refactor: dynamic ConversionRequest validation, remove 'or default' from adapters

- __post_init__: _apply_none_defaults() iterates dataclasses.fields() dynamically
- _NUMERIC_CONSTRAINTS and _ENUM_CONSTRAINTS dicts replace per-field if chains
- Both adapters pass values as-is (no 'or default' fallbacks)
- 18 validation tests + updated adapter tests for Enum assertions

abogen/application/conversion_request.py

@@ -9,6 +9,7 @@ into a ConversionRequest before calling ConversionService.run().
 
 from __future__ import annotations
 
+import dataclasses
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, Dict, List, Optional
@@ -16,12 +17,37 @@ from typing import Any, Dict, List, Optional
 from abogen.domain.enums import Language, OutputFormat, SaveMode, SubtitleFormat, SubtitleMode
 
 
+class ConversionRequestError(ValueError):
+    """Raised when ConversionRequest has invalid field values."""
+
+
+# Numeric field constraints: attr -> (min, max)
+_NUMERIC_CONSTRAINTS: dict[str, tuple[float, float | None]] = {
+    "max_subtitle_words": (1, 500),
+    "speed": (0.5, 3.0),
+    "supertonic_total_steps": (2, 15),
+    "silence_between_chapters": (0.0, None),
+    "chapter_intro_delay": (0.0, None),
+}
+
+# Enum-like fields that must be in allowed set
+_ENUM_CONSTRAINTS: dict[str, tuple[str, ...]] = {
+    "chunk_level": ("paragraph", "sentence"),
+    "speaker_mode": ("single", "multi"),
+}
+
+
 @dataclass
 class ConversionRequest:
     """Normalized request for a conversion job.
 
     Only contains fields that describe the conversion task itself.
     UI-only fields (display, logging, user prompts) stay in adapters.
+
+    Validation runs on creation via __post_init__:
+    - None values → replaced with field default (from declaration)
+    - Numeric fields → clamped to valid range
+    - String enums → validated against allowed set
     """
 
     # --- Source ---
@@ -83,3 +109,48 @@ class ConversionRequest:
     cover_image_path: Optional[Path] = None
     cover_image_mime: Optional[str] = None
     generate_epub3: bool = False
+
+    def __post_init__(self) -> None:
+        """Resolve None → default, then validate and clamp."""
+        _apply_none_defaults(self)
+        if not self.tts_provider:
+            self.tts_provider = "kokoro"
+        _clamp_numerics(self)
+        _validate_enums(self)
+
+
+def _apply_none_defaults(obj: ConversionRequest) -> None:
+    """Replace None values with field defaults from dataclass declaration."""
+    for f in dataclasses.fields(obj):
+        if getattr(obj, f.name) is not None:
+            continue
+        if f.default is not dataclasses.MISSING:
+            setattr(obj, f.name, f.default)
+        elif f.default_factory is not dataclasses.MISSING:
+            setattr(obj, f.name, f.default_factory())
+
+
+def _clamp_numerics(obj: ConversionRequest) -> None:
+    """Clamp numeric fields to valid ranges."""
+    for attr, (min_v, max_v) in _NUMERIC_CONSTRAINTS.items():
+        val = getattr(obj, attr)
+        if val is None:
+            continue
+        if not isinstance(val, (int, float)):
+            raise ConversionRequestError(
+                f"{attr} must be a number, got {type(val).__name__}"
+            )
+        clamped = max(min_v, float(val))
+        if max_v is not None:
+            clamped = min(max_v, clamped)
+        setattr(obj, attr, clamped)
+
+
+def _validate_enums(obj: ConversionRequest) -> None:
+    """Validate string enum fields against allowed values."""
+    for attr, allowed in _ENUM_CONSTRAINTS.items():
+        val = getattr(obj, attr)
+        if val not in allowed:
+            raise ConversionRequestError(
+                f"{attr} must be one of {allowed}, got {val!r}"
+            )

abogen/pyqt/conversion_adapter.py

@@ -60,28 +60,28 @@ def build_conversion_request_from_thread(thread: Any) -> ConversionRequest:
         direct_text=thread.file_name if is_direct_text else None,
         original_filename=original_filename,
         # TTS Settings
-        language=thread.lang_code or "a",
+        language=thread.lang_code,
         tts_provider="kokoro",  # PyQt uses Kokoro by default
-        voice=thread.voice or "M1",
+        voice=thread.voice,
         voice_profile=getattr(thread, "voice_profile", None),
-        speed=thread.speed or 1.0,
+        speed=thread.speed,
         use_gpu=thread.use_gpu,
-        supertonic_total_steps=getattr(thread, "supertonic_total_steps", None) or 5,
+        supertonic_total_steps=getattr(thread, "supertonic_total_steps", 5),
         # Output Format
-        output_format=thread.output_format or "wav",
-        subtitle_mode=thread.subtitle_mode or "Disabled",
+        output_format=thread.output_format,
+        subtitle_mode=thread.subtitle_mode,
         subtitle_format=getattr(thread, "subtitle_format", "srt"),
-        max_subtitle_words=getattr(thread, "max_subtitle_words", None) or 50,
+        max_subtitle_words=getattr(thread, "max_subtitle_words", 50),
         # Save Options
-        save_mode=thread.save_option or "save_next_to_input",
+        save_mode=thread.save_option,
         output_folder=output_folder,
         save_chapters_separately=getattr(thread, "save_chapters_separately", False),
         merge_chapters_at_end=getattr(thread, "merge_chapters_at_end", True),
         separate_chapters_format=getattr(thread, "separate_chapters_format", "wav"),
         save_as_project=getattr(thread, "save_as_project", False),
         # Timing
-        silence_between_chapters=getattr(thread, "silence_duration", None) or 2.0,
-        chapter_intro_delay=getattr(thread, "chapter_intro_delay", None) or 0.0,
+        silence_between_chapters=getattr(thread, "silence_duration", 2.0),
+        chapter_intro_delay=getattr(thread, "chapter_intro_delay", 0.0),
         # Content Processing
         replace_single_newlines=getattr(thread, "replace_single_newlines", False),
         read_title_intro=getattr(thread, "read_title_intro", False),

abogen/webui/conversion_adapter.py

@@ -38,28 +38,28 @@ def build_conversion_request_from_job(job: Any) -> ConversionRequest:
         source_path=Path(job.stored_path) if job.stored_path else None,
         original_filename=job.original_filename,
         # TTS Settings
-        language=job.language or "a",
-        tts_provider=job.tts_provider or "kokoro",
-        voice=job.voice or "M1",
+        language=job.language,
+        tts_provider=job.tts_provider,
+        voice=job.voice,
         voice_profile=job.voice_profile,
-        speed=job.speed or 1.0,
+        speed=job.speed,
         use_gpu=job.use_gpu,
-        supertonic_total_steps=job.supertonic_total_steps or 5,
+        supertonic_total_steps=job.supertonic_total_steps,
         # Output Format
-        output_format=job.output_format or "wav",
-        subtitle_mode=job.subtitle_mode or "Disabled",
-        subtitle_format=job.subtitle_format or "srt",
-        max_subtitle_words=job.max_subtitle_words or 50,
+        output_format=job.output_format,
+        subtitle_mode=job.subtitle_mode,
+        subtitle_format=job.subtitle_format,
+        max_subtitle_words=job.max_subtitle_words,
         # Save Options
-        save_mode=job.save_mode or "save_next_to_input",
+        save_mode=job.save_mode,
         output_folder=Path(job.output_folder) if job.output_folder else None,
         save_chapters_separately=job.save_chapters_separately,
         merge_chapters_at_end=job.merge_chapters_at_end,
-        separate_chapters_format=job.separate_chapters_format or "wav",
+        separate_chapters_format=job.separate_chapters_format,
         save_as_project=job.save_as_project,
         # Timing
-        silence_between_chapters=job.silence_between_chapters or 2.0,
-        chapter_intro_delay=job.chapter_intro_delay or 0.0,
+        silence_between_chapters=job.silence_between_chapters,
+        chapter_intro_delay=job.chapter_intro_delay,
         # Content Processing
         replace_single_newlines=job.replace_single_newlines,
         read_title_intro=job.read_title_intro,
@@ -74,8 +74,8 @@ def build_conversion_request_from_job(job: Any) -> ConversionRequest:
         # Chapter/Chunk Configuration
         chapter_overrides=job.chapters or [],
         chunks=job.chunks or [],
-        chunk_level=job.chunk_level or "paragraph",
-        speaker_mode=job.speaker_mode or "single",
+        chunk_level=job.chunk_level,
+        speaker_mode=job.speaker_mode,
         speakers=job.speakers or {},
         # Metadata
         metadata_tags=job.metadata_tags or {},