//
// Copyright © 2022 Hardcore Engineering Inc.
//
// Licensed under the Eclipse Public License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License. You may
// obtain a copy of the License at https://www.eclipse.org/legal/epl-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//
// See the License for the specific language governing permissions and
// limitations under the License.
//

import core, {
  Class,
  Doc,
  DocIndexState,
  DocumentQuery,
  DocumentUpdate,
  extractDocKey,
  IndexStageState,
  MeasureContext,
  Ref,
  ServerStorage,
  Storage
} from '@hcengineering/core'
import { deepEqual } from 'fast-equals'
import { IndexedDoc } from '../types'
import { contentStageId, DocUpdateHandler, fieldStateId, FullTextPipeline, FullTextPipelineStage } from './types'
import {
  collectPropagate,
  docKey,
  docUpdKey,
  getContent,
  getFullTextAttributes,
  getFullTextContext,
  isFullTextAttribute,
  loadIndexStageStage
} from './utils'

/**
 * @public
 */
export class IndexedFieldStage implements FullTextPipelineStage {
  require = []
  stageId = fieldStateId
  // Do not clear downloaded content
  clearExcept: string[] = [contentStageId]

  clearField: string[] = []

  updateFields: DocUpdateHandler[] = []

  enabled = true

  stageValue: boolean | string = true

  indexState?: IndexStageState

  constructor (private readonly dbStorage: ServerStorage) {}

  async initialize (storage: Storage, pipeline: FullTextPipeline): Promise<void> {
    const indexable = (
      await pipeline.model.findAll(core.class.Class, { [core.mixin.FullTextSearchContext + '.propagate']: true })
    ).map((it) => it._id)

    const forceIndexing = (
      await pipeline.model.findAll(core.class.Class, { [core.mixin.FullTextSearchContext + '.forceIndex']: true })
    ).map((it) => it._id)

    indexable.sort()
    ;[this.stageValue, this.indexState] = await loadIndexStageStage(storage, this.indexState, this.stageId, 'config', {
      classes: indexable,
      forceIndex: forceIndexing
    })
  }

  async search (
    _classes: Ref<Class<Doc>>[],
    search: DocumentQuery<Doc>,
    size?: number,
    from?: number
  ): Promise<{ docs: IndexedDoc[], pass: boolean }> {
    return { docs: [], pass: true }
  }

  async collect (toIndex: DocIndexState[], pipeline: FullTextPipeline, metrics: MeasureContext): Promise<void> {
    const byClass = toIndex.reduce<Record<Ref<Class<Doc>>, DocIndexState[]>>((p, c) => {
      p[c.objectClass] = [...(p[c.objectClass] ?? []), c]
      return p
    }, {})

    const processed: Set<Ref<DocIndexState>> = new Set()

    for (const [v, values] of Object.entries(byClass)) {
      // Obtain real documents
      const valueIds = new Map(values.map((it) => [it._id, it]))
      const objClass = v as Ref<Class<Doc>>
      const docs = await this.dbStorage.findAll(metrics, objClass, {
        _id: { $in: Array.from(valueIds.keys()) }
      })
      const attributes = getFullTextAttributes(pipeline.hierarchy, objClass)

      // Child docs.

      let allChildDocs: DocIndexState[] | undefined

      for (const doc of docs) {
        if (pipeline.cancelling) {
          return
        }
        processed.add(doc._id as Ref<DocIndexState>)
        const docState = valueIds.get(doc._id as Ref<DocIndexState>) as DocIndexState

        try {
          // Copy content attributes as well.
          const content = getContent(pipeline.hierarchy, attributes, doc)

          const docUpdate: DocumentUpdate<DocIndexState> = {}

          let changes = 0

          // Convert previous child fields to just
          for (const [k] of Object.entries(docState.attributes)) {
            const { attr, docId, _class } = extractDocKey(k)
            if (
              (docId !== undefined && attr !== '') ||
              (_class !== undefined && !pipeline.hierarchy.isDerived(docState.objectClass, _class))
            ) {
              // If it some previous indexed field.
              // ;(docUpdate as any)[docUpdKey(k)] = null
              ;(docUpdate as any).$unset = { ...((docUpdate as any).$unset ?? {}), [docUpdKey(k)]: '' }
            }
          }

          for (const [, v] of Object.entries(content)) {
            // Check for content changes and collect update
            const dKey = docKey(v.attr.name, { _class: v.attr.attributeOf })
            const dUKey = docUpdKey(v.attr.name, { _class: v.attr.attributeOf })

            // Full re-index in case stage value is changed
            if (!deepEqual(docState.attributes[dKey], v.value)) {
              changes++
              ;(docUpdate as any)[dUKey] = v.value
            }
          }
          if (docState.attachedTo != null && changes > 0) {
            const ctx = getFullTextContext(pipeline.hierarchy, objClass)
            if (ctx.parentPropagate ?? true) {
              // We need to clear field stage from parent, so it will be re indexed.
              await pipeline.update(docState.attachedTo as Ref<DocIndexState>, false, {})
            }
          }

          const propagate: Ref<Class<Doc>>[] = collectPropagate(pipeline, docState.objectClass)
          if (propagate.length > 0) {
            // We need to propagate all changes to all child's of following classes.
            if (allChildDocs === undefined) {
              allChildDocs = await this.dbStorage.findAll(metrics.newChild('propagate', {}), core.class.DocIndexState, {
                attachedTo: { $in: docs.map((it) => it._id) }
              })
            }
            const childs = allChildDocs.filter((it) => it.attachedTo === docState._id)
            for (const u of childs) {
              if (propagate.some((it) => pipeline.hierarchy.isDerived(u.objectClass, it))) {
                pipeline.add(u)
                await pipeline.update(u._id, false, {})
              }
            }
          }

          await pipeline.update(docState._id, this.stageValue, docUpdate)
        } catch (err: any) {
          console.error(err)
          continue
        }
      }
    }
    if (!pipeline.cancelling) {
      for (const d of toIndex) {
        if (!processed.has(d._id)) {
          await pipeline.markRemove(d)
        }
      }
    }
  }

  async remove (docs: DocIndexState[], pipeline: FullTextPipeline): Promise<void> {
    for (const doc of docs) {
      if (doc.attachedTo !== undefined) {
        const attachedTo = doc.attachedTo as Ref<DocIndexState>
        const parentDocUpdate: DocumentUpdate<DocIndexState> = {}

        for (const [k] of Object.entries(doc.attributes)) {
          const { _class, attr, extra, docId } = extractDocKey(k)

          if (_class !== undefined && docId === undefined) {
            const keyAttr = pipeline.hierarchy.getAttribute(_class, attr)
            if (isFullTextAttribute(keyAttr)) {
              ;(parentDocUpdate as any)[docUpdKey(attr, { _class, docId: doc._id, extra })] = null
            }
          }
        }

        if (Object.keys(parentDocUpdate).length > 0) {
          await pipeline.update(attachedTo, false, parentDocUpdate)
        }
      }
      await pipeline.update(doc._id, this.stageValue, {})
    }
  }
}