using System.Text.RegularExpressions;

namespace WxAgent.Core;

public sealed record WechatSearchExpansion(string Category, int RowIndex, int ExpectedCount);
public sealed record WechatSearchPage(
    IReadOnlyList<WechatSessionSearchResult> Results, IReadOnlyList<WechatSearchExpansion> Expansions);

public static class WechatSearchRules
{
    private static readonly Regex More = new(@"^查看全部\s*[(（](\d+)[)）]$", RegexOptions.CultureInvariant);

    public static bool IsLocalCategory(string? name) => name is "联系人" or "群聊" or "功能" or "最常使用";

    public static bool IsExpansionLabel(string name) => More.IsMatch(name.Trim());

    public static WechatSearchPage Parse(
        IReadOnlyList<(string AutomationId, string AccessibleName)> rows, string query, string? expandedCategory = null)
    {
        if (expandedCategory is not null && expandedCategory is not ("联系人" or "群聊"))
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "Only local contacts and group chats may be expanded.");
        var results = new List<WechatSessionSearchResult>();
        var expansions = new List<WechatSearchExpansion>();
        var category = expandedCategory;
        for (var index = 0; index < rows.Count; index++)
        {
            var row = rows[index];
            var name = row.AccessibleName.Trim();
            if (!row.AutomationId.StartsWith("search_item_", StringComparison.Ordinal))
            {
                if (IsLocalCategory(name)) { category = name; continue; }
                var more = More.Match(name);
                if (more.Success && category is "联系人" or "群聊")
                {
                    if (!int.TryParse(more.Groups[1].Value, out var count) || count is < 1 or > 10000)
                        throw new WxAgentException(WxAgentErrorCode.UiStructureChanged, "Invalid local search result count.");
                    expansions.Add(new WechatSearchExpansion(category, index, count));
                    continue;
                }
                // An unrecognized section must not inherit local trust from an expanded category.
                category = null;
                continue;
            }
            if (category is null || row.AutomationId.StartsWith("search_item_web_", StringComparison.Ordinal)
                || row.AutomationId.StartsWith("search_item_online_", StringComparison.Ordinal)) continue;
            var parsed = WechatSessionParser.ParseSearchResults([row], query).SingleOrDefault();
            if (parsed is null) continue;
            var lines = row.AccessibleName.Split(['\r', '\n'], StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
            var idName = row.AutomationId["search_item_".Length..];
            var displayName = lines.Contains(idName, StringComparer.Ordinal) ? idName
                : parsed.Name == category ? lines.LastOrDefault(line => line != category) ?? string.Empty : parsed.Name;
            if (displayName.Length == 0 || (category == "功能" && displayName != WechatLocators.FileTransferAssistant)) continue;
            // The promoted local row uses the same name-based ID as contacts/groups.
            // Do not admit arbitrary function, online, or future result families under this mixed header.
            if (category == "最常使用" && row.AutomationId != "search_item_" + displayName
                && row.AutomationId != WechatLocators.FileTransferAssistantSearchResult) continue;
            // Preserve duplicates: two same-named local conversations must be reported as ambiguous, not silently merged.
            results.Add(parsed with { Name = displayName, Category = category, IsExactMatch = string.Equals(displayName, query, StringComparison.Ordinal) });
        }
        return new WechatSearchPage(results, expansions);
    }

    public static WechatSessionSearchResult RequireExact(IReadOnlyList<WechatSessionSearchResult> results, string name)
    {
        var matches = results.Where(result => IsLocalCategory(result.Category)
            && string.Equals(result.Name, name, StringComparison.Ordinal)).ToArray();
        return matches.Length switch
        {
            1 => matches[0],
            0 => throw new WxAgentException(WxAgentErrorCode.ControlNotFound, "The exact local conversation was not found."),
            _ => throw new WxAgentException(WxAgentErrorCode.InvalidOperationState, "Multiple local conversations have the same name; refusing an ambiguous selection.")
        };
    }
}