using HandlebarsDotNet;
using StackExchange.Redis;

namespace GB5Shared.Export.HybridReport
{
    public class TemplateEngine
    {
        private readonly IHandlebars _hb;
        private readonly IDatabase _cache;

        public TemplateEngine(string redisConnection)
        {
            _hb = Handlebars.Create();
            RegisterHelpers();
            var mux = ConnectionMultiplexer.Connect(redisConnection);
            _cache = mux.GetDatabase();
        }

        public async Task<string> RenderTemplateAsync(string templateName, object context, string tenantId, int version = 1)
        {
            var cacheKey = $"tpl:{templateName}:v{version}";

            // Try get template from Redis
            var templateSource = await _cache.StringGetAsync(cacheKey);

            if (templateSource.IsNullOrEmpty)
            {
                var path = Path.Combine("reports", "templates", templateName + ".hbs");
                if (!File.Exists(path))
                    throw new FileNotFoundException($"Template file not found: {path}");

                templateSource = await File.ReadAllTextAsync(path);
                await _cache.StringSetAsync(cacheKey, templateSource, TimeSpan.FromHours(6));
            }

            var template = _hb.Compile(templateSource);

            // Get tenant metadata from Redis
            var tenantJson = await _cache.StringGetAsync($"tenant:meta:{tenantId}");
            object? tenantObj = null;

            if (!tenantJson.IsNullOrEmpty)
            {
                tenantObj = Newtonsoft.Json.JsonConvert.DeserializeObject<object>(tenantJson!);
            }

            // Build the context for Handlebars
            var finalContext = new
            {
                Tenant = tenantObj,
                Data = context,
                Now = DateTime.UtcNow
            };

            return template(finalContext);
        }


        private void RegisterHelpers()
        {
            _hb.RegisterHelper("formatDate", (w, c, p) => {
                if (p.Length >= 1 && DateTime.TryParse(p[0]?.ToString(), out var dt))
                {
                    var fmt = p.Length > 1 ? p[1]?.ToString() : "dd-MMM-yyyy";
                    w.WriteSafeString(dt.ToString(fmt));
                }
            });

            _hb.RegisterHelper("formatCurrency", (w, c, p) => {
                if (decimal.TryParse(p[0]?.ToString(), out var val)) w.WriteSafeString(val.ToString("N2"));
            });

            // sum helper
            _hb.RegisterHelper("sum", (w, c, p) => {
                var arr = p[0] as IEnumerable<object>;
                var fld = p[1]?.ToString();
                decimal total = 0;
                if (arr != null)
                {
                    foreach (var it in arr)
                    {
                        var dict = it as IDictionary<string, object>;
                        if (dict != null && dict.ContainsKey(fld!))
                        {
                            total += Convert.ToDecimal(dict[fld!]);
                        }
                    }
                }
                w.WriteSafeString(total.ToString("N2"));
            });
        }
    }
}