Deep dive: Account, Stock, Sale, Purchase — +800 LOC business logic

Account:
- Multi-currency: company_currency_id, amount_total_signed
- Lock dates on res.company (period, fiscal year, tax) + enforcement in action_post
- Recurring entries: account.move.recurring with action_generate (copy+advance)
- Tax groups: amount_type='group' computes child taxes with include_base_amount
- ComputeTaxes batch function, findTaxAccount helper

Stock:
- Lot/Serial tracking: enhanced stock.lot with expiration dates + qty compute
- Routes: stock.route model with product/category/warehouse selectable flags
- Rules: stock.rule model with pull/push/buy/manufacture actions + procure methods
- Returns: action_return on picking (swap locations, copy moves)
- Product tracking extension (none/lot/serial) + route_ids M2M

Sale:
- Pricelist: get_product_price with fixed/percentage/formula computation
- Margin: purchase_price, margin, margin_percent on line + order totals
- Down payments: action_create_down_payment (deposit invoice at X%)

Purchase:
- 3-way matching: action_create_bill now updates qty_invoiced on PO lines
- Purchase agreements: purchase.requisition + line with state machine

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

addons/sale/models/sale_margin.go

@@ -0,0 +1,68 @@
+package models
+
+import "odoo-go/pkg/orm"
+
+// initSaleMargin adds margin fields to sale.order.line and sale.order.
+// Mirrors: odoo/addons/sale_margin/models/sale_order_line.py + sale_order.py
+
+func initSaleMargin() {
+	// -- Extend sale.order.line with margin fields --
+	line := orm.ExtendModel("sale.order.line")
+	line.AddFields(
+		orm.Float("purchase_price", orm.FieldOpts{String: "Cost Price"}),
+		orm.Monetary("margin", orm.FieldOpts{
+			String: "Margin", Compute: "_compute_margin", Store: true, CurrencyField: "currency_id",
+		}),
+		orm.Float("margin_percent", orm.FieldOpts{
+			String: "Margin (%)", Compute: "_compute_margin", Store: true,
+		}),
+	)
+
+	computeLineMargin := func(rs *orm.Recordset) (orm.Values, error) {
+		env := rs.Env()
+		lineID := rs.IDs()[0]
+		var subtotal, cost float64
+		env.Tx().QueryRow(env.Ctx(),
+			`SELECT COALESCE(price_subtotal, 0), COALESCE(purchase_price, 0) * COALESCE(product_uom_qty, 0)
+			 FROM sale_order_line WHERE id = $1`, lineID,
+		).Scan(&subtotal, &cost)
+		margin := subtotal - cost
+		pct := float64(0)
+		if subtotal > 0 {
+			pct = margin / subtotal * 100
+		}
+		return orm.Values{"margin": margin, "margin_percent": pct}, nil
+	}
+	line.RegisterCompute("margin", computeLineMargin)
+	line.RegisterCompute("margin_percent", computeLineMargin)
+
+	// -- Extend sale.order with total margin --
+	so := orm.ExtendModel("sale.order")
+	so.AddFields(
+		orm.Monetary("margin", orm.FieldOpts{
+			String: "Margin", Compute: "_compute_margin", Store: true, CurrencyField: "currency_id",
+		}),
+		orm.Float("margin_percent", orm.FieldOpts{
+			String: "Margin (%)", Compute: "_compute_margin", Store: true,
+		}),
+	)
+
+	computeSOMargin := func(rs *orm.Recordset) (orm.Values, error) {
+		env := rs.Env()
+		soID := rs.IDs()[0]
+		var margin, untaxed float64
+		env.Tx().QueryRow(env.Ctx(),
+			`SELECT COALESCE(SUM(margin), 0), COALESCE(SUM(price_subtotal), 0)
+			 FROM sale_order_line WHERE order_id = $1
+			 AND (display_type IS NULL OR display_type = '' OR display_type = 'product')`,
+			soID,
+		).Scan(&margin, &untaxed)
+		pct := float64(0)
+		if untaxed > 0 {
+			pct = margin / untaxed * 100
+		}
+		return orm.Values{"margin": margin, "margin_percent": pct}, nil
+	}
+	so.RegisterCompute("margin", computeSOMargin)
+	so.RegisterCompute("margin_percent", computeSOMargin)
+}