mechanic-pwa/recon/findings/damage_model.md

Vendor Damage Data Model — Extraction Notes

Source: Ttc.dll (Xamarin Android app, reverse-engineered from assemblies.blob) Date: 2026-05-17

Core Objects

DetailDamageCoordinate

A single tap-point placed by the mechanic on the enlarged part SVG.

Field	Type	Notes
Id	int/Guid	PK
X	float	Relative X on the part SVG canvas
Y	float	Relative Y on the part SVG canvas
InspectionGuid	Guid	Ties this point to an inspection session
MetaId	int	Zone ID (0..56) — which part this point belongs to
GroupId	int	Groups multiple points belonging to ONE damage annotation
ImageWithLinesId	int	FK → the photo with polyline annotation
LinesId	int	FK → the DrawingLines set

Evidence: backing fields <X>k__BackingField, <Y>k__BackingField, <Id>k__BackingField, <MetaId>k__BackingField, <GroupId>k__BackingField, <ImageWithLinesId>k__BackingField, <LinesId>k__BackingField all found in contiguous block at 0x3baa0–0x3bd50 in Strings heap. GetByGroupId method confirms group-based querying.

DetailDamageCoordinateContract (API wire format)

Same fields as above, serialized as JSON. The JSON property for severity is "degree" (lowercase, confirmed at 0x3d752 in Strings heap alongside "damageDegree" widget name).

DetailDamageDrawPointContract

A single vertex in the finger-drawn polyline annotation on a photo.

Field	Type	Notes
X	float	Point X on the photo canvas
Y	float	Point Y on the photo canvas

The polyline is a list of DetailDamageDrawPointContract objects. The parent container is DrawingLines (backing field <DrawingLines>k__BackingField at 0x3cade). Method DrawLine (0x3e3c9) draws each segment. StrokeWidth (0x3f59a) controls line thickness.

The photo itself is stored as Image64StringWithLines (base64 JPEG) and ImageBase64StringWithLines (alternate field). The link between a damage group and its annotated photo is: DetailDamageCoordinate.ImageWithLinesId → VehicleStatePhotoInspection.Id.

Multi-Point Damage Grouping

Yes, multi-point damages are grouped via GroupId. The mechanic taps N spots on the part SVG — each tap creates a DetailDamageCoordinate with the same GroupId. All points in a group share:

• One damage_type (the vertical list selection)
• One degree (severity: 0=Легкое, 1=Среднее, 2=Тяжелое)
• One ImageWithLinesId (one photo with optional polyline)

The GetByGroupId method (found in Strings heap at 0x394c0) fetches all coordinates for a group. SaveByParts (0x42f4f) persists the full group in one call.

Photo + Polyline Link

Inspection
  └─ DetailDamageCoordinate[] (grouped by GroupId)
       ├─ GroupId = 42 (e.g.)
       ├─ MetaId = 0 (front bumper)
       ├─ [X1,Y1], [X2,Y2], [X3,Y3]   ← multiple tap points
       ├─ ImageWithLinesId = 7         ← FK → photo record
       └─ degree = 1 (Среднее)

VehicleStatePhotoInspection (id=7)
  ├─ Image64StringWithLines   ← base64 JPEG (the photo)
  ├─ DrawingLines[]           ← list of DetailDamageDrawPointContract
  │     └─ [{X:0.2, Y:0.4}, {X:0.5, Y:0.6}, ...]  ← polyline vertices
  └─ HistoryLines[]           ← read-only history of old polylines

Our Implementation Recommendation

1. DamageGroup table: { id, inspection_id, zone_id, damage_type, severity(0-2), photo_id, created_at }
2. DamagePoint table: { id, group_id, x REAL, y REAL, seq_order INT } — multiple rows per group
3. DamagePhoto table: { id, image_b64, polyline JSONB } where polyline is [[x,y], ...]
4. Severity stored as integer 0/1/2, displayed as Легкое/Среднее/Тяжелое

This mirrors the vendor model exactly while using a standard relational schema.

Known Unknowns

• The exact JSON shape returned by damage/details endpoint (API not captured live)
• Whether GroupId is a local UUID or server-assigned int
• Whether DrawingLines coordinates are normalized (0..1) or absolute pixels