/*
 * ============================================================================
 * Projekt.....: rs2322tcp
 * Datei.......: internal/client/application.go
 * Copyright (C) 2026 Dieter Lang
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * Beschreibung:
 * Gemeinsame Anwendungsschicht für den rs2322tcp-Client.
 *
 * Die Anwendungsschicht verbindet die Konfiguration, die Control-Verbindung
 * zum Server und die clientseitige Runtime. Sie stellt damit einen einfachen
 * Lebenszyklus für die spätere grafische Benutzeroberfläche bereit.
 *
 * Der technische Client wird bei Start und Reconnect vollständig neu
 * initialisiert:
 *
 *     Konfiguration laden
 *             |
 *             v
 *     Server verbinden
 *             |
 *             v
 *     Geräteliste abfragen
 *             |
 *             v
 *     Runtime starten
 *
 * Ein Reconnect beendet zunächst die bestehende Runtime und Control-
 * Verbindung und führt anschließend denselben Startablauf erneut aus.
 *
 * Die Anwendungsschicht enthält bewusst keine GUI-Logik und keine
 * Fyne-Abhängigkeit.
 * ============================================================================
 */
package client

import (
	"fmt"
	"sync"

	"git.lang-dieter.de/rs2322tcp/internal/config"
	"git.lang-dieter.de/rs2322tcp/internal/transport"
)

///////////////////////////////////////////////////////////////////////////////
// Application
///////////////////////////////////////////////////////////////////////////////

// Application represents one running rs2322tcp client application.
//
// Application owns the current client connection and Runtime. The
// configuration file is the persistent source of the client configuration.
//
// The Application is intended to be used by the command-line entry point
// as well as by the later graphical user interface.
type Application struct {
	mu sync.Mutex

	configFile string

	config  *config.ClientConfig
	client  *Client
	runtime *Runtime
	devices []transport.RemoteDeviceInfo

	runtimeDone chan error
}

// NewApplication creates a new client Application.
//
// The client configuration is loaded immediately. No network connection
// is established. Start must be called before the application connects to
// the server or starts the Runtime.
func NewApplication(configFile string) (*Application, error) {
	if configFile == "" {
		return nil, fmt.Errorf("configuration file is empty")
	}

	cfg, err := config.LoadClient(configFile)
	if err != nil {
		return nil, fmt.Errorf("load client configuration: %w", err)
	}

	return &Application{
		configFile: configFile,
		config:     cfg,
	}, nil
}

///////////////////////////////////////////////////////////////////////////////
// Start
///////////////////////////////////////////////////////////////////////////////

// Start loads the client configuration, connects to the server and starts
// the client Runtime.
//
// The Runtime is started asynchronously because Runtime.Run blocks while
// the configured virtual serial connections are active.
func (a *Application) Start() error {
	if a == nil {
		return fmt.Errorf("application is nil")
	}

	a.mu.Lock()

	if a.runtime != nil || a.client != nil {
		a.mu.Unlock()

		return fmt.Errorf("application is already running")
	}

	a.mu.Unlock()

	cfg, err := config.LoadClient(a.configFile)
	if err != nil {
		return fmt.Errorf("load client configuration: %w", err)
	}

	address := fmt.Sprintf(
		"%s:%d",
		cfg.Server.Address,
		cfg.Server.Port,
	)

	client, err := New(address)
	if err != nil {
		return err
	}

	devices, err := client.GetDevices()
	if err != nil {
		_ = client.Close()

		return fmt.Errorf("get remote devices: %w", err)
	}

	manager := NewVirtualPortManager(
		cfg.VirtualPortRange,
	)

	runtime, err := NewRuntime(
		client,
		manager,
	)
	if err != nil {
		_ = client.Close()

		return fmt.Errorf("create runtime: %w", err)
	}

	runtimeDone := make(chan error, 1)

	a.mu.Lock()

	a.config = cfg
	a.client = client
	a.runtime = runtime
	a.devices = append(
		[]transport.RemoteDeviceInfo(nil),
		devices...,
	)
	a.runtimeDone = runtimeDone

	a.mu.Unlock()

	go func() {
		runtimeDone <- runtime.Run(*cfg)
	}()

	return nil
}

///////////////////////////////////////////////////////////////////////////////
// Reconnect
///////////////////////////////////////////////////////////////////////////////

// Reconnect stops the current client connection and starts it again.
//
// The configuration file is loaded again during Start. This is intentional:
// changes made by the GUI are therefore picked up automatically.
//
// Reconnect is also useful when the server connection has been lost or the
// user explicitly requests a new connection.
func (a *Application) Reconnect() error {
	if a == nil {
		return fmt.Errorf("application is nil")
	}

	if err := a.Close(); err != nil {
		return fmt.Errorf("close current connection: %w", err)
	}

	return a.Start()
}

///////////////////////////////////////////////////////////////////////////////
// Close
///////////////////////////////////////////////////////////////////////////////

// Close stops the Runtime and closes the client control connection.
//
// Calling Close more than once is safe.
func (a *Application) Close() error {
	if a == nil {
		return nil
	}

	a.mu.Lock()

	runtime := a.runtime
	client := a.client

	a.runtime = nil
	a.client = nil
	a.devices = nil
	a.runtimeDone = nil

	a.mu.Unlock()

	var firstErr error

	if runtime != nil {
		if err := runtime.Close(); err != nil {
			firstErr = err
		}
	} else if client != nil {
		if err := client.Close(); err != nil {
			firstErr = err
		}
	}

	return firstErr
}

// Config returns a copy of the currently loaded client configuration.
//
// The configuration is available after NewApplication, even when the
// server connection has not yet been established.
func (a *Application) Config() *config.ClientConfig {
	if a == nil {
		return nil
	}

	a.mu.Lock()
	defer a.mu.Unlock()

	if a.config == nil {
		return nil
	}

	cfg := *a.config

	cfg.VirtualPorts = append(
		[]config.VirtualPortConfig(nil),
		a.config.VirtualPorts...,
	)

	return &cfg
}

///////////////////////////////////////////////////////////////////////////////
// Devices
///////////////////////////////////////////////////////////////////////////////

// Devices returns a copy of the remote devices received from the server.
//
// The returned slice belongs to the caller and can therefore be modified
// without changing the Application state.
func (a *Application) Devices() []transport.RemoteDeviceInfo {
	if a == nil {
		return nil
	}

	a.mu.Lock()
	defer a.mu.Unlock()

	return append(
		[]transport.RemoteDeviceInfo(nil),
		a.devices...,
	)
}

///////////////////////////////////////////////////////////////////////////////
// Runtime state
///////////////////////////////////////////////////////////////////////////////

// Running reports whether the application currently owns a Runtime and a
// client connection.
func (a *Application) Running() bool {
	if a == nil {
		return false
	}

	a.mu.Lock()
	defer a.mu.Unlock()

	return a.runtime != nil && a.client != nil
}
// SaveConfig saves the supplied client configuration to the configuration
// file used by this Application.
//
// After a successful save the supplied configuration also becomes the
// current in-memory configuration.
//
// The running Runtime is not restarted automatically. A subsequent
// Reconnect or application restart will use the saved configuration.
func (a *Application) SaveConfig(
	cfg *config.ClientConfig,
) error {
	if a == nil {
		return fmt.Errorf("application is nil")
	}

	if cfg == nil {
		return fmt.Errorf("client configuration is nil")
	}

	if err := config.SaveClient(a.configFile, cfg); err != nil {
		return err
	}

	a.mu.Lock()
	a.config = cfg
	a.mu.Unlock()

	return nil
}