using Microsoft.Extensions.Logging;
using StackExchange.Redis;
using System.Diagnostics;
using System.Text.Json;

namespace StellaOps.Provcache.Valkey;

public sealed partial class ValkeyProvcacheStore
{
    public async ValueTask<ProvcacheLookupResult> GetAsync(string veriKey, CancellationToken cancellationToken = default)
    {
        var sw = Stopwatch.StartNew();
        cancellationToken.ThrowIfCancellationRequested();

        try
        {
            var db = await GetDatabaseAsync(cancellationToken).ConfigureAwait(false);
            var redisKey = BuildKey(veriKey);

            var value = await db.StringGetAsync(redisKey).ConfigureAwait(false);
            sw.Stop();

            if (value.IsNullOrEmpty)
            {
                _logger.LogDebug("Cache miss for VeriKey {VeriKey} in {ElapsedMs}ms", veriKey, sw.Elapsed.TotalMilliseconds);
                return ProvcacheLookupResult.Miss(sw.Elapsed.TotalMilliseconds);
            }

            var entry = JsonSerializer.Deserialize<ProvcacheEntry>((string)value!, _jsonOptions);
            if (entry is null)
            {
                _logger.LogWarning("Failed to deserialize cache entry for VeriKey {VeriKey}", veriKey);
                return ProvcacheLookupResult.Miss(sw.Elapsed.TotalMilliseconds);
            }

            if (_options.SlidingExpiration)
            {
                var ttl = entry.ExpiresAt - _timeProvider.GetUtcNow();
                if (ttl > TimeSpan.Zero)
                {
                    await db.KeyExpireAsync(redisKey, ttl).ConfigureAwait(false);
                }
            }

            _logger.LogDebug("Cache hit for VeriKey {VeriKey} in {ElapsedMs}ms", veriKey, sw.Elapsed.TotalMilliseconds);
            return ProvcacheLookupResult.Hit(entry, ProviderName, sw.Elapsed.TotalMilliseconds);
        }
        catch (Exception ex)
        {
            sw.Stop();
            _logger.LogError(ex, "Error getting cache entry for VeriKey {VeriKey}", veriKey);
            return ProvcacheLookupResult.Miss(sw.Elapsed.TotalMilliseconds);
        }
    }
}