Add parallel processing for individual batch builds

tests/test_batch.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+import unittest
+from pathlib import Path
+from unittest.mock import patch
+
+import a1_swap_mod_packer.batch as batch
+from a1_swap_mod_packer.models import BuildOptions, BuildResult, PlateJob
+
+
+class IndividualBatchBuildTest(unittest.TestCase):
+    def test_worker_count_uses_task_count_and_caps_cpu_count(self) -> None:
+        self.assertEqual(batch.individual_batch_worker_count(0), 0)
+        self.assertEqual(batch.individual_batch_worker_count(3, max_workers=99), 3)
+        self.assertEqual(batch.individual_batch_worker_count(3, max_workers=0), 1)
+        with patch.object(batch.os, "cpu_count", return_value=32):
+            self.assertEqual(batch.individual_batch_worker_count(20), batch.INDIVIDUAL_BATCH_MAX_WORKERS)
+        with patch.object(batch.os, "cpu_count", return_value=None):
+            self.assertEqual(batch.individual_batch_worker_count(20), 1)
+
+    def test_serial_runner_keeps_success_order_and_collects_failures(self) -> None:
+        tasks = [
+            self.task("one.3mf", "one.out.3mf", copies=2),
+            self.task("fail.3mf", "fail.out.3mf", copies=3),
+            self.task("two.3mf", "two.out.3mf", copies=4),
+        ]
+
+        def fake_build(jobs: list[PlateJob], options: BuildOptions) -> BuildResult:
+            job = jobs[0]
+            if job.source_3mf.name == "fail.3mf":
+                raise ValueError("planned failure")
+            return BuildResult(
+                output_3mf=options.output_3mf,
+                plate_count=job.copies,
+                total_prediction_seconds=None,
+                total_weight_grams=None,
+                gcode_md5=job.source_3mf.stem,
+            )
+
+        with patch.object(batch, "build_packed_3mf", side_effect=fake_build):
+            result = batch.run_individual_batch_builds(tasks, max_workers=1)
+
+        self.assertEqual(result.worker_count, 1)
+        self.assertEqual(
+            [item.output_3mf.name for item in result.results],
+            ["one.out.3mf", "two.out.3mf"],
+        )
+        self.assertEqual([item.plate_count for item in result.results], [2, 4])
+        self.assertEqual(len(result.failures), 1)
+        self.assertEqual(result.failures[0].index, 1)
+        self.assertEqual(result.failures[0].job.source_3mf.name, "fail.3mf")
+        self.assertIn("planned failure", result.failures[0].error)
+
+    @staticmethod
+    def task(source_name: str, output_name: str, copies: int) -> batch.IndividualBuildTask:
+        return batch.IndividualBuildTask(
+            PlateJob(Path(source_name), copies),
+            BuildOptions(swap_gcode=Path("swap.gcode"), output_3mf=Path(output_name)),
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()