From a01d2cd266e96386b55476ff39af8da55b533c9c Mon Sep 17 00:00:00 2001
From: Ayrat Hudaygulov <szer.penguin@gmail.com>
Date: Mon, 5 Oct 2026 11:11:40 +0100
Subject: [PATCH] Overlap Azure OCR with local barcode decoding

---
 src/CouponHubBot/Services/CouponOcrEngine.fs | 11 ++--
 tests/CouponHubBot.Ocr.Tests/OcrTests.fs     | 60 ++++++++++++++++++++
 2 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/src/CouponHubBot/Services/CouponOcrEngine.fs b/src/CouponHubBot/Services/CouponOcrEngine.fs
index 6fbed1c..ceb172a 100644
--- a/src/CouponHubBot/Services/CouponOcrEngine.fs
+++ b/src/CouponHubBot/Services/CouponOcrEngine.fs
@@ -455,14 +455,9 @@ type CouponOcrEngine(azureTextOcr: IBotOcr, logger: ILogger<CouponOcrEngine>, ti
             if not (isNull activity) then
                 %activity.SetTag("image.size_bytes", imageBytes.Length)
             let nowUtc = time.GetUtcNow().UtcDateTime
-            let barcode = tryDecodeBarcode imageBytes
 
-            // The Azure OCR SDK already retried transient failures; if one still surfaces (network,
-            // timeout, or a non-2xx response after retries) AnalyzeImageBytes re-throws it. Catch it
-            // here (don't crash) and record that the OCR *backend* failed, so callers can tell "Azure
-            // was down/timed out/errored" apart from "Azure answered 200 but found no usable text".
-            // The ZXing barcode above is independent of Azure and may still be set.
-            let! ocrAnalysis, backendFailed =
+            // OCR runs while the local barcode decoder works; backend failure stays separate from empty text.
+            let ocrTask =
                 task {
                     use azure = botActivity.StartActivity("couponOcr.azure")
                     try
@@ -476,6 +471,8 @@ type CouponOcrEngine(azureTextOcr: IBotOcr, logger: ILogger<CouponOcrEngine>, ti
                         return (null: OcrAnalysis | null), true
                 }
 
+            let barcode = tryDecodeBarcode imageBytes
+            let! ocrAnalysis, backendFailed = ocrTask
             let ocrText = if isNull ocrAnalysis then null else ocrAnalysis.Text
             use parse = botActivity.StartActivity("couponOcr.parse")
 
diff --git a/tests/CouponHubBot.Ocr.Tests/OcrTests.fs b/tests/CouponHubBot.Ocr.Tests/OcrTests.fs
index 2fbb395..187c8c2 100644
--- a/tests/CouponHubBot.Ocr.Tests/OcrTests.fs
+++ b/tests/CouponHubBot.Ocr.Tests/OcrTests.fs
@@ -302,6 +302,66 @@ type OcrTests(output: ITestOutputHelper) =
             do! Task.WhenAll jobs
         }
 
+    [<Theory>]
+    [<InlineData("success")>]
+    [<InlineData("empty")>]
+    [<InlineData("failure")>]
+    [<InlineData("canceled")>]
+    member _.``Recognition awaits pending OCR and preserves the local barcode``(outcome: string) =
+        task {
+            let bytes = File.ReadAllBytes(Path.Combine(AppContext.BaseDirectory, "Images", "5_25_2026-02-08_2026-02-14_2706726228947.jpg"))
+            let completion = TaskCompletionSource<OcrAnalysis | null>(TaskCreationOptions.RunContinuationsAsynchronously)
+            let mutable requests = 0
+            let azure =
+                { new IBotOcr with
+                    member _.AnalyzeImageBytes _ =
+                        requests <- requests + 1
+                        completion.Task }
+            let time = BotInfra.Time.FixedTimeProvider(DateTimeOffset(2026, 2, 8, 0, 0, 0, TimeSpan.Zero))
+            let engine = CouponOcrEngine(azure, Microsoft.Extensions.Logging.Abstractions.NullLogger<CouponOcrEngine>.Instance, time)
+            let recognition = engine.Recognize(ReadOnlyMemory<byte>(bytes))
+            Assert.Equal(1, requests)
+            Assert.False(recognition.IsCompleted)
+
+            match outcome with
+            | "success" ->
+                completion.SetResult(
+                    { RawJson = "{}"
+                      Text = "€5 OFF €25\nValid 8 Feb - 14 Feb\n2706602781191" })
+            | "empty" -> completion.SetResult(null: OcrAnalysis | null)
+            | "failure" -> completion.SetException(InvalidOperationException("OCR unavailable"))
+            | "canceled" -> completion.SetCanceled()
+            | _ -> failwith "Unexpected OCR outcome"
+
+            let! result = recognition
+            Assert.Equal("2706726228947", result.barcode)
+            Assert.Equal(outcome = "failure" || outcome = "canceled", result.backendFailed)
+            match outcome with
+            | "success" ->
+                Assert.Equal(Nullable 5m, result.couponValue)
+                Assert.Equal(Nullable 25m, result.minCheck)
+                Assert.Equal(Nullable(DateTime(2026, 2, 8)), result.validFrom)
+                Assert.Equal(Nullable(DateTime(2026, 2, 14)), result.validTo)
+            | _ ->
+                Assert.False(result.couponValue.HasValue)
+                Assert.False(result.minCheck.HasValue)
+                Assert.False(result.validFrom.HasValue)
+                Assert.False(result.validTo.HasValue)
+        }
+
+    [<Fact>]
+    member _.``Immediate OCR failure preserves the local barcode``() =
+        task {
+            let bytes = File.ReadAllBytes(Path.Combine(AppContext.BaseDirectory, "Images", "5_25_2026-02-08_2026-02-14_2706726228947.jpg"))
+            let azure =
+                { new IBotOcr with
+                    member _.AnalyzeImageBytes _ = raise (InvalidOperationException("OCR unavailable")) }
+            let engine = CouponOcrEngine(azure, Microsoft.Extensions.Logging.Abstractions.NullLogger<CouponOcrEngine>.Instance, TimeProvider.System)
+            let! result = engine.Recognize(ReadOnlyMemory<byte>(bytes))
+            Assert.Equal("2706726228947", result.barcode)
+            Assert.True(result.backendFailed)
+        }
+
     [<Theory>]
     [<InlineData(17)>]
     [<InlineData(33)>]