using JobTrackerApi.Data;
using JobTrackerApi.Models;
using Microsoft.EntityFrameworkCore;

namespace JobTrackerApi.Services;

public static class OperationEventLog
{
    public const int RetentionDays = 30;
    public static string SafeStatus(string? value) => value is
        OperationStatuses.Queued or OperationStatuses.Running or OperationStatuses.WaitingForRetry or OperationStatuses.WaitingForExternalFallback
        or OperationStatuses.Succeeded or OperationStatuses.Failed or OperationStatuses.Cancelled ? value : "unknown";

    public static string? SafeStage(string? value) => value is "cv_validating_file" or "cv_extracting" or "cv_identifying_sections"
        or "cv_analysing" or "cv_validating_details" or "cv_preparing_review" or "cv_review_ready" ? value : null;

    public static IReadOnlyList<string> FailureCodes { get; } = Array.AsReadOnly(new[]
    {
        "timeout", "lease_expired", "deadline_exceeded", "entitlement_changed", "document_unavailable",
        "sidecar_unavailable", "upstream_unavailable", "invalid_response", "circuit_open", "rate_limited",
        "permission_denied", "cancelled", "upload_rejected", "parser_failed", "malformed_output", "provider_unavailable",
    });
    public static string? SafeFailure(string? value) => value is null ? null : FailureCodes.Contains(value, StringComparer.Ordinal) ? value : "processing_failed";

    public static UserOperationEvent Create(UserOperation operation, OperationEventKind kind, DateTime now,
        string? status = null, string? stage = null, string? failure = null, int? attempt = null) => new()
    {
        OperationId = operation.Id, OwnerUserId = operation.OwnerUserId, AtUtc = now, Kind = kind.ToString(),
        Status = SafeStatus(status ?? operation.Status), Stage = SafeStage(stage ?? operation.ProgressStage),
        Attempt = Math.Clamp(attempt ?? operation.AttemptCount, 0, 10), FailureCode = SafeFailure(failure),
    };

    public static async Task AppendAsync(JobTrackerContext db, UserOperation operation, OperationEventKind kind, DateTime now,
        CancellationToken token, string? status = null, string? stage = null, string? failure = null, int? attempt = null)
    {
        var item = Create(operation, kind, now, status, stage, failure, attempt);
        if (!db.Database.IsRelational())
        {
            db.UserOperationEvents.Add(item);
            await db.SaveChangesAsync(token);
            return;
        }
        if (db.Database.CurrentTransaction is null) throw new InvalidOperationException("Operation history requires the state transition transaction.");
        // Parameterized insert avoids flushing unrelated entities tracked by a caller.
        await db.Database.ExecuteSqlInterpolatedAsync($"INSERT INTO `UserOperationEvents` (`OperationId`,`OwnerUserId`,`AtUtc`,`Kind`,`Status`,`Stage`,`Attempt`,`FailureCode`) VALUES ({item.OperationId},{item.OwnerUserId},{item.AtUtc},{item.Kind},{item.Status},{item.Stage},{item.Attempt},{item.FailureCode})", token);
    }

    public static async Task<int> PruneAsync(JobTrackerContext db, DateTime now, CancellationToken token)
    {
        var cutoff = now.AddDays(-RetentionDays);
        var ids = await db.UserOperationEvents.IgnoreQueryFilters().Where(item => item.AtUtc < cutoff)
            .OrderBy(item => item.Id).Select(item => item.Id).Take(5000).ToListAsync(token);
        if (!db.Database.IsRelational())
        {
            var items = await db.UserOperationEvents.IgnoreQueryFilters().Where(item => ids.Contains(item.Id)).ToListAsync(token);
            db.UserOperationEvents.RemoveRange(items);
            return await db.SaveChangesAsync(token);
        }
        return await db.UserOperationEvents.IgnoreQueryFilters().Where(item => ids.Contains(item.Id)).ExecuteDeleteAsync(token);
    }
}