import {
  type AssetStatus,
  Prisma,
} from "@/generated/prisma/client"
import prisma from "@/lib/prisma"
import type {
  CreateAssetFormType,
  UpdateAssetFormType,
} from "@/schemas/asset.schema"
import { AssetService } from "@/services/asset.service"
import { AssignmentService } from "@/services/assignment.service"
import { ItemService } from "@/services/item.service"
import { MovementService } from "@/services/movement.service"
import type { Assignment } from "@/types"

type FieldErrors = Record<string, string[]>

type CreateAssetUseCaseInput = CreateAssetFormType & {
  actorId: string
}

type UpdateAssetUseCaseInput = UpdateAssetFormType & {
  actorId: string
}

type CreateAssetUseCaseResult =
  | {
      success: true
      assetId: string
    }
  | {
      success: false
      errors: FieldErrors
    }

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

function createAssetError(errors: FieldErrors): CreateAssetUseCaseResult {
  return {
    success: false,
    errors,
  }
}

function updateAssetError(errors: FieldErrors): UpdateAssetUseCaseResult {
  return {
    success: false,
    errors,
  }
}

class AssetTransitionError extends Error {
  constructor(readonly errors: FieldErrors) {
    super("Asset transition failed")
  }
}

type AssetTransitionInput = {
  previousStatus: AssetStatus
  nextStatus: AssetStatus
  previousItemId: string | null
  nextItemId: string
  activeAssignment: Assignment | null
  nextPersonId?: string
}

function getAssetTransition({
  previousStatus,
  nextStatus,
  previousItemId,
  nextItemId,
  activeAssignment,
  nextPersonId,
}: AssetTransitionInput) {
  return {
    previousStatus,
    nextStatus,
    previousItemId,
    nextItemId,
    statusChanged: previousStatus !== nextStatus,
    itemChanged: previousItemId !== nextItemId,
    activeAssignment,
    nextPersonId,
    hasPerson: Boolean(nextPersonId),
    wasAssigned: previousStatus === "ASSIGNED",
    willBeAssigned: nextStatus === "ASSIGNED",
    wasAvailable: previousStatus === "AVAILABLE",
    willBeAvailable: nextStatus === "AVAILABLE",
    personChanged: activeAssignment?.personId !== nextPersonId,
  }
}

export async function createAssetUseCase(
  input: CreateAssetUseCaseInput,
): Promise<CreateAssetUseCaseResult> {
  const {
    actorId,
    itemId,
    serialNumber,
    deliveryNote,
    status,
    notes,
    personId,
  } = input

  try {
    return await prisma.$transaction(async (tx) => {
      const item = await ItemService.findByIdWithCategory(itemId, tx)

      if (!item) {
        return createAssetError({ itemId: ["Item not found"] })
      }

      const existentAsset = await AssetService.findBySerialNumber(
        serialNumber,
        tx,
      )

      if (existentAsset) {
        return createAssetError({
          serialNumber: ["This serial number already exists"],
        })
      }

      const newAsset = await AssetService.create(
        {
          item: { connect: { id: itemId } },
          serialNumber,
          deliveryNote,
          status,
          notes,
        },
        tx,
      )

      const createdAssignment =
        status === "ASSIGNED" && personId
          ? await AssignmentService.create(
              {
                notes: "",
                itemId,
                assetId: newAsset.id,
                quantity: 1,
                personId,
                assignmentDate: new Date(),
                createdBy: actorId,
              },
              tx,
            )
          : null

      await MovementService.create(
        {
          itemId,
          assetId: newAsset.id,
          quantity: 1,
          type: status === "ASSIGNED" ? "ASSIGNMENT" : "IN",
          personId: createdAssignment?.personId || undefined,
          assignmentId: createdAssignment?.id,
          userId: actorId,
        },
        tx,
      )

      if (status === "AVAILABLE") {
        await ItemService.updateStock(itemId, 1, tx)
      }

      return {
        success: true,
        assetId: newAsset.id,
      }
    })
  } catch (error) {
    if (
      error instanceof Prisma.PrismaClientKnownRequestError &&
      error.code === "P2002"
    ) {
      return createAssetError({
        serialNumber: ["This serial number already exists"],
      })
    }

    throw error
  }
}

export async function updateAssetUseCase(
  input: UpdateAssetUseCaseInput,
): Promise<UpdateAssetUseCaseResult> {
  const {
    actorId,
    id,
    itemId,
    serialNumber,
    deliveryNote,
    status,
    notes,
    personId,
  } = input

  try {
    return await prisma.$transaction(async (tx) => {
      const item = await ItemService.findByIdWithCategory(itemId, tx)

      if (!item) {
        return updateAssetError({ itemId: ["Item not found"] })
      }

      const currentAsset = await AssetService.findById(id, tx)

      if (!currentAsset) {
        return updateAssetError({ id: ["Asset not found"] })
      }

      const transition = getAssetTransition({
        previousStatus: currentAsset.status,
        nextStatus: status,
        previousItemId: currentAsset.itemId,
        nextItemId: itemId,
        activeAssignment: currentAsset.assignment,
        nextPersonId: personId,
      })

      const existentAsset = await AssetService.findBySerialNumber(
        serialNumber,
        tx,
      )

      if (
        existentAsset &&
        id !== existentAsset.id &&
        existentAsset.serialNumber === serialNumber
      ) {
        return updateAssetError({
          serialNumber: ["This serial number already exists"],
        })
      }

      await AssetService.update(
        id,
        {
          item: { connect: { id: itemId } },
          serialNumber,
          deliveryNote,
          status,
          notes,
        },
        tx,
      )

      let closedActiveAssignment = false

      if (transition.activeAssignment && !transition.willBeAssigned) {
        const activeAssignment = transition.activeAssignment
        const assignmentWasReturned =
          await AssignmentService.markReturnedIfActive(
            activeAssignment.id,
            actorId,
            tx,
          )

        if (!assignmentWasReturned) {
          throw new AssetTransitionError({
            id: ["Assignment already returned"],
          })
        }

        await MovementService.create(
          {
            type: "RETURN",
            quantity: activeAssignment.quantity || 1,
            itemId: transition.willBeAvailable
              ? transition.nextItemId
              : activeAssignment.itemId || undefined,
            assetId: activeAssignment.assetId || undefined,
            personId: activeAssignment.personId || undefined,
            assignmentId: activeAssignment.id,
            userId: actorId,
          },
          tx,
        )

        closedActiveAssignment = true
      }

      const shouldIncrementNextItemStock =
        transition.willBeAvailable &&
        (!transition.wasAvailable || transition.itemChanged)
      const shouldDecrementPreviousItemStock =
        transition.wasAvailable &&
        (!transition.willBeAvailable || transition.itemChanged)

      if (
        transition.statusChanged &&
        !transition.hasPerson &&
        !closedActiveAssignment
      ) {
        const statusMovementItemId = transition.willBeAssigned
          ? transition.nextItemId
          : shouldDecrementPreviousItemStock &&
              !shouldIncrementNextItemStock &&
              transition.previousItemId
            ? transition.previousItemId
            : transition.nextItemId

        await MovementService.create(
          {
            itemId: statusMovementItemId,
            assetId: id,
            quantity: 1,
            type: transition.willBeAssigned
              ? "ASSIGNMENT"
              : transition.nextStatus === "AVAILABLE"
                ? "IN"
                : "ADJUSTMENT",
            details: `Status changed from ${transition.previousStatus} to ${transition.nextStatus}`,
            userId: actorId,
          },
          tx,
        )
      }

      if (
        transition.itemChanged &&
        transition.wasAvailable &&
        transition.willBeAvailable
      ) {
        if (!transition.previousItemId) {
          throw new AssetTransitionError({
            itemId: ["Previous item not found for available asset"],
          })
        }

        await MovementService.create(
          {
            itemId: transition.previousItemId,
            assetId: id,
            quantity: 1,
            type: "OUT",
            details: `Asset moved from item ${transition.previousItemId} to ${transition.nextItemId}`,
            userId: actorId,
          },
          tx,
        )

        await MovementService.create(
          {
            itemId: transition.nextItemId,
            assetId: id,
            quantity: 1,
            type: "IN",
            details: `Asset moved from item ${transition.previousItemId} to ${transition.nextItemId}`,
            userId: actorId,
          },
          tx,
        )
      }

      if (
        transition.itemChanged &&
        transition.wasAvailable &&
        transition.willBeAssigned
      ) {
        if (!transition.previousItemId) {
          throw new AssetTransitionError({
            itemId: ["Previous item not found for available asset"],
          })
        }

        await MovementService.create(
          {
            itemId: transition.previousItemId,
            assetId: id,
            quantity: 1,
            type: "OUT",
            details: `Asset assigned from item ${transition.previousItemId} to item ${transition.nextItemId}`,
            userId: actorId,
          },
          tx,
        )
      }

      if (shouldIncrementNextItemStock) {
        await ItemService.updateStock(transition.nextItemId, 1, tx)
      }

      if (shouldDecrementPreviousItemStock) {
        if (!transition.previousItemId) {
          throw new AssetTransitionError({
            itemId: ["Previous item not found for available asset"],
          })
        }

        const stockWasDecremented = await ItemService.decrementStockIfAvailable(
          transition.previousItemId,
          1,
          tx,
        )

        if (!stockWasDecremented) {
          throw new AssetTransitionError({
            stock: ["Item does not have enough stock"],
          })
        }
      }

      if (transition.willBeAssigned && transition.nextPersonId) {
        const activeAssignment = transition.activeAssignment

        if (activeAssignment) {
          if (transition.personChanged) {
            await MovementService.create(
              {
                type: "RETURN",
                quantity: activeAssignment.quantity || 1,
                itemId: activeAssignment.itemId || undefined,
                assetId: activeAssignment.assetId || undefined,
                personId: activeAssignment.personId || undefined,
                assignmentId: activeAssignment.id,
                userId: actorId,
              },
              tx,
            )

            await MovementService.create(
              {
                type: "ASSIGNMENT",
                quantity: 1,
                itemId,
                assetId: id,
                personId: transition.nextPersonId,
                assignmentId: activeAssignment.id,
                userId: actorId,
              },
              tx,
            )

            await AssignmentService.update(
              activeAssignment.id,
              {
                createdBy: actorId,
                itemId,
                assetId: id,
                personId: transition.nextPersonId,
                quantity: 1,
                returnDate: null,
              },
              tx,
            )
          } else {
            await AssignmentService.update(
              activeAssignment.id,
              {
                itemId,
                assetId: id,
                personId: transition.nextPersonId,
                quantity: 1,
                returnDate: null,
              },
              tx,
            )
          }
        } else {
          const createdAssignment = await AssignmentService.create(
            {
              itemId,
              assetId: id,
              quantity: 1,
              personId: transition.nextPersonId,
              assignmentDate: new Date(),
              createdBy: actorId,
            },
            tx,
          )

          await MovementService.create(
            {
              type: "ASSIGNMENT",
              quantity: 1,
              itemId,
              assetId: id,
              personId: transition.nextPersonId,
              assignmentId: createdAssignment.id,
              userId: actorId,
            },
            tx,
          )
        }
      }

      return {
        success: true,
      }
    })
  } catch (error) {
    if (error instanceof AssetTransitionError) {
      return updateAssetError(error.errors)
    }

    if (
      error instanceof Prisma.PrismaClientKnownRequestError &&
      error.code === "P2002"
    ) {
      return updateAssetError({
        serialNumber: ["This serial number already exists"],
      })
    }

    throw error
  }
}