using HSchool.People;
using HSchool.Schedule;
using HSchool.Server.Game;

namespace HSchool.Server.Api;

internal static class TimetableEndpoints
{
    private static readonly TimeSpan CommandTimeout = TimeSpan.FromSeconds(5);

    public static void MapTimetableEndpoints(this IEndpointRouteBuilder builder)
    {
        var schools = builder.MapGroup("/api/schools");

        schools.MapGet("/{id:int}/timetable", (
            int id,
            string? classId,
            string? personId,
            string? lang,
            GameLoopService loop) =>
        {
            var published = loop.FindPeople(id);
            if (published is null)
            {
                return Problem(StatusCodes.Status404NotFound, "unknown-school", "That school does not exist.");
            }

            return Results.Ok(MapTimetable(published, loop.Options.SchoolWeekDays, ParseLocale(lang), classId, personId));
        })
        .WithName("GetSchoolTimetable");

        schools.MapPost("/{id:int}/timetable/pin", async (
            int id,
            PinLessonRequest request,
            string? lang,
            GameCommandQueue commands,
            GameLoopService loop,
            CancellationToken cancellationToken) =>
        {
            if (!TryDefName(request.ClassId, "classId", out var classId, out var error)
                || !TryDefName(request.Subject, "subject", out var subject, out error)
                || !TryDefName(request.RoomId, "roomId", out var roomId, out error))
            {
                return Problem(StatusCodes.Status400BadRequest, "invalid-query", error);
            }

            var command = new GameCommand.PinLesson(
                id,
                classId,
                subject,
                roomId,
                request.Day,
                request.Period,
                NewCompletion<TimetableOutcome>());
            commands.Enqueue(command);
            var outcome = await command.Result.Task.WaitAsync(CommandTimeout, cancellationToken);
            return TimetableResult(id, outcome, loop, ParseLocale(lang), classId: null, personId: null);
        })
        .WithName("PinSchoolLesson");

        schools.MapDelete("/{id:int}/timetable/pin", async (
            int id,
            string? classId,
            string? subject,
            int? day,
            int? period,
            string? lang,
            GameCommandQueue commands,
            GameLoopService loop,
            CancellationToken cancellationToken) =>
        {
            if (!TryDefName(classId, "classId", out var classValue, out var error)
                || !TryDefName(subject, "subject", out var subjectValue, out error)
                || day is null
                || period is null)
            {
                return Problem(
                    StatusCodes.Status400BadRequest,
                    "invalid-query",
                    error.Length > 0 ? error : "classId, subject, day and period are required.");
            }

            var command = new GameCommand.UnpinLesson(
                id,
                classValue,
                subjectValue,
                day.Value,
                period.Value,
                NewCompletion<TimetableOutcome>());
            commands.Enqueue(command);
            var outcome = await command.Result.Task.WaitAsync(CommandTimeout, cancellationToken);
            return TimetableResult(id, outcome, loop, ParseLocale(lang), classId: null, personId: null);
        })
        .WithName("UnpinSchoolLesson");
    }

    private static TaskCompletionSource<T> NewCompletion<T>() =>
        new(TaskCreationOptions.RunContinuationsAsynchronously);

    private static string ParseLocale(string? lang) =>
        string.Equals(lang, "en", StringComparison.OrdinalIgnoreCase) ? "en" : "ru";

    private static TimetableResponse MapTimetable(
        PublishedSchoolPeople published,
        int weekDays,
        string locale,
        string? classId,
        string? personId)
    {
            var table = published.Timetable ?? new Timetable([], []);
            var roster = published.Roster ?? new Roster([], [], []);
            if (published.Catalog is null)
            {
                return new TimetableResponse(weekDays, 0, [], [], [], []);
            }

            return TimetableMapper.From(
                table,
                roster,
                published.Catalog,
                published.Map,
                weekDays,
                locale,
                classId,
                personId);
    }

    private static IResult TimetableResult(
        int schoolId,
        TimetableOutcome outcome,
        GameLoopService loop,
        string locale,
        string? classId,
        string? personId)
    {
        if (outcome.Error != TimetableError.None)
        {
            return TimetableProblem(outcome.Error);
        }

        var published = loop.FindPeople(schoolId);
        if (published is null)
        {
            return Problem(StatusCodes.Status404NotFound, "unknown-school", "That school does not exist.");
        }

        return Results.Ok(MapTimetable(published, loop.Options.SchoolWeekDays, locale, classId, personId));
    }

    private static IResult TimetableProblem(TimetableError error) =>
        error switch
        {
            TimetableError.UnknownClass =>
                Problem(StatusCodes.Status400BadRequest, "unknown-class", "That class is not in the school."),
            TimetableError.UnknownSubject =>
                Problem(StatusCodes.Status400BadRequest, "unknown-subject", "That subject is not in the catalog."),
            TimetableError.UnknownRoom =>
                Problem(StatusCodes.Status400BadRequest, "unknown-room", "That room is not on the map."),
            TimetableError.NoTeacher =>
                Problem(StatusCodes.Status409Conflict, "no-teacher", "Nobody is assigned that subject."),
            TimetableError.PinRejected =>
                Problem(StatusCodes.Status409Conflict, "pin-rejected", "That slot or room violates the timetable constraints."),
            TimetableError.UnknownLesson =>
                Problem(StatusCodes.Status404NotFound, "unknown-lesson", "That locked lesson is not on the timetable."),
            _ => Problem(StatusCodes.Status404NotFound, "unknown-school", "That school does not exist."),
        };

    private static bool TryDefName(string? value, string field, out string name, out string error)
    {
        name = value?.Trim() ?? string.Empty;
        if (name.Length is < 1 or > 64)
        {
            error = $"{field} is not valid.";
            return false;
        }

        error = string.Empty;
        return true;
    }

    private static IResult Problem(int statusCode, string code, string detail)
    {
        return Results.Problem(
            detail: detail,
            statusCode: statusCode,
            title: code,
            extensions: new Dictionary<string, object?> { ["code"] = code });
    }
}