import xlsx from 'xlsx'
import ProductService from '#services/product_service'
import LogService from '#services/log_service'

export interface ImportRowResult {
  row: number
  sku?: string
  status: 'created' | 'updated' | 'error'
  message?: string
}

export interface ImportSummary {
  total: number
  created: number
  updated: number
  failed: number
  rows: ImportRowResult[]
}

const VALID_HEADERS = ['sku', 'condition', 'qty', 'price']

/**
 * Import sản phẩm từ file Excel. Cột yêu cầu: sku, condition, qty, price.
 */
export default class ImportService {
  static async importFromFile(filePath: string, username: string): Promise<ImportSummary> {
    const wb = xlsx.readFile(filePath)
    const sheet = wb.Sheets[wb.SheetNames[0]]
    const rows = xlsx.utils.sheet_to_json<Record<string, any>>(sheet, { defval: null })
    return this.processRows(rows, username)
  }

  static async importFromBuffer(buffer: Buffer, username: string): Promise<ImportSummary> {
    const wb = xlsx.read(buffer, { type: 'buffer' })
    const sheet = wb.Sheets[wb.SheetNames[0]]
    const rows = xlsx.utils.sheet_to_json<Record<string, any>>(sheet, { defval: null })
    return this.processRows(rows, username)
  }

  private static async processRows(
    rows: Record<string, any>[],
    username: string
  ): Promise<ImportSummary> {
    const summary: ImportSummary = { total: rows.length, created: 0, updated: 0, failed: 0, rows: [] }

    for (let i = 0; i < rows.length; i++) {
      const rowNo = i + 2 // +1 header, +1 1-based
      const raw = this.normalizeKeys(rows[i])

      const error = this.validateRow(raw)
      if (error) {
        summary.failed++
        summary.rows.push({ row: rowNo, sku: raw.sku, status: 'error', message: error })
        continue
      }

      try {
        const { created } = await ProductService.upsert({
          sku: String(raw.sku).trim(),
          condition: String(raw.condition).trim(),
          qty: Number(raw.qty),
          price: Number(raw.price),
        })
        created ? summary.created++ : summary.updated++
        summary.rows.push({ row: rowNo, sku: raw.sku, status: created ? 'created' : 'updated' })
      } catch (e: any) {
        summary.failed++
        summary.rows.push({ row: rowNo, sku: raw.sku, status: 'error', message: e.message })
      }
    }

    await LogService.record({
      username,
      actionName: 'Import Excel',
      action: 'import',
      meta: { total: summary.total, created: summary.created, updated: summary.updated, failed: summary.failed },
    })

    return summary
  }

  private static normalizeKeys(row: Record<string, any>): Record<string, any> {
    const out: Record<string, any> = {}
    for (const [k, v] of Object.entries(row)) {
      out[String(k).trim().toLowerCase()] = v
    }
    return out
  }

  private static validateRow(raw: Record<string, any>): string | null {
    for (const h of VALID_HEADERS) {
      if (raw[h] === null || raw[h] === undefined || raw[h] === '') {
        return `Thiếu cột "${h}"`
      }
    }
    if (Number.isNaN(Number(raw.qty))) return 'qty không hợp lệ'
    if (Number.isNaN(Number(raw.price))) return 'price không hợp lệ'
    return null
  }
}