using System.Xml;
using System.Xml.Linq;
using Launcher.Next.Core;

namespace Launcher.Next.Application;

public sealed record LegacyPluginDefinition(string Id, string Renewal, string Catalog, string Install, int DefinitionOrder, IReadOnlyList<string>? Machines = null)
{
    public bool IsAllowedOn(string machineName) => Machines is null || Machines.Count == 0 || Machines.Contains(machineName, StringComparer.OrdinalIgnoreCase);
}
public sealed record LegacyProductPattern(string Name, string Filter, string Roster, IReadOnlyList<LegacyPluginDefinition> Plugins, IReadOnlyList<string>? Attributes = null, IReadOnlyList<string>? Sources = null, string? Target = null, string? Loader = null, string? ObjectPath = null);
public sealed record LegacyLauncherSettings(string Help, string CareMarker, IReadOnlyList<LegacyProductPattern> Patterns);
public sealed record LegacyDownloadListEntry(int ElementIndex, string RawId, string NormalizedId, int? FirstOccurrenceIndex, string SourceShape);
public sealed record LegacyDownloadSelection(IReadOnlyList<string> PluginIds, IReadOnlyList<LegacyDownloadListEntry>? Entries = null)
{
    public IReadOnlyList<string> EffectivePluginIds => PluginIds.Distinct(StringComparer.OrdinalIgnoreCase).ToArray();
}
public sealed record LegacyCompatibilityMapping(string LegacyId, string PackageId, string Version, string Channel);
public sealed record LegacyCompatibilityOverlay(string MappingId, string Product, int ProductYear, string Architecture, bool AllowOfflineFallback, IReadOnlyList<LegacyCompatibilityMapping> Plugins);

public sealed class LegacyConfigurationAdapter
{
    private static readonly XmlReaderSettings XmlSettings = new() { DtdProcessing = DtdProcessing.Prohibit, XmlResolver = null, MaxCharactersInDocument = 1_000_000 };

    public LegacyLauncherSettings ParseSettings(string xml)
    {
        using var reader = XmlReader.Create(new StringReader(xml), XmlSettings); var root = XDocument.Load(reader).Root ?? throw new InvalidOperationException("LEGACY_SETTINGS_INVALID");
        var path = root.Element("path") ?? throw new InvalidOperationException("LEGACY_SETTINGS_PATH_MISSING");
        var patterns = root.Elements("data").Select(data =>
        {
            var pattern = data.Element("pattern") ?? throw new InvalidOperationException("LEGACY_PATTERN_MISSING");
            string Value(string name) => pattern.Element(name)?.Value ?? throw new InvalidOperationException("LEGACY_PATTERN_FIELD_MISSING:" + name);
            var plugins = data.Elements("plugin").Select((plugin, index) => new LegacyPluginDefinition(
                plugin.Element("id")?.Value ?? throw new InvalidOperationException("LEGACY_PLUGIN_ID_MISSING"),
                plugin.Element("renewal")?.Value ?? throw new InvalidOperationException("LEGACY_RENEWAL_MISSING"),
                plugin.Element("catalog")?.Value ?? throw new InvalidOperationException("LEGACY_CATALOG_MISSING"),
                plugin.Element("install")?.Value ?? throw new InvalidOperationException("LEGACY_INSTALL_MISSING"), index,
                plugin.Elements("machine").Select(x => x.Value.Trim()).Where(x => x.Length > 0).ToArray())).ToArray();
            return new LegacyProductPattern(Value("name"), Value("filter"), Value("roster"), plugins,
                pattern.Elements("attrib").Select(x => x.Value).ToArray(),
                pattern.Elements("source").Elements("course").Select(x => x.Value).ToArray(),
                pattern.Element("target")?.Value, pattern.Element("loader")?.Value, pattern.Element("object")?.Value);
        }).ToArray();
        return new(path.Element("help")?.Value ?? throw new InvalidOperationException("LEGACY_HELP_MISSING"), path.Element("care")?.Value ?? throw new InvalidOperationException("LEGACY_CARE_MISSING"), patterns);
    }

    public LegacyDownloadSelection ParseDownloadList(string xml)
    {
        try
        {
            using var reader = XmlReader.Create(new StringReader(xml), XmlSettings);
            var root = XDocument.Load(reader).Root;
            if (root?.Name != "root") throw new InvalidOperationException("DOWNLOAD_LIST_ROOT_INVALID");
            // F2_Xml serialized only root/id and removed only exact empty strings. Real project files
            // also contain source-grouped <area><id> entries; preserve their document order as the
            // modern plan while retaining raw values and duplicate evidence.
            var direct = root.Elements("id").Select(x => (Element: x, Shape: "Root"));
            var grouped = root.Elements("area").SelectMany(area => area.Elements("id").Select(x => (Element: x, Shape: "Area")));
            var entries = (direct.Any() ? direct : grouped).Select((entry, index) =>
            {
                var raw = entry.Element.Value;
                var normalized = raw; // legacy F2_Xml did not Trim or case-normalize IDs.
                return new LegacyDownloadListEntry(index, raw, normalized, null, entry.Shape);
            }).ToArray();
            var seen = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
            var annotated = entries.Select(entry =>
            {
                if (entry.RawId == "") return entry;
                if (seen.TryGetValue(entry.NormalizedId, out var first)) return entry with { FirstOccurrenceIndex = first };
                seen[entry.NormalizedId] = entry.ElementIndex;
                return entry;
            }).ToArray();
            return new(annotated.Where(x => x.RawId != "").Select(x => x.RawId).ToArray(), annotated);
        }
        catch (XmlException) { throw new InvalidOperationException("DOWNLOAD_LIST_XML_MALFORMED"); }
    }

    public IReadOnlyList<PackageRequirement> Join(LegacyProductPattern pattern, LegacyDownloadSelection selection, LegacyCompatibilityOverlay overlay)
    {
        var result = new List<PackageRequirement>();
        foreach (var id in selection.EffectivePluginIds)
        {
            var definition = pattern.Plugins.Where(x => string.Equals(x.Id, id, StringComparison.OrdinalIgnoreCase)).ToArray();
            if (definition.Length == 0) throw new InvalidOperationException("LEGACY_PLUGIN_ID_NOT_DEFINED");
            if (definition.Length > 1) throw new InvalidOperationException("AMBIGUOUS_LEGACY_PLUGIN_DEFINITION");
            var mapping = overlay.Plugins.Where(x => string.Equals(x.LegacyId, id, StringComparison.OrdinalIgnoreCase)).ToArray();
            if (mapping.Length == 0) throw new InvalidOperationException("LEGACY_MAPPING_NOT_FOUND");
            if (mapping.Length > 1) throw new InvalidOperationException("LEGACY_MAPPING_DUPLICATE");
            result.Add(new(mapping[0].PackageId, overlay.Product, overlay.ProductYear, overlay.Architecture, mapping[0].Channel, mapping[0].Version, overlay.MappingId, overlay.AllowOfflineFallback));
        }
        return result;
    }
}