import { prisma } from '../lib/prisma';
import { AppError } from '../types/index';
import { MODULE_PORT_DEFAULTS, MODULE_U_DEFAULTS, type ModuleType, type PortType } from '../lib/constants';

const moduleInclude = {
  ports: {
    orderBy: { portNumber: 'asc' as const },
    include: {
      vlans: { include: { vlan: true } },
    },
  },
};

/** Check whether a U-range is occupied in a rack, optionally excluding one module (for moves). */
async function hasCollision(
  rackId: string,
  uPosition: number,
  uSize: number,
  excludeModuleId?: string
): Promise<boolean> {
  const modules = await prisma.module.findMany({
    where: { rackId, ...(excludeModuleId ? { id: { not: excludeModuleId } } : {}) },
    select: { uPosition: true, uSize: true },
  });

  const occupied = new Set<number>();
  for (const m of modules) {
    for (let u = m.uPosition; u < m.uPosition + m.uSize; u++) occupied.add(u);
  }

  for (let u = uPosition; u < uPosition + uSize; u++) {
    if (occupied.has(u)) return true;
  }
  return false;
}

export async function createModule(
  rackId: string,
  data: {
    name: string;
    type: ModuleType;
    uPosition: number;
    uSize?: number;
    manufacturer?: string;
    model?: string;
    ipAddress?: string;
    notes?: string;
    portCount?: number;
    portType?: PortType;
  }
) {
  const rack = await prisma.rack.findUnique({ where: { id: rackId } });
  if (!rack) throw new AppError('Rack not found', 404, 'NOT_FOUND');

  const uSize = data.uSize ?? MODULE_U_DEFAULTS[data.type] ?? 1;

  if (data.uPosition < 1 || data.uPosition + uSize - 1 > rack.totalU) {
    throw new AppError(
      `Module does not fit within rack (U1–U${rack.totalU})`,
      400,
      'OUT_OF_BOUNDS'
    );
  }

  if (await hasCollision(rackId, data.uPosition, uSize)) {
    throw new AppError('U-slot collision: another module occupies that space', 409, 'COLLISION');
  }

  const portCount = data.portCount ?? MODULE_PORT_DEFAULTS[data.type] ?? 0;
  const portType: PortType = data.portType ?? 'ETHERNET';

  return prisma.module.create({
    data: {
      rackId,
      name: data.name,
      type: data.type,
      uPosition: data.uPosition,
      uSize,
      manufacturer: data.manufacturer,
      model: data.model,
      ipAddress: data.ipAddress,
      notes: data.notes,
      ports: {
        create: Array.from({ length: portCount }, (_, i) => ({
          portNumber: i + 1,
          portType,
        })),
      },
    },
    include: moduleInclude,
  });
}

export async function updateModule(
  id: string,
  data: Partial<{
    name: string;
    uPosition: number;
    uSize: number;
    manufacturer: string;
    model: string;
    ipAddress: string;
    notes: string;
  }>
) {
  const existing = await prisma.module.findUnique({ where: { id } });
  if (!existing) throw new AppError('Module not found', 404, 'NOT_FOUND');

  const newPosition = data.uPosition ?? existing.uPosition;
  const newSize = data.uSize ?? existing.uSize;

  if (data.uPosition !== undefined || data.uSize !== undefined) {
    const rack = await prisma.rack.findUnique({ where: { id: existing.rackId } });
    if (!rack) throw new AppError('Rack not found', 404, 'NOT_FOUND');

    if (newPosition < 1 || newPosition + newSize - 1 > rack.totalU) {
      throw new AppError(
        `Module does not fit within rack (U1–U${rack.totalU})`,
        400,
        'OUT_OF_BOUNDS'
      );
    }

    if (await hasCollision(existing.rackId, newPosition, newSize, id)) {
      throw new AppError('U-slot collision', 409, 'COLLISION');
    }
  }

  return prisma.module.update({ where: { id }, data, include: moduleInclude });
}

export async function deleteModule(id: string) {
  const existing = await prisma.module.findUnique({ where: { id } });
  if (!existing) throw new AppError('Module not found', 404, 'NOT_FOUND');
  return prisma.module.delete({ where: { id } });
}

/**
 * Move a module to a new rack and/or U-position.
 * Ports and VLAN assignments move with the module (they're linked by moduleId).
 */
export async function moveModule(
  id: string,
  targetRackId: string,
  targetUPosition: number
) {
  const existing = await prisma.module.findUnique({ where: { id } });
  if (!existing) throw new AppError('Module not found', 404, 'NOT_FOUND');

  const targetRack = await prisma.rack.findUnique({ where: { id: targetRackId } });
  if (!targetRack) throw new AppError('Target rack not found', 404, 'NOT_FOUND');

  if (targetUPosition < 1 || targetUPosition + existing.uSize - 1 > targetRack.totalU) {
    throw new AppError(
      `Module does not fit within target rack (U1–U${targetRack.totalU})`,
      400,
      'OUT_OF_BOUNDS'
    );
  }

  // Collision check in target rack, excluding self (handles same-rack moves)
  const excludeInTarget = targetRackId === existing.rackId ? id : undefined;
  if (await hasCollision(targetRackId, targetUPosition, existing.uSize, excludeInTarget)) {
    throw new AppError('U-slot collision in target rack', 409, 'COLLISION');
  }

  return prisma.module.update({
    where: { id },
    data: { rackId: targetRackId, uPosition: targetUPosition },
    include: moduleInclude,
  });
}

export async function getModulePorts(id: string) {
  const existing = await prisma.module.findUnique({ where: { id } });
  if (!existing) throw new AppError('Module not found', 404, 'NOT_FOUND');

  return prisma.port.findMany({
    where: { moduleId: id },
    orderBy: { portNumber: 'asc' },
    include: { vlans: { include: { vlan: true } } },
  });
}