import { Writable } from 'node:stream'
import type {
    FileSystemWritableFileStream,
    FileSystemWriteChunkType,
    WriteParams
} from '@sugoidogo/importable-types-web'
import type { FileHandle } from 'node:fs/promises'

function isWriteParams(data: FileSystemWriteChunkType): data is WriteParams {
    return ["write", "seek", "truncate"].includes((data as WriteParams).type)
}

export default class NodeFileSystemWritableFileStream extends WritableStream implements FileSystemWritableFileStream {
    #position = 0
    #fileHandle: FileHandle
    constructor(fileHandle: FileHandle) {
        const writeStream = fileHandle.createWriteStream({ "encoding": "binary" })
        const writeableStream = Writable.toWeb(writeStream)
        super(writeableStream)
        this.#fileHandle = fileHandle
    }
    async seek(position: number): Promise<void> {
        if (this.locked) throw new Error("stream is locked")
        this.#position = position
    }
    async truncate(size: number): Promise<void> {
        if (this.locked) throw new Error("stream is locked")
        return this.#fileHandle.truncate(size)
    }
    async write(data: FileSystemWriteChunkType): Promise<void> {
        if (this.locked) throw new Error("stream is locked")
        let offset: number, length: number, position=this.#position
        if (isWriteParams(data)) {
            if (data.type === "seek") return this.seek(data.position)
            if (data.type === "truncate") return this.truncate(data.size)
            if (typeof data.position === "number") position = data.position
            length = data.size
            data = data.data
        }
        if (typeof data === 'string') data = new TextEncoder().encode(data)
        const { bytesWritten } = await this.#fileHandle.write(data as any, offset, length, position)
        this.#position=position+bytesWritten
    }
}