import { acceptedFamilies, getPortType, hasBridgingCableType } from './diagram'
import type { Catalog, Connection, Device, Diagram, PortType } from './types'

/**
 * Two ports connect if the sets of families they each accept (their own
 * family plus anything declared in `compatibleFamilyIds`) overlap at all.
 * This has to be a full set intersection, not just "does A's family appear
 * in B's list" — a pairing that only exists via a shared third "bridge"
 * family (e.g. USB-A Host and USB-B Device both listing 'usb-a-to-b', while
 * neither's own family is 'usb-a-to-b') would otherwise never match.
 */
export function portTypesCompatible(a: PortType, b: PortType): boolean {
  if (a.id === b.id) return true
  const aFamilies = acceptedFamilies(a)
  for (const family of acceptedFamilies(b)) {
    if (aFamilies.has(family)) return true
  }
  return false
}

export interface ConnectionCandidate {
  sourceDeviceId: string
  sourcePortId: string
  targetDeviceId: string
  targetPortId: string
}

export interface ConnectionValidation {
  valid: boolean
  reason?: string
}

/**
 * Central rule set for "can these two ports be wired together". Used both by
 * the canvas (to accept/reject a drag-to-connect gesture) and could be reused
 * server-side later since it only depends on plain domain data.
 */
export function validateConnection(
  diagram: Diagram,
  catalog: Catalog,
  candidate: ConnectionCandidate,
  existingConnections: Connection[] = diagram.connections,
): ConnectionValidation {
  const { sourceDeviceId, sourcePortId, targetDeviceId, targetPortId } = candidate

  if (sourceDeviceId === targetDeviceId && sourcePortId === targetPortId) {
    return { valid: false, reason: 'A port cannot connect to itself.' }
  }

  const sourceDevice = diagram.devices.find((d) => d.id === sourceDeviceId)
  const targetDevice = diagram.devices.find((d) => d.id === targetDeviceId)
  const sourcePort = sourceDevice?.ports.find((p) => p.id === sourcePortId)
  const targetPort = targetDevice?.ports.find((p) => p.id === targetPortId)

  if (!sourceDevice || !targetDevice || !sourcePort || !targetPort) {
    return { valid: false, reason: 'Unknown device or port.' }
  }

  if (sourcePort.direction === 'input' && targetPort.direction === 'input') {
    return { valid: false, reason: 'Cannot connect two input ports.' }
  }
  if (sourcePort.direction === 'output' && targetPort.direction === 'output') {
    return { valid: false, reason: 'Cannot connect two output ports.' }
  }

  const sourcePortType = getPortType(catalog, sourcePort.portTypeId)
  const targetPortType = getPortType(catalog, targetPort.portTypeId)
  if (!sourcePortType || !targetPortType) {
    return { valid: false, reason: 'Unknown port type.' }
  }
  // Directly compatible port types, or bridgeable by a specific adapter
  // cable (different connectors on each end, e.g. XLR-to-TRS) even when the
  // port types themselves declare no general compatibility.
  if (!portTypesCompatible(sourcePortType, targetPortType) && !hasBridgingCableType(catalog, sourcePortType, targetPortType)) {
    return {
      valid: false,
      reason: `${sourcePortType.name} is not compatible with ${targetPortType.name}.`,
    }
  }

  const maxSource = sourcePortType.maxConnections ?? 1
  const usedSource = existingConnections.filter(
    (c) => c.sourcePortId === sourcePortId || c.targetPortId === sourcePortId,
  ).length
  if (usedSource >= maxSource) {
    return { valid: false, reason: `${sourcePort.name} already has the maximum number of cables.` }
  }

  const maxTarget = targetPortType.maxConnections ?? 1
  const usedTarget = existingConnections.filter(
    (c) => c.sourcePortId === targetPortId || c.targetPortId === targetPortId,
  ).length
  if (usedTarget >= maxTarget) {
    return { valid: false, reason: `${targetPort.name} already has the maximum number of cables.` }
  }

  return { valid: true }
}

export function findDevicePort(devices: Device[], deviceId: string, portId: string) {
  const device = devices.find((d) => d.id === deviceId)
  const port = device?.ports.find((p) => p.id === portId)
  return device && port ? { device, port } : undefined
}