using System.Collections.Immutable;
using System.Linq;
using System.Globalization;
using System.Text.Json;

namespace StellaOps.Feedser.Source.Ru.Nkcki.Internal;

internal static class RuNkckiJsonParser
{
    public static RuNkckiVulnerabilityDto Parse(JsonElement element)
    {
        var fstecId = element.TryGetProperty("vuln_id", out var vulnIdElement) && vulnIdElement.TryGetProperty("FSTEC", out var fstec) ? Normalize(fstec.GetString()) : null;
        var mitreId = element.TryGetProperty("vuln_id", out vulnIdElement) && vulnIdElement.TryGetProperty("MITRE", out var mitre) ? Normalize(mitre.GetString()) : null;

        var datePublished = ParseDate(element.TryGetProperty("date_published", out var published) ? published.GetString() : null);
        var dateUpdated = ParseDate(element.TryGetProperty("date_updated", out var updated) ? updated.GetString() : null);
        var cvssRating = Normalize(element.TryGetProperty("cvss_rating", out var rating) ? rating.GetString() : null);
        bool? patchAvailable = element.TryGetProperty("patch_available", out var patch) ? patch.ValueKind switch
        {
            JsonValueKind.True => true,
            JsonValueKind.False => false,
            _ => null,
        } : null;

        var description = Normalize(element.TryGetProperty("description", out var desc) ? desc.GetString() : null);
        var mitigation = Normalize(element.TryGetProperty("mitigation", out var mitigationElement) ? mitigationElement.GetString() : null);
        var productCategory = Normalize(element.TryGetProperty("product_category", out var category) ? category.GetString() : null);
        var impact = Normalize(element.TryGetProperty("impact", out var impactElement) ? impactElement.GetString() : null);
        var method = Normalize(element.TryGetProperty("method_of_exploitation", out var methodElement) ? methodElement.GetString() : null);

        bool? userInteraction = element.TryGetProperty("user_interaction", out var uiElement) ? uiElement.ValueKind switch
        {
            JsonValueKind.True => true,
            JsonValueKind.False => false,
            _ => null,
        } : null;

        string? softwareText = null;
        bool? softwareHasCpe = null;
        if (element.TryGetProperty("vulnerable_software", out var softwareElement))
        {
            if (softwareElement.TryGetProperty("software_text", out var textElement))
            {
                softwareText = Normalize(textElement.GetString()?.Replace('\r', ' '));
            }

            if (softwareElement.TryGetProperty("cpe", out var cpeElement))
            {
                softwareHasCpe = cpeElement.ValueKind switch
                {
                    JsonValueKind.True => true,
                    JsonValueKind.False => false,
                    _ => null,
                };
            }
        }

        RuNkckiCweDto? cweDto = null;
        if (element.TryGetProperty("cwe", out var cweElement))
        {
            int? number = null;
            if (cweElement.TryGetProperty("cwe_number", out var numberElement))
            {
                if (numberElement.ValueKind == JsonValueKind.Number && numberElement.TryGetInt32(out var parsed))
                {
                    number = parsed;
                }
                else if (int.TryParse(numberElement.GetString(), NumberStyles.Integer, CultureInfo.InvariantCulture, out var parsedInt))
                {
                    number = parsedInt;
                }
            }

            var cweDescription = Normalize(cweElement.TryGetProperty("cwe_description", out var descElement) ? descElement.GetString() : null);
            if (number.HasValue || !string.IsNullOrWhiteSpace(cweDescription))
            {
                cweDto = new RuNkckiCweDto(number, cweDescription);
            }
        }

        double? cvssScore = element.TryGetProperty("cvss", out var cvssElement) && cvssElement.TryGetProperty("cvss_score", out var scoreElement)
            ? ParseDouble(scoreElement)
            : null;
        var cvssVector = element.TryGetProperty("cvss", out cvssElement) && cvssElement.TryGetProperty("cvss_vector", out var vectorElement)
            ? Normalize(vectorElement.GetString())
            : null;
        double? cvssScoreV4 = element.TryGetProperty("cvss", out cvssElement) && cvssElement.TryGetProperty("cvss_score_v4", out var scoreV4Element)
            ? ParseDouble(scoreV4Element)
            : null;
        var cvssVectorV4 = element.TryGetProperty("cvss", out cvssElement) && cvssElement.TryGetProperty("cvss_vector_v4", out var vectorV4Element)
            ? Normalize(vectorV4Element.GetString())
            : null;

        var urls = element.TryGetProperty("urls", out var urlsElement) && urlsElement.ValueKind == JsonValueKind.Array
            ? urlsElement.EnumerateArray()
                .Select(static url => Normalize(url.GetString()))
                .Where(static url => !string.IsNullOrWhiteSpace(url))
                .Cast<string>()
                .ToImmutableArray()
            : ImmutableArray<string>.Empty;

        return new RuNkckiVulnerabilityDto(
            fstecId,
            mitreId,
            datePublished,
            dateUpdated,
            cvssRating,
            patchAvailable,
            description,
            cweDto,
            productCategory,
            mitigation,
            softwareText,
            softwareHasCpe,
            cvssScore,
            cvssVector,
            cvssScoreV4,
            cvssVectorV4,
            impact,
            method,
            userInteraction,
            urls);
    }

    private static double? ParseDouble(JsonElement element)
    {
        if (element.ValueKind == JsonValueKind.Number && element.TryGetDouble(out var value))
        {
            return value;
        }

        if (element.ValueKind == JsonValueKind.String && double.TryParse(element.GetString(), NumberStyles.Any, CultureInfo.InvariantCulture, out var parsed))
        {
            return parsed;
        }

        return null;
    }

    private static DateTimeOffset? ParseDate(string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return null;
        }

        if (DateTimeOffset.TryParse(value, CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var parsed))
        {
            return parsed;
        }

        if (DateTimeOffset.TryParse(value, CultureInfo.GetCultureInfo("ru-RU"), DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var ruParsed))
        {
            return ruParsed;
        }

        return null;
    }

    private static string? Normalize(string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return null;
        }

        return value.Replace('\r', ' ').Replace('\n', ' ').Trim();
    }
}