94 lines
6.7 KiB
TypeScript
94 lines
6.7 KiB
TypeScript
/**
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* 临时显示资源的共享租约，按不透明 owner 对象+key 复用进行中的加载和 URL。
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* 不拥有上传/授权/原字节持久化，调用者取得租约前必须确认权限并保留字节；没有 idle URL 缓存。
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* 最后一个租约释放就 abort/清理来源；迟到 load 返回的资源也会被释放，不能跨退役 owner 重新采用。
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*/
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import { fault } from '../canvas-core/values.ts';
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/** 加载器返回的临时 URL 与可选清理回调（如 revokeObjectURL），不是永久资源身份。 */
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export type DisplaySource = { readonly url: string; release?(): void };
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/** 每个消费者独立 ready/release，共享来源不意味着一个 view 卸载可以释放其它 view 的租约。 */
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export type DisplayLease = { readonly ready: Promise<string>; release(): void };
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/** owner/key 的内存条目，controller 控制共享加载，leases 精确记录当前借用者，retired 防迟到结果。 */
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type Entry = { readonly key: string; readonly owner: object; readonly controller: AbortController; readonly leases: Set<() => void>; promise: Promise<DisplaySource>; source?: DisplaySource; retired: boolean };
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/** Ephemeral display ownership only. The caller checks authorization and pins
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* durable bytes before acquiring. Scope objects are never serialized or reused
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* across project engines/auth epochs. There is no idle URL retention.
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*/
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/** 创建纯显示生命周期容器，owners 两层 Map 用对象身份+字符串 key 索引共享条目。
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* owner 应绑定 engine/auth epoch；本模块不解释账号、资源 ID、URL 权限或实际文件 pin。
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* 没有容量上限/空闲保留，最后 lease 释放即清理；永久撤销 owner 则另记到 WeakSet。 */
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export function createDisplayCache(options: { onError?: (error: unknown) => void } = {}) {
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// owners 仅保留活条目；retired WeakSet 禁止退役 owner 再 acquire，但不强持有其内存。
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const owners = new Map<object, Map<string, Entry>>(), retired = new WeakSet<object>();
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let closed = false;
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/** 同步调用来源 release，隔离其抛错和 onError 的抛错；onError 只报告清理失败。
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* load 的失败通过各 lease.ready 传出，不在这里自动记录或重试；release 合同也不是异步清理任务。 */
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function dispose(source: DisplaySource) { try { source.release?.(); } catch (error) { try { options.onError?.(error); } catch { /* Reporting cannot interrupt cleanup. */ } } }
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/** 幂等退休共享条目，仅删除仍指向自己的表项，避免旧任务删掉同 key 的新 entry。 */
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function retire(entry: Entry) {
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if (entry.retired) return;
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entry.retired = true;
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const entries = owners.get(entry.owner);
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if (entries?.get(entry.key) === entry) { entries.delete(entry.key); if (!entries.size) owners.delete(entry.owner); }
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entry.controller.abort();
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if (entry.source) { dispose(entry.source); entry.source = undefined; }
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}
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/** 永久撤销一个 owner 的所有租约；逐租约拒绝尚未完成 ready，再清理来源/请求。 */
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function releaseOwner(owner: object) {
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retired.add(owner);
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for (const entry of [...(owners.get(owner)?.values() ?? [])]) {
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for (const release of [...entry.leases]) release();
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retire(entry);
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}
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}
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return Object.freeze({
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/** 同 owner/key 复用进行中或已加载来源，命中时忽略本次传入的 load，不逐次重验权限。
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* 每个调用者独立 ready/release；释放已兑现的 ready 不会改变 Promise 的成功结果，但 URL 可能随最后释放失效。
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* 不自动接收 AbortSignal，取消通过 lease.release；单个释放不取消仍有其它消费者的共享加载。 */
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acquire(owner: object, key: string, load: (signal: AbortSignal) => Promise<DisplaySource>): DisplayLease {
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if (closed || retired.has(owner)) throw fault('display_scope_closed');
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if (!owner || typeof owner !== 'object' || typeof key !== 'string' || !key) throw fault('invalid_display_key');
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let entries = owners.get(owner); if (!entries) { entries = new Map(); owners.set(owner, entries); }
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let entry = entries.get(key);
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// 先登记 created 再微任务调用外部 load，使同步异常也有清理句柄，不重复启动相同 key 加载。
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if (!entry) {
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const created: Entry = { owner, key, controller: new AbortController(), leases: new Set(), retired: false, promise: undefined as unknown as Promise<DisplaySource> };
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entry = created; entries.set(key, created);
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created.promise = Promise.resolve().then(() => {
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if (created.retired) throw fault('display_released');
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return load(created.controller.signal);
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}).then(source => {
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// 这里只检查 URL 为非空字符串及可选 release 为函数，不验证 URL 协议/可访问性或图片内容。
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if (!source || typeof source.url !== 'string' || !source.url || source.release !== undefined && typeof source.release !== 'function') { if (typeof source?.release === 'function') dispose(source); throw fault('invalid_display_source'); }
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// 即使 load 不响应 abort，迟到返回也只能 dispose，不允许挂回已无消费者的缓存。
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if (created.retired || !created.leases.size) { dispose(source); throw fault('display_released'); }
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created.source = source; return source;
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}, error => { retire(created); throw error; });
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}
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const shared = entry;
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let released = false, rejectReady: (error: unknown) => void = () => {};
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/** 只释放本租约；未结束 ready 用 display_released 拒绝，最后一个租约才退休共享 entry。 */
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const release = () => {
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if (released) return;
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released = true; shared.leases.delete(release); rejectReady(fault('display_released'));
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if (!shared.leases.size) retire(shared);
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};
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shared.leases.add(release);
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// 映射共享 promise 到各 lease.ready，失败逐个归还；校验 source 时抛错也沿这条失败路径清理。
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// 缓存不吞 ready 的拒绝，消费者需接住取消/加载错误；释放后迟到成功不能再次 resolve 本租约。
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const ready = new Promise<string>((resolve, reject) => {
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rejectReady = reject;
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shared.promise.then(source => { if (!released) resolve(source.url); }, error => { if (!released) { reject(error); release(); } });
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});
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return Object.freeze({ ready, release });
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},
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releaseOwner,
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/** 幂等关闭整个缓存并退休全部 owner，不删除文件或撤销已确认上传。 */
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close() { if (closed) return; closed = true; for (const owner of [...owners.keys()]) releaseOwner(owner); },
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});
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}
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/** 公共 API 由工厂推导；view 只借用 lease，不直接拥有该 workspace 级缓存。 */
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export type DisplayCache = ReturnType<typeof createDisplayCache>;
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