import { and, asc, eq, inArray } from 'drizzle-orm'
import type { NodePgDatabase } from 'drizzle-orm/node-postgres'

import * as schema from '#/db/schema.ts'
import { PaymentDeclinedError } from '#/lib/payment.ts'
import type { PaymentProvider } from '#/lib/payment.ts'

type Db = NodePgDatabase<typeof schema>
// The callback type `db.transaction()` hands its work to. Helpers below
// accept either a top-level Db or an in-flight transaction so they compose
// into one atomic unit of work when called from within `db.transaction()`.
type Tx = Parameters<Parameters<Db['transaction']>[0]>[0]
type DbOrTx = Db | Tx

// Drizzle types a `SELECT ... LIMIT 1`-shaped destructure's element as always
// present, even though zero rows is a real possibility at runtime (without
// noUncheckedIndexedAccess). Route those reads through this helper so their
// optionality is genuinely reflected in the type.
const firstRow = <T>(rows: Array<T>): T | undefined => rows[0]

export class OrderItemNotCancellableError extends Error {
  constructor(reason: string) {
    super(`This item can no longer be cancelled: ${reason}`)
    this.name = 'OrderItemNotCancellableError'
  }
}

export class OrderItemNotReadyError extends Error {
  constructor() {
    super('This item is not ready for pickup yet')
    this.name = 'OrderItemNotReadyError'
  }
}

export class NoStepInProgressError extends Error {
  constructor() {
    super('This item has no Preparation Step currently in progress')
    this.name = 'NoStepInProgressError'
  }
}

export class ForbiddenError extends Error {
  constructor() {
    super('You do not have access to this Order')
    this.name = 'ForbiddenError'
  }
}

export type MenuItemWithRecipe = {
  id: number
  name: string
  description: string | null
  priceCents: number
  steps: Array<{
    sequence: number
    machineTag: string
    estimatedDurationSeconds: number
  }>
}

export const getMenu = async (
  db: Db,
  brandId: number,
): Promise<Array<MenuItemWithRecipe>> => {
  const items = await db
    .select()
    .from(schema.menuItems)
    .where(eq(schema.menuItems.brandId, brandId))

  const steps = await db
    .select({
      menuItemId: schema.menuItemSteps.menuItemId,
      sequence: schema.menuItemSteps.sequence,
      machineTag: schema.machineTags.name,
      estimatedDurationSeconds: schema.menuItemSteps.estimatedDurationSeconds,
    })
    .from(schema.menuItemSteps)
    .innerJoin(
      schema.machineTags,
      eq(schema.menuItemSteps.machineTagId, schema.machineTags.id),
    )
    .where(
      inArray(
        schema.menuItemSteps.menuItemId,
        items.map((item) => item.id),
      ),
    )
    .orderBy(asc(schema.menuItemSteps.sequence))

  return items.map((item) => ({
    id: item.id,
    name: item.name,
    description: item.description,
    priceCents: item.priceCents,
    steps: steps
      .filter((step) => step.menuItemId === item.id)
      .map(({ sequence, machineTag, estimatedDurationSeconds }) => ({
        sequence,
        machineTag,
        estimatedDurationSeconds,
      })),
  }))
}

// Assigns queued Preparation Steps for a given Machine Tag to whichever
// Machine carrying that Tag is idle, FIFO by queue position. Called
// whenever a Step is created (order placed) or freed (a Step finishes) —
// see docs/adr/0003-machine-tag-pool-dynamic-assignment.md.
//
// Locks that Tag's Machine rows for the duration of the caller's
// transaction, so two concurrent calls for the same Tag (e.g. two orders
// placed at once) can't both read the same idle Machine as free and
// double-book it — the second call blocks here until the first commits.
export const assignQueuedStepsForTag = async (
  db: DbOrTx,
  machineTagId: number,
) => {
  const tagMachines = await db
    .select({ id: schema.machines.id })
    .from(schema.machines)
    .where(eq(schema.machines.machineTagId, machineTagId))
    .for('update')

  if (tagMachines.length === 0) return

  const busyMachineIds = new Set(
    (
      await db
        .select({ machineId: schema.preparationStepInstances.machineId })
        .from(schema.preparationStepInstances)
        .where(
          and(
            eq(schema.preparationStepInstances.machineTagId, machineTagId),
            eq(schema.preparationStepInstances.status, 'in_progress'),
          ),
        )
    )
      .map((row) => row.machineId)
      .filter((id): id is number => id !== null),
  )

  const idleMachineIds = tagMachines
    .map((machine) => machine.id)
    .filter((id) => !busyMachineIds.has(id))

  if (idleMachineIds.length === 0) return

  const queuedSteps = await db
    .select({ id: schema.preparationStepInstances.id })
    .from(schema.preparationStepInstances)
    .where(
      and(
        eq(schema.preparationStepInstances.machineTagId, machineTagId),
        eq(schema.preparationStepInstances.status, 'queued'),
      ),
    )
    .orderBy(asc(schema.preparationStepInstances.id))

  const assignments = queuedSteps.slice(0, idleMachineIds.length)

  for (const [index, step] of assignments.entries()) {
    await db
      .update(schema.preparationStepInstances)
      .set({
        status: 'in_progress',
        machineId: idleMachineIds[index],
        startedAt: new Date(),
      })
      .where(eq(schema.preparationStepInstances.id, step.id))
  }
}

// Copies the Menu Item's live Recipe into orderItemSteps for this Order
// Item, then creates its first Preparation Step instance from that copy —
// so a later edit to the live Recipe never reshapes an Order Item already
// in flight (see docs/adr/0005-recipe-snapshot-per-order-item.md).
const initializeOrderItemRecipe = async (
  db: DbOrTx,
  orderItemId: number,
  menuItemId: number,
) => {
  const liveSteps = await db
    .select()
    .from(schema.menuItemSteps)
    .where(eq(schema.menuItemSteps.menuItemId, menuItemId))
    .orderBy(asc(schema.menuItemSteps.sequence))

  // A menu item with no Preparation Steps at all is a data integrity bug
  // (see spec: every menu item's Recipe has at least one Step), not a valid
  // "nothing to do" case — surfacing it loudly here beats leaving the Order
  // Item permanently stuck with no Step and no way to progress or cancel.
  if (liveSteps.length === 0) {
    throw new Error(`Menu item ${menuItemId} has no Preparation Steps defined`)
  }

  const recipeSteps = await db
    .insert(schema.orderItemSteps)
    .values(
      liveSteps.map((step) => ({
        orderItemId,
        sequence: step.sequence,
        machineTagId: step.machineTagId,
        estimatedDurationSeconds: step.estimatedDurationSeconds,
      })),
    )
    .returning()

  const firstStep = recipeSteps.find((step) => step.sequence === 1)
  if (!firstStep) {
    throw new Error(
      `Menu item ${menuItemId} has no Preparation Step with sequence 1`,
    )
  }

  const [instance] = await db
    .insert(schema.preparationStepInstances)
    .values({
      orderItemId,
      sequence: firstStep.sequence,
      machineTagId: firstStep.machineTagId,
      estimatedDurationSeconds: firstStep.estimatedDurationSeconds,
      status: 'queued',
    })
    .returning()

  return instance
}

export type PlaceOrderInput = {
  items: Array<{ menuItemId: number }>
  customer:
    | { type: 'guest'; name: string; contact: string }
    | { type: 'account'; customerId: string }
}

export const placeOrder = async (
  db: Db,
  paymentProvider: PaymentProvider,
  input: PlaceOrderInput,
) => {
  if (input.items.length === 0) {
    throw new Error('An Order must contain at least one Order Item')
  }

  const menuItemIds = input.items.map((item) => item.menuItemId)
  const menuItemRows = await db
    .select()
    .from(schema.menuItems)
    .where(inArray(schema.menuItems.id, menuItemIds))
  const menuItemById = new Map(menuItemRows.map((row) => [row.id, row]))

  for (const id of menuItemIds) {
    if (!menuItemById.has(id)) {
      throw new Error(`Unknown menu item: ${id}`)
    }
  }

  // Catch the "menu item has no Recipe Steps" data bug before charging
  // anyone, rather than charging first and refunding once
  // initializeOrderItemRecipe discovers it mid-transaction.
  const itemIdsWithSteps = new Set(
    (
      await db
        .select({ menuItemId: schema.menuItemSteps.menuItemId })
        .from(schema.menuItemSteps)
        .where(inArray(schema.menuItemSteps.menuItemId, menuItemIds))
    ).map((row) => row.menuItemId),
  )
  for (const id of menuItemIds) {
    if (!itemIdsWithSteps.has(id)) {
      throw new Error(`Menu item ${id} has no Preparation Steps defined`)
    }
  }

  const totalCents = input.items.reduce(
    (sum, item) => sum + menuItemById.get(item.menuItemId)!.priceCents,
    0,
  )

  // Payment happens before anything is queued: a declined charge means no
  // Order Item is ever created (see spec: "Order rejected if payment fails").
  let charge
  try {
    charge = await paymentProvider.charge(totalCents)
  } catch (error) {
    if (error instanceof PaymentDeclinedError) throw error
    throw new PaymentDeclinedError()
  }

  try {
    return await db.transaction(async (tx) => {
      const [order] = await tx
        .insert(schema.orders)
        .values({
          customerId:
            input.customer.type === 'account'
              ? input.customer.customerId
              : null,
          guestName:
            input.customer.type === 'guest' ? input.customer.name : null,
          guestContact:
            input.customer.type === 'guest' ? input.customer.contact : null,
          guestAccessToken:
            input.customer.type === 'guest' ? crypto.randomUUID() : null,
          status: 'paid',
          paymentChargeId: charge.chargeId,
        })
        .returning()

      const tagsToAssign = new Set<number>()

      for (const item of input.items) {
        const menuItem = menuItemById.get(item.menuItemId)!
        const [orderItem] = await tx
          .insert(schema.orderItems)
          .values({
            orderId: order.id,
            menuItemId: menuItem.id,
            priceCents: menuItem.priceCents,
            status: 'paid',
          })
          .returning()

        const step = await initializeOrderItemRecipe(
          tx,
          orderItem.id,
          menuItem.id,
        )
        tagsToAssign.add(step.machineTagId)
      }

      for (const tagId of tagsToAssign) {
        await assignQueuedStepsForTag(tx, tagId)
      }

      return order
    })
  } catch (error) {
    // The charge already happened; a failed transaction must not leave the
    // customer paying for an Order that doesn't exist. If the compensating
    // refund itself fails, the transaction failure is still the real cause —
    // log the refund failure rather than letting it hide that error.
    try {
      await paymentProvider.refund(charge.chargeId, totalCents)
    } catch (refundError) {
      console.error(
        `Failed to refund charge ${charge.chargeId} after a failed order transaction:`,
        refundError,
      )
    }
    throw error
  }
}

export type OrderAccess = { customerId?: string; guestAccessToken?: string }

const assertOrderAccess = (
  order: Pick<
    typeof schema.orders.$inferSelect,
    'customerId' | 'guestAccessToken'
  >,
  access: OrderAccess,
) => {
  if (order.customerId) {
    if (access.customerId === order.customerId) return
  } else if (order.guestAccessToken) {
    if (access.guestAccessToken === order.guestAccessToken) return
  }
  throw new ForbiddenError()
}

// Steps are created one at a time (see createFirstStepForOrderItem /
// advanceOrderItemStep), so at most one non-done instance ever exists for a
// given Order Item at once.
const getCurrentStepInstance = async (db: DbOrTx, orderItemId: number) => {
  const instances = await db
    .select()
    .from(schema.preparationStepInstances)
    .where(eq(schema.preparationStepInstances.orderItemId, orderItemId))
    .orderBy(asc(schema.preparationStepInstances.sequence))

  return instances.find((row) => row.status !== 'done') ?? null
}

const updateOrderCompleteIfEverySiblingIsDone = async (
  db: DbOrTx,
  orderId: number,
) => {
  const siblingItems = await db
    .select({ status: schema.orderItems.status })
    .from(schema.orderItems)
    .where(eq(schema.orderItems.orderId, orderId))

  const orderComplete = siblingItems.every(
    (item) => item.status === 'picked_up' || item.status === 'cancelled',
  )

  if (orderComplete) {
    await db
      .update(schema.orders)
      .set({ status: 'complete' })
      .where(eq(schema.orders.id, orderId))
  }
}

export const cancelOrderItem = async (
  db: Db,
  paymentProvider: PaymentProvider,
  orderItemId: number,
  access: OrderAccess,
) => {
  const orderItem = firstRow(
    await db
      .select()
      .from(schema.orderItems)
      .where(eq(schema.orderItems.id, orderItemId)),
  )
  if (!orderItem) throw new Error('Order item not found')

  const order = firstRow(
    await db
      .select()
      .from(schema.orders)
      .where(eq(schema.orders.id, orderItem.orderId)),
  )
  if (!order) throw new Error('Order not found')
  assertOrderAccess(order, access)

  if (orderItem.status === 'cancelled') {
    throw new OrderItemNotCancellableError('it has already been cancelled')
  }
  if (orderItem.status === 'ready' || orderItem.status === 'picked_up') {
    throw new OrderItemNotCancellableError('it is already done cooking')
  }

  const currentStep = await getCurrentStepInstance(db, orderItemId)
  if (!currentStep || currentStep.status !== 'queued') {
    throw new OrderItemNotCancellableError('it has already started cooking')
  }

  // Refund before touching any state, mirroring placeOrder's charge-first
  // pattern: if the refund itself fails, nothing about this cancellation is
  // ever recorded, exactly like a declined charge leaves no Order behind.
  if (order.paymentChargeId) {
    await paymentProvider.refund(order.paymentChargeId, orderItem.priceCents)
  }

  try {
    await db.transaction(async (tx) => {
      // Re-check status = 'queued' as part of the delete itself, atomically:
      // a Machine may have claimed this Step (assignQueuedStepsForTag), or a
      // concurrent cancelOrderItem call may have already deleted it, in the
      // time since the read above (which can include the refund call, an
      // external network round trip). If so, zero rows match and the catch
      // below re-charges to undo the refund we already issued.
      const deletedSteps = await tx
        .delete(schema.preparationStepInstances)
        .where(
          and(
            eq(schema.preparationStepInstances.id, currentStep.id),
            eq(schema.preparationStepInstances.status, 'queued'),
          ),
        )
        .returning({ id: schema.preparationStepInstances.id })

      if (deletedSteps.length === 0) {
        throw new OrderItemNotCancellableError(
          'it has already started cooking',
        )
      }

      await tx
        .update(schema.orderItems)
        .set({ status: 'cancelled' })
        .where(eq(schema.orderItems.id, orderItemId))

      await updateOrderCompleteIfEverySiblingIsDone(tx, orderItem.orderId)
    })
  } catch (error) {
    // The refund already happened; an aborted cancellation must not leave
    // the customer refunded for an item that's still cooking. If the
    // compensating re-charge itself fails, the cancellation failure is
    // still the real cause — log the re-charge failure rather than letting
    // it hide that error.
    if (order.paymentChargeId) {
      try {
        await paymentProvider.charge(orderItem.priceCents)
      } catch (rechargeError) {
        console.error(
          `Failed to re-charge ${orderItem.priceCents} cents for order item ${orderItemId} after an aborted cancellation:`,
          rechargeError,
        )
      }
    }
    throw error
  }
}

export const advanceOrderItemStep = async (db: Db, orderItemId: number) => {
  await db.transaction(async (tx) => {
    const currentStep = await getCurrentStepInstance(tx, orderItemId)
    if (!currentStep || currentStep.status !== 'in_progress') {
      throw new NoStepInProgressError()
    }

    await tx
      .update(schema.preparationStepInstances)
      .set({ status: 'done', doneAt: new Date() })
      .where(eq(schema.preparationStepInstances.id, currentStep.id))

    const nextStepDefinition = firstRow(
      await tx
        .select()
        .from(schema.orderItemSteps)
        .where(
          and(
            eq(schema.orderItemSteps.orderItemId, orderItemId),
            eq(schema.orderItemSteps.sequence, currentStep.sequence + 1),
          ),
        ),
    )

    if (nextStepDefinition) {
      await tx.insert(schema.preparationStepInstances).values({
        orderItemId,
        sequence: nextStepDefinition.sequence,
        machineTagId: nextStepDefinition.machineTagId,
        estimatedDurationSeconds: nextStepDefinition.estimatedDurationSeconds,
        status: 'queued',
      })
      await assignQueuedStepsForTag(tx, nextStepDefinition.machineTagId)
    } else {
      await tx
        .update(schema.orderItems)
        .set({ status: 'ready' })
        .where(eq(schema.orderItems.id, orderItemId))
    }

    // Freeing this machine may unblock another queued Step for the same Tag.
    await assignQueuedStepsForTag(tx, currentStep.machineTagId)
  })
}

export const markOrderItemPickedUp = async (
  db: Db,
  orderItemId: number,
  access: OrderAccess,
) => {
  await db.transaction(async (tx) => {
    const orderItem = firstRow(
      await tx
        .select()
        .from(schema.orderItems)
        .where(eq(schema.orderItems.id, orderItemId)),
    )
    if (!orderItem) throw new Error('Order item not found')

    const order = firstRow(
      await tx
        .select()
        .from(schema.orders)
        .where(eq(schema.orders.id, orderItem.orderId)),
    )
    if (!order) throw new Error('Order not found')
    assertOrderAccess(order, access)

    if (orderItem.status !== 'ready') throw new OrderItemNotReadyError()

    await tx
      .update(schema.orderItems)
      .set({ status: 'picked_up' })
      .where(eq(schema.orderItems.id, orderItemId))

    await updateOrderCompleteIfEverySiblingIsDone(tx, orderItem.orderId)
  })
}

export type OrderItemStatusView = {
  id: number
  menuItemName: string
  status: schema.OrderItemStatus
  cancellable: boolean
  steps: Array<{
    sequence: number
    machineTag: string
    estimatedDurationSeconds: number
    status: 'done' | 'in_progress' | 'queued' | 'pending'
    queuePosition: number | null
  }>
  etaSeconds: number | null
}

export const getOrderStatus = async (
  db: Db,
  orderId: number,
  access: OrderAccess,
) => {
  const order = firstRow(
    await db.select().from(schema.orders).where(eq(schema.orders.id, orderId)),
  )
  if (!order) throw new Error('Order not found')
  assertOrderAccess(order, access)

  const items = await db
    .select()
    .from(schema.orderItems)
    .where(eq(schema.orderItems.orderId, orderId))

  const menuItemIds = [...new Set(items.map((item) => item.menuItemId))]
  const orderItemIds = items.map((item) => item.id)

  const menuItemsById = new Map(
    (
      await db
        .select()
        .from(schema.menuItems)
        .where(inArray(schema.menuItems.id, menuItemIds))
    ).map((row) => [row.id, row]),
  )

  const recipeRows =
    orderItemIds.length === 0
      ? []
      : await db
          .select({
            orderItemId: schema.orderItemSteps.orderItemId,
            sequence: schema.orderItemSteps.sequence,
            machineTag: schema.machineTags.name,
            machineTagId: schema.orderItemSteps.machineTagId,
            estimatedDurationSeconds:
              schema.orderItemSteps.estimatedDurationSeconds,
          })
          .from(schema.orderItemSteps)
          .innerJoin(
            schema.machineTags,
            eq(schema.orderItemSteps.machineTagId, schema.machineTags.id),
          )
          .where(inArray(schema.orderItemSteps.orderItemId, orderItemIds))
          .orderBy(asc(schema.orderItemSteps.sequence))

  const allInstances =
    orderItemIds.length === 0
      ? []
      : await db
          .select()
          .from(schema.preparationStepInstances)
          .where(
            inArray(schema.preparationStepInstances.orderItemId, orderItemIds),
          )

  const instancesByOrderItem = new Map<
    number,
    Array<(typeof allInstances)[number]>
  >()
  for (const instance of allInstances) {
    const list = instancesByOrderItem.get(instance.orderItemId) ?? []
    list.push(instance)
    instancesByOrderItem.set(instance.orderItemId, list)
  }

  const queuedTagIds = [
    ...new Set(
      allInstances
        .filter((instance) => instance.status === 'queued')
        .map((instance) => instance.machineTagId),
    ),
  ]

  const queuedStepsByTag = new Map<number, Array<{ id: number }>>()
  const machineCountByTag = new Map<number, number>()
  for (const tagId of queuedTagIds) {
    queuedStepsByTag.set(
      tagId,
      await db
        .select({ id: schema.preparationStepInstances.id })
        .from(schema.preparationStepInstances)
        .where(
          and(
            eq(schema.preparationStepInstances.machineTagId, tagId),
            eq(schema.preparationStepInstances.status, 'queued'),
          ),
        )
        .orderBy(asc(schema.preparationStepInstances.id)),
    )
    machineCountByTag.set(
      tagId,
      (
        await db
          .select({ id: schema.machines.id })
          .from(schema.machines)
          .where(eq(schema.machines.machineTagId, tagId))
      ).length,
    )
  }

  const itemViews: Array<OrderItemStatusView> = items.map((item) => {
    const menuItem = menuItemsById.get(item.menuItemId)
    const recipe = recipeRows.filter((step) => step.orderItemId === item.id)
    const instances = instancesByOrderItem.get(item.id) ?? []
    const instanceBySequence = new Map(
      instances.map((row) => [row.sequence, row]),
    )

    let etaSeconds: number | null = 0

    const steps = recipe.map((step) => {
      const instance = instanceBySequence.get(step.sequence)

      if (!instance) {
        if (etaSeconds !== null) etaSeconds += step.estimatedDurationSeconds
        return {
          sequence: step.sequence,
          machineTag: step.machineTag,
          estimatedDurationSeconds: step.estimatedDurationSeconds,
          status: 'pending' as const,
          queuePosition: null,
        }
      }

      if (instance.status === 'done') {
        return {
          sequence: step.sequence,
          machineTag: step.machineTag,
          estimatedDurationSeconds: step.estimatedDurationSeconds,
          status: 'done' as const,
          queuePosition: null,
        }
      }

      if (instance.status === 'in_progress') {
        const elapsedSeconds = instance.startedAt
          ? Math.floor((Date.now() - instance.startedAt.getTime()) / 1000)
          : 0
        if (etaSeconds !== null) {
          etaSeconds += Math.max(
            step.estimatedDurationSeconds - elapsedSeconds,
            0,
          )
        }
        return {
          sequence: step.sequence,
          machineTag: step.machineTag,
          estimatedDurationSeconds: step.estimatedDurationSeconds,
          status: 'in_progress' as const,
          queuePosition: 0,
        }
      }

      // Queued: rank among queued steps for the same Tag (batched above),
      // then spread across that Tag's Machines for a rough ETA.
      const queuedForTag = queuedStepsByTag.get(step.machineTagId) ?? []
      const position =
        queuedForTag.findIndex((row) => row.id === instance.id) + 1
      const machineCount = Math.max(
        machineCountByTag.get(step.machineTagId) ?? 0,
        1,
      )

      if (etaSeconds !== null) {
        const waitSeconds =
          Math.floor(Math.max(position - 1, 0) / machineCount) *
          step.estimatedDurationSeconds
        etaSeconds += waitSeconds + step.estimatedDurationSeconds
      }

      return {
        sequence: step.sequence,
        machineTag: step.machineTag,
        estimatedDurationSeconds: step.estimatedDurationSeconds,
        status: 'queued' as const,
        queuePosition: position,
      }
    })

    if (
      item.status === 'ready' ||
      item.status === 'picked_up' ||
      item.status === 'cancelled'
    ) {
      etaSeconds = null
    }

    const currentInstance = instances.find((row) => row.status !== 'done')

    return {
      id: item.id,
      menuItemName: menuItem?.name ?? '',
      status: item.status,
      cancellable:
        item.status !== 'cancelled' &&
        item.status !== 'ready' &&
        item.status !== 'picked_up' &&
        currentInstance?.status === 'queued',
      steps,
      etaSeconds,
    }
  })

  return {
    id: order.id,
    status: order.status,
    items: itemViews,
  }
}