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

package app

import (
	"context"
	"encoding/json"
	"errors"
	"path/filepath"
	"reflect"
	"sort"
	"time"

	"git.stormux.org/storm/cthulhu/internal/config"
	"git.stormux.org/storm/cthulhu/internal/interaction"
	"git.stormux.org/storm/cthulhu/internal/preferences"
	"git.stormux.org/storm/cthulhu/internal/tentacle"
	"git.stormux.org/storm/cthulhu/internal/tentaclewire"
)

type readerExtension struct {
	session  *tentacle.Session
	value    tentaclewire.Extensions
	revision uint64
}

type readerSettingsCall struct {
	ctx     context.Context
	session *tentacle.Session
	request tentaclewire.ReaderRequest
	result  chan readerSettingsResult
}
type readerSettingsResult struct {
	state *tentaclewire.ReaderState
	err   error
}
type readerTransaction struct {
	extensions map[string]*readerExtension
	override   *tentaclewire.SpeechConfiguration
	owner      string
}

func copy_reader_value[T any](value T) T {
	data, _ := json.Marshal(value)
	var result T
	_ = json.Unmarshal(data, &result)
	return result
}

func (runtime *tentacleRuntime) signal_extensions() {
	if runtime == nil {
		return
	}
	select {
	case runtime.extensionChanges <- struct{}{}:
	default:
	}
}
func (worker *preferencesWorker) extension_changes() <-chan struct{} {
	if worker.tentacles == nil {
		return nil
	}
	return worker.tentacles.extensionChanges
}
func (runtime *tentacleRuntime) reader_sessions() map[string]*tentacle.Session {
	sessions := map[string]*tentacle.Session{}
	if runtime == nil {
		return sessions
	}
	runtime.mutex.Lock()
	defer runtime.mutex.Unlock()
	if runtime.disabled {
		return sessions
	}
	for _, command := range runtime.commands {
		if state, _ := command.session.Status(); command.reader && state == tentacle.Active {
			sessions[command.session.Identity()] = command.session
		}
	}
	return sessions
}

// Called only by the settings owner. Revocation wakes this mailbox even if no
// preferences window is open. No native input callback waits for restoration.
func (worker *preferencesWorker) sync_extensions(ctx context.Context) {
	if ctx.Err() != nil {
		return
	}
	sessions := worker.tentacles.reader_sessions()
	if worker.extensions == nil {
		worker.extensions = map[string]*readerExtension{}
	}
	for id := range worker.extensions {
		if sessions[id] == nil {
			delete(worker.extensions, id)
		}
	}
	for id, session := range sessions {
		if worker.extensions[id] != nil {
			continue
		}
		value := session.Extensions()
		worker.load_page_store()
		for index := range value.Pages {
			page := &value.Pages[index]
			if saved := worker.savedPages[session.TentacleID()][page.ID]; saved != nil && tentaclewire.ValidatePageValues(*page, saved) == nil {
				page.Values = copy_reader_value(saved)
			}
		}
		worker.extensionRevision++
		worker.extensions[id] = &readerExtension{session: session, value: value, revision: worker.extensionRevision}
		if err := validate_reader_extensions(worker.extensions); err != nil {
			delete(worker.extensions, id)
			session.Disable()
			worker.announceSpeechSetting("A tentacle exceeded the reader settings limits and was disabled.")
		}
	}
	if worker.speechOverride != nil && sessions[worker.speechOverrideOwner] == nil {
		restoreCtx, cancel := context.WithTimeout(ctx, 6*time.Second)
		var err error
		if worker.settings.EnableSpeech {
			err = worker.updateSpeech(restoreCtx, worker.settings)
		}
		cancel()
		if err != nil {
			worker.logger.Error("restore speech after tentacle revocation", "error", err)
			worker.announceSpeechSetting("The tentacle stopped, but normal speech settings could not be restored. The working voice has been retained.")
			return
		}
		worker.speechOverride, worker.speechOverrideOwner = nil, ""
		if worker.live != nil {
			worker.live.Store(worker.settings)
		}
	}
}
func (worker *preferencesWorker) load_page_store() {
	if worker.pageStore != nil {
		return
	}
	worker.pageStore = &tentacle.PageStore{Path: filepath.Join(filepath.Dir(worker.settings.Path), "tentacle-preferences.json")}
	worker.savedPages, worker.pageLoadError = worker.pageStore.Load()
	if worker.savedPages == nil {
		worker.savedPages = tentacle.PageValues{}
	}
	if worker.pageLoadError != nil {
		worker.logger.Warn("load tentacle preferences", "error", worker.pageLoadError)
	}
}

func (worker *preferencesWorker) effective_settings(base config.Settings) config.Settings {
	if worker.speechOverride != nil {
		return worker.speechOverride.Apply(base)
	}
	return base
}
func (worker *preferencesWorker) extension_pages() []preferences.ExtensionPage {
	if worker.editApp != "" {
		return nil
	}
	var pages []preferences.ExtensionPage
	for _, id := range sorted_extension_ids(worker.extensions) {
		extension := worker.extensions[id]
		for _, page := range extension.value.Pages {
			pages = append(pages, preferences.ExtensionPage{Session: id, Revision: extension.revision, PreferencePage: copy_reader_value(page)})
		}
	}
	return pages
}
func sorted_extension_ids(extensions map[string]*readerExtension) []string {
	ids := make([]string, 0, len(extensions))
	for id := range extensions {
		ids = append(ids, id)
	}
	sort.Slice(ids, func(i, j int) bool {
		left, right := extensions[ids[i]].session.TentacleID(), extensions[ids[j]].session.TentacleID()
		if left != right {
			return left < right
		}
		return ids[i] < ids[j]
	})
	return ids
}
func (worker *preferencesWorker) reader_state(extension *readerExtension) tentaclewire.ReaderState {
	return copy_reader_value(tentaclewire.ReaderState{Speech: tentaclewire.SpeechFromSettings(worker.effective_settings(worker.settings)), DefaultSpeech: tentaclewire.SpeechFromSettings(worker.settings), Extensions: extension.value})
}
func (worker *preferencesWorker) request_reader(ctx context.Context, session *tentacle.Session, request tentaclewire.ReaderRequest) (*tentaclewire.ReaderState, error) {
	call := readerSettingsCall{ctx: ctx, session: session, request: request, result: make(chan readerSettingsResult, 1)}
	select {
	case worker.extensionRequests <- call:
	case <-ctx.Done():
		return nil, ctx.Err()
	default:
		return nil, tentacle.ErrBusy
	}
	select {
	case result := <-call.result:
		return result.state, result.err
	case <-ctx.Done():
		return nil, ctx.Err()
	case <-worker.done:
		return nil, tentacle.ErrUnavailable
	}
}
func (worker *preferencesWorker) handle_reader_call(ctx context.Context, call readerSettingsCall, windowOpen bool) {
	callCtx, cancel := context.WithCancel(ctx)
	defer cancel()
	stop := context.AfterFunc(call.ctx, cancel)
	defer stop()
	if call.session != nil {
		stopSession := context.AfterFunc(call.session.OutputContext(), cancel)
		defer stopSession()
	}
	worker.sync_extensions(ctx)
	state, err := worker.apply_reader_request(callCtx, call.session, call.request, windowOpen)
	call.result <- readerSettingsResult{state, err}
}
func (worker *preferencesWorker) reader_allowed(ctx context.Context, session *tentacle.Session) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	if session == nil {
		return tentacle.ErrUnavailable
	}
	if state, _ := session.Status(); state != tentacle.Active || worker.extensions[session.Identity()] == nil {
		return tentacle.ErrUnavailable
	}
	if worker.tentacles != nil && worker.tentacles.output != nil && worker.tentacles.output.gate != nil {
		if worker.tentacles.output.gate.Locked() || worker.tentacles.output.gate.Suspended() {
			return errors.New("reader interaction is unavailable")
		}
	}
	return nil
}
func (worker *preferencesWorker) reader_transaction() readerTransaction {
	extensions := map[string]*readerExtension{}
	for id, extension := range worker.extensions {
		extensions[id] = &readerExtension{session: extension.session, value: copy_reader_value(extension.value), revision: extension.revision}
	}
	return readerTransaction{extensions, copy_reader_value(worker.speechOverride), worker.speechOverrideOwner}
}
func (worker *preferencesWorker) stage_reader_request(ctx context.Context, transaction *readerTransaction, session *tentacle.Session, request tentaclewire.ReaderRequest) error {
	if err := worker.reader_allowed(ctx, session); err != nil {
		return err
	}
	if err := tentaclewire.ValidateReaderRequest(request); err != nil {
		return err
	}
	id := session.Identity()
	if request.Extensions != nil {
		allowed := map[string]bool{}
		for _, command := range session.Commands() {
			if command.Reader && !command.Settings {
				allowed[command.ID] = true
			}
		}
		for _, page := range request.Extensions.Pages {
			if !allowed[page.Command] {
				return tentacle.ErrProtocol
			}
		}
		for _, setting := range request.Extensions.QuickSettings {
			if !allowed[setting.Command] {
				return tentacle.ErrProtocol
			}
		}
		transaction.extensions[id].value = copy_reader_value(*request.Extensions)
		transaction.extensions[id].revision++
	}
	if request.Speech != nil || request.RestoreSpeech {
		if transaction.override != nil && transaction.owner != id {
			return errors.New("another tentacle owns the active speech override")
		}
		if request.RestoreSpeech {
			transaction.override, transaction.owner = nil, ""
		} else {
			next := request.Speech.Apply(worker.settings)
			if err := config.Validate(next); err != nil {
				return err
			}
			transaction.override, transaction.owner = copy_reader_value(request.Speech), id
		}
	}
	return validate_reader_extensions(transaction.extensions)
}
func (worker *preferencesWorker) commit_reader_transaction(ctx context.Context, session *tentacle.Session, transaction readerTransaction) error {
	if err := worker.reader_allowed(ctx, session); err != nil {
		return err
	}
	next := worker.settings
	if transaction.override != nil {
		next = transaction.override.Apply(next)
	}
	if !reflect.DeepEqual(transaction.override, worker.speechOverride) && next.EnableSpeech {
		operationCtx, cancel := context.WithTimeout(ctx, 6*time.Second)
		stop := context.AfterFunc(session.OutputContext(), cancel)
		err := worker.updateSpeech(operationCtx, next)
		stop()
		cancel()
		if err != nil {
			return err
		}
		if err := worker.reader_allowed(ctx, session); err != nil {
			restoreCtx, restoreCancel := context.WithTimeout(context.Background(), 6*time.Second)
			defer restoreCancel()
			if restoreErr := worker.updateSpeech(restoreCtx, worker.effective_settings(worker.settings)); restoreErr != nil {
				worker.logger.Error("restore revoked speech transaction", "error", restoreErr)
			}
			return err
		}
	}
	worker.extensions = transaction.extensions
	worker.speechOverride, worker.speechOverrideOwner = transaction.override, transaction.owner
	if worker.live != nil {
		worker.live.Store(next)
	}
	return nil
}
func (worker *preferencesWorker) apply_reader_request(ctx context.Context, session *tentacle.Session, request tentaclewire.ReaderRequest, windowOpen bool) (*tentaclewire.ReaderState, error) {
	if err := worker.reader_allowed(ctx, session); err != nil {
		return nil, err
	}
	if windowOpen && (request.Speech != nil || request.RestoreSpeech || request.Extensions != nil) {
		return nil, errors.New("close preferences before changing reader settings from a command")
	}
	transaction := worker.reader_transaction()
	if err := worker.stage_reader_request(ctx, &transaction, session, request); err != nil {
		return nil, err
	}
	if err := worker.commit_reader_transaction(ctx, session, transaction); err != nil {
		return nil, err
	}
	state := worker.reader_state(worker.extensions[session.Identity()])
	if request.Snapshot {
		catalogCtx, cancel := context.WithTimeout(ctx, 4*time.Second)
		catalog, err := worker.discover(catalogCtx, worker.socket)
		cancel()
		if err != nil {
			return &state, errors.New("speech voice catalog is unavailable")
		}
		for module := range catalog {
			if module != "" {
				state.Modules = append(state.Modules, module)
			}
		}
		sort.Strings(state.Modules)
		state.Voices = append(state.Voices, catalog[request.Module]...)
		// Keep a continuation below the RPC argument limit, explicitly marking
		// partial catalogs instead of silently dropping voices.
		for {
			data, _ := json.Marshal(tentaclewire.Submission{Reader: &state})
			if len(data) <= tentacle.MaxReaderArgumentBytes {
				break
			}
			state.CatalogTruncated = true
			if len(state.Voices) > 0 {
				state.Voices = state.Voices[:len(state.Voices)/2]
			} else if len(state.Modules) > 0 {
				state.Modules = state.Modules[:len(state.Modules)/2]
			} else {
				return nil, tentacle.ErrLimit
			}
		}
	}
	return &state, nil
}

func (worker *preferencesWorker) extension_effect(ctx context.Context, extension *readerExtension, command string, event tentaclewire.ExtensionEvent) (tentaclewire.ReaderRequest, error) {
	arguments := any(event)
	for transition := 0; transition < 16; transition++ {
		if err := worker.reader_allowed(ctx, extension.session); err != nil {
			return tentaclewire.ReaderRequest{}, err
		}
		data, err := json.Marshal(arguments)
		if err != nil {
			return tentaclewire.ReaderRequest{}, err
		}
		replies, err := extension.session.Invoke(ctx, command, data)
		if err != nil {
			return tentaclewire.ReaderRequest{}, err
		}
		result := <-replies
		if result.Err != nil {
			return tentaclewire.ReaderRequest{}, result.Err
		}
		value, err := tentaclewire.DecodeInteraction(result.Value)
		if err != nil || value.Reader == nil || value.Form != nil || value.Poll != "" || value.Source != "" || value.Clipboard != nil || value.Speech != "" || value.Braille != "" {
			return tentaclewire.ReaderRequest{}, errors.New("extension callback must return only a reader settings proposal")
		}
		if !value.Reader.Snapshot {
			if value.Next != "" {
				return tentaclewire.ReaderRequest{}, tentacle.ErrProtocol
			}
			return *value.Reader, nil
		}
		if !worker.tentacles.reader_continuation(tentacleCommand{session: extension.session}, value.Next) {
			return tentaclewire.ReaderRequest{}, tentacle.ErrProtocol
		}
		state, snapshotErr := worker.apply_reader_request(ctx, extension.session, *value.Reader, true)
		submission := tentaclewire.Submission{Reader: state}
		if snapshotErr != nil {
			submission.Error = snapshotErr.Error()
		}
		arguments, command = submission, value.Next
	}
	return tentaclewire.ReaderRequest{}, errors.New("reader callback continuation limit reached")
}

// Optional page loading happens before GTK constructs controls. Handlers may
// inspect the reader/catalog and replace declarations, but cannot apply speech.
func (worker *preferencesWorker) load_extension_pages(ctx context.Context) error {
	loadCtx, cancel := context.WithTimeout(ctx, 6*time.Second)
	defer cancel()
	var failures error
	for _, view := range worker.extension_pages() {
		if !view.Load {
			continue
		}
		extension := worker.extensions[view.Session]
		if extension == nil {
			continue
		}
		event := tentaclewire.ExtensionEvent{Event: "preferences.open", ID: view.ID, Reader: worker.reader_state(extension)}
		request, err := worker.extension_effect(loadCtx, extension, view.Command, event)
		if err == nil && (request.Speech != nil || request.RestoreSpeech || request.Extensions == nil) {
			err = errors.New("opening a preference page may only update its declarations")
		}
		transaction := worker.reader_transaction()
		if err == nil {
			err = worker.stage_reader_request(loadCtx, &transaction, extension.session, request)
		}
		if err == nil {
			worker.extensions = transaction.extensions
		} else {
			failures = errors.Join(failures, err)
		}
	}
	worker.sync_extensions(ctx)
	return failures
}

func (worker *preferencesWorker) prepare_extension_pages(ctx context.Context, drafts []preferences.PageDraft) (readerTransaction, error) {
	worker.sync_extensions(ctx)
	transaction := worker.reader_transaction()
	if len(drafts) == 0 {
		return transaction, nil
	}
	if worker.editApp != "" || worker.choosingApplication {
		return transaction, errors.New("tentacle pages are global preferences")
	}
	seen := map[string]bool{}
	speechProposals := 0
	for _, draft := range drafts {
		key := draft.Session + "/" + draft.ID
		extension := worker.extensions[draft.Session]
		if extension == nil || extension.revision != draft.Revision || seen[key] {
			return transaction, errors.New("tentacle page changed or was removed; reopen preferences")
		}
		seen[key] = true
		var page *tentaclewire.PreferencePage
		for _, candidate := range extension.value.Pages {
			if candidate.ID == draft.ID {
				copy := candidate
				page = &copy
				break
			}
		}
		if page == nil {
			return transaction, tentacle.ErrProtocol
		}
		if err := tentaclewire.ValidatePageValues(*page, draft.Values); err != nil {
			return transaction, err
		}
		for _, element := range page.Elements {
			if element.Disabled && !reflect.DeepEqual(page.Values[element.ID], draft.Values[element.ID]) {
				return transaction, tentacle.ErrProtocol
			}
		}
		if reflect.DeepEqual(page.Values, draft.Values) {
			continue
		}
		event := tentaclewire.ExtensionEvent{Event: "preferences.apply", ID: page.ID, Values: draft.Values, Reader: worker.reader_state(extension)}
		request, err := worker.extension_effect(ctx, extension, page.Command, event)
		if err != nil {
			return transaction, err
		}
		if request.Speech != nil || request.RestoreSpeech {
			speechProposals++
		}
		if speechProposals > 1 {
			return transaction, errors.New("multiple pages proposed conflicting speech changes")
		}
		if err := worker.stage_reader_request(ctx, &transaction, extension.session, request); err != nil {
			return transaction, err
		}
		staged := transaction.extensions[draft.Session]
		found := false
		for index := range staged.value.Pages {
			if staged.value.Pages[index].ID == page.ID {
				// A callback may replace choices or normalize input. Otherwise
				// the successfully submitted draft becomes its committed value.
				if request.Extensions == nil {
					staged.value.Pages[index].Values = copy_reader_value(draft.Values)
				}
				found = true
			}
		}
		if !found {
			return transaction, errors.New("an applied page cannot remove itself")
		}
		staged.revision++
	}
	return transaction, validate_reader_extensions(transaction.extensions)
}

func validate_reader_extensions(extensions map[string]*readerExtension) error {
	total := 0
	for _, extension := range extensions {
		if err := tentaclewire.ValidateExtensions(extension.value); err != nil {
			return err
		}
		data, err := json.Marshal(extension.value)
		if err != nil {
			return err
		}
		total += len(data)
	}
	if total > 256*1024 {
		return tentacle.ErrLimit
	}
	return nil
}
func (worker *preferencesWorker) save_extension_pages() error {
	if worker.pageStore == nil {
		return nil
	}
	if worker.pageLoadError != nil {
		return worker.pageLoadError
	}
	values := copy_reader_value(worker.savedPages)
	if values == nil {
		values = tentacle.PageValues{}
	}
	for _, extension := range worker.extensions {
		pages := map[string]map[string]interaction.Value{}
		for _, page := range extension.value.Pages {
			pages[page.ID] = copy_reader_value(page.Values)
		}
		if len(pages) > 0 {
			values[extension.session.TentacleID()] = pages
		}
	}
	if reflect.DeepEqual(values, worker.savedPages) {
		return nil
	}
	if err := worker.pageStore.Save(values); err != nil {
		return err
	}
	worker.savedPages = values
	return nil
}

type readerQuickSetting struct {
	key       string
	extension *readerExtension
	setting   tentaclewire.QuickSetting
}

func (worker *preferencesWorker) quick_settings() []readerQuickSetting {
	var result []readerQuickSetting
	for _, id := range sorted_extension_ids(worker.extensions) {
		extension := worker.extensions[id]
		for _, setting := range extension.value.QuickSettings {
			result = append(result, readerQuickSetting{id + "/" + setting.ID, extension, setting})
		}
	}
	return result
}
func (worker *preferencesWorker) handle_extension_quick(ctx context.Context, setting readerQuickSetting, adjust bool, delta int) {
	selected := 0
	for index, option := range setting.setting.Options {
		if option.ID == setting.setting.Selected {
			selected = index
			break
		}
	}
	candidate := selected
	if adjust {
		for index := selected + delta; index >= 0 && index < len(setting.setting.Options); index += delta {
			if !setting.setting.Options[index].Disabled {
				candidate = index
				break
			}
		}
	}
	option := setting.setting.Options[candidate]
	if candidate != selected {
		event := tentaclewire.ExtensionEvent{Event: "quick-setting", ID: setting.setting.ID, Selected: option.ID, Reader: worker.reader_state(setting.extension)}
		request, err := worker.extension_effect(ctx, setting.extension, setting.setting.Command, event)
		transaction := worker.reader_transaction()
		if err == nil {
			err = worker.stage_reader_request(ctx, &transaction, setting.extension.session, request)
		}
		if err == nil {
			found := false
			extension := transaction.extensions[setting.extension.session.Identity()]
			for index := range extension.value.QuickSettings {
				current := &extension.value.QuickSettings[index]
				if current.ID != setting.setting.ID {
					continue
				}
				for _, choice := range current.Options {
					if choice.ID == option.ID && !choice.Disabled {
						current.Selected = option.ID
						found = true
						break
					}
				}
			}
			if !found {
				err = errors.New("selected quick setting was removed by its callback")
			}
		}
		if err == nil {
			err = worker.commit_reader_transaction(ctx, setting.extension.session, transaction)
		}
		if err != nil {
			worker.logger.Warn("apply tentacle quick setting", "error", err)
			worker.announceSpeechSetting(setting.setting.Label + " was not changed")
			return
		}
	}
	worker.announceSpeechSetting(setting.setting.Label + " " + option.Label)
}

func (runtime *tentacleRuntime) reader_continuation(command tentacleCommand, id string) bool {
	for _, registered := range command.session.Commands() {
		if registered.ID == id {
			return registered.Reader && !registered.Settings
		}
	}
	return false
}