using System.Text.Json;

namespace SVSim.Bootstrap.Importers;

/// <summary>
/// Shared helpers for content importers. Loads a prod-capture JSON file by endpoint name from
/// a captures directory, returning the inner <c>data</c> element. Picks the latest matching dated
/// file (e.g. <c>load-index-2026-05-23.json</c>) if multiple exist for the same endpoint.
/// </summary>
public static class ImporterBase
{
    /// <summary>
    /// Returns the parsed <c>.data</c> JsonElement for the latest <c>{endpoint}-*.json</c> file in
    /// <paramref name="capturesDir"/>, or null if no file matches. Logs a warning when missing —
    /// caller decides whether absence is fatal.
    /// </summary>
    public static JsonElement? LoadCapture(string capturesDir, string endpoint)
    {
        if (!Directory.Exists(capturesDir))
        {
            Console.Error.WriteLine($"[ImporterBase] Captures dir missing: {capturesDir}");
            return null;
        }

        string? path = Directory.EnumerateFiles(capturesDir, $"{endpoint}-*.json")
            .OrderByDescending(p => p)
            .FirstOrDefault();

        if (path is null)
        {
            Console.Error.WriteLine($"[ImporterBase] No capture found for endpoint '{endpoint}' in {capturesDir}");
            return null;
        }

        using var fs = File.OpenRead(path);
        using var doc = JsonDocument.Parse(fs);
        if (!doc.RootElement.TryGetProperty("data", out var data))
        {
            Console.Error.WriteLine($"[ImporterBase] Capture file {path} has no top-level 'data' property.");
            return null;
        }
        // Clone so the JsonElement survives doc disposal.
        return data.Clone();
    }

    /// <summary>
    /// Generic upsert by primary key. Returns (created, updated, unchanged) counts.
    /// <paramref name="incoming"/> is the desired state from the capture; rows are matched by
    /// <paramref name="keySelector"/>. <paramref name="applyChanges"/> mutates an existing row to
    /// reflect incoming values and returns true if anything actually changed.
    /// </summary>
    public static (int created, int updated, int unchanged) Upsert<T, TKey>(
        IEnumerable<T> incoming,
        Dictionary<TKey, T> existingByKey,
        Func<T, TKey> keySelector,
        Action<T> addToContext,
        Func<T, T, bool> applyChanges) where TKey : notnull
    {
        int created = 0, updated = 0, unchanged = 0;
        foreach (var item in incoming)
        {
            var key = keySelector(item);
            if (existingByKey.TryGetValue(key, out var existing))
            {
                if (applyChanges(existing, item)) updated++;
                else unchanged++;
            }
            else
            {
                addToContext(item);
                existingByKey[key] = item;
                created++;
            }
        }
        return (created, updated, unchanged);
    }

    /// <summary>Serialize a JsonElement back to compact JSON text for jsonb storage.</summary>
    public static string Serialize(JsonElement el) =>
        JsonSerializer.Serialize(el, new JsonSerializerOptions { WriteIndented = false });

    /// <summary>Parse a wire date that may be ISO ("2026-05-23T..."), space-separated ("2026-05-23 16:32:31"), or empty.</summary>
    public static DateTime ParseWireDateTime(string? s)
    {
        if (string.IsNullOrWhiteSpace(s)) return DateTime.MinValue;
        if (DateTime.TryParse(s, System.Globalization.CultureInfo.InvariantCulture,
                System.Globalization.DateTimeStyles.AssumeUniversal | System.Globalization.DateTimeStyles.AdjustToUniversal,
                out var dt))
        {
            return dt;
        }
        return DateTime.MinValue;
    }

    /// <summary>Read a JsonElement string/number property as long, defaulting on missing/null.</summary>
    public static long GetLong(JsonElement el, string prop, long fallback = 0)
    {
        if (!el.TryGetProperty(prop, out var v) || v.ValueKind == JsonValueKind.Null) return fallback;
        if (v.ValueKind == JsonValueKind.Number) return v.GetInt64();
        if (v.ValueKind == JsonValueKind.String && long.TryParse(v.GetString(), out var n)) return n;
        return fallback;
    }

    public static int GetInt(JsonElement el, string prop, int fallback = 0)
    {
        if (!el.TryGetProperty(prop, out var v) || v.ValueKind == JsonValueKind.Null) return fallback;
        if (v.ValueKind == JsonValueKind.Number) return v.GetInt32();
        if (v.ValueKind == JsonValueKind.String && int.TryParse(v.GetString(), out var n)) return n;
        return fallback;
    }

    public static string GetString(JsonElement el, string prop, string fallback = "")
    {
        if (!el.TryGetProperty(prop, out var v) || v.ValueKind == JsonValueKind.Null) return fallback;
        return v.ValueKind == JsonValueKind.String ? v.GetString() ?? fallback : v.ToString();
    }

    public static bool GetBool(JsonElement el, string prop, bool fallback = false)
    {
        if (!el.TryGetProperty(prop, out var v) || v.ValueKind == JsonValueKind.Null) return fallback;
        if (v.ValueKind == JsonValueKind.True) return true;
        if (v.ValueKind == JsonValueKind.False) return false;
        if (v.ValueKind == JsonValueKind.Number) return v.GetInt32() != 0;
        if (v.ValueKind == JsonValueKind.String)
        {
            var s = v.GetString();
            if (bool.TryParse(s, out var b)) return b;
            if (int.TryParse(s, out var i)) return i != 0;
        }
        return fallback;
    }

    public static ulong GetULong(JsonElement el, string prop, ulong fallback = 0)
    {
        if (!el.TryGetProperty(prop, out var v) || v.ValueKind == JsonValueKind.Null) return fallback;
        if (v.ValueKind == JsonValueKind.Number) return v.GetUInt64();
        if (v.ValueKind == JsonValueKind.String && ulong.TryParse(v.GetString(), out var n)) return n;
        return fallback;
    }
}