Add a Storage provider

package.json

@@ -13,6 +13,7 @@
   ],
   "type": "module",
   "dependencies": {
+    "base32768": "^3.0.1",
     "lodash-es": "^4.17.21",
     "mute-stream": "1.0.0"
   },

src/dialog/browser/browser.ts

@@ -12,6 +12,7 @@ https://github.com/curiousdannii/asyncglk
 import {AsyncDialog, DialogDirectories, DialogOptions} from '../common/interface.js'
 import {DownloadOptions, DownloadProvider, ProgressCallback} from './download.js'
 import {Provider} from './interface.js'
+import {WebStorageProvider} from './storage.js'
 
 export class BrowserDialog implements AsyncDialog {
     'async' = true as const
@@ -26,8 +27,11 @@ export class BrowserDialog implements AsyncDialog {
 
     async init(options: DialogOptions & DownloadOptions): Promise<void> {
         this.downloader = new DownloadProvider(options)
+        // TODO: ensure that localStorage is wrapped in a try/catch in case it's disabled
         this.providers = [
             this.downloader,
+            new WebStorageProvider('/tmp', sessionStorage),
+            new WebStorageProvider('/', localStorage),
         ]
 
         for (const [i, provider] of this.providers.entries()) {
@@ -47,7 +51,7 @@ export class BrowserDialog implements AsyncDialog {
     }
 
     async prompt(extension: string, save: boolean): Promise<string | null> {
-        throw new Error('Method not implemented.')
+        return prompt('Filename')
     }
 
     set_storyfile_dir(path: string): Partial<DialogDirectories> {
@@ -59,7 +63,7 @@ export class BrowserDialog implements AsyncDialog {
     }
 
     async exists(path: string): Promise<boolean> {
-        return (await this.providers[0].exists(path))!
+        return !!(await this.providers[0].exists(path))
     }
 
     async read(path: string): Promise<Uint8Array | null> {

src/dialog/browser/interface.ts

@@ -31,6 +31,17 @@ export interface DirEntry {
     name: string
 }
 
+export interface FileData {
+    accessed: number
+    created: number
+    etag?: string
+    data: Uint8Array
+    'last-modified'?: string
+    modified: number
+    path_prefix: string
+    story_id?: string
+}
+
 export class NullProvider implements Provider {
     next: Provider = this
     async delete(_path: string) {

src/dialog/browser/storage.ts

@@ -0,0 +1,109 @@
+/*
+
+Web storage provider
+====================
+
+Copyright (c) 2024 Dannii Willis
+MIT licenced
+https://github.com/curiousdannii/asyncglk
+
+*/
+
+import {decode as base32768_decode, encode as base32768_encode} from 'base32768'
+
+import {DirEntry, FileData, NullProvider, Provider} from './interface.js'
+
+type WebStorageFileMetadata = Pick<FileData, 'accessed' | 'created' | 'modified'>
+
+const METADATA_KEY = 'dialog_metadata'
+
+const enum MetadataUpdateOperation {
+    DELETE = 1,
+    READ = 2,
+    WRITE = 3,
+}
+
+export class WebStorageProvider implements Provider {
+    next = new NullProvider()
+    prefix: string
+    store: Storage
+
+    constructor(prefix: string, store: Storage) {
+        this.prefix = prefix
+        this.store = store
+
+        // TODO: upgrade storage
+    }
+
+    async delete(path: string): Promise<void | null> {
+        if (path.startsWith(this.prefix)) {
+            this.store.removeItem(path)
+            this.update_metadata(path, MetadataUpdateOperation.DELETE)
+        }
+        else {
+            return this.next.delete(path)
+        }
+    }
+
+    async exists(path: string): Promise<boolean | null> {
+        if (path.startsWith(this.prefix)) {
+            return this.store.getItem(path) !== null
+        }
+        else {
+            return this.next.exists(path)
+        }
+    }
+
+    async list(path: string): Promise<DirEntry[] | null> {
+        throw new Error('Not implemented yet')
+    }
+
+    async read(path: string): Promise<Uint8Array | null> {
+        if (path.startsWith(this.prefix)) {
+            const res = this.store.getItem(path)
+            if (res !== null) {
+                this.update_metadata(path, MetadataUpdateOperation.READ)
+                return base32768_decode(res)
+            }
+            return null
+        }
+        else {
+            return this.next.read(path)
+        }
+    }
+
+    async write(path: string, data: Uint8Array): Promise<void | null> {
+        if (path.startsWith(this.prefix)) {
+            // TODO: detect out of space
+            this.store.setItem(path, base32768_encode(data))
+            this.update_metadata(path, MetadataUpdateOperation.WRITE)
+            return null
+        }
+        else {
+            return this.next.write(path, data)
+        }
+    }
+
+    update_metadata(path: string, op: MetadataUpdateOperation) {
+        const now = Date.now()
+        const metadata: Record<string, WebStorageFileMetadata> = JSON.parse(this.store.getItem(METADATA_KEY) || '{}')
+        switch (op) {
+            case MetadataUpdateOperation.DELETE:
+                delete metadata[path]
+                break
+            case MetadataUpdateOperation.READ:
+                metadata[path].accessed = now
+                break
+            case MetadataUpdateOperation.WRITE:
+                if (!metadata[path]) {
+                    metadata[path] = {
+                        accessed: now,
+                        created: now,
+                        modified: now,
+                    }
+                }
+                metadata[path].modified = now
+        }
+        this.store.setItem(METADATA_KEY, JSON.stringify(metadata))
+    }
+}