using System.Text.Json;
using Server.WatchBody.Core.Dal.Src.Repository;
using Server.WatchBody.Core.Programs;

namespace Server.WatchBody.Web.Services;

/// <summary>
/// Сводка план/факт по активной версии (spec 05 §2 m08): недели от
/// понедельника недели создания версии; performed — тренировки в
/// плановые дни недели; missed = planned − performed.
/// </summary>
public class PlanSummaryService(
    IWorkoutRepository workouts,
    IWorkoutMetricsRepository metrics,
    ProgramStore programs)
{
    private static readonly string[] DayNames =
        ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"];

    public object Summarize(int athleteId)
    {
        var active = programs.GetActive(athleteId);
        if (active == null || string.IsNullOrWhiteSpace(active.Body))
            return new { activeVersion = (int?)null, weeks = Array.Empty<object>() };

        var weeks = ParseWeeks(active.Body);
        var versionMonday = MondayOf(DateOnly.FromDateTime(active.CreatedAt));

        var rows = new List<object>();
        for (var i = 0; i < weeks.Count; i++)
        {
            var from = versionMonday.AddDays(7 * i);
            var to = from.AddDays(6);
            var plannedDays = weeks[i].ToHashSet(StringComparer.OrdinalIgnoreCase);
            var planned = weeks[i].Count;
            if (planned == 0) continue;

            var inWeek = workouts.Select(new WorkoutFilter
            {
                AthleteId = athleteId,
                DateFrom = from,
                DateTo = to,
            }).ToList();
            // performed — только в плановые дни недели (spec 05)
            var performedList = inWeek
                .Where(w => plannedDays.Contains(DayName(DateOnly.FromDateTime(w.StartedAt))))
                .ToList();
            var adherences = performedList
                .Select(w => metrics.Select(new WorkoutMetricsFilter
                    { AthleteId = athleteId, WorkoutId = w.Id }).FirstOrDefault()?.Adherence)
                .Where(a => a != null).ToList();
            rows.Add(new
            {
                week = i + 1,
                from = from.ToString("yyyy-MM-dd"),
                to = to.ToString("yyyy-MM-dd"),
                planned,
                performed = performedList.Count,
                missed = Math.Max(0, planned - performedList.Count),
                avgAdherence = adherences.Count > 0
                    ? Math.Round(adherences.Average(a => a!.Value), 1, MidpointRounding.AwayFromZero)
                    : (decimal?)null,
            });
        }
        return new { activeVersion = (int?)active.Version, weeks = rows };
    }

    /// <summary>Дни недели сессий по неделям body (v1 — каждая сессия
    /// = одна плановая тренировка; ротация недель — v2).</summary>
    private static List<List<string>> ParseWeeks(string body)
    {
        var result = new List<List<string>>();
        try
        {
            using var doc = JsonDocument.Parse(body);
            foreach (var week in doc.RootElement.GetProperty("weeks").EnumerateArray())
            {
                var days = new List<string>();
                if (week.TryGetProperty("sessions", out var sessionNodes))
                    foreach (var session in sessionNodes.EnumerateArray())
                        if (session.TryGetProperty("day", out var day) && day.ValueKind == JsonValueKind.String)
                            days.Add(day.GetString()!);
                result.Add(days);
            }
        }
        catch (Exception ex) when (ex is JsonException or KeyNotFoundException)
        {
            // кривой body — сводка пустая
        }
        return result;
    }

    private static DateOnly MondayOf(DateOnly date) =>
        date.AddDays(-(((int)date.DayOfWeek + 6) % 7));

    private static string DayName(DateOnly date) => DayNames[((int)date.DayOfWeek + 6) % 7];
}