import { BufferWriter } from "@node-lightning/bufio";
import { sha256 } from "@node-lightning/crypto";

const OP_0 = 0;
const OP_CHECKMULTISIG = 174;

export function fundingScript(pubkeys: Buffer[]) {
    const lower = lesser(pubkeys[0], pubkeys[1]);
    let node1: Buffer;
    let node2: Buffer;
    if (lower === -1) {
        node1 = pubkeys[0];
        node2 = pubkeys[1];
    } else {
        node1 = pubkeys[1];
        node2 = pubkeys[0];
    }

    const script = p2msScript(2, 2, [node1, node2]);
    const hash = sha256(script);
    return p2wshScript(hash);
}

function lesser(a: Buffer, b: Buffer) {
    for (let i = 0; i < a.length; i++) {
        if (a[i] < b[i]) return -1;
        if (a[i] > b[i]) return 1;
    }
    return 0;
}

function compileScript(chunks: Array<Buffer | number>): Buffer {
    let bufferSize = 0;
    for (const chunk of chunks) {
        if (Buffer.isBuffer(chunk)) {
            bufferSize += 1; // length
            bufferSize += chunk.length; // chunk length < 76 bytes
        } else {
            bufferSize += 1; // opcode
        }
    }

    const buffer = Buffer.alloc(bufferSize);
    const writer = new BufferWriter(buffer);

    for (const chunk of chunks) {
        if (Buffer.isBuffer(chunk)) {
            writer.writeUInt8(chunk.length); // chunk length < 76 bytes
            writer.writeBytes(chunk);
        } else {
            writer.writeUInt8(chunk);
        }
    }
    return buffer;
}

function p2msScript(m: number, n: number, pubkeys: Buffer[]): Buffer {
    return compileScript([
    80 + m,
    ...pubkeys,
    80 + n,
    OP_CHECKMULTISIG,
  ]); // prettier-ignore
}

function p2wshScript(hash160Script: Buffer): Buffer {
    return compileScript([
    OP_0,
    hash160Script,
  ]); // prettier-ignore
}