using System.Text;
using Microsoft.AspNetCore.Components;
using Microsoft.JSInterop;
using SharepointToolbox.Web.Services.Audit;
using SharepointToolbox.Web.Services.Session;

namespace SharepointToolbox.Web.Services.Export;

/// <summary>
/// Triggers browser file downloads from Blazor Server components.
/// Converts string export outputs to bytes and invokes JS download.
/// Every download is audit-logged as a report-export action.
/// </summary>
public class WebExportService
{
    private readonly IJSRuntime          _js;
    private readonly IAuditService        _audit;
    private readonly IUserSessionService  _session;

    public WebExportService(IJSRuntime js, IAuditService audit, IUserSessionService session)
    {
        _js      = js;
        _audit   = audit;
        _session = session;
    }

    public async Task DownloadCsvAsync(string content, string fileName)
    {
        var bytes = new UTF8Encoding(encoderShouldEmitUTF8Identifier: true).GetBytes(content);
        await _js.InvokeVoidAsync("sptb.downloadFile", fileName, "text/csv;charset=utf-8", Convert.ToBase64String(bytes));
        await LogExportAsync(fileName, bytes.Length);
    }

    public async Task DownloadHtmlAsync(string content, string fileName)
    {
        var bytes = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false).GetBytes(content);
        await _js.InvokeVoidAsync("sptb.downloadFile", fileName, "text/html;charset=utf-8", Convert.ToBase64String(bytes));
        await LogExportAsync(fileName, bytes.Length);
    }

    /// <summary>
    /// Downloads pre-encoded bytes (e.g. a ZIP or a merged report produced by
    /// <see cref="ReportMergeHelper"/>) with an explicit MIME type.
    /// </summary>
    public async Task DownloadBytesAsync(byte[] content, string fileName, string mime)
    {
        await _js.InvokeVoidAsync("sptb.downloadFile", fileName, mime, Convert.ToBase64String(content));
        await LogExportAsync(fileName, content.Length);
    }

    /// <summary>
    /// Records the download as a "ReportExport" audit entry. The file name encodes
    /// the report kind (search_, permissions_, storage_, …) and timestamp.
    /// </summary>
    private Task LogExportAsync(string fileName, int byteCount)
    {
        var client = _session.CurrentProfile?.Name ?? string.Empty;
        var sizeKb = (byteCount / 1024.0).ToString("F1");
        return _audit.LogAsync("ReportExport", client, Array.Empty<string>(), $"{fileName} ({sizeKb} KB)");
    }
}