// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
// SPDX-License-Identifier: GPL-3.0-or-later

package notification

import (
	"fmt"
	"math"
	"sync"
	"time"
)

var noMessages []string

const historySize = 55

const (
	MessageNotification    = "Notification"
	MessageListBottom      = "Bottom"
	MessageListTop         = "Top"
	MessageNoMessages      = "No notification messages"
	MessageUnavailable     = "Notification is no longer available"
	MessageNoActions       = "No notification actions available"
	MessageDismissed       = "Notification dismissed"
	MessageActionInvoked   = "Notification action invoked"
	SourceGeneric          = "generic"
	ListTitle              = "Notifications"
	ListColumnMessages     = "Notifications"
	ListColumnReceived     = "Received"
	ListDismissButton      = "Dismiss Notification"
	ListActionsButton      = "Notification Actions"
	ListActionsTitle       = "Notification Actions"
	ListInvokeActionButton = "Invoke Action"
	ListClearButton        = "Clear"
	ListCopyButton         = "Copy"
	ListCloseButton        = "Close"
)

type Entry struct {
	ID               string
	Message          string
	Timestamp        time.Time
	Source           string
	SourceGeneration int
	NotificationID   *int
	Live             bool
	Actions          map[string]string
	AppName          string
	Summary          string
	Body             string
	Urgency          int
	DesktopEntry     string
}

type SaveOptions struct {
	Source           string
	SourceGeneration int
	NotificationID   *int
	Live             bool
	Actions          map[string]string
	AppName          string
	Summary          string
	Body             string
	Urgency          int
	DesktopEntry     string
}

type LiveMetadata struct {
	Message      string
	Actions      map[string]string
	AppName      string
	Summary      string
	Body         string
	Urgency      int
	DesktopEntry string
}

type Presenter struct {
	mutex sync.Mutex
	now   func() time.Time
	mako  MakoController

	entries      []Entry
	currentIndex int
}

func NewPresenter() *Presenter {
	return &Presenter{now: time.Now, currentIndex: -1}
}

func NewPresenterAt(now func() time.Time) *Presenter {
	return &Presenter{now: now, currentIndex: -1}
}

func (presenter *Presenter) SetMakoController(controller MakoController) {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	presenter.mako = controller
}

func (presenter *Presenter) Save(message string, options ...SaveOptions) Entry {
	option := SaveOptions{}
	if len(options) != 0 {
		option = options[0]
	}
	if option.Source == "" {
		option.Source = SourceGeneric
	}

	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	if excess := len(presenter.entries) - historySize + 1; excess > 0 {
		presenter.entries = presenter.entries[excess:]
	}
	entry := Entry{
		Message:          message,
		Timestamp:        presenter.now(),
		Source:           option.Source,
		SourceGeneration: option.SourceGeneration,
		NotificationID:   option.NotificationID,
		Live:             option.Live,
		Actions:          cloneActions(option.Actions),
		AppName:          option.AppName,
		Summary:          option.Summary,
		Body:             option.Body,
		Urgency:          option.Urgency,
		DesktopEntry:     option.DesktopEntry,
	}
	presenter.entries = append(presenter.entries, entry)
	return entry
}

func (presenter *Presenter) Clear() {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	presenter.entries = nil
	presenter.currentIndex = -1
}

func (presenter *Presenter) Entries() []Entry {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	return append([]Entry(nil), presenter.entries...)
}

func (presenter *Presenter) EntriesForList() []Entry {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	return presenter.entriesForList()
}

func (presenter *Presenter) ListTitle() string {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	return presenter.listTitle()
}

func (presenter *Presenter) EntryText(entry Entry) string {
	presenter.mutex.Lock()
	now := presenter.now()
	presenter.mutex.Unlock()
	return entryText(entry, now)
}

func (presenter *Presenter) ReceivedTime(timestamp time.Time) string {
	presenter.mutex.Lock()
	now := presenter.now()
	presenter.mutex.Unlock()
	return relativeTime(timestamp, now)
}

func (presenter *Presenter) RefreshLive() bool {
	presenter.mutex.Lock()
	controller := presenter.mako
	presenter.mutex.Unlock()
	refresher, ok := controller.(interface{ Refresh(bool) bool })
	if !ok {
		return false
	}
	return refresher.Refresh(false)
}

func (presenter *Presenter) Remove(entry Entry) bool {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	for index, candidate := range presenter.entries {
		if entriesEqual(candidate, entry) {
			presenter.entries = append(presenter.entries[:index], presenter.entries[index+1:]...)
			presenter.removeIndex(index)
			return true
		}
	}
	return false
}

func (presenter *Presenter) SyncLive(source string, generation int, live map[int]LiveMetadata) {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	for index := range presenter.entries {
		entry := &presenter.entries[index]
		if entry.Source != source || entry.SourceGeneration != generation {
			continue
		}
		if entry.NotificationID == nil {
			continue
		}
		if metadata, exists := live[*entry.NotificationID]; exists {
			entry.Live = true
			if metadata.Message != "" {
				entry.Message = metadata.Message
			}
			entry.Actions = cloneActions(metadata.Actions)
			entry.AppName = metadata.AppName
			entry.Summary = metadata.Summary
			entry.Body = metadata.Body
			entry.Urgency = metadata.Urgency
			entry.DesktopEntry = metadata.DesktopEntry
		} else if entry.Live {
			entry.Live = false
		}
	}
}

func (presenter *Presenter) MarkSourceUnavailable(source string) {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	for index := range presenter.entries {
		if presenter.entries[index].Source == source && presenter.entries[index].Live {
			presenter.entries[index].Live = false
		}
	}
}

func (presenter *Presenter) CanControlEntry(entry Entry) bool {
	presenter.mutex.Lock()
	controller := presenter.mako
	presenter.mutex.Unlock()
	return entry.Live && entry.NotificationID != nil && controller != nil && controller.IsCurrent(entry)
}

func (presenter *Presenter) ActionsForEntry(entry Entry) map[string]string {
	if !presenter.CanControlEntry(entry) {
		return map[string]string{}
	}
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	return cloneActions(entry.Actions)
}

func (presenter *Presenter) DismissEntry(entry Entry) ([]string, bool) {
	if !presenter.CanControlEntry(entry) {
		return []string{MessageUnavailable}, false
	}
	presenter.mutex.Lock()
	controller := presenter.mako
	presenter.mutex.Unlock()
	if controller == nil || !controller.Dismiss(*entry.NotificationID) {
		return []string{MessageUnavailable}, false
	}
	entry.Live = false
	presenter.Remove(entry)
	return []string{MessageDismissed}, true
}

func (presenter *Presenter) InvokeActionEntry(entry Entry, actionKey string) ([]string, bool) {
	if !presenter.CanControlEntry(entry) {
		return []string{MessageUnavailable}, false
	}
	presenter.mutex.Lock()
	controller := presenter.mako
	presenter.mutex.Unlock()
	if controller == nil || !controller.InvokeAction(*entry.NotificationID, actionKey) {
		return []string{MessageUnavailable}, false
	}
	return []string{MessageActionInvoked}, true
}

func (presenter *Presenter) PresentLast() []string {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	if len(presenter.entries) == 0 {
		return []string{MessageNoMessages}
	}
	presenter.currentIndex = -1
	return []string{entryText(presenter.entries[len(presenter.entries)-1], presenter.now())}
}

func (presenter *Presenter) PresentPrevious() []string {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	if len(presenter.entries) == 0 {
		return []string{MessageNoMessages}
	}
	messages := noMessages
	next := presenter.currentIndex - 1
	if next < -len(presenter.entries) {
		messages = append(messages, MessageListTop)
	} else {
		presenter.currentIndex = next
	}
	current := len(presenter.entries) + presenter.currentIndex
	return append(messages, entryText(presenter.entries[current], presenter.now()))
}

func (presenter *Presenter) PresentNext() []string {
	presenter.mutex.Lock()
	defer presenter.mutex.Unlock()
	if len(presenter.entries) == 0 {
		return []string{MessageNoMessages}
	}
	messages := noMessages
	if presenter.currentIndex == -1 {
		messages = append(messages, MessageListBottom)
	} else {
		next := presenter.currentIndex + 1
		if next > -1 {
			messages = append(messages, MessageListBottom)
		} else {
			presenter.currentIndex = next
		}
	}
	current := len(presenter.entries) + presenter.currentIndex
	return append(messages, entryText(presenter.entries[current], presenter.now()))
}

func (presenter *Presenter) removeIndex(index int) {
	if len(presenter.entries) == 0 {
		presenter.currentIndex = -1
		return
	}
	if presenter.currentIndex == -1 {
		return
	}
	// Navigation uses negative offsets from the newest entry; removal receives
	// a forward slice index. Preserve the selected entry when it survives, or
	// select its successor when removed, without retaining an out-of-range offset.
	current := len(presenter.entries) + 1 + presenter.currentIndex
	if index < current {
		current--
	}
	current = min(current, len(presenter.entries)-1)
	presenter.currentIndex = current - len(presenter.entries)
}

func (presenter *Presenter) entriesForList() []Entry {
	entries := append([]Entry(nil), presenter.entries...)
	for left, right := 0, len(entries)-1; left < right; left, right = left+1, right-1 {
		entries[left], entries[right] = entries[right], entries[left]
	}
	return entries
}

func (presenter *Presenter) listTitle() string {
	return plural(len(presenter.entries), "%d notification", "%d notifications")
}

func entryText(entry Entry, now time.Time) string {
	return fmt.Sprintf("%s %s", entry.Message, relativeTime(entry.Timestamp, now))
}

func relativeTime(timestamp, now time.Time) string {
	elapsed := now.Sub(timestamp)
	switch {
	case elapsed < time.Minute:
		count := int(elapsed.Seconds())
		return plural(count, "%d second ago", "%d seconds ago")
	case elapsed < time.Hour:
		count := roundLikePython(elapsed.Minutes())
		return plural(count, "%d minute ago", "%d minutes ago")
	case elapsed < 24*time.Hour:
		count := roundLikePython(elapsed.Hours())
		return plural(count, "%d hour ago", "%d hours ago")
	default:
		count := roundLikePython(elapsed.Hours() / 24)
		return plural(count, "%d day ago", "%d days ago")
	}
}

func plural(count int, singular, pluralFormat string) string {
	if count == 1 {
		return fmt.Sprintf(singular, count)
	}
	return fmt.Sprintf(pluralFormat, count)
}

func roundLikePython(value float64) int {
	lower := math.Floor(value)
	fraction := value - lower
	switch {
	case fraction > 0.5:
		return int(lower) + 1
	case fraction == 0.5 && int(lower)%2 != 0:
		return int(lower) + 1
	default:
		return int(lower)
	}
}

func cloneActions(actions map[string]string) map[string]string {
	if len(actions) == 0 {
		return map[string]string{}
	}
	clone := make(map[string]string, len(actions))
	for key, value := range actions {
		clone[key] = value
	}
	return clone
}

func entriesEqual(left, right Entry) bool {
	return left.Message == right.Message &&
		left.Timestamp.Equal(right.Timestamp) &&
		left.Source == right.Source &&
		left.SourceGeneration == right.SourceGeneration &&
		notificationIDsEqual(left.NotificationID, right.NotificationID) &&
		actionsEqual(left.Actions, right.Actions) &&
		left.AppName == right.AppName &&
		left.Summary == right.Summary &&
		left.Body == right.Body &&
		left.Urgency == right.Urgency &&
		left.DesktopEntry == right.DesktopEntry
}

func notificationIDsEqual(left, right *int) bool {
	if left == nil || right == nil {
		return left == right
	}
	return *left == *right
}

func actionsEqual(left, right map[string]string) bool {
	if len(left) != len(right) {
		return false
	}
	for key, value := range left {
		if right[key] != value {
			return false
		}
	}
	return true
}