	s.publishLocked()
}

// Actionable reports whether a client is still listening on the id.
func (s *Store) Actionable(id uint32) bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	n, ok := s.entries[id]
	return ok && !n.Closed
}

// Reset makes the state empty, which is what a start needs: nothing from a
// previous run is resurrected.
func (s *Store) Reset() {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.order = nil
	s.entries = map[uint32]*live{}
	s.history = nil
	s.publishLocked()
}

// historySnapshot is for tests.
func (s *Store) historySnapshot() []*live {
	s.mu.Lock()
	defer s.mu.Unlock()
	return append([]*live(nil), s.history...)
}

func (s *Store) removeLocked(id uint32) {
	if n, ok := s.entries[id]; ok && s.removeImage != nil {
		s.removeImage(n.Image)
	}
	delete(s.entries, id)
	for i, v := range s.order {
		if v == id {
			s.order = append(s.order[:i], s.order[i+1:]...)
			return
		}
	}
}

func (s *Store) moveToFrontLocked(id uint32) {
	for i, v := range s.order {
		if v == id {
			s.order = append(s.order[:i], s.order[i+1:]...)
			break
		}
	}
	s.order = append([]uint32{id}, s.order...)
}

func (s *Store) fileLocked(n *live, reason uint32) {
	if !n.Closed {
		n.Closed = true
		s.emit(n.ID, reason)
	}
	s.history = append([]*live{n}, s.history...)
	if len(s.history) > historyCap {
		s.history = s.history[:historyCap]
	}
}

func (s *Store) evictLocked() {
	for len(s.order) > liveCap {
		id := s.order[len(s.order)-1]
		n := s.entries[id]
		s.removeLocked(id)
		s.fileLocked(n, 1)
	}
}

func (s *Store) publishLocked() {
	liveList := make([]Popup, 0, len(s.order))
	for _, id := range s.order {
		liveList = append(liveList, s.entries[id].Popup)
	}
	historyList := make([]Popup, 0, len(s.history))
	for _, n := range s.history {
		historyList = append(historyList, n.Popup)
	}
	s.publish(liveList, historyList)
}