/**
 * Entities Store
 */

import { ref, computed, readonly } from 'vue'
import { defineStore } from 'pinia'
import { entityService } from '../services'
import { EntityObject, MessageObject } from '../models'
import type {
  EntityListStreamRequest,
  EntityTransmitRequest,
  EntityTransmitResponse,
} from '../types/entity'
import type {
  CollectionIdentifier,
  EntityIdentifier,
  ListFilter,
  ListRange,
  ListSort,
} from '../types/common'
import type { MessageInterface } from '@/types/message'

export const useEntitiesStore = defineStore('mailEntitiesStore', () => {
  // State
  const _entities = ref<Record<string, EntityObject>>({})
  const transceiving = ref(false)

  /**
   * Get count of entities in store
   */
  const count = computed(() => Object.keys(_entities.value).length)

  /**
   * Check if any entities are present in store
   */
  const has = computed(() => count.value > 0)

  /**
   * Get all entities present in store
   */
  const entities = computed(() => Object.values(_entities.value))

  /**
   * Get a specific entity from store, with optional retrieval
   * 
   * @param provider - provider identifier
   * @param service - service identifier
   * @param collection - collection identifier
   * @param identifier - entity identifier
   * @param retrieve - Retrieve behavior: true = fetch if missing or refresh, false = cache only
   * 
   * @returns Entity object or null
   */
  function entity(target: EntityIdentifier, retrieve: boolean = false): EntityObject | null {
    if (retrieve === true && !_entities.value[target]) {
      console.debug(`[Mail Manager][Store] - Force fetching entity "${target}"`)
      fetch([target])
    }
    
    return _entities.value[target] || null
  }

  /**
   * Get all entities for a specific collection
   * 
   * @param provider - provider identifier
   * @param service - service identifier
   * @param collection - collection identifier
   * @param retrieve - Retrieve behavior: true = fetch if missing or refresh, false = cache only
   * 
   * @returns Array of entity objects
   */
  function entitiesForCollection(target: CollectionIdentifier, retrieve: boolean = false): EntityObject[] {
    const collectionEntities = Object.entries(_entities.value)
      .filter(([key]) => key.startsWith(target))
      .map(([_, entity]) => entity)
    
    if (retrieve === true && collectionEntities.length === 0) {
      console.debug(`[Mail Manager][Store] - Force fetching entities for collection "${target}"`)
      list([target])
    }
    
    return collectionEntities
  }

  // Actions
  
  /**
   * Retrieve all or specific entities, optionally filtered by source selector
   * 
   * @param sources - optional source selector
   * @param filter - optional list filter
   * @param sort - optional list sort
   * @param range - optional list range
   * 
   * @returns Promise with entity object list keyed by identifier
   */
  async function list(sources: CollectionIdentifier[], filter?: ListFilter, sort?: ListSort, range?: ListRange): Promise<Record<string, EntityObject>> {
    transceiving.value = true
    try {
      const entities: Record<string, EntityObject> = {}

      await entityService.listStream({ sources, filter, sort, range }, (entity: EntityObject) => {
        _entities.value[entity.identifier] = entity
        entities[entity.identifier] = entity
      })

      console.debug('[Mail Manager][Store] - Successfully retrieved', Object.keys(entities).length, 'entities')
      return entities
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to retrieve entities:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }
  
  /**
   * Retrieve specific entities by provider, service, collection, and identifiers
   * 
   * @param provider - provider identifier
   * @param service - service identifier
   * @param collection - collection identifier
   * @param identifiers - array of entity identifiers to fetch
   * 
   * @returns Promise with entity objects keyed by identifier
   */
  async function fetch(targets: EntityIdentifier[]): Promise<Record<string, EntityObject>> {
    transceiving.value = true
    try {
      const response = await entityService.fetch({ targets })
      
      // Merge fetched entities into state
      const entities: Record<string, EntityObject> = {}
      Object.entries(response).forEach(([identifier, entity]) => {
        entities[identifier] = entity
        _entities.value[identifier] = entity
      })

      console.debug('[Mail Manager][Store] - Successfully fetched', Object.keys(entities).length, 'entities')
      return entities
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to fetch entities:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Retrieve entity availability status for a given set of entity identifiers
   * 
   * @param targets - array of entity identifiers to check availability for
   * 
   * @returns Promise with entity availability status
   */
  async function extant(targets: EntityIdentifier[]) {
    transceiving.value = true
    try {
      const response = await entityService.extant({ targets })
      console.debug('[Mail Manager][Store] - Successfully checked entity availability')
      return response
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to check entity availability:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Retrieve delta changes for entities
   * 
   * @param sources - source selector for delta check
   * 
   * @returns Promise with delta changes (additions, modifications, deletions)
   * 
   * Note: Delta returns only identifiers, not full entities.
   * Caller should fetch full entities for additions/modifications separately.
   */
  async function delta(sources: CollectionIdentifier[]) {
    transceiving.value = true
    try {
      const response = await entityService.delta({ sources })
      
      // Process delta and update store
      Object.entries(response).forEach(([provider, providerData]) => {
        // Skip if no changes for provider
        if (providerData === false) return
        
        Object.entries(providerData).forEach(([service, serviceData]) => {
          // Skip if no changes for service
          if (serviceData === false) return
          
          Object.entries(serviceData).forEach(([collection, collectionData]) => {
            // Skip if no changes for collection
            if (collectionData === false) return
            
            // Process deletions (remove from store)
            if (collectionData.deletions && collectionData.deletions.length > 0) {
              collectionData.deletions.forEach((identifier) => {
                delete _entities.value[identifier]
              })
            }
          })
        })
      })

      console.debug('[Mail Manager][Store] - Successfully processed delta changes')
      return response
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to process delta:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Create a new empty entity object
   * 
   * @returns New entity object instance
   */
  function fresh(): EntityObject {
    return new EntityObject()
  }

  /**
   * Create a new entity with given collection identifier and properties
   * 
   * @param target - collection identifier for the new entity
   * @param properties - entity properties for creation
   * 
   * @returns Promise with created entity object
   */
  async function create(target: CollectionIdentifier, properties: MessageInterface | MessageObject): Promise<EntityObject> {
    transceiving.value = true
    try {
      if (properties instanceof MessageObject) {
        properties = properties.toJson()
      }
      const response = await entityService.create({ target, properties })
      
      // Add created entity to state
      _entities.value[response.identifier] = response

      console.debug('[Mail Manager][Store] - Successfully created entity:', response.identifier)
      return response
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to create entity:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Update an existing entity with given provider, service, collection, identifier, and data
   * 
   * @param provider - provider identifier for the entity to update
   * @param service - service identifier for the entity to update
   * @param collection - collection identifier for the entity to update
   * @param identifier - entity identifier for the entity to update
   * @param data - entity properties for update
   * 
   * @returns Promise with updated entity object
   */
  async function update(target: EntityIdentifier, properties: MessageInterface | MessageObject): Promise<EntityObject> {
    transceiving.value = true
    try {
      if (properties instanceof MessageObject) {
        properties = properties.toJson()
      }
      const response = await entityService.update({ target, properties })
      
      // Update entity in state
      _entities.value[response.identifier] = response

      console.debug('[Mail Manager][Store] - Successfully updated entity:', response.identifier)
      return response
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to update entity:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Delete entities by their identifiers.
   *
   * Removes successfully deleted entities from the local store.
   *
   * @param targets - entity identifiers to delete
   *
   * @returns Promise with deletion results keyed by target identifier
   */
  async function remove(targets: EntityIdentifier[]): Promise<{successes: EntityIdentifier[], failures: EntityIdentifier[]}> {
    transceiving.value = true
    try {
      const response = await entityService.delete({ targets })
      const successes: EntityIdentifier[] = []
      const failures: EntityIdentifier[] = []

      Object.entries(response).forEach(([targetIdentifier, result]) => {
        const originalIdentifier = targetIdentifier as EntityIdentifier
        if (!result.disposition || result.disposition === 'error') {
          console.warn(`[Mail Manager][Store] - Entity move on "${originalIdentifier}" returned an error: ${result.error})`)
          failures.push(originalIdentifier)
          return
        }

        if (!result.disposition || (result.disposition !== 'moved' && result.disposition !== 'deleted')) {
          console.warn(`[Mail Manager][Store] - Entity move on "${originalIdentifier}" returned invalid disposition: ${result.disposition})`)
          failures.push(originalIdentifier)
          return
        }

        const cachedEntity = _entities.value[originalIdentifier]
        if (!cachedEntity) {
          return
        }

        if (result.disposition === 'moved') {
          const movedEntity = cachedEntity.clone().fromJson({
            ...cachedEntity.toJson(),
            collection: result.destination,
            identifier: result.mutation,
          })
          _entities.value[result.mutation] = movedEntity
        }

        delete _entities.value[originalIdentifier]
        successes.push(originalIdentifier)
      })

      console.debug('[Mail Manager][Store] - Successfully deleted', successes.length, 'entities')
      return { successes, failures }
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to delete entities:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Patch existing entities with new properties
   */
  async function patch(properties: MessageInterface | MessageObject, targets: EntityIdentifier[]) {
    transceiving.value = true
    try {
      if (properties instanceof MessageObject) {
        properties = properties.toJson()
      }
      const response = await entityService.patch({ properties, targets })
      const successes: EntityIdentifier[] = []
      const failures: EntityIdentifier[] = []
      
      Object.entries(response).forEach(([targetIdentifier, result]) => {
        const originalIdentifier = targetIdentifier as EntityIdentifier
        if (!result.disposition || result.disposition === 'error') {
          console.warn(`[Mail Manager][Store] - Entity patch on "${originalIdentifier}" returned an error: ${result.error})`)
          failures.push(originalIdentifier)
          return
        }

        const cachedEntity = _entities.value[originalIdentifier]
        if (!cachedEntity) {
          return
        }

        if (result.disposition === 'patched') {
          const cachedEntityJson = cachedEntity.toJson()
          const mutatedEntity = cachedEntity.clone().fromJson({
            ...cachedEntityJson,
            properties: {
              ...cachedEntityJson.properties,
              ...properties,
            },
          })
          _entities.value[originalIdentifier] = mutatedEntity
        }

        successes.push(originalIdentifier)
      })

      console.debug('[Mail Manager][Store] - Successfully patched', successes.length, 'entities')
      return { successes, failures }
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to patch entities:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Move entities to another collection.
   *
   * Updates local store keys for successfully moved entities when they are
   * already present in cache.
   *
   * @param target - target collection identifier
   * @param sources - source entity identifiers
   *
   * @returns Promise with move results keyed by source identifier
   */
  async function move(target: CollectionIdentifier, sources: EntityIdentifier[]): Promise<{successes: EntityIdentifier[], failures: EntityIdentifier[]}> {
    transceiving.value = true
    try {
      const response = await entityService.move({ target, sources })
      const successes: EntityIdentifier[] = []
      const failures: EntityIdentifier[] = []

      Object.entries(response).forEach(([sourceIdentifier, result]) => {
        const originalIdentifier = sourceIdentifier as EntityIdentifier
        if (!result.disposition || result.disposition === 'error') {
          console.warn(`[Mail Manager][Store] - Entity move on "${originalIdentifier}" returned an error: ${result.error})`)
          failures.push(originalIdentifier)
          return
        }

        if (!result.disposition || result.disposition !== 'moved') {
          console.warn(`[Mail Manager][Store] - Entity move on "${originalIdentifier}" returned invalid disposition: ${result.disposition})`)
          failures.push(originalIdentifier)
          return
        }

        const cachedEntity = _entities.value[originalIdentifier]
        if (!cachedEntity) {
          return
        }

        const movedEntity = cachedEntity.clone().fromJson({
          ...cachedEntity.toJson(),
          collection: result.destination,
          identifier: result.mutation,
        })
        _entities.value[result.mutation] = movedEntity

        delete _entities.value[originalIdentifier]
        successes.push(originalIdentifier)
      })

      console.debug('[Mail Manager][Store] - Successfully moved', successes.length, 'entities')
      return { successes, failures }
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to move entities:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  /**
   * Send/transmit an entity
   * 
   * @param request - transmit request parameters
   * 
   * @returns Promise with transmission result
   */
  async function transmit(request: EntityTransmitRequest): Promise<EntityTransmitResponse> {
    transceiving.value = true
    try {
      const response = await entityService.transmit(request)
      console.debug('[Mail Manager][Store] - Successfully transmitted entity')
      return response
    } catch (error: any) {
      console.error('[Mail Manager][Store] - Failed to transmit entity:', error)
      throw error
    } finally {
      transceiving.value = false
    }
  }

  // Return public API
  return {
    // State (readonly)
    transceiving: readonly(transceiving),
    // Getters
    count,
    has,
    entities,
    entitiesForCollection,
    entity,
    list,
    fetch,
    extant,
    fresh,
    create,
    update,
    patch,
    delete: remove,
    delta,
    move,
    transmit,
  }
})