using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using StellaOps.Scheduler.Models;
using StellaOps.Scheduler.Persistence.Postgres.Repositories;

namespace StellaOps.Scheduler.WebService.Runs;

internal sealed class InMemoryRunRepository : IRunRepository
{
    private readonly ConcurrentDictionary<string, Run> _runs = new(StringComparer.Ordinal);

    public Task InsertAsync(
        Run run,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(run);
        _runs[run.Id] = run;
        return Task.CompletedTask;
    }

    public Task<bool> UpdateAsync(
        Run run,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(run);

        if (!_runs.TryGetValue(run.Id, out var existing))
        {
            return Task.FromResult(false);
        }

        if (!string.Equals(existing.TenantId, run.TenantId, StringComparison.Ordinal))
        {
            return Task.FromResult(false);
        }

        _runs[run.Id] = run;
        return Task.FromResult(true);
    }

    public Task<Run?> GetAsync(
        string tenantId,
        string runId,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(tenantId))
        {
            throw new ArgumentException("Tenant id must be provided.", nameof(tenantId));
        }

        if (string.IsNullOrWhiteSpace(runId))
        {
            throw new ArgumentException("Run id must be provided.", nameof(runId));
        }

        if (_runs.TryGetValue(runId, out var run) && string.Equals(run.TenantId, tenantId, StringComparison.Ordinal))
        {
            return Task.FromResult<Run?>(run);
        }

        return Task.FromResult<Run?>(null);
    }

    public Task<IReadOnlyList<Run>> ListAsync(
        string tenantId,
        RunQueryOptions? options = null,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(tenantId))
        {
            throw new ArgumentException("Tenant id must be provided.", nameof(tenantId));
        }

        options ??= new RunQueryOptions();

        IEnumerable<Run> query = _runs.Values
            .Where(run => string.Equals(run.TenantId, tenantId, StringComparison.Ordinal));

        if (!string.IsNullOrWhiteSpace(options.ScheduleId))
        {
            query = query.Where(run => string.Equals(run.ScheduleId, options.ScheduleId, StringComparison.Ordinal));
        }

        if (!options.States.IsDefaultOrEmpty)
        {
            var allowed = options.States.ToImmutableHashSet();
            query = query.Where(run => allowed.Contains(run.State));
        }

        if (options.CreatedAfter is { } createdAfter)
        {
            query = query.Where(run => run.CreatedAt > createdAfter);
        }

        if (options.Cursor is { } cursor)
        {
            query = options.SortAscending
                ? query.Where(run => run.CreatedAt > cursor.CreatedAt ||
                                     (run.CreatedAt == cursor.CreatedAt &&
                                      string.Compare(run.Id, cursor.RunId, StringComparison.Ordinal) > 0))
                : query.Where(run => run.CreatedAt < cursor.CreatedAt ||
                                     (run.CreatedAt == cursor.CreatedAt &&
                                      string.Compare(run.Id, cursor.RunId, StringComparison.Ordinal) < 0));
        }

        query = options.SortAscending
            ? query.OrderBy(run => run.CreatedAt).ThenBy(run => run.Id, StringComparer.Ordinal)
            : query.OrderByDescending(run => run.CreatedAt).ThenByDescending(run => run.Id, StringComparer.Ordinal);

        var limit = options.Limit is { } specified && specified > 0 ? specified : 50;
        var result = query.Take(limit).ToArray();
        return Task.FromResult<IReadOnlyList<Run>>(result);
    }

    public Task<IReadOnlyList<Run>> ListByStateAsync(
        RunState state,
        int limit = 50,
        CancellationToken cancellationToken = default)
    {
        if (limit <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(limit), limit, "Limit must be greater than zero.");
        }

        var result = _runs.Values
            .Where(run => run.State == state)
            .OrderBy(run => run.CreatedAt)
            .ThenBy(run => run.Id, StringComparer.Ordinal)
            .Take(limit)
            .ToArray();

        return Task.FromResult<IReadOnlyList<Run>>(result);
    }
}