import { EventHub } from '@furystack/utils'
import { NotFoundError } from './errors/not-found-error.js'
import { filterItems } from './filter-items.js'
import type { Constructable } from './models/constructable.js'
import type { CreateResult, FilterType, FindOptions, PartialResult, PhysicalStore } from './models/physical-store.js'
import { selectFields } from './models/physical-store.js'

/**
 * In-memory {@link PhysicalStore} backed by a `Map`. Intended for tests, dev
 * fixtures and small reference datasets — entries are lost on process exit.
 * Production deployments should bind a real adapter (filesystem, MongoDB,
 * Sequelize, Redis) via `defineXxxStore`.
 */
export class InMemoryStore<T, TPrimaryKey extends keyof T>
  extends EventHub<{
    onEntityAdded: { entity: T }
    onEntityUpdated: { id: T[TPrimaryKey]; change: Partial<T> }
    onEntityRemoved: { key: T[TPrimaryKey] }
  }>
  implements PhysicalStore<T, TPrimaryKey, T>
{
  public async remove(...keys: Array<T[TPrimaryKey]>): Promise<void> {
    keys.forEach((key) => {
      this.cache.delete(key)
      this.emit('onEntityRemoved', { key })
    })
  }

  public async add(...entries: T[]): Promise<CreateResult<T>> {
    const created = entries.map((e) => {
      const entry = { ...e }
      if (this.cache.has(entry[this.primaryKey])) {
        throw new Error('Item with the primary key already exists.')
      }
      this.cache.set(entry[this.primaryKey], entry)
      this.emit('onEntityAdded', { entity: entry })
      return entry
    })
    return { created }
  }

  public cache: Map<T[TPrimaryKey], T> = new Map()
  public get = (key: T[TPrimaryKey], select?: Array<keyof T>) => {
    const item = this.cache.get(key)
    return Promise.resolve(item && select ? selectFields(item, ...select) : item)
  }

  public async find<TFields extends Array<keyof T>>(searchOptions: FindOptions<T, TFields>) {
    let value: Array<PartialResult<T, TFields>> = filterItems([...this.cache.values()], searchOptions.filter)

    if (searchOptions.order) {
      const orderRecord = searchOptions.order as Record<string, 'ASC' | 'DESC'>
      for (const fieldName of Object.keys(searchOptions.order) as Array<keyof T>) {
        value = value.sort((a, b) => {
          const order = orderRecord[fieldName as string]
          if (a[fieldName] < b[fieldName]) return order === 'ASC' ? -1 : 1
          if (a[fieldName] > b[fieldName]) return order === 'ASC' ? 1 : -1
          return 0
        })
      }
    }

    if (searchOptions.top || searchOptions.skip) {
      value = value.slice(searchOptions.skip, (searchOptions.skip || 0) + (searchOptions.top || this.cache.size))
    }

    if (searchOptions.select) {
      value = value.map((item) => {
        return selectFields(item, ...(searchOptions.select as TFields))
      })
    }

    return value
  }

  public async count(filter?: FilterType<T>) {
    return filterItems([...this.cache.values()], filter).length
  }

  public async update(id: T[TPrimaryKey], data: T) {
    if (!this.cache.has(id)) {
      throw new NotFoundError(`Entity not found with id '${id as string}', cannot update`)
    }
    this.cache.set(id, {
      ...this.cache.get(id),
      ...data,
    })
    this.emit('onEntityUpdated', { id, change: data })
  }

  public [Symbol.dispose]() {
    this.cache.clear()
    super[Symbol.dispose]()
  }

  public readonly primaryKey: TPrimaryKey
  public readonly model: Constructable<T>

  constructor(options: { primaryKey: TPrimaryKey; model: Constructable<T> }) {
    super()
    this.primaryKey = options.primaryKey
    this.model = options.model
  }
}