using AutoMapper;
using FileService.Application.Ports;
using FileService.Application.StorageContracts;
using FileService.Domain.IReposities;
using FileService.Domain.ValueObjects;
using IM.Commons;
using IM.InitCommon;
using Microsoft.Extensions.Options;
using System.Security.Cryptography;

namespace FileService.Application.UploadFile
{
    public class UploadFileService
    {
        private readonly IUploadFileReposity reposity;
        private readonly IMapper mapper;
        private readonly IObjectStorageRouter router;
        private readonly IOptions<StorageOptions> options;
        private readonly IGroupAccessService groupAccessService; private readonly IM.InitCommon.Management.RuntimePolicy runtime;

        public UploadFileService(IUploadFileReposity reposity, IMapper mapper,
            IObjectStorageRouter router, IOptionsSnapshot<StorageOptions> options,
            IGroupAccessService groupAccessService, IM.InitCommon.Management.RuntimePolicy runtime)
        {
            this.reposity = reposity;
            this.mapper = mapper;
            this.router = router;
            this.options = options;
            this.groupAccessService = groupAccessService; this.runtime = runtime;
        }

        public async Task<Result<FileResponse>> GetFileInfoAsync(Guid id, Guid requesterId)
        {
            var file = await reposity.FindByIdAsync(id);
            if (file == null)
            {
                return Result.Fail<FileResponse>(ResultCode.FILE_NOT_FOUND);
            }
            if (!await CanAccessAsync(file, requesterId))
            {
                return Result.Fail<FileResponse>(ResultCode.PERMISSION_DENIED);
            }

            var response = mapper.Map<FileResponse>(file);
            response.Url = router.Route(file.StorageLocation.StorageProvider)
                .GetPublicUrl(file.StorageLocation);
            response.IsPublic = response.IsPublic || response.Url != null;
            return Result.Success(response);
        }

        /// <summary>
        /// 单次直传：一次性写入存储并同步落库（不分片、不走 MQ）。
        /// 上传前按 checksum 检查是否已存在（秒传）。
        /// </summary>
        public async Task<Result<FileResponse>> SimpleUploadAsync(SimpleUploadCommand command, CancellationToken token = default)
        {
            runtime.CheckFile(command.FileName, command.FileSize);
            if (command.FileSize <= 0 || command.FileSize > options.Value.Providers[options.Value.DefaultProviderCode].MaxObjectSizeBytes) return Result.Fail<FileResponse>(ResultCode.FILE_TOO_LARGE);
            var checksum = command.CheckSum;
            if (string.IsNullOrWhiteSpace(checksum))
            {
                var hash = await MD5.HashDataAsync(command.Content, token);
                checksum = Convert.ToHexString(hash).ToLowerInvariant();
                if (command.Content.CanSeek)
                {
                    command.Content.Position = 0;
                }
            }
            // 秒传：相同 checksum 的文件已存在则直接返回已有记录
            if (!string.IsNullOrEmpty(checksum))
            {
                var existing = await reposity.FindByCheckSumGlobalAsync("md5", checksum);
                var existingPublicUrl = existing == null
                    ? null
                    : router.Route(existing.StorageLocation.StorageProvider).GetPublicUrl(existing.StorageLocation);
                if (existing != null && (existingPublicUrl != null ||
                    (!command.IsPublic && existing.OwnerId == command.OwnerId)))
                {
                    var hit = mapper.Map<FileResponse>(existing);
                    hit.Url = existingPublicUrl;
                    hit.IsPublic = hit.IsPublic || hit.Url != null;
                    return Result.Success(hit);
                }
            }

            var providerOption = options.Value.Providers[options.Value.DefaultProviderCode];
            var storage = router.Route(providerOption.ProviderCode);

            // 公开文件落公开桶/目录，否则落私有桶
            var bucket = command.IsPublic
                ? (providerOption.PublicBucket ?? providerOption.Bucket)
                : providerOption.Bucket;

            var ext = Path.GetExtension(command.FileName);
            var date = DateTime.Now;
            var objectKey = $"{date:yyyy/MM/dd}/{Guid.NewGuid():N}{ext}";

            var location = await storage.PutObjectAsync(new PutObjectCommand(
                ProviderCode: providerOption.ProviderCode,
                Bucket: bucket,
                ObjectKey: objectKey,
                ContentType: command.ContentType,
                Content: command.Content,
                ContentLength: command.FileSize), token);

            var file = new Domain.Entities.UploadFile(
                ownerId: command.OwnerId,
                fileName: SafeFileName(command.FileName),
                fileSize: command.FileSize,
                contentType: command.ContentType,
                storageLocation: location,
                checkSum: new CheckSum("md5", checksum),
                isPublic: command.IsPublic);

            reposity.Create(file);

            var response = mapper.Map<FileResponse>(file);
            response.Url = storage.GetPublicUrl(location);
            return Result.Success(response);
        }

        /// <summary>
        /// 打开文件下载流（鉴权下载）。返回流、内容类型与原始文件名。
        /// </summary>
        public async Task<Result<FileDownload>> OpenDownloadAsync(Guid id, Guid requesterId, CancellationToken token = default)
        {
            var file = await reposity.FindByIdAsync(id);
            if (file == null)
            {
                return Result.Fail<FileDownload>(ResultCode.FILE_NOT_FOUND);
            }
            if (!await CanAccessAsync(file, requesterId))
            {
                return Result.Fail<FileDownload>(ResultCode.PERMISSION_DENIED);
            }

            var stream = await router.Route(file.StorageLocation.StorageProvider)
                .OpenReadAsync(file.StorageLocation, token);

            return Result.Success(new FileDownload(
                stream,
                file.ContentType.Value,
                file.FileName.Value));
        }

        private async Task<bool> CanAccessAsync(Domain.Entities.UploadFile file, Guid requesterId)
        {
            var publicUrl = router.Route(file.StorageLocation.StorageProvider).GetPublicUrl(file.StorageLocation);
            if (file.IsPublic || publicUrl != null || file.OwnerId == requesterId) return true;
            if (string.Equals(file.ChatType, "PRIVATE", StringComparison.OrdinalIgnoreCase))
            {
                return file.TargetId == requesterId;
            }
            if (string.Equals(file.ChatType, "GROUP", StringComparison.OrdinalIgnoreCase) && file.TargetId.HasValue)
            {
                return await groupAccessService.CheckMemberAsync(requesterId, file.TargetId.Value);
            }
            return false;
        }

        // 文件名超长时安全截断（保留扩展名），真实存储键由 objectKey 保证唯一。
        private static FileName SafeFileName(string fileName)
        {
            const int maxFileNameLength = 255;
            if (fileName.Length <= maxFileNameLength)
            {
                return new FileName(fileName);
            }

            var ext = Path.GetExtension(fileName);
            var stem = Path.GetFileNameWithoutExtension(fileName);
            var keep = Math.Max(0, maxFileNameLength - ext.Length);
            return new FileName(stem[..Math.Min(stem.Length, keep)] + ext);
        }
    }
}