import type { Paise } from './money'
import type { IsoDate } from './business-day'

/**
 * Documents are immutable events (02-ARCHITECTURE §3 rule 2). A committed bill
 * is never edited; corrections are new documents referencing the original.
 */
export type DocType = 'SALE' | 'SALE_RETURN' | 'PURCHASE' | 'PURCHASE_RETURN' | 'STOCK_ADJUST'

export interface BillLine {
  itemId: string
  name: string
  hsn: string
  qty: number
  unitCode: string
  unitPricePaise: Paise
  mrpPaise?: Paise
  grossPaise: Paise
  discountPaise: Paise
  taxablePaise: Paise
  taxRateBp: number
  cgstPaise: Paise
  sgstPaise: Paise
  igstPaise: Paise
  cessPaise: Paise
  lineTotalPaise: Paise
  batchId?: string
}

export type PaymentMode = 'CASH' | 'UPI' | 'CARD' | 'KHATA'

export interface Payment {
  mode: PaymentMode
  amountPaise: Paise
  reference?: string
}

export interface BillTotals {
  grossPaise: Paise
  discountPaise: Paise
  taxablePaise: Paise
  cgstPaise: Paise
  sgstPaise: Paise
  igstPaise: Paise
  cessPaise: Paise
  roundOffPaise: Paise
  payablePaise: Paise
  savingsVsMrpPaise: Paise
}

export interface BillDoc {
  id: string // uuidv7, client-generated
  tenantId: string
  storeId: string
  counterId: string
  docType: DocType
  docNo: string
  /** Working date from Day Begin — never the machine clock. */
  businessDate: IsoDate
  cashierId: string
  shiftId: string
  customerId?: string
  refDocId?: string // returns/corrections point at the original
  lines: BillLine[]
  payments: Payment[]
  totals: BillTotals
  /** Wall clock is display metadata only; ordering uses (lamport, deviceId). */
  createdAtWallClock: string
  lamport: number
  deviceId: string
  deviceSeq: number
}