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

// Package interaction implements focus-free controls. It owns no keyboard,
// accessibility objects, output services or callbacks; the reader owns those.
package interaction

import (
	"errors"
	"fmt"
	ui "git.stormux.org/storm/screenreader-common/internalui"
	"strings"
	"unicode"
	"unicode/utf8"
)

type Kind uint8

const (
	List Kind = iota + 1
	Entry
	CheckBox
	Button
)

type Item struct {
	ID       string `json:"id"`
	Label    string `json:"label"`
	Disabled bool   `json:"disabled,omitempty"`
}
type Element struct {
	ID        string `json:"id"`
	Label     string `json:"label"`
	Kind      Kind   `json:"kind"`
	Items     []Item `json:"items,omitempty"`
	Text      string `json:"text,omitempty"`
	Checked   bool   `json:"checked,omitempty"`
	Disabled  bool   `json:"disabled,omitempty"`
	Required  bool   `json:"required,omitempty"`
	MaxLength int    `json:"max_length,omitempty"`
	// Secret is supported only on transient entries, never preference pages.
	Secret bool `json:"secret,omitempty"`
}
type Form struct {
	Title    string    `json:"title"`
	Elements []Element `json:"elements"`
}
type Key uint8

const (
	Text Key = iota
	Up
	Down
	Left
	Right
	Home
	End
	PageUp
	PageDown
	Tab
	Enter
	Escape
	Backspace
	Delete
)

type Event struct {
	Key                 Key
	Text                string
	Shift, Control, Alt bool
}
type Presentation struct {
	Speech, Braille string
	Cursor          int
}

// Effect describes a host operation. Activation does not close the form: the
// caller can validate, replace it with another form, or finish the interaction.
type Effect struct {
	Presentation
	Activated        string
	Cancelled, Paste bool
	Copy             *string
}
type Value struct {
	Text     string `json:"text,omitempty"`
	Selected string `json:"selected,omitempty"`
	Checked  bool   `json:"checked,omitempty"`
}
type elementState struct {
	element  Element
	selected int
}
type Session struct {
	core     *ui.Session
	title    string
	grid     bool
	checkbox string
}

const maxTextLength = 8192

func NewSession(form Form) (*Session, error) {
	return new_session(form, 256, 64)
}

// ValidatePreferences shares control validation with internal forms, while
// allowing a native, scrolling page to contain several full voice editors.
func ValidatePreferences(form Form) error {
	for _, element := range form.Elements {
		if element.Secret {
			return errors.New("secret entries are not supported in preferences")
		}
	}
	_, err := new_session(form, 256, 256)
	return err
}

// NewNavigationSession is for core document lists. External forms retain
// their smaller protocol limit. The selected row follows the reading caret.
func NewNavigationSession(title string, items []Item, selected int) (*Session, error) {
	session, err := new_session(Form{Title: title, Elements: []Element{{ID: "items", Label: title, Kind: List, Items: items}}}, 65536, 64)
	if err == nil && selected >= 0 && selected < len(items) && !items[selected].Disabled {
		session.core.Select("form", "items", selected)
	}
	return session, err
}

func new_session(form Form, maxItems, maxElements int) (*Session, error) {
	if form.Title == "" || len(form.Title) > 1024 || len(form.Elements) == 0 || len(form.Elements) > maxElements {
		return nil, fmt.Errorf("a titled form with 1 to %d controls is required", maxElements)
	}
	session := struct {
		elements []elementState
		focus    int
	}{focus: -1}
	ids := map[string]bool{}
	for _, element := range form.Elements {
		if element.ID == "" || len(element.ID) > 1024 || element.Label == "" || len(element.Label) > 1024 || ids[element.ID] || element.Kind < List || element.Kind > Button {
			return nil, errors.New("controls need unique IDs, labels and supported kinds")
		}
		ids[element.ID] = true
		if element.Secret && element.Kind != Entry {
			return nil, errors.New("only entries may be secret")
		}
		if element.MaxLength == 0 {
			element.MaxLength = maxTextLength
		}
		if element.MaxLength < 1 || element.MaxLength > maxTextLength || len([]rune(element.Text)) > element.MaxLength {
			return nil, errors.New("invalid entry length")
		}
		if !utf8.ValidString(element.Text) || strings.ContainsAny(element.Text, "\r\n\x00") {
			return nil, errors.New("entries must contain single-line text")
		}
		for _, character := range element.Text {
			if unicode.IsControl(character) {
				return nil, errors.New("entries must contain single-line text")
			}
		}
		element.Items = append([]Item(nil), element.Items...)
		state := elementState{element: element, selected: -1}
		itemIDs := map[string]bool{}
		if len(element.Items) > maxItems {
			return nil, errors.New("too many list items")
		}
		for index, item := range element.Items {
			if item.ID == "" || len(item.ID) > 1024 || item.Label == "" || len(item.Label) > 1024 || itemIDs[item.ID] {
				return nil, errors.New("list items need unique IDs and labels")
			}
			itemIDs[item.ID] = true
			if state.selected < 0 && !item.Disabled {
				state.selected = index
			}
		}
		if element.Kind == List && state.selected < 0 {
			state.element.Disabled = true
		}
		session.elements = append(session.elements, state)
		if session.focus < 0 && !state.element.Disabled {
			session.focus = len(session.elements) - 1
		}
	}
	if session.focus < 0 {
		return nil, errors.New("form has no enabled controls")
	}
	controls := make([]ui.Control, 0, len(session.elements))
	for _, state := range session.elements {
		e := state.element
		c := ui.Control{ID: e.ID, Label: e.Label, Text: e.Text, Checked: e.Checked, Disabled: state.element.Disabled, Required: e.Required, Secret: e.Secret, MaxLength: e.MaxLength, Selected: state.selected, Action: e.ID}
		switch e.Kind {
		case List:
			c.Kind = ui.List
			c.SelectAction = true
			for _, item := range e.Items {
				c.Choices = append(c.Choices, ui.Choice{ID: item.ID, Label: item.Label, Literal: true, Disabled: item.Disabled})
			}
		case Entry:
			c.Kind = ui.Entry
		case CheckBox:
			c.Kind = ui.CheckBox
		case Button:
			c.Kind = ui.Button
		}
		// Empty disabled lists need no selectable placeholder in the shared model.
		controls = append(controls, c)
	}
	core, err := ui.NewSession(ui.Form{Type: ui.FlatForm, Title: form.Title, Detailed: true, Tabs: []ui.Tab{{ID: "form", Label: form.Title, Controls: controls}}}, ui.Messages{})
	if err != nil {
		return nil, err
	}
	return &Session{core: core, title: form.Title}, nil
}

func (s *Session) Presentation() Presentation {
	r := s.core.Presentation()
	return Presentation{Speech: r.Speech, Braille: r.Braille, Cursor: r.Cursor}
}
func (s *Session) Opening() Presentation {
	r := s.Presentation()
	if !s.grid {
		c, ok := s.core.Focused_control()
		if ok && c.Kind == ui.List && len(s.core.Values()) > 1 {
			r.Speech = c.Label + ". " + r.Speech
		}
	}
	r.Speech = s.title + ". " + r.Speech
	return r
}
func (s *Session) Values() map[string]Value {
	values := s.core.Values()
	if values == nil {
		return nil
	}
	result := map[string]Value{}
	if s.grid {
		for _, c := range values {
			if c.ID == s.checkbox {
				result[c.ID] = Value{Checked: c.Checked}
				break
			}
		}
		c, ok := s.core.Focused_control()
		if ok && c.Kind == ui.Grid && c.Selected >= 0 {
			v := c.Choices[c.Selected]
			result["grid"] = Value{Selected: v.ID, Text: v.Label}
		}
		return result
	}
	for _, c := range values {
		v := Value{Text: c.Text, Checked: c.Checked}
		if c.Kind == ui.List {
			v.Text = ""
			if c.Selected >= 0 && c.Selected < len(c.Choices) {
				v.Selected = c.Choices[c.Selected].ID
			}
		}
		result[c.ID] = v
	}
	return result
}
func (s *Session) Close() { s.core.Close() }
func (s *Session) Handle(event Event) Effect {
	name := map[Key]string{Up: "up", Down: "down", Left: "left", Right: "right", Home: "home", End: "end", PageUp: "pageup", PageDown: "pagedown", Tab: "tab", Enter: "enter", Escape: "escape", Backspace: "backspace", Delete: "delete"}[event.Key]
	if event.Key == Text && event.Text == " " {
		name = "space"
	}
	r := s.core.Handle(ui.Key{Name: name, Text: event.Text, Shift: event.Shift, Ctrl: event.Control, Alt: event.Alt})
	if s.grid {
		c, ok := s.core.Focused_control()
		if ok && c.Kind == ui.CheckBox {
			s.core.SetChecked(c.ID, c.Checked)
		}
	}
	if !s.grid && event.Key == Tab && r.Speech != "" {
		c, ok := s.core.Focused_control()
		if ok && c.Kind == ui.List && len(s.core.Values()) > 1 {
			r.Speech = c.Label + ". " + r.Speech
		}
	}
	return effect(r)
}
func effect(r ui.Result) Effect {
	return Effect{Presentation: Presentation{Speech: r.Speech, Braille: r.Braille, Cursor: r.Cursor}, Activated: r.Action, Cancelled: r.Cancelled, Paste: r.Paste, Copy: r.Copy}
}
func (s *Session) Insert(text string) Effect { return effect(s.core.Insert(text)) }

// NewUnifiedSession exposes the full toolkit to core reader features. External
// protocol forms continue through NewSession and its bounded validation.
func NewUnifiedSession(form ui.Form, messages ui.Messages) (*Session, error) {
	core, err := ui.NewSession(form, messages)
	if err != nil {
		return nil, err
	}
	return &Session{core: core, title: form.Title}, nil
}

// ControlValues includes rich typed values keyed by page.control, including
// plaintext secrets. Use only for submission; never log or persist secrets.
func (s *Session) ControlValues() map[string]ui.Control { return s.core.Values() }