package app

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"sync"
	"time"

	"git.stormux.org/storm/cthulhu/internal/braille"
	"git.stormux.org/storm/cthulhu/internal/review"
)

// brailleWorker keeps all BrlAPI calls in a disposable child process. Only the
// newest frame is retained; focus and input callbacks never wait for the display.
// mu owns frames, flash generations, routing cancellation and session flags.
// The session joins its child and pipe workers before reconnecting; routing
// events retain their own bounded FIFO and validate the current frame identity.
type brailleWorker struct {
	internalUIFrame *braille.Frame
	router          brailleRouter
	document        *review.Worker
	ocr             *ocrSession
	sequence        uint64
	routeCancel     context.CancelFunc
	secure          bool
	stopping        bool
	connected       bool
	logger          *slog.Logger
	path            string
	mu              sync.Mutex
	frame           braille.Frame
	baseFrame       braille.Frame
	flashTimer      *time.Timer
	flashGeneration uint64
	flashContext    context.Context // A tentacle flash expires with its command/session.
	protectedFlash  bool            // Focus updates retain baseFrame until expiry or user input.
	contracted      bool
	wordWrap        bool
	table           string
	wake            chan struct{}
	cancel          context.CancelFunc
	done            chan struct{}
}

func newBrailleWorker(logger *slog.Logger) (*brailleWorker, error) {
	executable, err := os.Executable()
	if err != nil {
		return nil, err
	}
	return &brailleWorker{logger: logger, path: filepath.Join(filepath.Dir(executable), "cthulhu-braille"),
		frame: braille.Frame{Cursor: -1}, baseFrame: braille.Frame{Cursor: -1}, wake: make(chan struct{}, 1)}, nil
}

func (worker *brailleWorker) Start() error {
	worker.mu.Lock()
	defer worker.mu.Unlock()
	if worker.stopping {
		return errors.New("braille helper shutdown is still pending")
	}
	if worker.cancel != nil {
		return nil
	}
	info, err := os.Stat(worker.path)
	if err != nil || info.IsDir() || info.Mode()&0111 == 0 {
		return fmt.Errorf("braille helper %q is unavailable; build cthulhu-braille with -tags brlapi", worker.path)
	}
	ctx, cancel := context.WithCancel(context.Background())
	worker.cancel = cancel
	worker.done = make(chan struct{})
	go worker.run(ctx, worker.done)
	return nil
}

func (worker *brailleWorker) Stop(ctx context.Context) error {
	worker.mu.Lock()
	cancel, done := worker.cancel, worker.done
	if cancel == nil {
		worker.mu.Unlock()
		return nil
	}
	worker.stopping = true
	if worker.routeCancel != nil {
		worker.routeCancel()
	}
	worker.mu.Unlock()
	cancel()
	select {
	case <-done:
		worker.mu.Lock()
		if worker.done == done {
			worker.cancel, worker.done = nil, nil
			worker.stopping = false
			worker.connected = false
			worker.protectedFlash = false
			worker.flashContext = nil
			worker.frame = braille.Frame{Cursor: -1}
			worker.baseFrame = braille.Frame{Cursor: -1}
			if worker.flashTimer != nil {
				worker.flashTimer.Stop()
				worker.flashTimer = nil
			}
		}
		worker.mu.Unlock()
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}

func (worker *brailleWorker) Configure(ctx context.Context, enabled bool) error {
	if enabled {
		return worker.Start()
	}
	return worker.Stop(ctx)
}

func (worker *brailleWorker) Running() bool {
	worker.mu.Lock()
	defer worker.mu.Unlock()
	return worker.cancel != nil && !worker.stopping && worker.connected
}