test(ci): dynamic iteration control for emulator tests

this is the same idea from the unit test workflow that lets us
dynamically expand our matrix based on manual workflow input
from GitHub web UI

.github/workflows/tests_emulator.yml

@@ -2,6 +2,12 @@ name: 🛠️ Emulator Tests
 
 on:
   workflow_dispatch:
+    inputs:
+      iterations:
+        description: "Number of iterations to run. Default 1. Max 256."
+        required: true
+        default: 1
+        type: number
   pull_request:
   push:
     # Ignore merge queue branches on push; avoids merge_group+push concurrency race since ref is same
@@ -14,8 +20,71 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  # We want to generate our matrix dynamically
+  # Initial job generates the matrix as a JSON, and following job will use deserialize and use the result
+  matrix_prep:
+    # Do not run the scheduled jobs on forks
+    if: (github.event_name == 'schedule' && github.repository == 'ankidroid/Anki-Android') || (github.event_name != 'schedule')
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.build-matrix.outputs.result }}
+    steps:
+      - id: build-matrix
+        uses: actions/github-script@v7
+        with:
+          script: |
+            // by default, we will run one iteration
+            let iterationArray = [1]
+
+            // workflow dispatch will be a drop-down of different options
+            if (context.eventName === "workflow_dispatch") {
+              const inputs = ${{ toJSON(inputs) }}
+              console.log('inputs is: ' + JSON.stringify(inputs))
+
+              const iterationInput = inputs.iterations
+              console.log('iterations input is: ' + iterationInput)
+              // this will expand for example with input 5 => [1, 2, 3, 4, 5]
+              iterationArray = []
+              for (let i = 1; i <= iterationInput; i++) {
+                iterationArray.push(i);
+              }
+              console.log('iterationArray is: ' + iterationArray)
+            }
+
+            // If we are running on a schedule it's our periodic passive scan for flakes
+            // Goal is to run enough iterations on all systems that we have confidence there are no flakes
+            if (context.eventName === "schedule") {
+              const iterationCount = 15
+              for (let i = 1; i <= iterationCount; i++) {
+                iterationArray.push(i);
+              }
+            }
+
+            // TODO Refactor to make these dynamic with a low/high bracket only on schedule, not push
+            // For now this is the latest supported API. Previously API 29 was fastest.
+            // #13695: This was reverted to API 30, 31 was unstable. This should be fixed
+            let apiLevel = [30];
+
+            // These are used for performance tuning what emulator to use.
+            // try different architectures, targets, delays etc
+            let arch = [x86_64];
+            let target = [google_apis];
+            let firstBootDelay = [600];
+
+            return {
+              "iteration": iterationArray,
+              "api-level": apiLevel,
+              "arch": arch,
+              "target": target,
+              "first-boot-delay": firstBootDelay
+            }
+      - name: Debug Output
+        run: echo "${{ steps.build-matrix.outputs.result }}"
+
+  # This uses the matrix generated from the matrix-prep stage
+  # it will run unit tests on whatever OS combinations are desired
   emulator_test:
-    name: Android Emulator Test
+    name: Android Emulator Test (run ${{ matrix.iteration }})
     runs-on: ubuntu-latest
     timeout-minutes: 75
     env:
@@ -29,16 +98,7 @@ jobs:
       KEYALIAS: nrkeystorealias
     strategy:
       fail-fast: false
-      matrix:
-        # Refactor to make these dynamic with a low/high bracket only on schedule, not push
-        # For now this is the latest supported API. Previously API 29 was fastest.
-        # #13695: This was reverted to API 30, 31 was unstable. This should be fixed
-        api-level: [30]
-        arch: [x86_64]
-        target: [google_apis]
-        first-boot-delay: [600]
-        # This is useful for benchmarking, do 0, 1, 2, etc (up to 256 max job-per-matrix limit) for averages
-        iteration: [0]
+      matrix: ${{fromJson(needs.matrix_prep.outputs.matrix)}}
     steps:
       - name: Free Disk Space (Ubuntu)
         uses: insightsengineering/disk-space-reclaimer@v1