namespace marlin.web.Services;

using Data;
using Microsoft.EntityFrameworkCore;

public class DatabaseUpgrader : IHostedService
{
    private readonly ILogger<DatabaseUpgrader> _logger;
    private readonly IServiceProvider _serviceProvider;
    
    public DatabaseUpgrader(ILogger<DatabaseUpgrader> logger, IServiceProvider serviceProvider)
    {
        this._logger = logger;
        this._serviceProvider = serviceProvider;
    }

    public async Task StartAsync(CancellationToken ct)
    {
        await using AsyncServiceScope scope = this._serviceProvider.CreateAsyncScope();
        DbContext dbContext = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();

        var migrations = await dbContext.Database.GetPendingMigrationsAsync(ct);
        int pendingCount = migrations.Count();

        if (pendingCount == 0)
        {
            this._logger.LogInformation("Database is up to date.");
            return;
        }

        this._logger.LogInformation("Upgrading database {count} versions.", pendingCount);

        try
        {
            await dbContext.Database.MigrateAsync(ct);
            this._logger.LogInformation("Database upgraded.");
        }
        catch (Exception ex)
        {
            this._logger.LogError(ex, "Database upgrade failed, {count} behind.", pendingCount);
        }
    }

    public Task StopAsync(CancellationToken ct) => Task.CompletedTask;
}