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

// Package quicksettings implements the reader-independent quick settings
// menu: categories of entries, a remembered position in each category,
// value stepping and the spoken announcement. Readers own their settings:
// they describe entries, report current values and apply each change.
package quicksettings

import (
	"strconv"

	"git.stormux.org/storm/screenreader-common/internalui/message"
)

type Messages = message.Messages

type Kind uint8

const (
	// Toggle is announced as checked or unchecked; either step flips it.
	Toggle Kind = iota + 1
	// Choice steps through Options and wraps at both ends.
	Choice
	// Range steps by Step and stops at Min and Max.
	Range
)

type Option struct{ ID, Label string }

// Entry describes one setting. Label and option labels are English message
// IDs passed through the menu's translator.
type Entry struct {
	ID    string
	Label string
	Kind  Kind
	// Range limits and step size.
	Min, Max, Step int
	// EmptyIsDefault announces a Choice whose selected ID is empty as
	// "<label> default", such as an unset speech module or voice.
	EmptyIsDefault bool
}

type Category struct {
	ID, Label string
	Entries   []Entry
}

// Value holds an entry's value; only the field matching its Kind is used.
type Value struct {
	Checked bool
	Choice  string
	Number  int
}

// Host reports current values and the options of Choice entries. The menu
// calls it synchronously from Handle.
type Host interface {
	Value(Entry) Value
	Options(Entry) []Option
}

type Command uint8

const (
	CurrentEntry Command = iota + 1
	CurrentValue
	NextEntry
	PreviousEntry
	NextValue
	PreviousValue
	NextCategory
	PreviousCategory
)

// Result is one handled command. When Changed is true the host applies
// Value to Entry before speaking Text; an asynchronous host speaks Text when
// the change succeeds. Available is false for an empty menu or an entry
// without options, and Text then explains why.
type Result struct {
	Entry     Entry
	Value     Value
	Changed   bool
	Available bool
	Text      string
}

// Menu is not safe for concurrent use. Copy it with Clone.
type Menu struct {
	Messages   Messages
	categories []Category
	category   int
	positions  []int
}

// New drops categories without entries.
func New(categories []Category, messages Messages) *Menu {
	menu := &Menu{Messages: messages}
	menu.Replace(categories)
	return menu
}

// IsValueChange reports whether command changes the selected entry's value.
func IsValueChange(command Command) bool { return command == NextValue || command == PreviousValue }

// Replace installs a new entry set, keeping the selected category and each
// category's selected entry when their IDs are still present. kept is false
// when the previously selected entry no longer exists; hosts should then not
// apply a value change to whichever entry is selected instead.
func (m *Menu) Replace(categories []Category) (kept bool) {
	var selectedCategory, selectedEntry string
	if entry, ok := m.Selected(); ok {
		selectedEntry = entry.ID
	}
	selectedEntries := make(map[string]string)
	for index, category := range m.categories {
		if index == m.category {
			selectedCategory = category.ID
		}
		selectedEntries[category.ID] = category.Entries[m.positions[index]].ID
	}
	m.categories, m.positions, m.category = nil, nil, 0
	for _, category := range categories {
		if len(category.Entries) == 0 {
			continue
		}
		category.Entries = append([]Entry(nil), category.Entries...)
		position := 0
		for index, entry := range category.Entries {
			if entry.ID == selectedEntries[category.ID] {
				position = index
				break
			}
		}
		if category.ID == selectedCategory {
			m.category = len(m.categories)
		}
		m.categories = append(m.categories, category)
		m.positions = append(m.positions, position)
	}
	entry, ok := m.Selected()
	return selectedEntry == "" || ok && entry.ID == selectedEntry
}

func (m *Menu) Clone() *Menu {
	clone := *m
	clone.categories = append([]Category(nil), m.categories...)
	clone.positions = append([]int(nil), m.positions...)
	return &clone
}

func (m *Menu) Categories() []Category {
	categories := append([]Category(nil), m.categories...)
	for index := range categories {
		categories[index].Entries = append([]Entry(nil), categories[index].Entries...)
	}
	return categories
}

// Selected reports the current entry; ok is false for an empty menu.
func (m *Menu) Selected() (entry Entry, ok bool) {
	if len(m.categories) == 0 {
		return Entry{}, false
	}
	return m.categories[m.category].Entries[m.positions[m.category]], true
}

func (m *Menu) Handle(command Command, host Host) Result {
	if len(m.categories) == 0 {
		return Result{Text: m.Messages.T("Quick menu not available")}
	}
	categoryChanged := command == NextCategory || command == PreviousCategory
	switch command {
	case NextCategory:
		m.category = (m.category + 1) % len(m.categories)
	case PreviousCategory:
		m.category = (m.category + len(m.categories) - 1) % len(m.categories)
	}
	entries := m.categories[m.category].Entries
	position := &m.positions[m.category]
	switch command {
	case NextEntry:
		*position = (*position + 1) % len(entries)
	case PreviousEntry:
		*position = (*position + len(entries) - 1) % len(entries)
	}
	entry := entries[*position]
	result := Result{Entry: entry, Value: host.Value(entry), Available: true}
	step := 0
	switch command {
	case NextValue:
		step = 1
	case PreviousValue:
		step = -1
	}
	var options []Option
	switch entry.Kind {
	case Toggle:
		if step != 0 {
			result.Value.Checked = !result.Value.Checked
			result.Changed = true
		}
	case Choice:
		options = host.Options(entry)
		if len(options) == 0 {
			result.Available = false
			result.Text = m.Messages.Format("{0} not available", m.Messages.T(entry.Label))
			if categoryChanged {
				result.Text = m.Messages.T(m.categories[m.category].Label) + ". " + result.Text
			}
			return result
		}
		if step != 0 {
			index := -1
			for candidate, option := range options {
				if option.ID == result.Value.Choice {
					index = candidate
					break
				}
			}
			if index < 0 {
				if step > 0 {
					index = 0
				} else {
					index = len(options) - 1
				}
			} else {
				index = (index + step + len(options)) % len(options)
			}
			result.Changed = options[index].ID != result.Value.Choice
			result.Value.Choice = options[index].ID
		}
	case Range:
		if step != 0 {
			next := max(entry.Min, min(entry.Max, result.Value.Number+step*entry.Step))
			result.Changed = next != result.Value.Number
			result.Value.Number = next
		}
	}
	text, labelled := m.describe(entry, result.Value, options)
	if !labelled && (categoryChanged || command == CurrentEntry || command == NextEntry || command == PreviousEntry) {
		text = m.Messages.T(entry.Label) + " " + text
	}
	if categoryChanged {
		text = m.Messages.T(m.categories[m.category].Label) + ". " + text
	}
	result.Text = text
	return result
}

// Describe returns the value announcement used after a value change.
func (m *Menu) Describe(entry Entry, value Value, options []Option) string {
	text, _ := m.describe(entry, value, options)
	return text
}

func (m *Menu) describe(entry Entry, value Value, options []Option) (text string, labelled bool) {
	switch entry.Kind {
	case Toggle:
		if value.Checked {
			return m.Messages.T("checked"), false
		}
		return m.Messages.T("unchecked"), false
	case Choice:
		if entry.EmptyIsDefault && value.Choice == "" {
			return m.Messages.T(entry.Label) + " " + m.Messages.T("default"), true
		}
		for _, option := range options {
			if option.ID == value.Choice {
				return m.Messages.T(option.Label), false
			}
		}
		if len(options) > 0 {
			return m.Messages.Format("{0} not available", value.Choice), false
		}
		return value.Choice, false
	}
	return strconv.Itoa(value.Number), false
}

// MessageIDs lists the menu's own English messages for translation catalogs.
func MessageIDs() []string {
	return []string{"Quick menu not available", "{0} not available", "checked", "unchecked", "default"}
}