import 'dart:convert';
import 'dart:math';

import 'package:cached_network_image_ce/cached_network_image.dart';
import 'package:crypto/crypto.dart';
import 'package:flutter/widgets.dart';

import '../media/media_item.dart';
import '../media/media_server_client.dart';
import '../services/device_performance.dart';
import '../services/image_cache_service.dart';
import '../services/settings_service.dart' show EpisodePosterMode;
import 'platform_detector.dart';

/// Image types for different transcoding strategies
enum ImageType {
  poster, // 2:3 ratio posters
  art, // Wide background art
  thumb, // 16:9 episode thumbnails
  logo, // Variable ratio clear logos
  heroLogo, // Large hero clear logos
  avatar, // Small square-ish avatars (user profiles, inline person headers)
  square, // 1:1 grid-cell artwork (albums, artists, tracks, cast cards)
}

/// Backend-neutral image URL helper.
///
/// Builds optimally-sized image URLs that go through the right server-side
/// transcode path:
/// - **Plex**: `/photo/:/transcode?width=W&height=H&url=...&X-Plex-Token=...`
///   constructed by [MediaServerClient.thumbnailUrl] (PlexClient impl).
/// - **Jellyfin**: `/Items/{id}/Images/{type}?MaxWidth=W&MaxHeight=H&api_key=...`
///   constructed by [MediaServerClient.thumbnailUrl] (JellyfinClient impl).
///
/// Self-contained absolute URLs (Jellyfin items pre-absolutized at the
/// model layer) get sized via query-param append so they pick up the same
/// DPR scaling and cache-bucket rounding as Plex.
///
/// External URLs (EPG provider images, etc.) that the local server doesn't
/// host get proxied through Plex's photo transcoder when a Plex client is
/// available; otherwise they pass through unchanged.
class MediaImageHelper {
  static const int _widthRoundingFactor = 40;
  static const int _heightRoundingFactor = 60;

  /// 1080p baseline; scaled by [DevicePerformance.displayBudgetFactor] so
  /// 4K-surface displays can fetch up to 3840×2160 instead of upscaling.
  static const int _maxTranscodedWidth = 1920;
  static const int _maxTranscodedHeight = 1080;

  static const int _minTranscodedWidth = 160;
  static const int _minTranscodedHeight = 240;

  /// Minimum DPR for TV to ensure sharp artwork on large screens
  static const double _tvMinDpr = 2.0;

  /// Reduced tier caps: tiles at 1.5× DPR, backdrops at ~720p. Smaller
  /// transcodes mean fewer bytes fetched AND cheaper decodes on weak 32-bit
  /// hardware; the art cap is masked by the gradient scrims drawn over it.
  static const double _reducedMaxDpr = 1.5;
  static const int _reducedMaxArtWidth = 1280;
  static const int _reducedMaxArtHeight = 720;

  /// Rounds a value up to the next multiple of [factor]. Shared between the
  /// URL dimension rounding (transcode bucket) and the mem-cache dimension
  /// rounding (decode bucket) so both snap to the same grid.
  static int _bucketUp(num value, int factor) => (value / factor).ceil() * factor;

  /// Rounds dimensions to cache-friendly values to increase cache hit rate
  static (int width, int height) roundDimensions(double width, double height) {
    final budget = DevicePerformance.displayBudgetFactor();
    return (
      _bucketUp(width, _widthRoundingFactor).clamp(_minTranscodedWidth, (_maxTranscodedWidth * budget).round()),
      _bucketUp(height, _heightRoundingFactor).clamp(_minTranscodedHeight, (_maxTranscodedHeight * budget).round()),
    );
  }

  /// Computes an effective device pixel ratio that accounts for displays where
  /// the platform-reported DPR doesn't reflect the true physical density
  /// (common on Linux X11 with compositor scaling).
  static double effectiveDevicePixelRatio(BuildContext context) {
    final reportedDpr = MediaQuery.devicePixelRatioOf(context);
    double dpr;
    try {
      final displayWidth = View.of(context).display.size.width;
      // Scale quality with display resolution: 1920px = baseline (1.0x)
      final displayBasedDpr = (displayWidth / 1920).clamp(1.0, 3.0);
      dpr = max(reportedDpr, displayBasedDpr);
    } catch (_) {
      dpr = reportedDpr;
    }
    if (DevicePerformance.isReduced) return min(dpr, _reducedMaxDpr);
    if (PlatformDetector.isTV()) dpr = max(dpr, _tvMinDpr);
    return dpr;
  }

  /// Calculates optimal image dimensions based on image type and constraints
  static (int width, int height) calculateOptimalDimensions({
    required double maxWidth,
    required double maxHeight,
    required double devicePixelRatio,
    ImageType imageType = ImageType.poster,
  }) {
    final targetWidth = maxWidth.isFinite ? maxWidth * devicePixelRatio : 300 * devicePixelRatio;
    final targetHeight = maxHeight.isFinite ? maxHeight * devicePixelRatio : 450 * devicePixelRatio;

    switch (imageType) {
      case ImageType.art:
        if (DevicePerformance.isReduced) {
          // No 1.1× cover overshoot, capped at ~720p.
          return roundDimensions(
            min(targetWidth, _reducedMaxArtWidth.toDouble()),
            min(targetHeight, _reducedMaxArtHeight.toDouble()),
          );
        }
        final coverWidth = targetWidth * 1.1;
        final coverHeight = targetHeight * 1.1;

        return roundDimensions(coverWidth, coverHeight);

      case ImageType.logo:
      case ImageType.heroLogo:
        final logoWidth = targetWidth;
        final logoHeight = targetHeight;
        return roundDimensions(logoWidth, logoHeight);

      case ImageType.thumb:
        final thumbHeight = targetHeight;
        final thumbWidth = min(targetWidth, thumbHeight * (16 / 9));
        return roundDimensions(thumbWidth, thumbHeight);

      case ImageType.avatar:
      case ImageType.square:
        final size = min(targetWidth, targetHeight);
        return roundDimensions(size, size);

      case ImageType.poster:
        final calculatedWidth = min(targetWidth, targetHeight * (2 / 3));
        final calculatedHeight = calculatedWidth * (3 / 2);
        return roundDimensions(calculatedWidth, calculatedHeight);
    }
  }

  /// Whether [type] fills its slot ([BoxFit.cover]) or sits inside it
  /// ([BoxFit.contain]), which is what [MediaServerClient.thumbnailUrl]'s
  /// `cover` flag selects. Logos are the contain case: asking Plex to cover
  /// their slot overshoots the long axis by 20-30% in bytes, and the decode
  /// bounds throw those pixels away again.
  static bool _coversSlot(ImageType type) => switch (type) {
    ImageType.logo || ImageType.heroLogo => false,
    ImageType.art || ImageType.thumb || ImageType.poster || ImageType.avatar || ImageType.square => true,
  };

  /// Creates an optimized image URL.
  ///
  /// Falls back to the raw [thumbPath] when the path is empty, when no
  /// client is available (offline mode), or when transcoding is suppressed
  /// for this path.
  static String getOptimizedImageUrl({
    MediaServerClient? client,
    required String? thumbPath,
    required double maxWidth,
    required double maxHeight,
    required double devicePixelRatio,
    bool enableTranscoding = true,
    ImageType imageType = ImageType.poster,
  }) {
    if (thumbPath == null || thumbPath.isEmpty) return '';
    final basePath = thumbPath;

    if (basePath.startsWith('http://') || basePath.startsWith('https://')) {
      // Self-contained Jellyfin URLs already carry their own auth
      // (`api_key=...`). Append `maxWidth/maxHeight` so we still get DPR
      // scaling and cache-bucket rounding — Jellyfin's image endpoint
      // honours those query params.
      if (basePath.contains('api_key=')) {
        if (!enableTranscoding) return basePath;
        final (width, height) = calculateOptimalDimensions(
          maxWidth: maxWidth,
          maxHeight: maxHeight,
          devicePixelRatio: devicePixelRatio,
          imageType: imageType,
        );
        final uri = Uri.parse(basePath);
        final params = Map<String, String>.from(uri.queryParameters);
        final lowerKeys = params.keys.map((k) => k.toLowerCase()).toSet();
        if (!lowerKeys.contains('maxwidth') && !lowerKeys.contains('width')) {
          params['maxWidth'] = '$width';
        }
        if (!lowerKeys.contains('maxheight') && !lowerKeys.contains('height')) {
          params['maxHeight'] = '$height';
        }
        return uri.replace(queryParameters: params).toString();
      }

      // EPG / external URL — proxy through the server's transcoder. Plex
      // implements [externalImageUrl] via `/photo/:/transcode?url=...`;
      // backends without a comparable endpoint return the URL unchanged.
      if (client == null || !enableTranscoding) return basePath;
      final (width, height) = calculateOptimalDimensions(
        maxWidth: maxWidth,
        maxHeight: maxHeight,
        devicePixelRatio: devicePixelRatio,
        imageType: imageType,
      );
      return client.externalImageUrl(basePath, width: width, height: height, cover: _coversSlot(imageType));
    }

    // Relative path — let the client build the sized URL using its native
    // size-hint params (`/photo/:/transcode` for Plex, `MaxWidth/MaxHeight`
    // for Jellyfin). The interface guarantees both honour width/height.
    if (client == null) {
      // Offline + relative path: the cached entry already exists under the
      // URL originally fetched, so returning '' matches pre-refactor behaviour.
      return '';
    }

    if (!enableTranscoding || !shouldTranscode(basePath)) {
      return client.thumbnailUrl(basePath);
    }

    final (width, height) = calculateOptimalDimensions(
      maxWidth: maxWidth,
      maxHeight: maxHeight,
      devicePixelRatio: devicePixelRatio,
      imageType: imageType,
    );

    // Always request a sized transcode — even tiny slots. An unsized URL
    // hands the full original to the decoder, and a multi-megapixel
    // original behind a 40px avatar is exactly the decode spike that OOMs
    // low-RAM devices. The floor is 160×240 via [roundDimensions].
    return client.thumbnailUrl(basePath, width: width, height: height, cover: _coversSlot(imageType));
  }

  /// Generates cache-friendly dimensions for memory caching.
  ///
  /// Max bounds are type-aware so large originals (e.g. failed server
  /// transcodes or external EPG images) are capped at a resolution
  /// appropriate for the display context.
  static (int memWidth, int memHeight) getMemCacheDimensions({
    required int displayWidth,
    required int displayHeight,
    double scaleFactor = 1.0,
    ImageType imageType = ImageType.poster,
  }) {
    // Bucket to match roundDimensions() so the mem-cache key and CNIP
    // maxHeight stay stable across sub-bucket resize deltas. Without this,
    // LayoutBuilder rebuilds during window resize churn the cache key on
    // every pixel and evict valid entries from Flutter's image cache.
    final bucketedWidth = _bucketUp(displayWidth * scaleFactor, _widthRoundingFactor);
    final bucketedHeight = _bucketUp(displayHeight * scaleFactor, _heightRoundingFactor);

    // Full-tier caps are a 1080p baseline scaled to the display, so slots on
    // a 4K surface decode at the resolution they render at instead of being
    // GPU-upscaled from phone-sized budgets. Reduced-tier caps stay fixed
    // (the factor is pinned to 1.0 there, and the explicit pairs keep the
    // low-RAM budget independent of display probing).
    final budget = DevicePerformance.displayBudgetFactor();
    int scaled(int cap) => (cap * budget).round();
    final (int maxW, int maxH) = switch (imageType) {
      // Reduced-tier caps match the smaller fetch sizes so oversized
      // originals (failed transcodes, external images) can't decode past
      // the tile budget on low-RAM hardware.
      ImageType.poster when DevicePerformance.isReduced => (480, 720),
      ImageType.poster => (scaled(720), scaled(1080)),
      // Square music artwork fills the same grid cells as posters, so both
      // axes cap at the poster width budget.
      ImageType.square when DevicePerformance.isReduced => (480, 480),
      ImageType.square => (scaled(720), scaled(720)),
      ImageType.thumb when DevicePerformance.isReduced => (640, 360),
      ImageType.thumb => (scaled(960), scaled(540)),
      ImageType.art when DevicePerformance.isReduced => (_reducedMaxArtWidth, _reducedMaxArtHeight),
      ImageType.art => (scaled(1920), scaled(1080)),
      ImageType.logo => (scaled(600), scaled(300)),
      ImageType.heroLogo => (scaled(1000), scaled(500)),
      ImageType.avatar => (scaled(300), scaled(300)),
    };

    return (bucketedWidth.clamp(120, maxW), bucketedHeight.clamp(180, maxH));
  }

  /// Wraps [provider] so the decode is bounded on **both** axes.
  ///
  /// `fit` policy keeps aspect ratio and never upscales, so an over-generous
  /// bound is harmless — but an oversized original (failed server transcode,
  /// local artwork file, ultra-wide banner) can no longer decode past the
  /// display budget the way a single-axis bound allows.
  static ImageProvider boundedDecode(ImageProvider provider, {required int memWidth, required int memHeight}) {
    final width = memWidth > 0 ? memWidth : null;
    final height = memHeight > 0 ? memHeight : null;
    if (width == null && height == null) return provider;
    return ResizeImage(provider, width: width, height: height, policy: ResizeImagePolicy.fit);
  }

  /// Selects the decode/transcode shape used by media cards and their
  /// prefetchers. Keeping this derived from [MediaItem.cardShape] prevents the
  /// renderer and prefetch pipeline from assigning different cache budgets.
  static ImageType cardImageType(MediaItem item, EpisodePosterMode episodePosterMode, {bool mixedHubContext = false}) {
    return switch (item.cardShape(episodePosterMode, mixedHubContext: mixedHubContext)) {
      CardShape.square => ImageType.square,
      CardShape.wide => ImageType.thumb,
      CardShape.poster => ImageType.poster,
    };
  }

  /// Creates the final provider for server-hosted artwork.
  ///
  /// The disk key deliberately depends only on the fully bucketed URL. Decode
  /// dimensions belong to Flutter's memory-cache key and must not fragment the
  /// shared disk cache during small layout changes.
  static ImageProvider serverArtworkProvider({
    required String imageUrl,
    required int memWidth,
    required int memHeight,
    String? cacheKey,
  }) {
    final provider = CachedNetworkImageProvider(
      imageUrl,
      cacheKey: cacheKey ?? _serverArtworkCacheKey(imageUrl),
      cacheManager: PlexImageCacheManager.instance,
      headers: const {'User-Agent': 'Plezy'},
    );
    return boundedDecode(provider, memWidth: memWidth, memHeight: memHeight);
  }

  static final _serverArtworkCacheKeys = <String, String>{};
  static const _serverArtworkCacheKeyLimit = 512;

  static String _serverArtworkCacheKey(String imageUrl) {
    final cached = _serverArtworkCacheKeys.remove(imageUrl);
    if (cached != null) {
      _serverArtworkCacheKeys[imageUrl] = cached;
      return cached;
    }

    final key = 'plex_optimized_${sha1.convert(utf8.encode(imageUrl))}';
    if (_serverArtworkCacheKeys.length >= _serverArtworkCacheKeyLimit) {
      _serverArtworkCacheKeys.remove(_serverArtworkCacheKeys.keys.first);
    }
    _serverArtworkCacheKeys[imageUrl] = key;
    return key;
  }

  /// Determines if an image path is suitable for transcoding
  static bool shouldTranscode(String? imagePath) {
    if (imagePath == null || imagePath.isEmpty) return false;

    if (imagePath.contains('/photo/:/transcode') ||
        imagePath.startsWith('http://') ||
        imagePath.startsWith('https://')) {
      return false;
    }

    return true;
  }
}