Accession App Architecture

Domain Responsibility

What This App Owns

Sample lifecycle - Collection, storage, tracking
Barcoding - Sample identification
Batching - Sample grouping for processing
Accession patterns - Lab-specific numbering
Sample racks - Physical storage management

What It Depends On

core/ - BaseModel, utilities
admin/ - Labs, departments, tests
finance/ - Billing for sample context

What Should NOT Be Added Here

Device interfacing (belongs in interfacing/)
Report generation (belongs in report/)
Patient demographics (belongs in patient/)

Model-Centric Design (Fat Models)

Key Models

Model	Responsibility	Key Fields	Cross-App Relations
`Sample`	Sample type master	`name`, `code`, `container_type`	`admin.AllTests`
`CollectedSample`	Collected instance	`barcode`, `status`, `collected_at`	`finance.Billing`
`Batches`	Sample grouping	`batch_number`, `status`	`Sample`
`SampleBatches`	Batch-sample relation	`batch_id`, `sample_id`
`AccessionPatterns`	Numbering rules	`pattern`, `current_sequence`	`admin.Labs`
`SampleRack`	Physical storage	`rack_number`, `position`	`CollectedSample`

Business Logic in Models

Sample (accession/models/sample.py) - 339 lines

Key Methods:

Method	Purpose
`prepare_sample_barcode_data()`	Generate barcode labels
`filter_dict()`	Filter sample attributes

CollectedSample (accession/models/collected_sample.py)

Status Transitions:

Status	Meaning
`COLLECTED`	Sample taken from patient
`RECEIVED`	Arrived at lab
`IN_PROGRESS`	Being processed
`COMPLETED`	Testing done
`REJECTED`	Quality issue

Why Fat Model Style Here

Sample lifecycle is critical for:

Chain of custody tracking
Barcode uniqueness
Batch processing workflow

All logic in models ensures consistent tracking.

Data Access Patterns

Sample Lookup

# accession/models/collected_sample.py
CollectedSample.objects.filter(
    labId_id=lab_id,
    barcode=barcode
).select_related(
    "sample",
    "billing"
)

Batch Processing

# Get samples in batch
SampleBatches.objects.filter(
    batch_id=batch_id
).select_related(
    "collected_sample",
    "collected_sample__billing"
)

API Layer (Wiring)

Endpoint Map

Endpoint	View	Purpose
`GET /accession/samples`	`SampleListView`	List samples
`POST /accession/collect`	`CollectView`	Record collection
`POST /accession/batch`	`BatchView`	Create batch
`GET /accession/barcode/{id}`	`BarcodeView`	Generate barcode

Safe Extension Guide

Adding New Sample Status

Add to status choices
Update state transition logic
Add to activity logging

Patterns to Follow

Track all sample movements
Atomic batch operations
Validate barcode uniqueness

File Map

File	Purpose
accession/models/sample.py	Sample master (339 lines)
accession/models/collected_sample.py	Collected samples
accession/models/batches.py	Batch management
accession/models/sample_rack.py	Physical storage
accession/models/accession_patterns.py	Numbering rules
accession/views/	API views

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