using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using Sozsoft.Platform.Entities;

namespace Sozsoft.Reports.PredefinedReports;

internal static class DynamicReportGridStateHelper
{
    public static string GetFilterName(ListForm listForm, string prefix) =>
        $"{prefix}-{GetStateStorageKey(listForm)}";

    public static List<ListFormField> GetVisibleFields(
        IReadOnlyList<ListFormField> availableFields,
        string gridStateJson)
    {
        if (!TryGetColumnStates(gridStateJson, out var statesByField))
        {
            return availableFields
                .Where(x => x.Visible == true)
                .ToList();
        }

        return availableFields
            .Where(field => statesByField.TryGetValue(field.FieldName, out var state)
                ? state.Visible
                : field.Visible == true)
            .OrderBy(field => statesByField.TryGetValue(field.FieldName, out var state)
                ? state.VisibleIndex
                : int.MaxValue)
            .ToList();
    }

    private static string GetStateStorageKey(ListForm listForm)
    {
        if (!string.IsNullOrWhiteSpace(listForm.StateStoringJson))
        {
            try
            {
                using var document = JsonDocument.Parse(listForm.StateStoringJson);
                if (TryGetProperty(document.RootElement, "storageKey", out var storageKey) &&
                    storageKey.ValueKind == JsonValueKind.String &&
                    !string.IsNullOrWhiteSpace(storageKey.GetString()))
                {
                    return storageKey.GetString();
                }
            }
            catch (JsonException)
            {
                // Fall back to the same default value used by GridOptionsDto.
            }
        }

        return $"listFormGridStorage-{listForm.ListFormCode}";
    }

    private static bool TryGetColumnStates(
        string gridStateJson,
        out Dictionary<string, GridColumnState> statesByField)
    {
        statesByField = null;
        if (string.IsNullOrWhiteSpace(gridStateJson))
        {
            return false;
        }

        try
        {
            using var document = JsonDocument.Parse(gridStateJson);
            if (!TryGetProperty(document.RootElement, "columns", out var columns) ||
                columns.ValueKind != JsonValueKind.Array)
            {
                return false;
            }

            var states = new List<GridColumnState>();
            AddColumnStates(columns, true, states);
            statesByField = states
                .Where(x => !string.IsNullOrWhiteSpace(x.FieldName))
                .GroupBy(x => x.FieldName, StringComparer.OrdinalIgnoreCase)
                .ToDictionary(x => x.Key, x => x.First(), StringComparer.OrdinalIgnoreCase);
            return statesByField.Count > 0;
        }
        catch (JsonException)
        {
            return false;
        }
    }

    private static void AddColumnStates(JsonElement columns, bool parentVisible, ICollection<GridColumnState> states)
    {
        foreach (var column in columns.EnumerateArray())
        {
            var visible = parentVisible &&
                          (!TryGetProperty(column, "visible", out var visibleProperty) ||
                           visibleProperty.ValueKind != JsonValueKind.False);
            var fieldName = GetColumnFieldName(column);
            var visibleIndex = TryGetProperty(column, "visibleIndex", out var visibleIndexProperty) &&
                               visibleIndexProperty.TryGetInt32(out var value)
                ? value
                : states.Count;

            if (!string.IsNullOrWhiteSpace(fieldName))
            {
                states.Add(new GridColumnState(fieldName, visible, visibleIndex));
            }

            if (TryGetProperty(column, "columns", out var childColumns) &&
                childColumns.ValueKind == JsonValueKind.Array)
            {
                AddColumnStates(childColumns, visible, states);
            }
        }
    }

    private static string GetColumnFieldName(JsonElement column)
    {
        if (TryGetProperty(column, "dataField", out var dataField) &&
            dataField.ValueKind == JsonValueKind.String)
        {
            return dataField.GetString();
        }

        if (TryGetProperty(column, "name", out var name) &&
            name.ValueKind == JsonValueKind.String)
        {
            return name.GetString();
        }

        return null;
    }

    private static bool TryGetProperty(JsonElement element, string name, out JsonElement value)
    {
        if (element.ValueKind == JsonValueKind.Object)
        {
            foreach (var property in element.EnumerateObject())
            {
                if (string.Equals(property.Name, name, StringComparison.OrdinalIgnoreCase))
                {
                    value = property.Value;
                    return true;
                }
            }
        }

        value = default;
        return false;
    }

    private sealed record GridColumnState(string FieldName, bool Visible, int VisibleIndex);
}