// Package order is the platform's shared order seam: the exported wire shape of
// the `order.created` domain event (B4.1). It is the contract between the order
// service (producer) and every reactor — inventory commit, fulfillment
// allocation, loyalty, ERP sync — none of which the order service knows about.
//
// Like platform/catalog and platform/inventory, it holds only the wire value
// types + encode/decode, and imports only the stdlib.
//
// `order.created` is a FACT, not a request: by the time it is emitted the order
// is placed and paid. Reactors must be idempotent (the transport is
// at-least-once) and must not assume they can refuse it — the sale already
// happened. Oversell on commit is reconciled downstream (backorder), not
// prevented here.
package order

import "encoding/json"

// Line is one ordered line item, reduced to what reactors need: the SKU, how
// many units sold, the inventory location to commit against, and whether the
// item is drop-ship (fulfilled by the supplier, never decremented from local
// stock). Pricing/tax live in the order grain, not on this seam.
type Line struct {
	SKU      string `json:"sku"`
	Quantity int    `json:"quantity"`
	// Location is the inventory location / store id to decrement. Empty means
	// "use the order's Country" (central stock) — see Created.Country.
	Location string `json:"location,omitempty"`
	// DropShip marks items fulfilled directly by the supplier. The inventory
	// reactor must skip the stock decrement for these lines.
	DropShip bool `json:"drop_ship,omitempty"`
}

// Created is the payload of an event.OrderCreated envelope.
//
// Country is the default inventory location for the commit (central stock). A
// Line may override it with its own Location (store id); when a line's Location
// is empty the commit falls back to Country. See docs/inventory-shape.md.
type Created struct {
	OrderID        string `json:"order_id"`
	OrderReference string `json:"order_reference,omitempty"`
	CartID         string `json:"cart_id,omitempty"`
	Country        string `json:"country"`
	Currency       string `json:"currency,omitempty"`
	CustomerEmail  string `json:"customer_email,omitempty"`
	// CustomerID is the customer profile ID for identity linking (B0.4). Reactors
	// (e.g. profile service) use this to link the order to the customer profile.
	CustomerID  string `json:"customer_id,omitempty"`
	Lines       []Line `json:"lines"`
	PlacedAtMs  int64  `json:"placed_at_ms,omitempty"`
}

// Encode serialises the payload for event.Event.Payload.
func (c Created) Encode() ([]byte, error) { return json.Marshal(c) }

// Decode parses an order.created payload — the consumer side of Encode.
func Decode(raw []byte) (Created, error) {
	var c Created
	err := json.Unmarshal(raw, &c)
	return c, err
}

// VatBucket is one VAT rate's split on an issued invoice: the net basis and
// the VAT amount, both in minor units. RateBp is basis points (2500 = 25 %).
// Summing ExVat+Vat across buckets equals AmountIncVat — the ledger reactor
// books the invoice from these (revenue accounts per rate, e.g. 3041/3042/3043
// and 2611/2621/2631 in BAS), so it needs the split, not just the total.
type VatBucket struct {
	RateBp int   `json:"rate_bp"`
	ExVat  int64 `json:"ex_vat"`
	Vat    int64 `json:"vat"`
}

// InvoiceIssued is the payload of an event.InvoiceIssued envelope.
type InvoiceIssued struct {
	OrderID       string      `json:"order_id"`
	InvoiceNumber string      `json:"invoice_number"`
	CompanyID     string      `json:"company_id,omitempty"`
	CustomerEmail string      `json:"customer_email,omitempty"`
	AmountIncVat  int64       `json:"amount_inc_vat"`
	VatBuckets    []VatBucket `json:"vat_buckets,omitempty"`
	DueDate       string      `json:"due_date"`
	OCRReference  string      `json:"ocr_reference"`
	IssuedAtMs    int64       `json:"issued_at_ms"`
}

func (i InvoiceIssued) Encode() ([]byte, error) { return json.Marshal(i) }

func DecodeInvoiceIssued(raw []byte) (InvoiceIssued, error) {
	var i InvoiceIssued
	err := json.Unmarshal(raw, &i)
	return i, err
}

// InvoicePaid is the payload of an event.InvoicePaid envelope.
type InvoicePaid struct {
	OrderID       string `json:"order_id"`
	InvoiceNumber string `json:"invoice_number"`
	CompanyID     string `json:"company_id,omitempty"`
	AmountPaid    int64  `json:"amount_paid"`
	PaidAtMs      int64  `json:"paid_at_ms"`
	// OcrReference lets the ledger settle the exact receivable (the payment's
	// 1510 credit references the invoice's OCR) without depending on the
	// invoice.issued event having been booked first.
	OcrReference string `json:"ocr_reference,omitempty"`
}

func (i InvoicePaid) Encode() ([]byte, error) { return json.Marshal(i) }

func DecodeInvoicePaid(raw []byte) (InvoicePaid, error) {
	var i InvoicePaid
	err := json.Unmarshal(raw, &i)
	return i, err
}

// InvoiceCredited is the payload of an event.InvoiceCredited envelope: a
// credit note was issued against an issued invoice. The credited amount and
// per-rate VAT split mirror the credited lines (line total × qty / line
// quantity, VAT proportionally — the same math as the order grain's
// InvoiceCreditedAmount). The ledger books the reversal voucher
// (1510 C / 304x D / 261x D per rate), idempotent per credit number.
type InvoiceCredited struct {
	OrderID       string      `json:"order_id"`
	InvoiceNumber string      `json:"invoice_number"`   // the original invoice
	CreditNumber  string      `json:"credit_number"`    // from the same gap-free series
	CompanyID     string      `json:"company_id,omitempty"`
	OcrReference  string      `json:"ocr_reference,omitempty"`
	AmountIncVat  int64       `json:"amount_inc_vat"`
	VatBuckets    []VatBucket `json:"vat_buckets,omitempty"`
	CreditedAtMs  int64       `json:"credited_at_ms"`
}

func (c InvoiceCredited) Encode() ([]byte, error) { return json.Marshal(c) }

func DecodeInvoiceCredited(raw []byte) (InvoiceCredited, error) {
	var c InvoiceCredited
	err := json.Unmarshal(raw, &c)
	return c, err
}