Add Stock

Defaults

• Cost set: actual (the job's latest actual cost set). Override if user specifies estimate or quote.
• Pricing: Pull unit_cost and unit_revenue from the matched Stock record. User can override.
• Quantity: Must be provided by the user.

Creating a cost line

Use the proper data model. Required fields:

from apps.job.models import CostLine, CostSet, Job
from apps.purchasing.models import Stock
from django.utils import timezone

CostLine.objects.create(
    cost_set=cost_set,          # The job's actual CostSet
    kind="material",
    desc=stock_item.description, # From the Stock record
    quantity=qty,                # User-provided
    unit_cost=stock_item.unit_cost,
    unit_rev=stock_item.unit_revenue,
    accounting_date=timezone.now().date(),
    ext_refs={"stock_id": str(stock_item.id)},  # Links back to Stock record
    meta={"consumed_by": "a9bd99fa-c9fb-43e3-8b25-578c35b56fa6"},  # Corrin Lakeland
)

Important rules

1. Always use a script with dry-run pattern for creating/modifying data. Write the script to scripts/, run dry first, show the user what will happen, then run live after confirmation.
2. Never run data changes directly — always use transaction.atomic() with rollback for dry runs.
3. Check for duplicates before adding — if a material line with the same description already exists on the cost set, warn the user and ask if they want to update it instead.
4. Validate the Stock record exists and is active before using it.

Updating existing lines

If the user asks to update a price or quantity on an existing line:

1. Find the line on the job's cost set
2. Show current values
3. Write a script to update with dry-run
4. Confirm and run live

Sheet material quantity conventions — "tenths"

A standard sheet (2400x1200) is divided into a 5x2 grid of 10 segments (called "tenths"), each 480x600mm:

        480     480     480     480     480
      ┌───────┬───────┬───────┬───────┬───────┐
      │       │       │       │       │       │
 600  │   1   │   2   │   3   │   4   │   5   │
      │       │       │       │       │       │
      ├───────┼───────┼───────┼───────┼───────┤
      │       │       │       │       │       │
 600  │   6   │   7   │   8   │   9   │  10   │
      │       │       │       │       │       │
      └───────┴───────┴───────┴───────┴───────┘
        ◄─────────── 2400mm ──────────────►

When a piece is cut from a sheet, count how many segments are touched (even partially). That count is the quantity in tenths.

Examples:

• 700x700mm piece → touches a 2x2 area of segments → 4 tenths (0.4 of a sheet)
• 1200x600mm piece → spans 2 segments wide, 2 tall → 4 tenths
• 500x400mm piece → fits within 1 segment → 1 tenth (0.1 of a sheet)
• Full sheet 2400x1200 → all 10 segments → 10 tenths (1.0)

The quantity field stores tenths as a decimal fraction of a whole sheet: 4 tenths = 0.4, 10 tenths = 1.0.

Always show the user the segment calculation and confirm before creating the cost line.