/*
 * ============================================================================
 * Projekt.....: rs2322tcp
 * Datei.......: internal/client/virtual_port_validation.go
 * Copyright (C) 2026 Dieter Lang
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * Beschreibung:
 * Plattformneutrale Prüfung der in client.json definierten virtuellen Ports
 * gegen die tatsächlich vorhandenen virtuellen Schnittstellen.
 *
 * Die Ermittlung der vorhandenen Ports erfolgt über die
 * plattformabhängige Funktion existingVirtualPortLinks().
 * ============================================================================
 */
package client

import (
	"fmt"
	"sort"
	"strings"

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

///////////////////////////////////////////////////////////////////////////////
// Virtual port validation
///////////////////////////////////////////////////////////////////////////////

// VirtualPortValidationResult contains the differences between configured
// and locally available virtual ports.
type VirtualPortValidationResult struct {
	Missing []string
	Extra   []string
}

// compareVirtualPorts compares the configured virtual ports with the
// locally available virtual ports.
//
// Missing contains ports configured in client.json that are not available
// locally.
//
// Extra contains locally available ports that are not configured in
// client.json.
//
// The order of both input lists is irrelevant.
func compareVirtualPorts(
	configured []string,
	available []string,
) VirtualPortValidationResult {
	configuredSet := make(map[string]struct{}, len(configured))

	for _, port := range configured {
		configuredSet[port] = struct{}{}
	}

	availableSet := make(map[string]struct{}, len(available))

	for _, port := range available {
		availableSet[port] = struct{}{}
	}

	result := VirtualPortValidationResult{
		Missing: make([]string, 0),
		Extra:   make([]string, 0),
	}

	for port := range configuredSet {
		if _, ok := availableSet[port]; ok {
			continue
		}

		result.Missing = append(result.Missing, port)
	}

	for port := range availableSet {
		if _, ok := configuredSet[port]; ok {
			continue
		}

		result.Extra = append(result.Extra, port)
	}

	sort.Strings(result.Missing)
	sort.Strings(result.Extra)

	return result
}

///////////////////////////////////////////////////////////////////////////////
// Local virtual-port validation
///////////////////////////////////////////////////////////////////////////////

// validateLocalVirtualPorts compares the virtual ports defined in
// client.json with the virtual ports currently available on the local
// computer.
//
// The detection of available ports is performed by the platform-specific
// existingVirtualPortLinks() implementation.
//
// A mismatch prevents the client from starting.
func validateLocalVirtualPorts(
	cfg *config.ClientConfig,
) error {
	if cfg == nil {
		return fmt.Errorf("client configuration is nil")
	}

	configured := make(
		[]string,
		0,
		len(cfg.VirtualPorts),
	)

	for _, virtualPort := range cfg.VirtualPorts {
		configured = append(
			configured,
			virtualPort.Port,
		)
	}

	available, err := existingVirtualPortLinks(
		cfg.VirtualPortRange,
	)
	if err != nil {
		return fmt.Errorf(
			"prüfen der virtuellen Ports fehlgeschlagen: %w",
			err,
		)
	}

	result := compareVirtualPorts(
		configured,
		available,
	)

	if len(result.Missing) == 0 &&
		len(result.Extra) == 0 {
		return nil
	}

	var message strings.Builder

	////////////////////////////////////////////////////////////////////////////
	// Missing ports
	////////////////////////////////////////////////////////////////////////////

	if len(result.Missing) > 0 &&
		len(result.Extra) == 0 {

		message.WriteString(
			"Virtuelle Ports nicht eingerichtet",
		)

		message.WriteString(
			"\n\nFolgende Ports sind in client.json " +
				"eingetragen, aber auf diesem Rechner " +
				"nicht eingerichtet:\n\n",
		)

		for _, port := range result.Missing {
			message.WriteString("  ")
			message.WriteString(port)
			message.WriteByte('\n')
		}

		message.WriteString(
			"\nBitte richten Sie diese virtuellen Ports " +
				"entsprechend der Installationsanleitung ein.",
		)

		return fmt.Errorf(
			"%s",
			strings.TrimSpace(message.String()),
		)
	}

	////////////////////////////////////////////////////////////////////////////
	// Extra ports
	////////////////////////////////////////////////////////////////////////////

	if len(result.Missing) == 0 &&
		len(result.Extra) > 0 {

		message.WriteString(
			"Virtuelle Ports nicht konfiguriert",
		)

		message.WriteString(
			"\n\nFolgende virtuelle Ports sind auf diesem " +
				"Rechner eingerichtet, aber nicht in " +
				"client.json eingetragen:\n\n",
		)

		for _, port := range result.Extra {
			message.WriteString("  ")
			message.WriteString(port)
			message.WriteByte('\n')
		}

		message.WriteString(
			"\nBitte ergänzen Sie die entsprechenden " +
				"Einträge in client.json.",
		)

		return fmt.Errorf(
			"%s",
			strings.TrimSpace(message.String()),
		)
	}

	////////////////////////////////////////////////////////////////////////////
	// Missing and extra ports
	////////////////////////////////////////////////////////////////////////////

	message.WriteString(
		"Virtuelle Portkonfiguration stimmt nicht überein",
	)

	message.WriteString(
		"\n\nIn client.json eingetragen, aber nicht " +
			"eingerichtet:\n\n",
	)

	for _, port := range result.Missing {
		message.WriteString("  ")
		message.WriteString(port)
		message.WriteByte('\n')
	}

	message.WriteString(
		"\nEingerichtet, aber nicht in client.json " +
			"eingetragen:\n\n",
	)

	for _, port := range result.Extra {
		message.WriteString("  ")
		message.WriteString(port)
		message.WriteByte('\n')
	}

	message.WriteString(
		"\nBitte korrigieren Sie die virtuelle " +
			"Portkonfiguration.",
	)

	return fmt.Errorf(
		"%s",
		strings.TrimSpace(message.String()),
	)
}