import { Prisma } from "@/generated/prisma/client"
import prisma from "@/lib/prisma"
import type { CreateItemData, UpdateItemData } from "@/schemas/item.schema"
import { ItemService } from "@/services/item.service"
import { MovementService } from "@/services/movement.service"
import { buildItemSku } from "./item.helpers"

type FieldErrors = Record<string, string[]>

type CreateItemUseCaseInput = Omit<CreateItemData, "trackingType" | "status"> &
  Partial<Pick<CreateItemData, "trackingType" | "status">> & {
  actorId: string
}

type UpdateItemUseCaseInput = UpdateItemData & {
  actorId: string
}

type ItemUseCaseResult =
  | {
      success: true
    }
  | {
      success: false
      errors: FieldErrors
    }

function itemError(errors: FieldErrors): ItemUseCaseResult {
  return {
    success: false,
    errors,
  }
}

function isUniqueConstraintError(error: unknown) {
  return (
    error instanceof Prisma.PrismaClientKnownRequestError &&
    error.code === "P2002"
  )
}

export async function createItemUseCase(
  input: CreateItemUseCaseInput,
): Promise<ItemUseCaseResult> {
  const {
    actorId,
    name,
    categoryId,
    stock,
    trackingType = "QUANTITY",
    status = "ACTIVE",
    minStock,
    targetStock,
  } = input

  if (stock < 0) {
    return itemError({ stock: ["Stock cannot be negative"] })
  }

  try {
    return await prisma.$transaction(async (tx) => {
      const existingItem = await ItemService.findByName(name, tx)

      if (existingItem) {
        return itemError({
          name: ["An item with this name already exists"],
        })
      }

      const skuBase = buildItemSku(name)
      const existingSkuCount = await tx.item.count({
        where: {
          sku: {
            startsWith: skuBase,
          },
        },
      })

      const item = await ItemService.create(
        {
          sku: buildItemSku(name, existingSkuCount),
          name,
          trackingType,
          status,
          minStock,
          targetStock,
          category: { connect: { id: categoryId } },
          stock: stock || 0,
        },
        tx,
      )

      if (stock > 0) {
        await MovementService.create(
          {
            type: "IN",
            itemId: item.id,
            userId: actorId,
            quantity: stock,
          },
          tx,
        )
      }

      return {
        success: true,
      }
    })
  } catch (error) {
    if (isUniqueConstraintError(error)) {
      return itemError({ name: ["An item with this name already exists"] })
    }

    throw error
  }
}

export async function updateItemUseCase(
  input: UpdateItemUseCaseInput,
): Promise<ItemUseCaseResult> {
  const {
    actorId,
    id,
    stock,
    name,
    categoryId,
    trackingType,
    status,
    minStock,
    targetStock,
  } = input

  try {
    return await prisma.$transaction(async (tx) => {
      const existingItem = await ItemService.findByIdWithAssetCount(id, tx)

      if (!existingItem) {
        return itemError({ id: ["Item not found"] })
      }

      const existingItemByName = await ItemService.findByName(name, tx)

      if (existingItemByName && existingItemByName.id !== id) {
        return itemError({ name: ["An item with this name already exists"] })
      }

      await ItemService.update(
        id,
        {
          stock: stock ?? existingItem.stock,
          name: name || existingItem.name,
          trackingType: trackingType ?? existingItem.trackingType,
          status: status ?? existingItem.status,
          minStock: minStock ?? existingItem.minStock,
          targetStock: targetStock ?? existingItem.targetStock,
          category: { connect: { id: categoryId } },
        },
        tx,
      )

      const updatedStock = stock ?? existingItem.stock

      if (updatedStock > existingItem.stock) {
        await MovementService.create(
          {
            type: "IN",
            itemId: id,
            quantity: updatedStock - existingItem.stock,
            userId: actorId,
          },
          tx,
        )
      }

      return {
        success: true,
      }
    })
  } catch (error) {
    if (isUniqueConstraintError(error)) {
      return itemError({ name: ["An item with this name already exists"] })
    }

    throw error
  }
}

export async function deleteItemUseCase(
  id: string,
): Promise<ItemUseCaseResult> {
  return prisma.$transaction(async (tx) => {
    const existingItem = await ItemService.findByIdWithAssetCount(id, tx)

    if (!existingItem) {
      return itemError({ id: ["Item not found"] })
    }

    if (existingItem._count.assets > 0) {
      return itemError({ id: ["Item has assets, you cannot delete it"] })
    }

    if (existingItem.stock > 0) {
      return itemError({ id: ["Item has stock, you cannot delete it"] })
    }

    await ItemService.delete(id, tx)

    return {
      success: true,
    }
  })
}