export async function openInputStream(path, init = {}) {
    const mergedInit = {
        ...readableStreamInit,
        ...init
    }

    return new Promise((resolve, reject) => {
        const chunks = []
        let aborted = false

        const onAbort = () => {
            aborted = true
            cleanup()
            reject(new DOMException("The operation was aborted.", "AbortError"))
        }

        if (mergedInit.signal) {
            if (mergedInit.signal.aborted) {
                onAbort()
                return
            }
            mergedInit.signal.addEventListener("abort", onAbort)
        }

        function cleanup() {
            if (mergedInit.signal) {
                mergedInit.signal.removeEventListener("abort", onAbort)
            }
            window.FsInputStream.onmessage = null
        }

        window.FsInputStream.addEventListener("message", (event) => {
            if (aborted) return

            const msg = event.data

            if (msg instanceof ArrayBuffer) {
                chunks.push(new Uint8Array(msg))
            } else if (typeof msg === "string") {
                cleanup()
                reject(new Error(msg))
                return
            }

            // Once we have the full file (or a single chunk for now), create a stream
            const stream = new ReadableStream({
                start(controller) {
                    try {
                        for (const chunk of chunks) {
                            controller.enqueue(chunk)
                        }
                        controller.close()
                        cleanup()
                    } catch (e) {
                        cleanup()
                        controller.error(e)
                    }
                },
                cancel(reason) {
                    console.warn("Stream canceled:", reason)
                    cleanup()
                }
            })

            resolve(new Response(stream, mergedInit))
        })

        // Send the request to Android
        window.FsInputStream.postMessage(path)
    })
}

export const readableStreamInit = {
    headers: {
        "Content-Type": "application/octet-stream"
    }
}