import { Prisma, UserStatus } from "@/generated/prisma/client"
import { normalizeEmail } from "@/lib/email"
import prisma from "@/lib/prisma"
import { getPasswordHash } from "@/lib/security"
import type {
  CreatePersonFormType,
  UpdatePersonFormType,
} from "@/schemas/person.schema"
import type {
  UnifiedCreateFormType,
  UnifiedUpdateFormType,
} from "@/schemas/user.schema"
import { PersonService } from "@/services/person.service"
import { getUserByEmail } from "@/services/user.service"

type FieldErrors = Record<string, string[]>

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

function personError(errors: FieldErrors): PersonUseCaseResult {
  return {
    success: false,
    errors,
  }
}

function uniqueErrorFor(error: unknown): FieldErrors | null {
  if (
    !(error instanceof Prisma.PrismaClientKnownRequestError) ||
    error.code !== "P2002"
  ) {
    return null
  }

  const target = Array.isArray(error.meta?.target) ? error.meta.target : []

  if (target.includes("email")) {
    return { email: ["Email already exists"] }
  }

  return { email: ["Email already exists"] }
}

export async function createPersonUseCase(
  input: CreatePersonFormType,
): Promise<PersonUseCaseResult> {
  const { firstName, lastName, department, email, phone, userId } = input

  try {
    return await prisma.$transaction(async (tx) => {
      if (email) {
        const existingPersonEmail = await PersonService.findByEmail(email, tx)

        if (existingPersonEmail) {
          return personError({ email: ["Email already exists"] })
        }
      }

      await PersonService.create(
        {
          firstName,
          lastName,
          department,
          email: email || null,
          phone: phone || null,
          ...(userId ? { user: { connect: { id: userId } } } : {}),
        },
        tx,
      )

      return {
        success: true,
      }
    })
  } catch (error) {
    const errors = uniqueErrorFor(error)

    if (errors) {
      return personError(errors)
    }

    throw error
  }
}

export async function updatePersonUseCase(
  input: UpdatePersonFormType,
): Promise<PersonUseCaseResult> {
  const { id, firstName, lastName, department, email, phone, userId } = input

  try {
    return await prisma.$transaction(async (tx) => {
      if (email) {
        const existingPersonEmail = await PersonService.findByEmail(email, tx)

        if (existingPersonEmail && existingPersonEmail.id !== id) {
          return personError({ email: ["Email already exists"] })
        }
      }

      await PersonService.update(
        id,
        {
          firstName,
          lastName,
          department,
          email: email || null,
          phone: phone || null,
          ...(userId
            ? { user: { connect: { id: userId } } }
            : { userId: null }),
        },
        tx,
      )

      return {
        success: true,
      }
    })
  } catch (error) {
    const errors = uniqueErrorFor(error)

    if (errors) {
      return personError(errors)
    }

    throw error
  }
}

export async function createPersonUserUseCase(
  input: UnifiedCreateFormType,
): Promise<PersonUseCaseResult> {
  const {
    firstName,
    lastName,
    department,
    email,
    phone,
    role,
    password,
    isActive,
  } = input

  try {
    return await prisma.$transaction(async (tx) => {
      // Cross-table email uniqueness: check both Person and User tables
      const existingPersonEmail = await PersonService.findByEmail(email, tx)
      if (existingPersonEmail) {
        return personError({ email: ["Email already exists"] })
      }

      const existingUserEmail = await getUserByEmail(email, tx)
      if (existingUserEmail) {
        return personError({ email: ["Email already exists"] })
      }

      if (role === "NO_USER") {
        // Person-only creation — no User record
        await PersonService.create(
          {
            firstName,
            lastName,
            department,
            email,
            phone: phone ?? null,
          },
          tx,
        )

        return { success: true }
      }

      // Person + User creation
      if (!password) {
        return personError({ password: ["Password is required"] })
      }

      const person = await PersonService.create(
        {
          firstName,
          lastName,
          department,
          email,
          phone: phone ?? null,
        },
        tx,
      )

      const userName = `${firstName} ${lastName}`
      const hashedPassword = await getPasswordHash(password)
      const status = isActive ? UserStatus.ACTIVE : UserStatus.DISABLED
      const now = new Date()

      const user = await tx.user.create({
        data: {
          name: userName,
          email,
          emailNormalized: normalizeEmail(email),
          passwordHash: hashedPassword,
          role,
          status,
          ...(status === UserStatus.ACTIVE ? { activatedAt: now } : {}),
          passwordChangedAt: now,
        },
      })

      await PersonService.update(
        person.id,
        { user: { connect: { id: user.id } } },
        tx,
      )

      return { success: true }
    })
  } catch (error) {
    const errors = uniqueErrorFor(error)

    if (errors) {
      return personError(errors)
    }

    throw error
  }
}

export async function updatePersonUserUseCase(
  input: UnifiedUpdateFormType,
): Promise<PersonUseCaseResult> {
  const {
    id,
    firstName,
    lastName,
    department,
    email,
    phone,
    role,
    isActive,
    password,
  } = input

  try {
    return await prisma.$transaction(async (tx) => {
      const existing = await PersonService.findById(id, tx)

      if (!existing) {
        return personError({ id: ["Person not found"] })
      }

      if (email) {
        const existingPersonEmail = await PersonService.findByEmail(email, tx)
        if (existingPersonEmail && existingPersonEmail.id !== id) {
          return personError({ email: ["Email already exists"] })
        }
      }

      await PersonService.update(
        id,
        {
          firstName,
          lastName,
          department,
          email: email || null,
          phone: phone || null,
        },
        tx,
      )

      // If the person has a linked user, update User fields.
      if (existing.userId) {
        const userData: Prisma.UserUpdateInput = {}

        if (role !== undefined) {
          userData.role = role
        }
        if (isActive !== undefined) {
          userData.status = isActive ? UserStatus.ACTIVE : UserStatus.DISABLED
          if (isActive) {
            userData.activatedAt = new Date()
          }
        }
        if (password && password.length >= 8) {
          userData.passwordHash = await getPasswordHash(password)
          userData.passwordChangedAt = new Date()
        }

        if (Object.keys(userData).length > 0) {
          await tx.user.update({
            where: { id: existing.userId },
            data: userData,
          })
        }
      }

      return { success: true }
    })
  } catch (error) {
    const errors = uniqueErrorFor(error)

    if (errors) {
      return personError(errors)
    }

    throw error
  }
}