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using PagerParser.Sites;
namespace PagerParser;
// Self-explanatory... Hosted background services that periodically fetches
// pager messages, tries to parse them, then adds both the raw pager message
// as well as the parsed message contents to the DB, ignoring already fetched
// messages in the process.
public class PagerFetchService : IHostedService {
private readonly TimeSpan FetchInterval = TimeSpan.FromMinutes(15);
private IServiceProvider serviceProvider;
private IPagerMessageParserService parser;
private Timer fetchTimer;
private PagerMon pagerMon = new();
public PagerFetchService(IServiceProvider serviceProvider, IPagerMessageParserService parser) {
this.serviceProvider = serviceProvider;
this.parser = parser;
fetchTimer = new Timer(Fetch);
}
public Task StartAsync(CancellationToken cancellationToken) {
fetchTimer.Change(TimeSpan.Zero, FetchInterval);
return Task.CompletedTask;
}
public Task StopAsync(CancellationToken cancellationToken) {
fetchTimer.Change(Timeout.Infinite, Timeout.Infinite);
return Task.CompletedTask;
}
private void Fetch(object? state) {
using var scope = serviceProvider.CreateScope();
var db = scope.ServiceProvider.GetRequiredService<PagerContext>();
// Fetch pager messages, ignoring message we've already got
var messages = pagerMon
.Fetch()
.Where(m =>
!db.PagerMessages
.Select(m => m.Message)
.Contains(m.Message));
// Attempt to parse each newly-fetched message.
// Failure to parse isn't critical, as we still keep the raw message.
foreach(var message in messages) {
message.ParsedMessage = parser.TryParse(message.Message);
if(message.ParsedMessage is not null)
message.ParsedMessage.GpsPosition =
PositionCalculator.GetGpsPosition(message.ParsedMessage);
}
db.AddRange(messages);
db.SaveChanges();
}
public void Dispose() =>
fetchTimer.Dispose();
}
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