/*
 * Copyright (c) 2019 - present Nimbella Corp.
 *
 * This file is licensed to you under the Apache 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 http://www.apache.org/licenses/LICENSE-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 REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

import {
  StorageProvider, StorageClient, RemoteFile, DeleteFilesOptions, DownloadOptions, GetFilesOptions, SaveOptions,
  SignedUrlOptions, UploadOptions, StorageKey, SettableFileMetadata, WebsiteOptions, FileMetadata
}
  from './interface'
import {
  S3Client, GetObjectCommand, PutObjectCommand, ListObjectsCommand, DeleteObjectCommand, DeleteObjectsCommand,
  PutBucketWebsiteCommand, CopyObjectCommand, HeadObjectCommand
} from '@aws-sdk/client-s3'
import { getSignedUrl } from '@aws-sdk/s3-request-presigner'
import { Readable, Writable } from 'stream'
import { createWriteStream, createReadStream } from 'fs'
import { WritableStream } from 'memory-streams'
import { isWeb, getBucketFromCredentials } from './common'
import makeDebug from 'debug'
const debug = makeDebug('nim:storage-s3')

export class S3RemoteFile implements RemoteFile {
  private s3: S3Client
  private bucketName: string
  private web: boolean
  name: string

  constructor(s3: S3Client, bucketName: string, fileName: string, web: boolean) {
    debug('created file handle for %s', fileName)
    this.s3 = s3
    this.bucketName = bucketName
    this.name = fileName
    this.web = web
  }

  getImplementation(): any {
    return this.s3
  }

  save(data: Buffer, options?: SaveOptions): Promise<any> {
    // Set public read iff web bucket
    debug('save was called for file %s', this.name)
    const ACL = this.web ? 'public-read' : undefined
    const cmd = new PutObjectCommand({
      Bucket: this.bucketName,
      Key: this.name,
      Body: data,
      ContentType: options?.metadata?.contentType,
      CacheControl: options?.metadata?.cacheControl,
      ACL
    })
    return this.s3.send(cmd)
  }

  setMetadata(meta: SettableFileMetadata): Promise<any> {
    debug('setMetadata was called for file %s', this.name)
    const CopySource = `${this.bucketName}/${this.name}`
    const { cacheControl: CacheControl, contentType: ContentType } = meta
    const ACL = this.web ? 'public-read' : undefined
    const cmd = new CopyObjectCommand({ CopySource, Bucket: this.bucketName, Key: this.name, CacheControl, ContentType, MetadataDirective: 'REPLACE', ACL })
    return this.s3.send(cmd)
  }

  async getMetadata(): Promise<FileMetadata> {
    debug('getMetadata was called for file %s', this.name)
    const cmd = new HeadObjectCommand({ Bucket: this.bucketName, Key: this.name })
    const response = await this.s3.send(cmd)
    const { StorageClass: storageClass, ContentLength, ETag: etag } = response
    return { name: this.name, storageClass, size: String(ContentLength), etag, updated: response.LastModified?.toISOString() }
  }

  async exists(): Promise<boolean> {
    debug('exists was called for file %s', this.name)
    try {
      await this.getMetadata()
    } catch (err) {
      if (err?.$metadata?.httpStatusCode === 404) {
        return false
      }
      throw err
    }
    return true
  }

  delete(): Promise<any> {
    debug('delete was called for file %s', this.name)
    const cmd = new DeleteObjectCommand({ Bucket: this.bucketName, Key: this.name })
    return this.s3.send(cmd)
  }

  async download(options?: DownloadOptions): Promise<Buffer> {
    debug('download was called for file %s', this.name)
    const destination = options?.destination
      ? createWriteStream(options.destination)
      : new WritableStream({ highWaterMark: 1024 * 1024 })
    debug('download: created destination for options %O', options)
    const cmd = new GetObjectCommand({ Bucket: this.bucketName, Key: this.name })
    debug('will send command: %O', cmd)
    const result = await this.s3.send(cmd)
    debug('got back result: %O', result)
    const content = result.Body as Readable // Body has type ReadableStream<any>|Readable|Blob.  Readable seems to work in practice
    debug('about to pipe')
    await pipe(content, destination)
    debug('piping complete')
    return options?.destination ? Buffer.from('') : (destination as WritableStream).toBuffer()
  }

  async getSignedUrl(options: SignedUrlOptions): Promise<string> {
    debug('getSignedUrl was called for file %s', this.name)
    const { action, expires, version, contentType: ContentType } = options
    if (version !== 'v4') {
      throw new Error('Signing version v4 is required for s3')
    }

    let cmd
    const ACL = this.web ? 'public-read' : undefined
    switch (action) {
    case 'read':
      cmd = new GetObjectCommand({ Bucket: this.bucketName, Key: this.name })
      break
    case 'write':
      cmd = new PutObjectCommand({ Bucket: this.bucketName, Key: this.name, ContentType, ACL })
      break
    case 'delete':
      cmd = new DeleteObjectCommand({ Bucket: this.bucketName, Key: this.name })
    }
    if (!cmd) {
      throw new Error('The action for a signed URL must be one of \'read\' | \'write\' | \'delete\'')
    }
    if (expires) {
      // The interface expects something that can be passed to new Date()
      // to get an absolute time.  The s3 getSignedUrl options expect a value in seconds
      // from now
      const expiresIn = Math.round((new Date(expires).getTime() - Date.now()) / 1000)
      return getSignedUrl(this.s3, cmd, { expiresIn })
    }

    return getSignedUrl(this.s3, cmd, {})
  }
}

function pipe(input: Readable, output: Writable): Promise<unknown> {
  const toWait = new Promise(function(resolve) {
    output.on('close', () => {
      resolve(true)
    })
    output.on('finish', () => {
      resolve(true)
    })
  })
  input.pipe(output)
  return toWait
}

class NimS3Client implements StorageClient {
  private s3: S3Client
  private bucketName: string
  private url: string // defined iff web

  constructor(s3: S3Client, bucketName: string, url = '') {
    debug('s3client: %O, bucketName=%s, url=%s', s3.config, bucketName, url)
    this.s3 = s3
    this.bucketName = bucketName
    this.url = url
  }

  getImplementation(): any {
    return this.s3
  }

  getURL(): string {
    return this.url
  }

  getBucketName(): string {
    return this.bucketName
  }

  setWebsite(website: WebsiteOptions): Promise<any> {
    debug('setWebsite was called for bucket %s', this.bucketName)
    const { notFoundPage: Key, mainPageSuffix: Suffix } = website
    const cmd = new PutBucketWebsiteCommand({ Bucket: this.bucketName, WebsiteConfiguration: { ErrorDocument: { Key }, IndexDocument: { Suffix } } })
    return this.s3.send(cmd)
  }

  async deleteFiles(options?: DeleteFilesOptions): Promise<any> {
    debug('deleteFiles was called for bucket %s', this.bucketName)
    // s3 does not support 'prefix' on DeleteObjects, only on ListObjects.
    // The multi-object delete takes a list of objects.  So this takes two round trips.
    const listCmd = new ListObjectsCommand({ Bucket: this.bucketName, Prefix: options?.prefix })
    const listResult = await this.s3.send(listCmd)
    if (!listResult.Contents) {
      return true
    }
    const Objects = listResult.Contents.map(obj => ({ Key: obj.Key }))
    const deleteCmd = new DeleteObjectsCommand({ Bucket: this.bucketName, Delete: { Objects } })
    return this.s3.send(deleteCmd)
  }

  file(destination: string): RemoteFile {
    return new S3RemoteFile(this.s3, this.bucketName, destination, !!this.url)
  }

  upload(path: string, options?: UploadOptions): Promise<any> {
    debug('upload was called for path %s to bucket %s', path, this.bucketName)
    const data = createReadStream(path)
    const Key = options?.destination || path
    // Set public read iff web bucket
    const ACL = this.url ? 'public-read' : undefined
    const cmd = new PutObjectCommand({
      Bucket: this.bucketName,
      Key,
      ContentType: options?.metadata?.contentType,
      CacheControl: options?.metadata?.cacheControl,
      Body: data,
      ACL
    })
    return this.s3.send(cmd)
  }

  async getFiles(options?: GetFilesOptions): Promise<RemoteFile[]> {
    debug('getFiles was called for bucket %s', this.bucketName)
    const cmd = new ListObjectsCommand({ Bucket: this.bucketName, Prefix: options?.prefix })
    const response = await this.s3.send(cmd)
    const files = fileNames((response.Contents || []).map(obj => obj.Key))
    return files.map(key => new S3RemoteFile(this.s3, this.bucketName, key, !!this.url))
  }
}

// Typeguard function to ensure we ignore any file objects without keys
// This won't happen when we are calling the service - but type definition
// for this field is optional.
function fileNames(keys: (string|undefined)[] = []): string[] {
  return keys.filter((obj): obj is string => !!obj)
}

// Compute the actual name of a bucket, minus the s3:// prefix.
// Bucket names must be globally unique, which is hard to achieve
// while at the same time being able to calculate the name deterministically from
// namespace and API host.  We append `-nimbella-io` as a weak reservation of a
// block of names.  We extract the deployment name from the API host to disambiguate
// nimbella deployments.  Then we rely on the fact that namespace names are unique
// within a deployment.  Global collisions are further avoided by the practice
// (not followed 100% of the time) of including random characters in namespace names,
// but we can't use further randomness here since determinism is required.
function computeBucketStorageName(apiHost: string, namespace: string, web: boolean): string {
  const deployment = apiHost.replace('https://', '').split('.')[0]
  debug('calculated deployment %s from apihost %s', deployment, apiHost)
  const bucketName = `${namespace}-${deployment}-nimbella-io`
  return web ? bucketName : `data-${bucketName}`
}

// This computes the minimal function bucket endpoint for cases where we don't
// have a web url in the credentials but do have an endpoint URL there.
// It might prove to be a historical artifact and may be eliminated.  It can
// only provide http access to the bucket, without any path routing for /api
// paths.  It's possible advantage is that it will provide minimal functionality
// even on non-AWS implementations of S3 where there is no cloudfront or similar
// service.
function computeBucketUrl(endpoint: string, bucketName: string): string {
  if (!endpoint) {
    throw new Error('Every credential set on AWS must have either a web URL or an endpoint URL')
  }
  const url = new URL(endpoint)
  return `http://${bucketName}.${url.hostname}`
}

const provider: StorageProvider = {
  prepareCredentials: (original: Record<string, any>): StorageKey => {
    // For s3 we will arrange to have the stored information be exactly what we need so
    // this function is an identity map
    debug('preparing credentials: %O', original)
    return original as StorageKey
  },
  getClient: (namespace: string, apiHost: string, type: boolean|string, credentials: Record<string, any>) => {
    debug('making S3Client with credentials %O', credentials)
    const s3 = new S3Client(credentials)
    debug('have client: %O', s3)
    const web = isWeb(type)
    const bucketName = getBucketFromCredentials(type, credentials) || computeBucketStorageName(apiHost, namespace, web)
    if (web) {
      const url: string = credentials.weburl || computeBucketUrl(credentials.endpoint, bucketName)
      return new NimS3Client(s3, bucketName, url)
    }

    return new NimS3Client(s3, bucketName)
  },
  identifier: '@nimbella/storage-s3'
}

export default provider
export { NimS3Client }