using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using RobotNet10.MapManager.Data;

namespace RobotNet10.MapManager.Services;

/// <summary>
/// Service for generating unique node and edge names using 8-character GUIDs
/// Concurrent-safe and optimized for Import/Export scenarios
/// </summary>
public class LayoutLevelNamingService(MapDbContext context)
{
    private readonly MapDbContext _context = context;
    
    private const int GUID_LENGTH = 8;
    private const int MAX_RETRIES = 5;

    /// <summary>
    /// Generate unique node name using 8-character GUID
    /// Format: "Node_a7f2e3b1"
    /// </summary>
    /// <param name="levelId">Layout level ID</param>
    /// <returns>Generated node name or empty string if auto-generate is disabled</returns>
    /// <exception cref="InvalidOperationException">If cannot generate unique name after retries</exception>
    public async Task<string> GenerateNodeNameAsync(Guid levelId)
    {
        var settings = await GetOrCreateSettingsAsync(levelId);

        if (!settings.NodeNameAutoGenerate)
            return string.Empty;

        // Try to generate unique name with retries
        for (int attempt = 0; attempt < MAX_RETRIES; attempt++)
        {
            var guid = Guid.NewGuid().ToString("N"); // No hyphens
            var shortGuid = guid[..GUID_LENGTH];
            var nodeName = $"N_{shortGuid}";

            // Check uniqueness (indexed query, very fast)
            bool exists = await _context.Nodes
                .AnyAsync(n => n.LevelId == levelId && n.NodeName == nodeName);

            if (!exists) return nodeName;
        }

        // Extremely unlikely to reach here (probability < 0.00001%)
        throw new InvalidOperationException(
            $"Failed to generate unique node name after {MAX_RETRIES} attempts. " +
            "This is extremely unlikely. Please contact system administrator.");
    }

    /// <summary>
    /// Generate unique edge name using 8-character GUID
    /// Format: "Edge_a7f2e3b1"
    /// </summary>
    /// <param name="levelId">Layout level ID</param>
    /// <returns>Generated edge name or empty string if auto-generate is disabled</returns>
    /// <exception cref="InvalidOperationException">If cannot generate unique name after retries</exception>
    public async Task<string> GenerateEdgeNameAsync(Guid levelId)
    {
        var settings = await GetOrCreateSettingsAsync(levelId);

        if (!settings.EdgeNameAutoGenerate)
            return string.Empty;

        // Try to generate unique name with retries
        for (int attempt = 0; attempt < MAX_RETRIES; attempt++)
        {
            var guid = Guid.NewGuid().ToString("N"); // No hyphens
            var shortGuid = guid.Substring(0, GUID_LENGTH);
            var edgeName = $"E_{shortGuid}";

            // Check uniqueness (indexed query, very fast)
            bool exists = await _context.Edges
                .AnyAsync(e => e.LevelId == levelId && e.EdgeName == edgeName);

            if (!exists) return edgeName;
        }

        // Extremely unlikely to reach here (probability < 0.00001%)
        throw new InvalidOperationException(
            $"Failed to generate unique edge name after {MAX_RETRIES} attempts. " +
            "This is extremely unlikely. Please contact system administrator.");
    }

    /// <summary>
    /// Preview example generated names
    /// </summary>
    /// <param name="count">Number of examples to generate</param>
    /// <returns>Array of example names</returns>
    public static string[] PreviewNodeNames(int count = 5)
    {
        var examples = new string[count];
        for (int i = 0; i < count; i++)
        {
            var guid = Guid.NewGuid().ToString("N");
            examples[i] = $"Node_{guid.Substring(0, GUID_LENGTH)}";
        }
        return examples;
    }

    /// <summary>
    /// Preview example generated edge names
    /// </summary>
    /// <param name="count">Number of examples to generate</param>
    /// <returns>Array of example names</returns>
    public static string[] PreviewEdgeNames(int count = 5)
    {
        var examples = new string[count];
        for (int i = 0; i < count; i++)
        {
            var guid = Guid.NewGuid().ToString("N");
            examples[i] = $"Edge_{guid.Substring(0, GUID_LENGTH)}";
        }
        return examples;
    }

    /// <summary>
    /// Get or create editor settings for a layout level
    /// </summary>
    private async Task<LayoutLevelEditorSettings> GetOrCreateSettingsAsync(Guid levelId)
    {
        var settings = await _context.LayoutLevelEditorSettings
            .FirstOrDefaultAsync(s => s.LevelId == levelId);

        if (settings == null)
        {
            // Auto-create settings with defaults if not exists
            settings = new LayoutLevelEditorSettings
            {
                LevelId = levelId,
                // Defaults are set in the entity class
            };

            _context.LayoutLevelEditorSettings.Add(settings);
            await _context.SaveChangesAsync();
        }

        return settings;
    }

    /// <summary>
    /// Update editor settings for a layout level
    /// </summary>
    public async Task UpdateSettingsAsync(Guid levelId, Action<LayoutLevelEditorSettings> updateAction)
    {
        var settings = await GetOrCreateSettingsAsync(levelId);
        updateAction(settings);
        settings.ModifiedDate = DateTime.UtcNow;
        await _context.SaveChangesAsync();
    }

    /// <summary>
    /// Get current editor settings (read-only)
    /// </summary>
    public async Task<LayoutLevelEditorSettings?> GetSettingsAsync(Guid levelId)
    {
        return await _context.LayoutLevelEditorSettings
            .AsNoTracking()
            .FirstOrDefaultAsync(s => s.LevelId == levelId);
    }

    /// <summary>
    /// Get collision statistics (for monitoring)
    /// </summary>
    public async Task<(int TotalNodes, int TotalEdges)> GetLevelStatisticsAsync(Guid levelId)
    {
        var nodeCount = await _context.Nodes.CountAsync(n => n.LevelId == levelId);
        var edgeCount = await _context.Edges.CountAsync(e => e.LevelId == levelId);
        return (nodeCount, edgeCount);
    }
}