using Microsoft.SharePoint.Client;
using Microsoft.SharePoint.Client.Search.Query;
using SharepointToolbox.Core.Helpers;
using SharepointToolbox.Core.Models;

namespace SharepointToolbox.Services;

/// <summary>
/// Duplicate file and folder detection.
/// Files: Search API (same KQL engine as SearchService) + client-side composite key grouping.
/// Folders: CSOM CAML FSObjType=1 via SharePointPaginationHelper + composite key grouping.
/// Port of PS Find-DuplicateFiles / Find-DuplicateFolders (PS lines 4942-5036).
/// </summary>
public class DuplicatesService : IDuplicatesService
{
    private const int BatchSize = 500;
    private const int MaxStartRow = 50_000;

    public async Task<IReadOnlyList<DuplicateGroup>> ScanDuplicatesAsync(
        ClientContext ctx,
        DuplicateScanOptions options,
        IProgress<OperationProgress> progress,
        CancellationToken ct)
    {
        ct.ThrowIfCancellationRequested();

        List<DuplicateItem> allItems;

        if (options.Mode == "Folders")
            allItems = await CollectFolderItemsAsync(ctx, options, progress, ct);
        else
            allItems = await CollectFileItemsAsync(ctx, options, progress, ct);

        progress.Report(OperationProgress.Indeterminate($"Grouping {allItems.Count:N0} items by duplicate key\u2026"));

        var groups = allItems
            .GroupBy(item => MakeKey(item, options))
            .Where(g => g.Count() >= 2)
            .Select(g => new DuplicateGroup
            {
                GroupKey = g.Key,
                Name     = g.First().Name,
                Items    = g.ToList()
            })
            .OrderByDescending(g => g.Items.Count)
            .ThenBy(g => g.Name)
            .ToList();

        return groups;
    }

    // ── File collection via Search API ────────────────────────────────────────

    private static async Task<List<DuplicateItem>> CollectFileItemsAsync(
        ClientContext ctx,
        DuplicateScanOptions options,
        IProgress<OperationProgress> progress,
        CancellationToken ct)
    {
        // KQL: all documents, optionally scoped to a library
        var kqlParts = new List<string> { "ContentType:Document" };
        if (!string.IsNullOrEmpty(options.Library))
            kqlParts.Add($"Path:\"{ctx.Url.TrimEnd('/')}/{options.Library.TrimStart('/')}*\"");
        string kql = string.Join(" AND ", kqlParts);

        var allItems = new List<DuplicateItem>();
        int startRow = 0;

        do
        {
            ct.ThrowIfCancellationRequested();

            var kq = new KeywordQuery(ctx)
            {
                QueryText      = kql,
                StartRow       = startRow,
                RowLimit       = BatchSize,
                TrimDuplicates = false
            };
            foreach (var prop in new[] { "Title", "Path", "FileExtension", "Created",
                "LastModifiedTime", "Size", "ParentLink" })
                kq.SelectProperties.Add(prop);

            var executor = new SearchExecutor(ctx);
            ClientResult<ResultTableCollection> clientResult = executor.ExecuteQuery(kq);
            await ExecuteQueryRetryHelper.ExecuteQueryRetryAsync(ctx, progress, ct);

            var table = clientResult.Value
                .FirstOrDefault(t => t.TableType == KnownTableTypes.RelevantResults);
            if (table == null || table.RowCount == 0) break;

            foreach (System.Collections.Hashtable row in table.ResultRows)
            {
                var dict = row.Cast<System.Collections.DictionaryEntry>()
                    .ToDictionary(e => e.Key.ToString()!, e => e.Value ?? (object)string.Empty);

                string path = GetStr(dict, "Path");
                if (path.Contains("/_vti_history/", StringComparison.OrdinalIgnoreCase))
                    continue;

                string name = System.IO.Path.GetFileName(path);
                if (string.IsNullOrEmpty(name))
                    name = GetStr(dict, "Title");

                string raw = GetStr(dict, "Size");
                string digits = System.Text.RegularExpressions.Regex.Replace(raw, "[^0-9]", "");
                long size = long.TryParse(digits, out var sv) ? sv : 0L;

                DateTime? created  = ParseDate(GetStr(dict, "Created"));
                DateTime? modified = ParseDate(GetStr(dict, "LastModifiedTime"));

                // Derive library from path segments
                string library = ExtractLibraryFromPath(path, ctx.Url);

                allItems.Add(new DuplicateItem
                {
                    Name      = name,
                    Path      = path,
                    Library   = library,
                    SizeBytes = size,
                    Created   = created,
                    Modified  = modified
                });
            }

            progress.Report(new OperationProgress(allItems.Count, MaxStartRow,
                $"Collected {allItems.Count:N0} files\u2026"));

            startRow += BatchSize;
        }
        while (startRow <= MaxStartRow);

        return allItems;
    }

    // ── Folder collection via CAML ────────────────────────────────────────────

    private static async Task<List<DuplicateItem>> CollectFolderItemsAsync(
        ClientContext ctx,
        DuplicateScanOptions options,
        IProgress<OperationProgress> progress,
        CancellationToken ct)
    {
        // Load all document libraries on the site
        ctx.Load(ctx.Web,
            w => w.Lists.Include(
                l => l.Title, l => l.Hidden, l => l.BaseType));
        await ExecuteQueryRetryHelper.ExecuteQueryRetryAsync(ctx, progress, ct);

        var libs = ctx.Web.Lists
            .Where(l => !l.Hidden && l.BaseType == BaseType.DocumentLibrary)
            .ToList();

        // Filter to specific library if requested
        if (!string.IsNullOrEmpty(options.Library))
        {
            libs = libs
                .Where(l => l.Title.Equals(options.Library, StringComparison.OrdinalIgnoreCase))
                .ToList();
        }

        var camlQuery = new CamlQuery
        {
            ViewXml = """
                <View Scope='RecursiveAll'>
                  <Query>
                    <Where>
                      <Eq>
                        <FieldRef Name='FSObjType' />
                        <Value Type='Integer'>1</Value>
                      </Eq>
                    </Where>
                  </Query>
                  <RowLimit>2000</RowLimit>
                </View>
                """
        };

        var allItems = new List<DuplicateItem>();

        foreach (var lib in libs)
        {
            ct.ThrowIfCancellationRequested();
            progress.Report(OperationProgress.Indeterminate($"Scanning folders in {lib.Title}\u2026"));

            await foreach (var item in SharePointPaginationHelper.GetAllItemsAsync(ctx, lib, camlQuery, ct))
            {
                ct.ThrowIfCancellationRequested();

                var fv = item.FieldValues;
                string name      = fv["FileLeafRef"]?.ToString() ?? string.Empty;
                string fileRef   = fv["FileRef"]?.ToString() ?? string.Empty;
                int subCount     = Convert.ToInt32(fv["FolderChildCount"] ?? 0);
                int childCount   = Convert.ToInt32(fv["ItemChildCount"] ?? 0);
                int fileCount    = Math.Max(0, childCount - subCount);
                DateTime? created  = fv["Created"] is DateTime cr ? cr : (DateTime?)null;
                DateTime? modified = fv["Modified"] is DateTime md ? md : (DateTime?)null;

                allItems.Add(new DuplicateItem
                {
                    Name        = name,
                    Path        = fileRef,
                    Library     = lib.Title,
                    FolderCount = subCount,
                    FileCount   = fileCount,
                    Created     = created,
                    Modified    = modified
                });
            }
        }

        return allItems;
    }

    // ── Composite key builder (matches test scaffold in DuplicatesServiceTests) ──

    internal static string MakeKey(DuplicateItem item, DuplicateScanOptions opts)
    {
        var parts = new List<string> { item.Name.ToLowerInvariant() };
        if (opts.MatchSize     && item.SizeBytes.HasValue)    parts.Add(item.SizeBytes.Value.ToString());
        if (opts.MatchCreated  && item.Created.HasValue)      parts.Add(item.Created.Value.Date.ToString("yyyy-MM-dd"));
        if (opts.MatchModified && item.Modified.HasValue)     parts.Add(item.Modified.Value.Date.ToString("yyyy-MM-dd"));
        if (opts.MatchSubfolderCount && item.FolderCount.HasValue) parts.Add(item.FolderCount.Value.ToString());
        if (opts.MatchFileCount && item.FileCount.HasValue)   parts.Add(item.FileCount.Value.ToString());
        return string.Join("|", parts);
    }

    // ── Private utilities ─────────────────────────────────────────────────────

    private static string GetStr(IDictionary<string, object> r, string key) =>
        r.TryGetValue(key, out var v) ? v?.ToString() ?? string.Empty : string.Empty;

    private static DateTime? ParseDate(string s) =>
        DateTime.TryParse(s, out var dt) ? dt : (DateTime?)null;

    private static string ExtractLibraryFromPath(string path, string siteUrl)
    {
        // Extract first path segment after the site URL as library name
        // e.g. https://tenant.sharepoint.com/sites/MySite/Shared Documents/file.docx -> "Shared Documents"
        if (string.IsNullOrEmpty(path) || string.IsNullOrEmpty(siteUrl))
            return string.Empty;

        string relative = path.StartsWith(siteUrl.TrimEnd('/'), StringComparison.OrdinalIgnoreCase)
            ? path.Substring(siteUrl.TrimEnd('/').Length).TrimStart('/')
            : path;

        int slash = relative.IndexOf('/');
        return slash > 0 ? relative.Substring(0, slash) : relative;
    }
}