import { allCableTypes } from './project'
import type { CableType, Catalog, Connection, Device, Project } from './types'

/** One length within a cable type's group — e.g. "3 × 10ft". `distance`
 *  is undefined for the bucket of connections that have no length entered
 *  (kept separate rather than folded into a 0ft bucket, same reasoning as
 *  connectionsMissingLength on the parent line). */
export interface BomCableLengthLine {
  distance: number | undefined
  count: number
  totalLength: number
  totalCost: number
  connectionsMissingCost: number
}

export interface BomCableLine {
  cableTypeId: string
  cableTypeName: string
  unit: string
  count: number
  /** Sum of user-entered distances; connections with no distance are excluded. */
  totalLength: number
  connectionsMissingLength: number
  /** Sum of each connection's cost (its own override, or `costPerUnit *
   *  distance` when both are known); connections with no computable cost are
   *  excluded rather than counted as zero. */
  totalCost: number
  connectionsMissingCost: number
  /** This type's connections grouped by length, most common use case for
   *  "how many N-foot cables do I need to buy" — see organized-ideas.md §7.
   *  Sorted shortest first, with the no-length-entered bucket (if any) last. */
  lengths: BomCableLengthLine[]
}

export interface BomDeviceLine {
  key: string
  name: string
  category: string
  manufacturer?: string
  model?: string
  count: number
  /** Sum of `device.cost` across instances; devices with no cost set are
   *  excluded rather than counted as zero. */
  totalCost: number
  devicesMissingCost: number
}

export interface Bom {
  cables: BomCableLine[]
  devices: BomDeviceLine[]
  /** Sum of all cable line totals (missing-cost connections already excluded). */
  totalCableCost: number
  /** Sum of all device line totals (missing-cost devices already excluded). */
  totalDeviceCost: number
  /** `totalCableCost + totalDeviceCost`. Missing costs are excluded, not
   *  treated as zero, so this is a lower bound whenever anything is flagged
   *  as missing below. */
  grandTotalCost: number
}

function deviceGroupKey(device: Device): string {
  return device.templateId ?? `${device.category}:${device.manufacturer ?? ''}:${device.model ?? device.name}`
}

/** A connection's cost for BOM purposes: its own override if set, else
 *  `costPerUnit * distance` if both the cable type's rate and the
 *  connection's distance are known. Undefined means "not computable" —
 *  callers must exclude it from totals rather than treating it as zero. */
function connectionCost(connection: Connection, cableType: CableType | undefined): number | undefined {
  if (typeof connection.cost === 'number' && !Number.isNaN(connection.cost)) {
    return connection.cost
  }
  if (
    cableType &&
    typeof cableType.costPerUnit === 'number' &&
    !Number.isNaN(cableType.costPerUnit) &&
    typeof connection.distance === 'number' &&
    !Number.isNaN(connection.distance)
  ) {
    return cableType.costPerUnit * connection.distance
  }
  return undefined
}

export function computeBom(project: Project, catalog: Catalog): Bom {
  const cableTypes = new Map(allCableTypes(catalog).map((ct) => [ct.id, ct]))

  const cableLines = new Map<string, BomCableLine>()
  // Nested by cableTypeId, then by distance (undefined key for "no length
  // entered") — a separate map from cableLines since a Map key can't itself
  // be a nested Map, and it's convenient to keep the length-line objects
  // addressable by (cableTypeId, distance) while building them up.
  const lengthLines = new Map<string, Map<number | undefined, BomCableLengthLine>>()

  for (const connection of project.connections) {
    const cableType = cableTypes.get(connection.cableTypeId)
    const name = cableType?.name ?? 'Unknown Cable'
    const unit = cableType?.unit ?? 'ft'
    const existing = cableLines.get(connection.cableTypeId) ?? {
      cableTypeId: connection.cableTypeId,
      cableTypeName: name,
      unit,
      count: 0,
      totalLength: 0,
      connectionsMissingLength: 0,
      totalCost: 0,
      connectionsMissingCost: 0,
      lengths: [],
    }
    existing.count += 1
    const distance =
      typeof connection.distance === 'number' && !Number.isNaN(connection.distance) ? connection.distance : undefined
    if (distance !== undefined) {
      existing.totalLength += distance
    } else {
      existing.connectionsMissingLength += 1
    }
    const cost = connectionCost(connection, cableType)
    if (cost !== undefined) {
      existing.totalCost += cost
    } else {
      existing.connectionsMissingCost += 1
    }
    cableLines.set(connection.cableTypeId, existing)

    const byLength = lengthLines.get(connection.cableTypeId) ?? new Map<number | undefined, BomCableLengthLine>()
    const lengthLine = byLength.get(distance) ?? {
      distance,
      count: 0,
      totalLength: 0,
      totalCost: 0,
      connectionsMissingCost: 0,
    }
    lengthLine.count += 1
    if (distance !== undefined) lengthLine.totalLength += distance
    if (cost !== undefined) {
      lengthLine.totalCost += cost
    } else {
      lengthLine.connectionsMissingCost += 1
    }
    byLength.set(distance, lengthLine)
    lengthLines.set(connection.cableTypeId, byLength)
  }

  for (const [cableTypeId, line] of cableLines) {
    const byLength = [...(lengthLines.get(cableTypeId)?.values() ?? [])]
    // Shortest first; the no-length-entered bucket (distance undefined)
    // always sorts last rather than mixing in as "smallest".
    byLength.sort((a, b) => {
      if (a.distance === undefined) return 1
      if (b.distance === undefined) return -1
      return a.distance - b.distance
    })
    line.lengths = byLength
  }

  const deviceLines = new Map<string, BomDeviceLine>()
  for (const device of project.devices) {
    const key = deviceGroupKey(device)
    const existing = deviceLines.get(key) ?? {
      key,
      name: device.name,
      category: device.category,
      manufacturer: device.manufacturer,
      model: device.model,
      count: 0,
      totalCost: 0,
      devicesMissingCost: 0,
    }
    existing.count += 1
    if (typeof device.cost === 'number' && !Number.isNaN(device.cost)) {
      existing.totalCost += device.cost
    } else {
      existing.devicesMissingCost += 1
    }
    deviceLines.set(key, existing)
  }

  const cables = [...cableLines.values()].sort((a, b) => a.cableTypeName.localeCompare(b.cableTypeName))
  const devices = [...deviceLines.values()].sort((a, b) => a.name.localeCompare(b.name))
  const totalCableCost = cables.reduce((sum, line) => sum + line.totalCost, 0)
  const totalDeviceCost = devices.reduce((sum, line) => sum + line.totalCost, 0)

  return {
    cables,
    devices,
    totalCableCost,
    totalDeviceCost,
    grandTotalCost: totalCableCost + totalDeviceCost,
  }
}