using ClaudeDo.Data;
using ClaudeDo.Data.Repositories;
using ClaudeDo.Worker.Config;
using ClaudeDo.Worker.Hub;
using ClaudeDo.Worker.Usage.Interfaces;
using Microsoft.EntityFrameworkCore;

namespace ClaudeDo.Worker.Usage;

/// <summary>
/// Builds the Hub-facing usage snapshot DTO from UsageState + IUsageGate + AppSettings
/// thresholds. Shared by WorkerHub.GetUsageSnapshot and UsageMonitorService's post-poll
/// broadcast so both surfaces agree on staleness/threshold logic.
/// </summary>
public sealed class UsageSnapshotBuilder
{
    private readonly UsageState _state;
    private readonly IUsageGate _gate;
    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
    private readonly WorkerConfig _cfg;

    public UsageSnapshotBuilder(
        UsageState state, IUsageGate gate, IDbContextFactory<ClaudeDoDbContext> dbFactory, WorkerConfig cfg)
    {
        _state = state;
        _gate = gate;
        _dbFactory = dbFactory;
        _cfg = cfg;
    }

    public async Task<UsageSnapshotDto> BuildAsync(CancellationToken ct = default)
    {
        var snapshot = _state.Snapshot;
        var lastError = _state.LastError;

        Data.Models.AppSettingsEntity settings;
        using (var context = _dbFactory.CreateDbContext())
            settings = await new AppSettingsRepository(context).GetAsync(ct);

        var decision = await _gate.EvaluateAsync(ct);

        // Measured against the *slowest* cadence — the idle interval — so a genuinely idle
        // worker on its 15-minute heartbeat isn't reported stale just for not polling.
        var maxAge = TimeSpan.FromSeconds(
            Math.Max(_cfg.UsagePollIntervalActiveSeconds, _cfg.UsagePollIntervalIdleSeconds) * 3);
        var isStale = snapshot is null || lastError is not null || (DateTime.UtcNow - snapshot.FetchedAtUtc) > maxAge;

        var limits = (snapshot?.Limits ?? Array.Empty<UsageLimitRow>())
            .Select(l => new UsageLimitDto(l.Kind, l.Group, l.Percent, l.Severity, l.ResetsAt, l.ScopeModelDisplayName, l.IsActive))
            .ToList();

        var fiveHourThresholds = new UsageThresholds(
            settings.UsageThrottleFiveHourSoftPct, settings.UsageThrottleFiveHourHardPct, settings.UsageGateFiveHourPct);
        var sevenDayThresholds = new UsageThresholds(
            settings.UsageThrottleSevenDaySoftPct, settings.UsageThrottleSevenDayHardPct, settings.UsageGateSevenDayPct);

        var configuredSlots = Math.Max(1, settings.MaxParallelExecutions);
        var effectiveSlots = snapshot is null || lastError is not null
            ? configuredSlots
            : UsageThrottle.EffectiveSlots(
                configuredSlots,
                snapshot.FiveHour?.Utilization, fiveHourThresholds,
                snapshot.SevenDay?.Utilization, sevenDayThresholds);
        var throttleBucket = effectiveSlots < configuredSlots
            ? DecisiveBucket(snapshot?.FiveHour?.Utilization, snapshot?.SevenDay?.Utilization)
            : null;

        return new UsageSnapshotDto(
            snapshot?.FiveHour?.Utilization,
            snapshot?.FiveHour?.ResetsAt,
            snapshot?.SevenDay?.Utilization,
            snapshot?.SevenDay?.ResetsAt,
            limits,
            settings.UsageGateFiveHourPct,
            settings.UsageGateSevenDayPct,
            decision.IsBlocked,
            decision.Reason,
            snapshot?.FetchedAtUtc,
            isStale,
            lastError,
            configuredSlots,
            effectiveSlots,
            throttleBucket,
            fiveHourThresholds.SoftPct,
            fiveHourThresholds.HardPct,
            sevenDayThresholds.SoftPct,
            sevenDayThresholds.HardPct);
    }

    private static string? DecisiveBucket(double? fiveHourPct, double? sevenDayPct)
    {
        if (fiveHourPct is null && sevenDayPct is null) return null;
        return (fiveHourPct ?? 0) >= (sevenDayPct ?? 0) ? "five_hour" : "seven_day";
    }
}