Migrate to rescript.json and wire background/content PDF detection

Author: Jonathan D.A. Jewell

bsconfig.json rescript.jsonbsconfig.json renamed to rescript.json

@@ -7,7 +7,7 @@
     }
   ],
   "package-specs": {
-    "module": "es6",
+    "module": "esmodule",
     "in-source": true
   },
   "suffix": ".bs.js",

src/background.res

@@ -1,3 +1,72 @@
 /* SPDX-License-Identifier: AGPL-3.0-or-later WITH Palimpsest */
 
+type runtime
+type onMessage
+
+@val @scope("browser")
+external runtime: runtime = "runtime"
+
+@get
+external onMessage: runtime => onMessage = "onMessage"
+
+@send
+external addListener: (onMessage, Js.Json.t => Js.Promise.t<Js.Json.t>) => unit = "addListener"
+
+let unsafeJson = (value: 'a): Js.Json.t => Obj.magic(value)
+
+let makeResponse = (
+  ~ok: bool,
+  ~blocks: array<PdfTool.block>=[],
+  ~error: option<string>=None,
+): Js.Json.t => {
+  let response = Js.Dict.empty()
+  Js.Dict.set(response, "ok", Js.Json.boolean(ok))
+  Js.Dict.set(response, "blocks", unsafeJson(blocks))
+  switch error {
+  | Some(message) => Js.Dict.set(response, "error", Js.Json.string(message))
+  | None => ()
+  }
+  unsafeJson(response)
+}
+
+let decodeDetectRequest = (message: Js.Json.t): option<string> => {
+  switch Js.Json.decodeObject(message) {
+  | Some(payload) =>
+    let action =
+      payload->Js.Dict.get("action")->Belt.Option.flatMap(Js.Json.decodeString)->Belt.Option.getWithDefault("")
+    let url =
+      payload->Js.Dict.get("url")->Belt.Option.flatMap(Js.Json.decodeString)->Belt.Option.getWithDefault("")
+    if action == "detectBlocks" && url != "" {
+      Some(url)
+    } else {
+      None
+    }
+  | None => None
+  }
+}
+
+let detectFromUrl = (url: string): Js.Promise.t<Js.Json.t> => {
+  let detectPromise =
+    Js.Promise2.then(Webapi.Fetch.fetch(url), response =>
+        Js.Promise2.then(response->Webapi.Fetch.Response.arrayBuffer, pdfBuffer =>
+          Js.Promise2.then(PdfTool.detectBlocks(pdfBuffer), blocks =>
+            Js.Promise.resolve(makeResponse(~ok=true, ~blocks))
+          )
+        )
+      )
+
+  Js.Promise2.catch(detectPromise, err => {
+    Js.log2("detect blocks failed", err)
+    Js.Promise.resolve(makeResponse(~ok=false, ~error=Some("detectBlocks failed")))
+  })
+}
+
+let _ =
+  addListener(onMessage(runtime), message =>
+    switch decodeDetectRequest(message) {
+    | Some(url) => detectFromUrl(url)
+    | None => Js.Promise.resolve(makeResponse(~ok=false, ~error=Some("unsupported action")))
+    }
+  )
+
 Js.log("Blocky Writer background service worker loaded")

src/content.res

@@ -1,8 +1,91 @@
 /* SPDX-License-Identifier: AGPL-3.0-or-later WITH Palimpsest */
 
-@val
-external href: string = "window.location.href"
+type runtime
 
-if href->Js.String2.includes("gov.uk") {
-  Js.log2("Blocky Writer active on", href)
+@val @scope("browser")
+external runtime: runtime = "runtime"
+
+@send
+external sendMessage: (runtime, Js.Json.t) => Js.Promise.t<Js.Json.t> = "sendMessage"
+
+let unsafeJson = (value: 'a): Js.Json.t => Obj.magic(value)
+
+let makeDetectMessage = (url: string): Js.Json.t => {
+  let payload = Js.Dict.empty()
+  Js.Dict.set(payload, "action", Js.Json.string("detectBlocks"))
+  Js.Dict.set(payload, "url", Js.Json.string(url))
+  unsafeJson(payload)
+}
+
+let isPdfUrl = (url: string): bool => url->Js.String2.toLowerCase->Js.String2.endsWith(".pdf")
+
+let findPdfTarget = (): option<string> => {
+  let currentUrl = Webapi.Dom.location->Webapi.Dom.Location.href
+  if isPdfUrl(currentUrl) {
+    Some(currentUrl)
+  } else {
+    switch Webapi.Dom.document->Webapi.Dom.Document.querySelector("a[href$='.pdf']") {
+    | Some(linkElement) =>
+      switch Webapi.Dom.Element.asHtmlElement(linkElement) {
+      | Some(link) =>
+        let linkHref = link->Webapi.Dom.HtmlElement.href
+        if isPdfUrl(linkHref) {
+          Some(linkHref)
+        } else {
+          None
+        }
+      | None => None
+      }
+    | None => None
+    }
+  }
+}
+
+let logDetectionResponse = (response: Js.Json.t): unit => {
+  switch Js.Json.decodeObject(response) {
+  | Some(payload) =>
+    let ok =
+      payload->Js.Dict.get("ok")->Belt.Option.flatMap(Js.Json.decodeBoolean)->Belt.Option.getWithDefault(false)
+    if ok {
+      let count =
+        payload
+        ->Js.Dict.get("blocks")
+        ->Belt.Option.flatMap(Js.Json.decodeArray)
+        ->Belt.Option.map(Belt.Array.length)
+        ->Belt.Option.getWithDefault(0)
+      Js.log2("Blocky Writer detected blocks", count)
+    } else {
+      let message =
+        payload
+        ->Js.Dict.get("error")
+        ->Belt.Option.flatMap(Js.Json.decodeString)
+        ->Belt.Option.getWithDefault("unknown error")
+      Js.log2("Blocky Writer detection failed", message)
+    }
+  | None => Js.log("Blocky Writer received non-object response")
+  }
+}
+
+let requestBlockDetection = (targetUrl: string): unit => {
+  Js.log2("Blocky Writer detectBlocks target", targetUrl)
+  let request = makeDetectMessage(targetUrl)
+  let sendPromise = sendMessage(runtime, request)
+  let loggedPromise = Js.Promise2.then(sendPromise, response => {
+    logDetectionResponse(response)
+    Js.Promise.resolve(response)
+  })
+  let _ = Js.Promise2.catch(loggedPromise, err => {
+    Js.log2("Blocky Writer message failed", err)
+    Js.Promise.resolve(Js.Json.null)
+  })
+  ()
+}
+
+let currentUrl = Webapi.Dom.location->Webapi.Dom.Location.href
+
+if currentUrl->Js.String2.includes("gov.uk") {
+  switch findPdfTarget() {
+  | Some(targetUrl) => requestBlockDetection(targetUrl)
+  | None => Js.log("Blocky Writer found no PDF target on page")
+  }
 }

src/core/PdfTool.res

@@ -8,25 +8,55 @@ type block = {
   height: float,
 }
 
-type arrayBuffer = Js.Typed_array.ArrayBuffer.t
+type arrayBuffer = Webapi.Fetch.arrayBuffer
+type uint8Array = Js.Typed_array.Uint8Array.t
 
-type wasmModule
+@module("../../rust/pdftool_core/pkg/pdftool_core.js")
+external initWasm: unit => Js.Promise.t<unit> = "default"
+
+@module("../../rust/pdftool_core/pkg/pdftool_core.js")
+external detectBlocksNative: uint8Array => array<block> = "detect_blocks"
 
 @module("../../rust/pdftool_core/pkg/pdftool_core.js")
-external wasm: wasmModule = "default"
+external fillBlocksNative: (uint8Array, array<block>, Js.Dict.t<string>) => uint8Array = "fill_blocks"
+
+let initState: ref<option<Js.Promise.t<unit>>> = ref(None)
 
-@send
-external detectBlocksRaw: (wasmModule, arrayBuffer) => Js.Promise.t<array<block>> = "detect_blocks"
+let toNativeArrayBuffer = (buffer: arrayBuffer): Js.Typed_array.ArrayBuffer.t => Obj.magic(buffer)
 
-@send
-external fillBlocksRaw: (wasmModule, arrayBuffer, array<block>, Js.Dict.t<string>) => Js.Promise.t<arrayBuffer> = "fill_blocks"
+let fromNativeArrayBuffer = (buffer: Js.Typed_array.ArrayBuffer.t): arrayBuffer => Obj.magic(buffer)
 
-let detectBlocks = (pdfData: arrayBuffer): Js.Promise.t<array<block>> =>
-  detectBlocksRaw(wasm, pdfData)
+let ensureInitialized = (): Js.Promise.t<unit> => {
+  switch initState.contents {
+  | Some(promise) => promise
+  | None =>
+    let promise = initWasm()
+    initState.contents = Some(promise)
+    promise
+  }
+}
+
+let detectBlocks = (pdfData: arrayBuffer): Js.Promise.t<array<block>> => {
+  let bytes = Js.Typed_array.Uint8Array.fromBuffer(toNativeArrayBuffer(pdfData))
+  let detection = Js.Promise2.then(ensureInitialized(), _ => Js.Promise.resolve(detectBlocksNative(bytes)))
+  Js.Promise2.catch(detection, err => {
+    Js.log2("detectBlocks error", err)
+    Js.Promise.resolve([])
+  })
+}
 
 let fillBlocks = (
   pdfData: arrayBuffer,
   blocks: array<block>,
   fields: Js.Dict.t<string>,
-): Js.Promise.t<arrayBuffer> =>
-  fillBlocksRaw(wasm, pdfData, blocks, fields)
+): Js.Promise.t<arrayBuffer> => {
+  let bytes = Js.Typed_array.Uint8Array.fromBuffer(toNativeArrayBuffer(pdfData))
+  let fill = Js.Promise2.then(ensureInitialized(), _ => {
+    let filled = fillBlocksNative(bytes, blocks, fields)
+    Js.Promise.resolve(fromNativeArrayBuffer(Js.Typed_array.Uint8Array.buffer(filled)))
+  })
+  Js.Promise2.catch(fill, err => {
+    Js.log2("fillBlocks error", err)
+    Js.Promise.resolve(fromNativeArrayBuffer(Js.Typed_array.ArrayBuffer.make(0)))
+  })
+}