using Microsoft.Extensions.Options;
using MyHomePage.Api.Common;
using MyHomePage.Api.Infrastructure.Configuration;
using MyHomePage.Api.Models.Dtos;

namespace MyHomePage.Api.Services;

/// <inheritdoc />
public class UploadService : IUploadService
{
    /// <summary>允许的图片扩展名白名单（与 SaveAsync 共用）</summary>
    private static readonly string[] AllowedExtensions = { ".png", ".jpg", ".jpeg", ".gif", ".webp", ".svg", ".ico" };

    /// <summary>Content-Type 到扩展名的兜底映射</summary>
    private static readonly Dictionary<string, string> ContentTypeToExt = new(StringComparer.OrdinalIgnoreCase)
    {
        ["image/png"] = ".png",
        ["image/jpeg"] = ".jpg",
        ["image/jpg"] = ".jpg",
        ["image/gif"] = ".gif",
        ["image/webp"] = ".webp",
        ["image/svg+xml"] = ".svg",
        ["image/x-icon"] = ".ico",
        ["image/vnd.microsoft.icon"] = ".ico",
        ["image/ico"] = ".ico",
    };

    private readonly UploadOptions _options;
    private readonly IWebHostEnvironment _env;
    private readonly ILogger<UploadService> _logger;

    /// <summary>P51 诊断：是否已记录过 upload root（避免每次保存重复 log）</summary>
    private bool _rootLogged;

    public UploadService(
        IOptions<UploadOptions> options,
        IWebHostEnvironment env,
        ILogger<UploadService> logger)
    {
        _options = options.Value;
        _env = env;
        _logger = logger;
    }

    /// <inheritdoc />
    public string EnsureRoot()
    {
        var root = Path.IsPathRooted(_options.Path)
            ? _options.Path
            : Path.Combine(_env.ContentRootPath, _options.Path);
        Directory.CreateDirectory(root);

        // P51 诊断：第一次调用时 log 一次实际 root（暴露容器内 /uploads 路径覆盖问题）
        if (!_rootLogged)
        {
            _rootLogged = true;
            _logger.LogInformation(
                "Upload root resolved: Path='{Path}' (IsRooted={IsRooted}) → Actual='{Actual}' | env={Env}",
                _options.Path, Path.IsPathRooted(_options.Path), root, _env.EnvironmentName);
        }
        return root;
    }

    /// <summary>P51 诊断兼容：保留旧方法名（Program.cs 启动期若想强制 log 可调）</summary>
    public string EnsureRootWithLog() => EnsureRoot();

    /// <inheritdoc />
    public async Task<UploadResultDto> SaveAsync(IFormFile file)
    {
        if (file is null || file.Length == 0) throw new BusinessException("文件为空", 400);
        if (file.Length > _options.MaxSizeBytes) throw new BusinessException($"文件大小超过限制（{_options.MaxSizeBytes / 1024 / 1024}MB）", 400);

        var ext = Path.GetExtension(file.FileName).ToLowerInvariant();
        if (string.IsNullOrEmpty(ext)) throw new BusinessException("文件必须包含扩展名", 400);
        if (Array.IndexOf(AllowedExtensions, ext) < 0) throw new BusinessException("仅支持图片格式", 400);

        await using var stream = file.OpenReadStream();
        return await SaveStreamInternalAsync(stream, file.FileName, file.ContentType, ext, subDir: null);
    }

    /// <inheritdoc />
    public async Task<UploadResultDto> SaveStreamAsync(Stream stream, string fileName, string contentType, string? subDir = null)
    {
        if (stream is null) throw new BusinessException("数据流为空", 400);

        // 推断扩展名：优先文件名 → 兜底 content-type
        var ext = Path.GetExtension(fileName).ToLowerInvariant();
        if (string.IsNullOrEmpty(ext))
        {
            if (string.IsNullOrEmpty(contentType)) throw new BusinessException("无法推断文件扩展名", 400);
            if (!ContentTypeToExt.TryGetValue(contentType, out ext))
                throw new BusinessException($"不支持的内容类型：{contentType}", 400);
        }
        if (Array.IndexOf(AllowedExtensions, ext) < 0) throw new BusinessException("仅支持图片格式", 400);

        return await SaveStreamInternalAsync(stream, fileName, contentType, ext, subDir);
    }

    /// <summary>实际写文件的内部流程（SaveAsync / SaveStreamAsync 共用）</summary>
    private async Task<UploadResultDto> SaveStreamInternalAsync(Stream stream, string fileName, string contentType, string ext, string? subDir)
    {
        var root = EnsureRoot();
        // 按日期分目录：2026/07/04[/favicons]
        var datePath = DateTime.UtcNow.ToString("yyyy/MM/dd");
        var relativeDir = string.IsNullOrEmpty(subDir) ? datePath : Path.Combine(datePath, subDir);
        var dir = Path.Combine(root, relativeDir);

        var name = $"{DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()}_{Guid.NewGuid():N}{ext}";
        var fullPath = Path.Combine(dir, name);

        // P51 诊断：把 IO 异常（容器权限/路径/磁盘满）原样抛出 + 完整上下文日志
        try
        {
            Directory.CreateDirectory(dir);
            await using (var fs = new FileStream(fullPath, FileMode.CreateNew, FileAccess.Write, FileShare.None))
            {
                await stream.CopyToAsync(fs);
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex,
                "Upload save failed: file={File}, contentType={ContentType}, ext={Ext}, subDir={SubDir}, " +
                "UploadOptions.Path={OptPath} (IsRooted={IsRooted}), ContentRoot={ContentRoot}, env={Env}, " +
                "computed root={Root}, dir={Dir}, fullPath={FullPath}",
                fileName, contentType, ext, subDir,
                _options.Path, Path.IsPathRooted(_options.Path), _env.ContentRootPath, _env.EnvironmentName,
                root, dir, fullPath);
            throw new BusinessException($"文件保存失败: {ex.GetType().Name}: {ex.Message}", 500);
        }

        var relative = Path.Combine(relativeDir, name).Replace('\\', '/');
        var url = (_options.BaseUrl ?? "/uploads").TrimEnd('/') + "/" + relative;
        _logger.LogInformation("Upload saved: {Path} ({ContentType})", fullPath, contentType);

        return new UploadResultDto
        {
            Path = relative,
            Url = url,
            FileName = fileName,
            Size = new FileInfo(fullPath).Length
        };
    }
}