import {FileMetadata, Filesystem, Stat} from "./Filesystem"
import * as ssh2 from "ssh2"
import * as path from "path"
import * as fs from "fs"
import ReadableStream = NodeJS.ReadableStream
import {UniversalPath} from "../path"

/**
 * A Filesystem implementation that stores files on remote hosts via SFTP/SSH.
 */
export class SSHFilesystem extends Filesystem {
    private _ssh?: ssh2.Client

    constructor(
        protected readonly baseConfig: { ssh: ssh2.ConnectConfig, baseDir: string },
    ) { super() }

    getPrefix(): string {
        return `sftp+${this.baseConfig.ssh.host}://`
    }

    async getStoreFileAsTemp(args: { storePath: string }): Promise<UniversalPath> {
        const temp = this.tempName()
        const write = fs.createWriteStream(temp)
        const read = await this.getStoreFileAsStream(args)

        return new Promise<UniversalPath>((res, rej) => {
            write.on('finish', () => {
                res(new UniversalPath(temp))
            })

            write.on('error', rej)
            read.on('error', rej)
            read.pipe(write)
        })
    }

    async getStoreFileAsStream(args: { storePath: string }): Promise<ReadableStream> {
        const sftp = await this.getSFTP()
        return sftp.createReadStream(this.storePath(args.storePath))
    }

    async putLocalFile(args: { localPath: string; storePath: string; mimeType?: string; tags?: string[]; tag?: string }): Promise<void> {
        const read = fs.createReadStream(args.localPath)
        const write = await this.putStoreFileAsStream({storePath: args.storePath})

        // write the metadata first
        const sftp = await this.getSFTP()
        await sftp.writeFile(this.metadataPath(args.storePath), JSON.stringify({
            mimeType: args.mimeType,
            tags: this._normalizeTags(args.tag, args.tags)
        }))

        // pipe the local file to the store
        await new Promise<void>((res, rej) => {
            write.on('finish', () => res())
            write.on('error', rej)
            read.on('error', rej)
            read.pipe(write)
        })
    }

    async putStoreFileAsStream(args: { storePath: string }): Promise<NodeJS.WritableStream> {
        const sftp = await this.getSFTP()
        return sftp.createWriteStream(this.storePath(args.storePath))
    }

    async mkdir(args: { storePath: string }): Promise<void> {
        const sftp = await this.getSFTP()
        await new Promise<void>((res, rej) => {
            sftp.mkdir(this.storePath(args.storePath), err => {
                if ( err ) rej(err)
                else res()
            })
        })
    }

    async remove(args: { storePath: string; recursive?: boolean }): Promise<void> {
        const sftp = await this.getSFTP()

        await new Promise<void>((res, rej) => {
            sftp.unlink(this.storePath(args.storePath), err => {
                if ( err ) return rej(err)
                else {
                    sftp.unlink(this.metadataPath(args.storePath), err2 => {
                        if ( err2 ) rej(err2)
                        else res()
                    })
                }
            })
        })
    }

    async stat(args: { storePath: string }): Promise<Stat> {
        const sftp = await this.getSFTP()

        try {
            const stat = await new Promise<any>((res, rej) => {
                sftp.stat(this.storePath(args.storePath), (err, stat) => {
                    if ( err ) return rej(err)
                    res(stat)
                })
            })

            const jsonStream = sftp.createReadStream(this.metadataPath(args.storePath))
            const json = await this.streamToString(jsonStream)
            const meta = JSON.parse(json)

            return {
                path: new UniversalPath(args.storePath, this),
                exists: true,
                sizeInBytes: stat.size,
                mimeType: meta.mimeType,
                tags: meta.tags,
                accessed: stat.atime,
                modified: stat.mtime,
                created: stat.ctime,
            }
        } catch (e) {
            return {
                path: new UniversalPath(args.storePath, this),
                exists: false,
                sizeInBytes: 0,
                tags: []
            }
        }
    }

    async touch(args: { storePath: string }): Promise<void> {
        const sftp = await this.getSFTP()

        return new Promise<void>((res, rej) => {
            const storePath = this.storePath(args.storePath)
            const time = new Date()
            sftp.utimes(storePath, time, time, err => {
                if ( err ) {
                    sftp.open(storePath, 'w', (err2, fd) => {
                        if ( err2 ) return rej(err2)
                        sftp.close(fd, err3 => {
                            if ( err3 ) return rej(err3)
                            res()
                        })
                    })
                } else {
                    res()
                }
            })
        })
    }

    async getMetadata(storePath: string): Promise<FileMetadata> {
        try {
            const sftp = await this.getSFTP()
            return new Promise((res, rej) => {
                sftp.readFile(this.metadataPath(storePath), (err, buffer) => {
                    if ( err ) rej(err)
                    res(JSON.parse(buffer.toString('utf-8')))
                })
            })
        } catch (e) {
            return {
                tags: []
            }
        }
    }

    async setMetadata(storePath: string, meta: FileMetadata): Promise<void> {
        const sftp = await this.getSFTP()
        const metaPath = this.metadataPath(storePath)
        await new Promise<void>((res, rej) => {
            sftp.writeFile(metaPath, JSON.stringify(meta), err => {
                if ( err ) rej(err)
                else res()
            })
        })
    }

    async close(): Promise<void> {
        await this._ssh?.end()
    }

    /**
     * Using the provided `hostConfig`, create and cache the SSH connection to the host.
     * If a connection already exists, re-use it.
     */
    async getSSH(): Promise<ssh2.Client> {
        if ( this._ssh ) return this._ssh

        return new Promise((res, rej) => {
            const client = new ssh2.Client()

            client.on('ready', () => {
                this._ssh = client
                res(client)
            }).connect(this.baseConfig.ssh)

            client.on('error', rej)
        })
    }

    /**
     * Using `getSSH()`, create a new SFTP helper based on that connection.
     */
    async getSFTP(): Promise<ssh2.SFTPWrapper> {
        const ssh = await this.getSSH()

        return new Promise((res, rej) => {
            ssh.sftp((err, sftp) => {
                if ( err ) rej(err)
                else res(sftp)
            })
        })
    }

    /**
     * Resolve the given store path to an absolute path on the remote filesystem.
     * @param storePath
     * @protected
     */
    protected storePath(storePath: string): string {
        return path.resolve(this.baseConfig.baseDir, 'data', storePath)
    }

    /**
     * Resolve the given store path to an absolute path of a metadata file on the remote filesystem.
     * @param storePath
     * @protected
     */
    protected metadataPath(storePath: string): string {
        return path.resolve(this.baseConfig.baseDir, 'meta', storePath + '.json')
    }

    /**
     * Given a readable stream, cast it to a string.
     * @param stream
     * @protected
     */
    protected streamToString(stream: NodeJS.ReadableStream): Promise<string> {
        const chunks: Buffer[] = [];
        return new Promise((resolve, reject) => {
            stream.on('data', (chunk) => chunks.push(Buffer.from(chunk)))
            stream.on('error', (err) => reject(err))
            stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')))
        })
    }
}