using System.Text.Json;
using WIDESEAWCS_S7Simulator.Application.Protocol;
using WIDESEAWCS_S7Simulator.Core.Protocol;

namespace WIDESEAWCS_S7Simulator.Server.Services;

public class FileProtocolTemplateService : IProtocolTemplateService
{
    private readonly string _filePath;
    private readonly SemaphoreSlim _lock = new(1, 1);
    private readonly JsonSerializerOptions _jsonOptions = new()
    {
        WriteIndented = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase
    };

    public FileProtocolTemplateService(string dataPath)
    {
        Directory.CreateDirectory(dataPath);
        _filePath = Path.Combine(dataPath, "protocol-templates.json");
    }

    public async Task<IReadOnlyList<ProtocolTemplate>> GetAllAsync()
    {
        await _lock.WaitAsync();
        try
        {
            var templates = await LoadUnsafeAsync();
            return templates.AsReadOnly();
        }
        finally
        {
            _lock.Release();
        }
    }

    public async Task<ProtocolTemplate?> GetByIdAsync(string id)
    {
        if (string.IsNullOrWhiteSpace(id))
        {
            return null;
        }

        await _lock.WaitAsync();
        try
        {
            var templates = await LoadUnsafeAsync();
            return templates.FirstOrDefault(t => string.Equals(t.Id, id, StringComparison.OrdinalIgnoreCase));
        }
        finally
        {
            _lock.Release();
        }
    }

    public async Task<ProtocolTemplate> UpsertAsync(ProtocolTemplate template)
    {
        if (template == null) throw new ArgumentNullException(nameof(template));
        if (string.IsNullOrWhiteSpace(template.Id)) throw new ArgumentException("Template id is required.", nameof(template));

        await _lock.WaitAsync();
        try
        {
            var templates = await LoadUnsafeAsync();
            var idx = templates.FindIndex(t => string.Equals(t.Id, template.Id, StringComparison.OrdinalIgnoreCase));
            if (idx >= 0)
            {
                templates[idx] = template;
            }
            else
            {
                templates.Add(template);
            }

            await SaveUnsafeAsync(templates);
            return template;
        }
        finally
        {
            _lock.Release();
        }
    }

    public async Task<bool> DeleteAsync(string id)
    {
        if (string.IsNullOrWhiteSpace(id))
        {
            return false;
        }

        await _lock.WaitAsync();
        try
        {
            var templates = await LoadUnsafeAsync();
            var removed = templates.RemoveAll(t => string.Equals(t.Id, id, StringComparison.OrdinalIgnoreCase)) > 0;
            if (removed)
            {
                await SaveUnsafeAsync(templates);
            }

            return removed;
        }
        finally
        {
            _lock.Release();
        }
    }

    public async Task<bool> ExistsAsync(string id)
    {
        return (await GetByIdAsync(id)) != null;
    }

    private async Task<List<ProtocolTemplate>> LoadUnsafeAsync()
    {
        if (!File.Exists(_filePath))
        {
            var defaults = CreateDefaultTemplates();
            await SaveUnsafeAsync(defaults);
            return defaults;
        }

        var content = await File.ReadAllTextAsync(_filePath);
        if (string.IsNullOrWhiteSpace(content))
        {
            return new List<ProtocolTemplate>();
        }

        return JsonSerializer.Deserialize<List<ProtocolTemplate>>(content, _jsonOptions) ?? new List<ProtocolTemplate>();
    }

    private async Task SaveUnsafeAsync(List<ProtocolTemplate> templates)
    {
        var content = JsonSerializer.Serialize(templates, _jsonOptions);
        await File.WriteAllTextAsync(_filePath, content);
    }

    private static List<ProtocolTemplate> CreateDefaultTemplates()
    {
        return new List<ProtocolTemplate>
        {
            new()
            {
                Id = "wcs-line-v260202",
                Name = "WCS-输送线对接协议 V260202",
                Version = "V260202",
                Fields = new List<ProtocolFieldMapping>
                {
                    // SEG01
                    new() { FieldKey = "SEG01_WCS_ACK", DbNumber = 1, Offset = 0, DataType = ProtocolDataType.Byte, Direction = ProtocolFieldDirection.WcsToPlc },
                    new() { FieldKey = "SEG01_WCS_TASK_ID", DbNumber = 1, Offset = 2, DataType = ProtocolDataType.DInt, Direction = ProtocolFieldDirection.WcsToPlc },
                    new() { FieldKey = "SEG01_WCS_TARGET_ID", DbNumber = 1, Offset = 6, DataType = ProtocolDataType.Int, Direction = ProtocolFieldDirection.WcsToPlc },
                    new() { FieldKey = "SEG01_PLC_STB", DbNumber = 1, Offset = 10, DataType = ProtocolDataType.Byte, Direction = ProtocolFieldDirection.PlcToWcs },
                    new() { FieldKey = "SEG01_PLC_TASK_ID", DbNumber = 1, Offset = 20, DataType = ProtocolDataType.DInt, Direction = ProtocolFieldDirection.PlcToWcs },
                    new() { FieldKey = "SEG01_PLC_TARGET_ID", DbNumber = 1, Offset = 24, DataType = ProtocolDataType.Int, Direction = ProtocolFieldDirection.PlcToWcs },
                    new() { FieldKey = "SEG01_PALLET_CODE", DbNumber = 1, Offset = 30, DataType = ProtocolDataType.String, Length = 32, Direction = ProtocolFieldDirection.Bidirectional },
                    // SEG02
                    new() { FieldKey = "SEG02_WCS_ACK", DbNumber = 2, Offset = 0, DataType = ProtocolDataType.Byte, Direction = ProtocolFieldDirection.WcsToPlc },
                    new() { FieldKey = "SEG02_WCS_TASK_ID", DbNumber = 2, Offset = 2, DataType = ProtocolDataType.DInt, Direction = ProtocolFieldDirection.WcsToPlc },
                    new() { FieldKey = "SEG02_WCS_TARGET_ID", DbNumber = 2, Offset = 6, DataType = ProtocolDataType.Int, Direction = ProtocolFieldDirection.WcsToPlc },
                    new() { FieldKey = "SEG02_PLC_STB", DbNumber = 2, Offset = 10, DataType = ProtocolDataType.Byte, Direction = ProtocolFieldDirection.PlcToWcs },
                    new() { FieldKey = "SEG02_PLC_TASK_ID", DbNumber = 2, Offset = 20, DataType = ProtocolDataType.DInt, Direction = ProtocolFieldDirection.PlcToWcs },
                    new() { FieldKey = "SEG02_PLC_TARGET_ID", DbNumber = 2, Offset = 24, DataType = ProtocolDataType.Int, Direction = ProtocolFieldDirection.PlcToWcs },
                    new() { FieldKey = "SEG02_PALLET_CODE", DbNumber = 2, Offset = 30, DataType = ProtocolDataType.String, Length = 32, Direction = ProtocolFieldDirection.Bidirectional }
                }
            }
        };
    }
}