namespace SeaHaven.Services.Helpers
{
    /// <summary>
    /// Client-confirmed media contract (2026-09-22): photos up to 10 MB (JPEG/PNG/HEIC),
    /// videos up to 100 MB and 90 seconds (MP4/MOV), at most 10 photos and 3 videos per work
    /// order, across the dispatcher media modal, the completion-doc media tab and the vendor
    /// portal upload. Documents (PDF/DOC/DOCX) keep the 50 MB document cap. Duration is read
    /// from the MP4/MOV movie header (<see cref="VideoDurationProbe"/>); the browser pre-checks
    /// it and the server enforces it, and unreadable metadata never blocks an upload.
    /// </summary>
    public static class WorkOrderMediaContract
    {
        public const long MaxPhotoBytes = 10_000_000;
        public const long MaxVideoBytes = 100_000_000;
        public const long MaxDocumentBytes = 50_000_000;
        public const int MaxPhotosPerWorkOrder = 10;
        public const int MaxVideosPerWorkOrder = 3;
        public const int MaxVideoDurationSeconds = 90;

        /// <summary>
        /// Request-level ceiling for media endpoints (RequestSizeLimit / multipart limit). It sits
        /// above <see cref="MaxVideoBytes"/> plus multipart overhead so an oversize file reaches the
        /// per-kind check and gets its generic message instead of a framework 413. The EB nginx
        /// proxy (.platform/nginx/conf.d/01_upload_body_size.conf) must stay above this value.
        /// </summary>
        public const long MaxUploadRequestBytes = 110_000_000;

        public enum UploadKind
        {
            Photo,
            Video,
            Document,
            Unknown
        }

        private static readonly Dictionary<string, UploadKind> KindByContentType =
            new(StringComparer.OrdinalIgnoreCase)
            {
                ["image/jpeg"] = UploadKind.Photo,
                ["image/jpg"] = UploadKind.Photo,
                ["image/png"] = UploadKind.Photo,
                ["image/heic"] = UploadKind.Photo,
                ["video/mp4"] = UploadKind.Video,
                ["video/quicktime"] = UploadKind.Video,
                ["application/pdf"] = UploadKind.Document,
                ["application/msword"] = UploadKind.Document,
                ["application/vnd.openxmlformats-officedocument.wordprocessingml.document"] =
                    UploadKind.Document,
            };

        private static readonly Dictionary<string, UploadKind> KindByExtension =
            new(StringComparer.OrdinalIgnoreCase)
            {
                [".jpg"] = UploadKind.Photo,
                [".jpeg"] = UploadKind.Photo,
                [".png"] = UploadKind.Photo,
                [".heic"] = UploadKind.Photo,
                [".mp4"] = UploadKind.Video,
                [".mov"] = UploadKind.Video,
                [".pdf"] = UploadKind.Document,
                [".doc"] = UploadKind.Document,
                [".docx"] = UploadKind.Document,
            };

        /// <summary>
        /// Classifies an upload. Pass the validated (resolved) content type: it decides whenever
        /// it is an allowlisted type, so a misleading file name cannot move a file into a larger
        /// size class. The extension only decides when no allowlisted type is known (for example
        /// counting stored attachment URLs).
        /// </summary>
        public static UploadKind ResolveKind(string? contentType, string? fileName)
        {
            var type = (contentType ?? string.Empty).Trim();
            if (KindByContentType.TryGetValue(type, out var byType))
                return byType;

            var extension = Path.GetExtension(fileName ?? string.Empty);
            return KindByExtension.TryGetValue(extension, out var byExtension)
                ? byExtension
                : UploadKind.Unknown;
        }

        /// <summary>
        /// Per-work-order count check across both upload surfaces: dispatcher attachments
        /// (classified by stored URL) and vendor-portal documents (classified by validated
        /// content type). Returns the stable rejection message, or null when there is room.
        /// </summary>
        public static string? ValidateCount(
            UploadKind kind,
            IEnumerable<string> attachmentUrls,
            IEnumerable<string> vendorContentTypes)
        {
            if (kind != UploadKind.Photo && kind != UploadKind.Video)
                return null;

            var (photos, videos) = CountKinds(attachmentUrls, vendorContentTypes);

            if (kind == UploadKind.Photo && photos >= MaxPhotosPerWorkOrder)
                return "A work order can have at most 10 photos.";
            if (kind == UploadKind.Video && videos >= MaxVideosPerWorkOrder)
                return "A work order can have at most 3 videos.";
            return null;
        }

        /// <summary>
        /// Photos and videos on a work order: dispatcher attachments (kind from the stored URL)
        /// plus current vendor-portal documents (kind from the validated content type).
        /// </summary>
        public static (int Photos, int Videos) CountKinds(
            IEnumerable<string> attachmentUrls,
            IEnumerable<string> vendorContentTypes)
        {
            var kinds = attachmentUrls.Select(url => ResolveKind(null, url))
                .Concat(vendorContentTypes.Select(type => ResolveKind(type, null)))
                .ToList();
            return (kinds.Count(k => k == UploadKind.Photo), kinds.Count(k => k == UploadKind.Video));
        }

        /// <summary>
        /// 90-second video limit, read from the MP4/QuickTime movie header. A video whose
        /// duration cannot be read is not blocked. Returns the stable message or null.
        /// </summary>
        public static string? ValidateVideoDuration(Stream? content)
        {
            var seconds = VideoDurationProbe.TryReadDurationSeconds(content);
            return seconds > MaxVideoDurationSeconds
                ? $"Videos must be {MaxVideoDurationSeconds} seconds or shorter."
                : null;
        }

        /// <summary>Stable, generic per-kind size message; never echoes file metadata.</summary>
        public static string? ValidateSize(long length, UploadKind kind)
        {
            return kind switch
            {
                UploadKind.Photo when length > MaxPhotoBytes => "Photos must be 10 MB or smaller.",
                UploadKind.Video when length > MaxVideoBytes => "Videos must be 100 MB or smaller.",
                UploadKind.Document when length > MaxDocumentBytes =>
                    "Documents must be 50 MB or smaller.",
                UploadKind.Unknown when length > MaxVideoBytes =>
                    "Files must be 100 MB or smaller.",
                _ => null
            };
        }

        public static string? ValidateSize(string? contentType, string? fileName, long length)
            => ValidateSize(length, ResolveKind(contentType, fileName));
    }
}