//
// 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 { Analytics } from '@hcengineering/analytics'
import core, {
  docKey,
  isFullTextAttribute,
  isIndexedAttribute,
  toFindResult,
  type AttachedDoc,
  type Class,
  type Collection,
  type Doc,
  type DocumentQuery,
  type FindOptions,
  type FindResult,
  type FullTextSearchContext,
  type MeasureContext,
  type ObjQueryType,
  type Ref,
  type SearchOptions,
  type SearchQuery,
  type SearchResult
} from '@hcengineering/core'
import type { IndexedDoc, Middleware, MiddlewareCreator, PipelineContext } from '@hcengineering/server-core'
import { BaseMiddleware } from '@hcengineering/server-core'
/**
 * @public
 */
export class FullTextMiddleware extends BaseMiddleware implements Middleware {
  fulltextEndpoint: string
  contexts = new Map<Ref<Class<Doc>>, FullTextSearchContext>()

  constructor (
    context: PipelineContext,
    next: Middleware | undefined,
    fulltextUrl: string,
    readonly token: string
  ) {
    super(context, next)
    const fulltextEndpoints = fulltextUrl.split(';').map((it) => it.trim())

    const hash = this.hashWorkspace(context.workspace.uuid)
    this.fulltextEndpoint = fulltextEndpoints[Math.abs(hash % fulltextEndpoints.length)]
  }

  hashWorkspace (dbWorkspaceName: string): number {
    return [...dbWorkspaceName].reduce((hash, c) => (Math.imul(31, hash) + c.charCodeAt(0)) | 0, 0)
  }

  static create (url: string, token: string): MiddlewareCreator {
    return async (ctx, context, next): Promise<Middleware> => {
      const middleware = new FullTextMiddleware(context, next, url, token)
      await middleware.init(ctx)
      return middleware
    }
  }

  async init (ctx: MeasureContext): Promise<void> {
    this.contexts = new Map(
      this.context.modelDb.findAllSync(core.class.FullTextSearchContext, {}).map((it) => [it.toClass, it])
    )
  }

  async search<T extends Doc>(
    _classes: Ref<Class<T>>[],
    query: DocumentQuery<T>,
    fullTextLimit: number
  ): Promise<IndexedDoc[]> {
    try {
      return await (
        await fetch(this.fulltextEndpoint + '/api/v1/search', {
          method: 'PUT',
          keepalive: true,
          headers: {
            'Content-Type': 'application/json'
          },
          body: JSON.stringify({
            token: this.token,
            workspace: this.context.workspace.uuid,
            _classes,
            query,
            fullTextLimit
          })
        })
      ).json()
    } catch (err: any) {
      if (err?.cause?.code === 'ECONNRESET' || err?.cause?.code === 'ECONNREFUSED') {
        // TODO:  We need to send event about indexing is complete after a while
        return []
      }
      Analytics.handleError(err)
      return []
    }
  }

  async findAll<T extends Doc>(
    ctx: MeasureContext,
    _class: Ref<Class<T>>,
    query: DocumentQuery<T>,
    options?: FindOptions<T>
  ): Promise<FindResult<T>> {
    if (query?.$search === undefined) {
      return await this.provideFindAll(ctx, _class, query, options)
    }

    const { _id, $search, ...mainQuery } = query
    if ($search === undefined) {
      return toFindResult<T>([])
    }

    const ids: Set<Ref<Doc>> = new Set<Ref<Doc>>()
    const childIds: Set<Ref<Doc>> = new Set<Ref<Doc>>()
    const baseClass = this.context.hierarchy.getBaseClass(_class)
    let classes = this.context.hierarchy.getDescendants(baseClass).filter((it) => !this.context.hierarchy.isMixin(it))

    const attrs = this.context.hierarchy.getAllAttributes(_class)

    // We need to filter all non indexed fields from query to make it work properly
    const findQuery: DocumentQuery<Doc> = {
      $search: query.$search
    }

    const childClasses = new Set<Ref<Class<Doc>>>()
    try {
      for (const [k, attr] of attrs) {
        if (isFullTextAttribute(attr) || isIndexedAttribute(attr)) {
          const vv = (query as any)[k]
          if (vv != null) {
            if (
              k === '_class' ||
              k === 'modifiedBy' ||
              k === 'modifiedOn' ||
              k === 'space' ||
              k === 'attachedTo' ||
              k === 'attachedToClass'
            ) {
              findQuery[k] = vv
            } else {
              const docKeyValue = docKey(attr.name, attr.attributeOf)
              findQuery[docKeyValue] = vv
            }
          }
        }
        if (attr.type._class === core.class.Collection) {
          // we need attached documents to be in classes
          const coll = attr.type as Collection<AttachedDoc>
          const dsc = this.context.hierarchy.getDescendants(coll.of).filter((it) => !this.context.hierarchy.isMixin(it))
          for (const d of dsc) {
            childClasses.add(d)
          }
        }
      }
    } catch (err: any) {
      Analytics.handleError(err)
    }

    classes = classes.filter((it, idx, arr) => arr.indexOf(it) === idx)

    classes = classes.filter((it) => {
      if (typeof query._class === 'object') {
        if (query._class?.$in !== undefined) {
          return query._class.$in.includes(it)
        }
        if (query._class?.$nin !== undefined) {
          return !query._class.$nin.includes(it)
        }
      }
      return true
    })

    const fullTextLimit = Math.min(5000, (options?.limit ?? 200) * 100)

    // Find main documents, not attached ones.
    const { indexedDocMap } = await this.findDocuments<T>(classes, findQuery, fullTextLimit, baseClass, ids)

    for (const c of classes) {
      // We do not need to overlap
      childClasses.delete(c)
    }

    const childQuery: DocumentQuery<AttachedDoc> = {
      $search: findQuery.$search,
      attachedToClass: { $in: classes }
    }
    if (findQuery.space !== undefined) {
      childQuery.space = findQuery.space
    }
    const { childDocs, childIndexedDocMap } =
      childClasses !== undefined && childClasses.size > 0
        ? await this.findChildDocuments(Array.from(childClasses), childQuery, fullTextLimit, baseClass, childIds)
        : {
            childDocs: [],
            childIndexedDocMap: new Map()
          }

    const scoreSearch: number | undefined = (options?.sort as any)?.['#score']

    const resultIds = Array.from(this.getResultIds(ids, _id))
    const childResultIds = Array.from(this.getResultIds(childIds, _id))
    resultIds.push(...childResultIds)

    let result =
      resultIds.length > 0
        ? await this.provideFindAll(
          ctx,
          _class,
          { _id: { $in: Array.from(new Set(resultIds)) }, ...mainQuery },
          options
        )
        : toFindResult([])

    // Just assign scores based on idex
    result.forEach((it) => {
      const idDoc = indexedDocMap.get(it._id) ?? childIndexedDocMap.get(it._id)
      const { _score } = idDoc

      const maxScore = childDocs.reduceRight((p, cur) => (p > cur.$score ? p : cur.$score), _score)

      it.$source = {
        $score: maxScore
      }
    })
    if (scoreSearch !== undefined) {
      result.sort((a, b) => scoreSearch * ((a.$source?.$score ?? 0) - (b.$source?.$score ?? 0)))
      if (options?.limit !== undefined && options?.limit < result.length) {
        result = toFindResult(result.slice(0, options?.limit), result.total)
      }
    }
    return result
  }

  private async findDocuments<T extends Doc>(
    classes: Ref<Class<Doc>>[],
    findQuery: DocumentQuery<Doc>,
    fullTextLimit: number,
    baseClass: Ref<Class<T>>,
    ids: Set<Ref<Doc>>
  ): Promise<{ docs: IndexedDoc[], indexedDocMap: Map<Ref<Doc>, IndexedDoc> }> {
    const docs = await this.search(classes, findQuery, fullTextLimit)

    const indexedDocMap = new Map<Ref<Doc>, IndexedDoc>()

    for (const doc of docs) {
      if (
        doc._class != null &&
        Array.isArray(doc._class) &&
        doc._class.some((cl) => this.context.hierarchy.isDerived(cl, baseClass))
      ) {
        ids.add(doc.id)
        indexedDocMap.set(doc.id, doc)
      }
      if (
        doc._class !== null &&
        !Array.isArray(doc._class) &&
        this.context.hierarchy.isDerived(doc._class, baseClass)
      ) {
        ids.add(doc.id)
        indexedDocMap.set(doc.id, doc)
      }
    }
    return { docs, indexedDocMap }
  }

  private async findChildDocuments<T extends Doc>(
    classes: Ref<Class<Doc>>[],
    findQuery: DocumentQuery<Doc>,
    fullTextLimit: number,
    baseClass: Ref<Class<T>>,
    ids: Set<Ref<Doc>>
  ): Promise<{ childDocs: IndexedDoc[], childIndexedDocMap: Map<Ref<Doc>, IndexedDoc> }> {
    const childDocs = await this.search(classes, findQuery, fullTextLimit)

    const childIndexedDocMap = new Map<Ref<Doc>, IndexedDoc>()

    for (const doc of childDocs) {
      if (doc.attachedTo != null) {
        if (doc.attachedToClass != null && this.context.hierarchy.isDerived(doc.attachedToClass, baseClass)) {
          if (this.context.hierarchy.isDerived(doc.attachedToClass, baseClass)) {
            ids.add(doc.attachedTo)
            childIndexedDocMap.set(doc.attachedTo, doc)
          }
        } else {
          ids.add(doc.attachedTo)
          childIndexedDocMap.set(doc.attachedTo, doc)
        }
      }
    }
    return { childDocs, childIndexedDocMap }
  }

  async searchFulltext (ctx: MeasureContext, query: SearchQuery, options: SearchOptions): Promise<SearchResult> {
    try {
      return await ctx.with('full-text-search', {}, async (ctx) => {
        return await (
          await fetch(this.fulltextEndpoint + '/api/v1/full-text-search', {
            method: 'PUT',
            keepalive: true,
            headers: {
              'Content-Type': 'application/json'
            },
            body: JSON.stringify({
              workspace: this.context.workspace.uuid,
              token: this.token,
              query,
              options
            })
          })
        ).json()
      })
    } catch (err: any) {
      if (err?.cause?.code === 'ECONNRESET' || err?.cause?.code === 'ECONNREFUSED') {
        // TODO:  We need to send event about indexing is complete after a while
        return { docs: [] }
      }
      Analytics.handleError(err)
      return { docs: [] }
    }
  }

  async close (): Promise<void> {
    try {
      await fetch(this.fulltextEndpoint + '/api/v1/close', {
        method: 'PUT',
        keepalive: true,
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          token: this.token
        })
      })
    } catch (err: any) {
      if (err?.cause?.code === 'ECONNRESET' || err?.cause?.code === 'ECONNREFUSED') {
        return
      }
      Analytics.handleError(err)
    }
  }

  getResultIds (ids: Set<Ref<Doc>>, _id: ObjQueryType<Ref<Doc>> | undefined): Set<Ref<Doc>> {
    const result = new Set<Ref<Doc>>()
    if (_id !== undefined) {
      if (typeof _id === 'string') {
        if (ids.has(_id)) {
          result.add(_id)
        }
      } else if (_id.$in !== undefined) {
        for (const id of _id.$in) {
          if (ids.has(id)) {
            result.add(id)
          }
        }
      } else if (_id.$nin !== undefined) {
        for (const id of _id.$nin) {
          ids.delete(id)
        }
        return ids
      } else if (_id.$ne !== undefined) {
        ids.delete(_id.$ne)
        return ids
      }
    } else {
      return ids
    }
    return result
  }
}