/**
 * 历史订单项收入口径回填（迁移 104 只建列，不再做全表更新）。
 *
 * 背景：375,447 行的全表 UPDATE 实测约 34 秒，超过默认语句超时，放在单事务迁移里
 * 会拖住启动；因此迁到本脚本，按 id 分批执行。
 *
 * 口径（与 order-item-repo 写入规则一致）：
 *   item_count = 1 → revenue = 订单实付，revenue_basis = 'order_total'
 *   item_count > 1 → 等额拆分，余数给最后一项，revenue_basis = 'equal_split'
 *
 * 幂等：只处理 revenue_basis = 'unknown' 的行，重复执行不会二次拆分。
 *
 * 用法：
 *   npm run revenue:backfill                       # 默认每批 5000 行
 *   npm run revenue:backfill -- --batch-size=2000 --max-batches=100
 *   npm run revenue:backfill -- --dry-run          # 只统计并抽样预览，不写库
 */
import process from 'node:process'

import { closeDb, query } from '../src/db/client.js'

const options = parseOptions(process.argv.slice(2))
const batchSize = normalizeInteger(options.batchSize, 5000, 1, 50_000)
const maxBatches = normalizeInteger(options.maxBatches, 1000, 1, 10_000)
const dryRun = options.dryRun === 'true'

const BATCH_SQL = `
  WITH target AS (
    SELECT id, order_id
    FROM order_items
    WHERE revenue_basis = 'unknown'
    ORDER BY id
    LIMIT $1
  ),
  item_counts AS (
    SELECT oi.order_id, COUNT(*)::int AS item_count
    FROM order_items oi
    WHERE oi.order_id IN (SELECT order_id FROM target)
    GROUP BY oi.order_id
  ),
  ranked AS (
    SELECT
      oi.id,
      GREATEST(COALESCE(o.total_amount, 0), 0)::bigint AS order_revenue_fen,
      ic.item_count,
      ROW_NUMBER() OVER (PARTITION BY oi.order_id ORDER BY oi.id ASC) AS item_rank
    FROM order_items oi
    JOIN orders o ON o.id = oi.order_id
    JOIN item_counts ic ON ic.order_id = oi.order_id
    WHERE oi.id IN (SELECT id FROM target)
  )
  UPDATE order_items oi
  SET
    revenue_amount_fen = CASE
      WHEN r.item_count = 1 THEN r.order_revenue_fen
      ELSE (r.order_revenue_fen / r.item_count)
        + CASE WHEN r.item_rank = r.item_count THEN (r.order_revenue_fen % r.item_count) ELSE 0 END
    END,
    revenue_basis = CASE WHEN r.item_count = 1 THEN 'order_total' ELSE 'equal_split' END,
    updated_at = NOW()
  FROM ranked r
  WHERE oi.id = r.id
    AND oi.revenue_basis = 'unknown'
  RETURNING oi.id
`

async function main() {
  await assertColumnExists()

  const before = await countUnknown()
  const startedAt = Date.now()

  if (dryRun) {
    const samples = await previewSamples()
    console.log(
      JSON.stringify(
        {
          dryRun: true,
          pendingCount: before,
          batchSize,
          estimatedBatches: Math.ceil(before / batchSize),
          samples,
          durationMs: Date.now() - startedAt,
        },
        null,
        2,
      ),
    )
    return
  }

  let batches = 0
  let updated = 0
  while (batches < maxBatches) {
    const result = await query(BATCH_SQL, [batchSize])
    const affected = result.rowCount ?? 0
    if (affected === 0) break
    batches += 1
    updated += affected
    if (affected < batchSize) break
  }

  const remaining = await countUnknown()
  console.log(
    JSON.stringify(
      {
        dryRun: false,
        batchSize,
        maxBatches,
        batches,
        updatedCount: updated,
        pendingBefore: before,
        remainingCount: remaining,
        durationMs: Date.now() - startedAt,
      },
      null,
      2,
    ),
  )

  if (remaining > 0) {
    console.error(`仍有 ${remaining} 个订单项未回填；请增大 --max-batches 后重跑（幂等）。`)
    process.exitCode = 2
  }
}

async function assertColumnExists() {
  const { rows } = await query<{ exists: boolean }>(
    `
      SELECT EXISTS (
        SELECT 1
        FROM information_schema.columns
        WHERE table_schema = 'public'
          AND table_name = 'order_items'
          AND column_name = 'revenue_basis'
      ) AS exists
    `,
  )
  if (!rows[0]?.exists) {
    throw new Error('order_items.revenue_basis 不存在，请先执行 npm run db:migrate（迁移 104）')
  }
}

async function countUnknown() {
  const { rows } = await query<{ count: number }>(
    `SELECT COUNT(*)::int AS count FROM order_items WHERE revenue_basis = 'unknown'`,
  )
  return rows[0]?.count ?? 0
}

async function previewSamples() {
  const { rows } = await query<{
    order_id: number
    item_count: number
    order_total: number
    item_ids: number[]
  }>(
    `
      SELECT
        oi.order_id,
        COUNT(*)::int AS item_count,
        MAX(GREATEST(COALESCE(o.total_amount, 0), 0))::bigint AS order_total,
        array_agg(oi.id ORDER BY oi.id) AS item_ids
      FROM order_items oi
      JOIN orders o ON o.id = oi.order_id
      WHERE oi.revenue_basis = 'unknown'
      GROUP BY oi.order_id
      ORDER BY oi.order_id
      LIMIT 3
    `,
  )
  return rows
}

main()
  .catch((error) => {
    console.error(error instanceof Error ? error.message : error)
    process.exitCode = 1
  })
  .finally(async () => {
    await closeDb()
  })

function parseOptions(args: string[]) {
  const result: Record<string, string> = {}
  for (const arg of args) {
    if (!arg.startsWith('--')) continue
    const body = arg.slice(2)
    const index = body.indexOf('=')
    const key = index === -1 ? body : body.slice(0, index)
    const value = index === -1 ? 'true' : body.slice(index + 1)
    // 同时接受 --batch-size 与 --batchSize 两种写法。
    result[key] = value
    result[toCamelCase(key)] = value
  }
  return result
}

function toCamelCase(value: string) {
  return value.replace(/-([a-z])/g, (_, char: string) => char.toUpperCase())
}

function normalizeInteger(value: unknown, fallback: number, min: number, max: number) {
  const parsed = Number(value)
  if (!Number.isInteger(parsed)) return fallback
  return Math.min(max, Math.max(min, parsed))
}