tane/apps/app_seeds/lib/services/offer_thumbnail.dart
vjrj 3de01bd948 perf(inventory): lazy list, photo thumbnails, indexes, debounced reload
Scale the local inventory to 10k+ varieties:
- Render the list with ListView.builder over a flattened header/item model
  instead of building every tile upfront.
- Store a small regenerable JPEG thumbnail per photo (schema v14) and use it
  for the 48px list avatar; full bytes stay for offer image hosting. Existing
  photos are backfilled lazily at startup. Thumbnail is local-only (excluded
  from CRDT sync and backups by the JSON codec).
- Add indexes on varieties(is_deleted,is_draft), attachments(parent_type,
  parent_id,kind), lots(variety_id) via @TableIndex.
- Debounce watchInventoryView (~250ms) so a burst of table writes triggers one
  reload, not seven.
- cacheWidth/cacheHeight on the list avatar decode.
- Scale test raised 3k -> 10k; migration test v13 -> v14.
2026-07-20 22:53:48 +02:00

76 lines
2.8 KiB
Dart

import 'dart:convert';
import 'dart:typed_data';
import 'package:image/image.dart' as img;
/// Builds a tiny `data:image/jpeg;base64,…` thumbnail from a full photo, small
/// enough to ride *inside* a Nostr offer event — no media server, fully
/// decentralized. The full-resolution photo stays in the encrypted local
/// inventory; only this shrunken preview is published so peers can see the seed.
///
/// Relays cap event size, so we downscale (longest edge) and re-encode until the
/// base64 fits under [maxBytes]. Returns null when the bytes aren't a decodable
/// image or no size small enough is reachable — the offer then publishes without
/// a photo (graceful, never a hard failure).
String? offerThumbnailDataUri(
Uint8List bytes, {
int maxBytes = 40000,
List<int> edges = const [320, 256, 192, 128],
int quality = 68,
}) {
try {
final decoded = img.decodeImage(bytes);
if (decoded == null) return null;
for (final edge in edges) {
final resized = _fitWithin(decoded, edge);
final jpeg = img.encodeJpg(resized, quality: quality);
final b64 = base64.encode(jpeg);
if (b64.length <= maxBytes) return 'data:image/jpeg;base64,$b64';
}
return null; // even the smallest edge didn't fit — skip the image
} catch (_) {
return null; // undecodable/corrupt bytes — publish without a photo
}
}
/// Builds a small JPEG thumbnail (longest edge [edge]px) for the inventory-list
/// avatar, so the list never has to decode the full-resolution photo. Returns
/// raw JPEG bytes, or null on undecodable input (the caller falls back to the
/// full photo). Kept as local bytes — regenerable, so it is excluded from sync
/// and backups.
Uint8List? inventoryThumbnailBytes(
Uint8List bytes, {
int edge = 96,
int quality = 72,
}) {
try {
final decoded = img.decodeImage(bytes);
if (decoded == null) return null;
final resized = _fitWithin(decoded, edge);
return Uint8List.fromList(img.encodeJpg(resized, quality: quality));
} catch (_) {
return null;
}
}
/// Extracts the raw bytes from a `data:...;base64,…` URI, or null when [uri] is
/// not a base64 data URI. Used by the UI to render an inline thumbnail with
/// `Image.memory` instead of a network fetch.
Uint8List? decodeDataUri(String uri) {
if (!uri.startsWith('data:')) return null;
try {
return Uri.parse(uri).data?.contentAsBytes();
} on FormatException {
return null;
}
}
/// Resizes [image] so its longest edge is at most [edge], preserving aspect
/// ratio. Never upscales a photo that's already smaller.
img.Image _fitWithin(img.Image image, int edge) {
if (image.width <= edge && image.height <= edge) return image;
return image.width >= image.height
? img.copyResize(image, width: edge)
: img.copyResize(image, height: edge);
}