using System.Text.Json;

namespace GB5Shared.DTO.Framework.Criteria
{
    /// <summary>
    /// Dynamically parses any CriteriaDTO into a typed dictionary keyed by FieldName (case-insensitive).
    /// Type conversion is driven entirely by CriteriaAttributeType — no field-name switch required.
    ///
    ///   CriteriaAttributeType byte values (from DB config):
    ///     0 = PICKLIST      → List&lt;int&gt;   (single or comma-separated IDs)
    ///     3 = LIST          → List&lt;string&gt;
    ///     4 = DATE          → DateTime UTC  (epoch seconds, 100% DB-accurate via AddSeconds)
    ///     5 = NUMERICENTRY  → decimal
    ///     * = default       → string
    /// </summary>
    public static class CriteriaParser
    {
        private static readonly DateTime Epoch = new(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

        private const byte TYPE_PICKLIST     = 0;
        private const byte TYPE_LIST         = 3;
        private const byte TYPE_DATE         = 4;
        private const byte TYPE_NUMERICENTRY = 5;

        /// <summary>
        /// Flattens all sections/attributes of a CriteriaDTO into one dictionary.
        /// Each entry is typed based on CriteriaAttributeType — no caller switch needed.
        /// </summary>
        public static Dictionary<string, object> Parse(CriteriaDTO criteriaDTO)
        {
            var result = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);

            if (criteriaDTO?.SectionCriteriaList == null)
                return result;

            foreach (var section in criteriaDTO.SectionCriteriaList)
            {
                if (section?.AttributesCriteriaList == null) continue;

                foreach (var attr in section.AttributesCriteriaList)
                {
                    if (attr.FieldValue == null || string.IsNullOrEmpty(attr.FieldName))
                        continue;

                    string raw = RawString(attr.FieldValue);
                    if (string.IsNullOrWhiteSpace(raw)) continue;

                    object parsed = attr.CriteriaAttributeType switch
                    {
                        TYPE_DATE         => EpochSecondsToDateTime(attr.FieldValue),
                        TYPE_PICKLIST     => ToIntList(raw),
                        TYPE_NUMERICENTRY => decimal.TryParse(raw, out decimal d) ? d : 0m,
                        TYPE_LIST         => raw.Split(',', StringSplitOptions.RemoveEmptyEntries)
                                               .Select(s => s.Trim())
                                               .Where(s => s.Length > 0)
                                               .ToList(),
                        _                 => raw
                    };

                    // Last writer wins if the same FieldName appears in multiple sections
                    result[attr.FieldName] = parsed;
                }
            }

            return result;
        }

        // ── Typed accessors ───────────────────────────────────────────────────

        public static DateTime GetDate(Dictionary<string, object> c, string field, DateTime fallback = default)
            => c.TryGetValue(field, out var v) && v is DateTime dt ? dt : fallback;

        public static int GetInt(Dictionary<string, object> c, string field, int fallback = 0)
        {
            if (!c.TryGetValue(field, out var v)) return fallback;
            if (v is List<int> list) return list.Count > 0 ? list[0] : fallback;
            if (v is string s && int.TryParse(s, out int i)) return i;
            return fallback;
        }

        public static List<int> GetIntList(Dictionary<string, object> c, string field)
            => c.TryGetValue(field, out var v) && v is List<int> list ? list : new List<int>();

        public static decimal GetDecimal(Dictionary<string, object> c, string field, decimal fallback = 0m)
            => c.TryGetValue(field, out var v) && v is decimal d ? d : fallback;

        public static List<string> GetStringList(Dictionary<string, object> c, string field)
            => c.TryGetValue(field, out var v) && v is List<string> list ? list : new List<string>();

        public static string GetString(Dictionary<string, object> c, string field, string fallback = "")
        {
            if (!c.TryGetValue(field, out var v) || v == null) return fallback;
            if (v is List<int> intList) return intList.Count > 0 ? intList[0].ToString() : fallback;
            if (v is List<string> strList) return strList.Count > 0 ? strList[0] : fallback;
            return v.ToString() ?? fallback;
        }

        // ── Private helpers ───────────────────────────────────────────────────

        /// <summary>
        /// Converts epoch seconds (as stored by the DB) to UTC DateTime.
        /// Uses AddSeconds — identical to GB5CommonFunction.FromEpoch — for 100% DB accuracy.
        /// </summary>
        private static DateTime EpochSecondsToDateTime(object fieldValue)
        {
            long seconds;
            if (fieldValue is JsonElement je)
                seconds = je.ValueKind == JsonValueKind.Number
                    ? je.GetInt64()
                    : long.Parse(je.GetString()!);
            else
                seconds = Convert.ToInt64(fieldValue);

            return Epoch.AddSeconds(seconds);
        }

        private static List<int> ToIntList(string raw)
            => raw.Split(',', StringSplitOptions.RemoveEmptyEntries)
                  .Select(s => int.TryParse(s.Trim(), out int v) ? v : 0)
                  .Where(v => v != 0)
                  .ToList();

        private static string RawString(object value)
            => value is JsonElement je ? je.ToString() : value?.ToString() ?? string.Empty;
    }
}