feat: Add SQL persistence for MIGs too (similar to AHBs)

.gitignore

@@ -136,3 +136,6 @@ dmypy.json
 src/_your_package_version.py
 
 src/_fundamend_version.py
+
+# Claude Code
+.claude/

README.md

@@ -122,7 +122,7 @@ Das Ergebnis sieht dann so aus:
 ```
 
 ### SQL Models
-Die Daten aus den XML-Dateien (Stand 2025-02-10 nur AHBs) lassen sich auch in Datenbanken persistieren.
+Die Daten aus den XML-Dateien lassen sich auch in Datenbanken persistieren.
 Die dazu verwendeten [SQLModel](https://sqlmodel.tiangolo.com/)-Klassen lassen sich mit `fundamend[sqlmodels]` installieren.
 Instanzen der Pydantic-Klassen lassen sich in SQL-Models überführen und umgekehrt:
 ```python
@@ -133,6 +133,15 @@ my_sql_model = SqlAnwendungshandbuch.from_model(pydantic_ahb)
 pydantic_ahb = my_sql_model.to_model()
 ```
 
+Analog dazu funktioniert es auch für MIGs:
+```python
+from fundamend.models.messageimplementationguide import MessageImplementationGuide as PydanticMig
+from fundamend.sqlmodels import MessageImplementationGuide as SqlMig
+
+my_sql_model = SqlMig.from_model(pydantic_mig)
+pydantic_mig = my_sql_model.to_model()
+```
+
 #### Befüllen einer Datenbank mit AHB-Informationen
 In den XML-Rohdaten sind die Informationen aus den AHBs theoretisch beliebig tief verschachtelt, weil jede Segmentgruppe ihrerseits wieder Segmentgruppen enthalten kann.
 Diese Rekursion ist so auch in den SQL-Model-Klassen und der Datenbank abgebildet.

docs/plans/2026-01-07-mig-sqlmodels-design.md

@@ -0,0 +1,183 @@
+# MIG SQLModels Design
+
+## Overview
+
+Add SQLModel support for Message Implementation Guides (MIGs), mirroring the existing AHB SQLModel implementation. This enables persisting MIG data to SQL databases with the same patterns used for AHBs.
+
+## File Structure
+
+Create new file: `src/fundamend/sqlmodels/messageimplementationguide.py`
+
+## Classes
+
+| SQL Model Class | Pydantic Source | Has `position`? |
+|-----------------|-----------------|-----------------|
+| `MigCode` | `models.messageimplementationguide.Code` | Yes |
+| `MigDataElement` | `models.messageimplementationguide.DataElement` | Yes |
+| `MigDataElementGroup` | `models.messageimplementationguide.DataElementGroup` | Yes |
+| `MigSegment` | `models.messageimplementationguide.Segment` | Yes |
+| `MigSegmentGroupLink` | (artificial join table) | No |
+| `MigSegmentGroup` | `models.messageimplementationguide.SegmentGroup` | Yes |
+| `MessageImplementationGuide` | `models.messageimplementationguide.MessageImplementationGuide` | No |
+
+## Field Mappings
+
+### MigCode
+- `primary_key: UUID`
+- `name: str`
+- `description: str | None`
+- `value: str | None`
+- `position: Optional[int]`
+- FK: `data_element_primary_key`
+
+### MigDataElement
+- `primary_key: UUID`
+- `id: str`
+- `name: str`
+- `description: str | None`
+- `status_std: str` (MigStatus stored as string)
+- `status_specification: str`
+- `format_std: str`
+- `format_specification: str`
+- `codes: list[MigCode]`
+- `position: Optional[int]`
+- FK: `data_element_group_primary_key` (optional)
+- FK: `segment_primary_key` (optional)
+
+### MigDataElementGroup
+- `primary_key: UUID`
+- `id: str`
+- `name: str`
+- `description: str | None`
+- `status_std: str`
+- `status_specification: str`
+- `data_elements: list[MigDataElement]`
+- `position: Optional[int]`
+- FK: `segment_primary_key`
+
+### MigSegment
+- `primary_key: UUID`
+- `id: str`
+- `name: str`
+- `description: str | None`
+- `counter: str`
+- `level: int`
+- `number: str`
+- `max_rep_std: int`
+- `max_rep_specification: int`
+- `status_std: str`
+- `status_specification: str`
+- `example: str | None`
+- `is_on_uebertragungsdatei_level: bool`
+- `data_elements: list[MigDataElement]`
+- `data_element_groups: list[MigDataElementGroup]`
+- `position: Optional[int]`
+- FK: `segmentgroup_primary_key` (optional)
+- FK: `mig_primary_key` (optional)
+
+### MigSegmentGroupLink
+- `parent_id: UUID` (FK to MigSegmentGroup, PK)
+- `child_id: UUID` (FK to MigSegmentGroup, PK)
+
+### MigSegmentGroup
+- `primary_key: UUID`
+- `id: str`
+- `name: str`
+- `counter: str`
+- `level: int`
+- `max_rep_std: int`
+- `max_rep_specification: int`
+- `status_std: str`
+- `status_specification: str`
+- `segments: list[MigSegment]`
+- `segment_groups: list[MigSegmentGroup]` (via MigSegmentGroupLink)
+- `parent_segment_group: MigSegmentGroup | None` (via MigSegmentGroupLink)
+- `position: Optional[int]`
+- FK: `mig_primary_key` (optional)
+
+### MessageImplementationGuide
+- `primary_key: UUID`
+- `veroeffentlichungsdatum: date`
+- `autor: str`
+- `versionsnummer: str`
+- `format: EdifactFormat`
+- `segments: list[MigSegment]`
+- `segment_groups: list[MigSegmentGroup]`
+- SQL-only fields:
+  - `gueltig_von: Optional[date]`
+  - `gueltig_bis: Optional[date]`
+  - `edifact_format_version: Optional[EdifactFormatVersion]`
+
+## Relationships
+
+```
+MessageImplementationGuide
+├── segments: list[MigSegment]          (FK: mig_primary_key)
+└── segment_groups: list[MigSegmentGroup]  (FK: mig_primary_key)
+
+MigSegmentGroup
+├── segments: list[MigSegment]          (FK: segmentgroup_primary_key)
+├── segment_groups: list[MigSegmentGroup]  (via MigSegmentGroupLink)
+└── parent_segment_group: MigSegmentGroup  (via MigSegmentGroupLink)
+
+MigSegment
+├── data_elements: list[MigDataElement]      (FK: segment_primary_key)
+└── data_element_groups: list[MigDataElementGroup]  (FK: segment_primary_key)
+
+MigDataElementGroup
+└── data_elements: list[MigDataElement]  (FK: data_element_group_primary_key)
+
+MigDataElement
+└── codes: list[MigCode]  (FK: data_element_primary_key)
+```
+
+## UniqueConstraints
+
+Following AHB pattern - position unique within parent:
+- `MigCode`: `(data_element_primary_key, position)`
+- `MigDataElementGroup`: `(segment_primary_key, position)`
+- `MigSegment`: position unique per parent (MIG or SegmentGroup) - separate constraints
+- `MigSegmentGroup`: `(mig_primary_key, position)`
+
+## Conversion Logic
+
+### `from_model()` pattern
+- Classmethod taking Pydantic model + optional `position` parameter
+- Direct field mappings
+- Enumerate children to get position index
+- Use `isinstance` checks for union types to route to correct list
+
+### `to_model()` pattern
+- Instance method returning Pydantic model
+- Merge union-type lists, sort by `position`
+- Return `tuple()` for Pydantic tuple fields
+- MigStatus enum restored via Pydantic validation
+
+## Exports
+
+Update `sqlmodels/__init__.py`:
+```python
+from .messageimplementationguide import (
+    MigCode,
+    MigDataElement,
+    MigDataElementGroup,
+    MigSegment,
+    MigSegmentGroup,
+    MessageImplementationGuide,
+)
+```
+
+## Testing
+
+New file: `unittests/test_sqlmodels_messageimplementationguide.py`
+
+Tests:
+1. Single MIG roundtrip: XML → Pydantic → SQL → Pydantic → compare equality
+2. All MIGs from private submodule (skip if not checked out)
+
+Reuse `sqlite_session` fixture from conftest.
+
+## Future Work (out of scope)
+
+- `MigHierarchyMaterialized` view for flattening
+- Prefix AHB classes (`AhbCode`, `AhbDataElement`, etc.) for consistency

src/fundamend/sqlmodels/__init__.py

@@ -28,6 +28,15 @@
     Segment,
     SegmentGroup,
 )
+from .messageimplementationguide import (
+    MessageImplementationGuide,
+    MigCode,
+    MigDataElement,
+    MigDataElementGroup,
+    MigSegment,
+    MigSegmentGroup,
+    MigSegmentGroupLink,
+)
 
 __all__ = [
     "create_ahb_view",
@@ -46,4 +55,11 @@
     "Anwendungsfall",
     "Bedingung",
     "Anwendungshandbuch",
+    "MessageImplementationGuide",
+    "MigCode",
+    "MigDataElement",
+    "MigDataElementGroup",
+    "MigSegment",
+    "MigSegmentGroup",
+    "MigSegmentGroupLink",
 ]

src/fundamend/sqlmodels/anwendungshandbuch.py

@@ -7,7 +7,7 @@
 
 from efoli import EdifactFormat, EdifactFormatVersion
 
-# pylint: disable=too-few-public-methods, duplicate-code, missing-function-docstring
+# pylint: disable=too-few-public-methods, duplicate-code, missing-function-docstring, no-member
 
 # the structures are similar, still we decided against inheritance, so there's naturally a little bit of duplication