using System.ComponentModel;
using System.Linq.Expressions;
using ErsatzTV.Application.Logs;
using ErsatzTV.Core.Api.Logs;
using ErsatzTV.Filters;
using MediatR;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace ErsatzTV.Controllers.Api;

[ApiController]
[RequiresAuthentication]
public class LogsController(IMediator mediator) : ControllerBase
{
    private const int MaxPageSize = 100;

    // Mirrors the sortable columns from the legacy Blazor Logs.razor (MudTableSortLabel on
    // Timestamp/Level; Message was never sortable there either).
    private static readonly System.Collections.Generic.HashSet<string> AllowedSortFields =
        new(StringComparer.OrdinalIgnoreCase) { "timestamp", "level" };

    [HttpGet("/api/v1/logs", Name = "GetLogs")]
    [Tags("Logs")]
    [EndpointSummary("Get recent log entries")]
    [EndpointDescription(
        "sortField is validated against an allow-list (timestamp, level); an unrecognized value " +
        "falls back to timestamp. sortDirection accepts asc/desc and falls back to desc (the " +
        "pre-existing default, newest first).")]
    [EndpointGroupName("general")]
    [ProducesResponseType(typeof(PagedLogEntriesResponseModel), StatusCodes.Status200OK)]
    public async Task<PagedLogEntriesResponseModel> GetLogs(
        [FromQuery]
        [Description("0-based page index: the first page is 0, not 1. A negative value is clamped to 0.")]
        int pageNum = 0,
        [FromQuery]
        [Description("Rows per page (default 100); capped at 100 for this endpoint. The page offset is derived from the effective (capped) size, so a larger value narrows the page instead of widening the offset.")]
        int pageSize = 100,
        [FromQuery] string filter = "",
        [FromQuery] string sortField = "timestamp",
        [FromQuery] string sortDirection = "desc",
        CancellationToken cancellationToken = default)
    {
        int clampedPageNum = Math.Max(0, pageNum);
        int clampedPageSize = Math.Clamp(pageSize, 1, MaxPageSize);

        string normalizedSortField = AllowedSortFields.Contains(sortField ?? string.Empty)
            ? sortField!.ToLowerInvariant()
            : "timestamp";
        bool descending = !string.Equals(sortDirection, "asc", StringComparison.OrdinalIgnoreCase);

        Expression<Func<LogEntryViewModel, object>> sortExpression = normalizedSortField switch
        {
            "level" => le => le.Level,
            _ => le => le.Timestamp
        };

        PagedLogEntriesViewModel result = await mediator.Send(
            new GetRecentLogEntries(clampedPageNum, clampedPageSize, filter ?? string.Empty)
            {
                SortExpression = sortExpression,
                SortDescending = descending
            },
            cancellationToken);

        return new PagedLogEntriesResponseModel(
            result.TotalCount,
            result.Page.Map(ProjectToResponseModel).ToList());
    }

    private static LogEntryResponseModel ProjectToResponseModel(LogEntryViewModel viewModel) =>
        new(viewModel.Timestamp, viewModel.Level.ToString(), viewModel.Message);
}