using System.Text.Json;
using System.Text.Json.Serialization;
using FinlyticAssets.Models;
using FinlyticAssets.Util;

namespace FinlyticAssets.Services;

/// <summary>
/// Provides methods for generating the indexed asset reference file and downloading local asset logos strictly on demand.
/// </summary>
public interface IAssetsIndexService
{
    /// <summary>
    /// Recreates the index file containing basic asset identifiers (ISIN and Name) for all active, valid assets.
    /// </summary>
    /// <param name="cancellationToken">A token to monitor for cancellation requests.</param>
    /// <returns>A task that represents the asynchronous operation.</returns>
    public Task ReCreateIndexFileAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Strictly On Demand: Downloads and saves the logo SVG for a requested ISIN into the local assets/logos folder.
    /// </summary>
    public Task<string?> DownloadAndSaveLogoAsync(string isin, CancellationToken cancellationToken = default);
}

/// <summary>
/// Implements the <see cref="IAssetsIndexService"/> to maintain local asset index references and logo file storage.
/// </summary>
public class AssetsIndexService : IAssetsIndexService
{
    private readonly ILogger<AssetsIndexService> _logger;
    private readonly IAssetsDbService _assetsDbService;
    private static readonly HttpClient _httpClient = new();

    /// <summary>
    /// Initializes a new instance of the <see cref="AssetsIndexService"/> class.
    /// </summary>
    /// <param name="logger">The logger for documenting indexing events and errors.</param>
    /// <param name="assetsDbService">The database service to query the assets from.</param>
    public AssetsIndexService(ILogger<AssetsIndexService> logger, IAssetsDbService assetsDbService)
    {
        _logger = logger;
        _assetsDbService = assetsDbService;
    }

    /// <summary>Inherits documentation from interface.</summary>
    public async Task ReCreateIndexFileAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            var assets = await _assetsDbService.GetAllValidAssetsAsync();
            if (assets == null || !assets.Any())
            {
                _logger.LogWarning("[{Channel}] No valid assets found in the database to index.", "AssetsChannel");
                return;
            }

            var indexAssets = assets
                .DistinctBy(a => a.Isin)
                .Select(a => {
                    string cleanIsin = a.Isin.Trim().ToUpperInvariant();
                    // Point directly to our own local backend logo endpoint
                    string imageUrl = $"/api/v1/logo/{cleanIsin}";
                    return new AssetIndex(cleanIsin, a.Name, imageUrl);
                }).ToList();

            var directoryPath = Volumes.IndexRelativePath;
            var filePath = Path.Combine(directoryPath, "index.json");

            if (!Directory.Exists(directoryPath))
            {
                Directory.CreateDirectory(directoryPath);
            }

            using (var fileStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, 4096,
                       useAsync: true))
            {
                await JsonSerializer.SerializeAsync(fileStream, indexAssets, cancellationToken: cancellationToken);
            }

            _logger.LogInformation("[{Channel}] Successfully recreated asset index file with {Count} entries pointing to local logos at {Path}",
                "AssetsChannel", indexAssets.Count, filePath);
        }
        catch (IOException ex)
        {
            _logger.LogError(ex, "[{Channel}] Disk I/O error occurred while writing the asset index file.", "AssetsChannel");
            throw;
        }
        catch (JsonException ex)
        {
            _logger.LogError(ex, "[{Channel}] Failed to serialize the asset index data to JSON.", "AssetsChannel");
            throw;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "[{Channel}] An unexpected error occurred while recreating the asset index file.", "AssetsChannel");
            throw;
        }
    }

    /// <summary>Inherits documentation from interface.</summary>
    public async Task<string?> DownloadAndSaveLogoAsync(string isin, CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(isin)) return null;

        string cleanIsin = isin.Trim().ToUpperInvariant();
        string directoryPath = Volumes.LogosRelativePath;
        string filePath = Path.Combine(directoryPath, $"{cleanIsin}.svg");

        if (!Directory.Exists(directoryPath))
        {
            Directory.CreateDirectory(directoryPath);
        }

        if (File.Exists(filePath))
        {
            return filePath;
        }

        string targetUrl = $"https://assets.traderepublic.com/img/logos/{cleanIsin}/v2/dark.min.svg";

        try
        {
            using var request = new HttpRequestMessage(HttpMethod.Get, targetUrl);
            request.Headers.TryAddWithoutValidation("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36");
            request.Headers.TryAddWithoutValidation("Accept", "image/svg+xml,image/*,*/*");
            request.Headers.TryAddWithoutValidation("Referer", "https://traderepublic.com/");

            using var response = await _httpClient.SendAsync(request, cancellationToken);
            if (response.IsSuccessStatusCode)
            {
                byte[] data = await response.Content.ReadAsByteArrayAsync(cancellationToken);
                await File.WriteAllBytesAsync(filePath, data, cancellationToken);
                _logger.LogInformation("[{Channel}] Successfully saved logo SVG for ISIN {Isin} to {Path} on demand", "AssetsChannel", cleanIsin, filePath);
                return filePath;
            }
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "[{Channel}] Failed to download logo for ISIN {Isin} from {Url}", "AssetsChannel", cleanIsin, targetUrl);
        }

        return null;
    }
}