using System.Collections.Immutable;
using Microsoft.Extensions.Logging;
using StellaOps.Scheduler.Models;
using StellaOps.Scheduler.Storage.Mongo.Documents;
using StellaOps.Scheduler.Storage.Mongo.Projections;
using StellaOps.Scheduler.Storage.Mongo.Repositories;

namespace StellaOps.Scheduler.Storage.Mongo.Services;

internal sealed class RunSummaryService : IRunSummaryService
{
    private const int RecentLimit = 20;

    private readonly IRunSummaryRepository _repository;
    private readonly TimeProvider _timeProvider;
    private readonly ILogger<RunSummaryService> _logger;

    public RunSummaryService(
        IRunSummaryRepository repository,
        TimeProvider? timeProvider,
        ILogger<RunSummaryService> logger)
    {
        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
        _timeProvider = timeProvider ?? TimeProvider.System;
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public async Task<RunSummaryProjection> ProjectAsync(
        Run run,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(run);
        if (string.IsNullOrWhiteSpace(run.ScheduleId))
        {
            throw new ArgumentException("Run must contain a scheduleId to project summary data.", nameof(run));
        }

        var document = await _repository
            .GetAsync(run.TenantId, run.ScheduleId!, cancellationToken)
            .ConfigureAwait(false)
            ?? new RunSummaryDocument
            {
                TenantId = run.TenantId,
                ScheduleId = run.ScheduleId!,
            };

        UpdateDocument(document, run);
        document.UpdatedAt = _timeProvider.GetUtcNow().UtcDateTime;

        await _repository.UpsertAsync(document, cancellationToken).ConfigureAwait(false);
        _logger.LogDebug(
            "Projected run summary for tenant {TenantId} schedule {ScheduleId} using run {RunId}.",
            run.TenantId,
            run.ScheduleId,
            run.Id);
        return ToProjection(document);
    }

    public async Task<RunSummaryProjection?> GetAsync(
        string tenantId,
        string scheduleId,
        CancellationToken cancellationToken = default)
    {
        var document = await _repository
            .GetAsync(tenantId, scheduleId, cancellationToken)
            .ConfigureAwait(false);

        return document is null ? null : ToProjection(document);
    }

    public async Task<IReadOnlyList<RunSummaryProjection>> ListAsync(
        string tenantId,
        CancellationToken cancellationToken = default)
    {
        var documents = await _repository.ListAsync(tenantId, cancellationToken).ConfigureAwait(false);
        return documents.Select(ToProjection).ToArray();
    }

    private static void UpdateDocument(RunSummaryDocument document, Run run)
    {
        var entry = document.Recent.FirstOrDefault(item => string.Equals(item.RunId, run.Id, StringComparison.Ordinal));
        if (entry is null)
        {
            entry = new RunSummaryEntryDocument
            {
                RunId = run.Id,
            };
            document.Recent.Add(entry);
        }

        entry.Trigger = run.Trigger;
        entry.State = run.State;
        entry.CreatedAt = run.CreatedAt.UtcDateTime;
        entry.StartedAt = run.StartedAt?.UtcDateTime;
        entry.FinishedAt = run.FinishedAt?.UtcDateTime;
        entry.Error = run.Error;
        entry.Stats = run.Stats;

        document.Recent = document.Recent
            .OrderByDescending(item => item.CreatedAt)
            .ThenByDescending(item => item.RunId, StringComparer.Ordinal)
            .Take(RecentLimit)
            .ToList();

        document.LastRun = document.Recent.FirstOrDefault();
        document.Counters = ComputeCounters(document.Recent);
    }

    private static RunSummaryCountersDocument ComputeCounters(IEnumerable<RunSummaryEntryDocument> entries)
    {
        var counters = new RunSummaryCountersDocument();

        foreach (var entry in entries)
        {
            counters.Total++;
            switch (entry.State)
            {
                case RunState.Planning:
                    counters.Planning++;
                    break;
                case RunState.Queued:
                    counters.Queued++;
                    break;
                case RunState.Running:
                    counters.Running++;
                    break;
                case RunState.Completed:
                    counters.Completed++;
                    break;
                case RunState.Error:
                    counters.Error++;
                    break;
                case RunState.Cancelled:
                    counters.Cancelled++;
                    break;
                default:
                    break;
            }

            counters.TotalDeltas += entry.Stats.Deltas;
            counters.TotalNewCriticals += entry.Stats.NewCriticals;
            counters.TotalNewHigh += entry.Stats.NewHigh;
            counters.TotalNewMedium += entry.Stats.NewMedium;
            counters.TotalNewLow += entry.Stats.NewLow;
        }

        return counters;
    }

    private static RunSummaryProjection ToProjection(RunSummaryDocument document)
    {
        var updatedAt = new DateTimeOffset(DateTime.SpecifyKind(document.UpdatedAt, DateTimeKind.Utc));
        var lastRun = document.LastRun is null
            ? null
            : ToSnapshot(document.LastRun);

        var recent = document.Recent
            .Select(ToSnapshot)
            .ToImmutableArray();

        var counters = new RunSummaryCounters(
            document.Counters.Total,
            document.Counters.Planning,
            document.Counters.Queued,
            document.Counters.Running,
            document.Counters.Completed,
            document.Counters.Error,
            document.Counters.Cancelled,
            document.Counters.TotalDeltas,
            document.Counters.TotalNewCriticals,
            document.Counters.TotalNewHigh,
            document.Counters.TotalNewMedium,
            document.Counters.TotalNewLow);

        return new RunSummaryProjection(
            document.TenantId,
            document.ScheduleId,
            updatedAt,
            lastRun,
            recent,
            counters);
    }

    private static RunSummarySnapshot ToSnapshot(RunSummaryEntryDocument entry)
    {
        var createdAt = new DateTimeOffset(DateTime.SpecifyKind(entry.CreatedAt, DateTimeKind.Utc));
        DateTimeOffset? startedAt = entry.StartedAt is null
            ? null
            : new DateTimeOffset(DateTime.SpecifyKind(entry.StartedAt.Value, DateTimeKind.Utc));
        DateTimeOffset? finishedAt = entry.FinishedAt is null
            ? null
            : new DateTimeOffset(DateTime.SpecifyKind(entry.FinishedAt.Value, DateTimeKind.Utc));

        return new RunSummarySnapshot(
            entry.RunId,
            entry.Trigger,
            entry.State,
            createdAt,
            startedAt,
            finishedAt,
            entry.Stats,
            entry.Error);
    }
}