import { Database } from "jsr:@db/sqlite";
import {join} from "jsr:@std/path";
let db = new Database("./db.sqlite3")
const stmt = db.prepare("SELECT id, basepath, filename from document");
let ds = [...stmt.all()];

async function oshash(
    path: string
){
    const chunkSize = 4096;
    const minFileSize = chunkSize * 2;

    const fd = await Deno.open(path);
    const st = await fd.stat();
    let hash = BigInt(st.size);

    if (st.size < minFileSize){
        throw new Error("File is too small to hash");
    }

    // read first and last chunk
    const firstChunk = new Uint8Array(chunkSize);
    await fd.read(firstChunk, 0, chunkSize, 0);
    const lastChunk = new Uint8Array(chunkSize);
    await fd.read(lastChunk, 0, chunkSize, st.size - chunkSize);
    // iterate over first and last chunk.
    // for each uint64_t, add it to the hash.
    const firstChunkView = new DataView(firstChunk.buffer);
    for (let i = 0; i < chunkSize; i += 8){
        hash += firstChunkView.getBigUint64(i, true);
        // prevent overflow
        hash = (hash & 0xFFFFFFFFFFFFFFFFn);
    }
    const lastChunkView = new DataView(lastChunk.buffer);
    for (let i = 0; i < chunkSize; i += 8){
        hash += lastChunkView.getBigUint64(i, true);
        // prevent overflow
        hash = (hash & 0xFFFFFFFFFFFFFFFFn);
    }
    return hash;
}

async function updateHash(ds: {id: number, basepath: string, filename: string}[]) {
    const content_hashs = await Promise.all(ds.map(async (d) => {
        const p = join(d.basepath, d.filename);
        return await oshash(p);
    }));
    db.transaction(() => {
        for (let i = 0; i < ds.length; i++) {
            db.run(`UPDATE document SET content_hash = ? where id = ?`, content_hashs[i].toString(), ds[i].id)
        }
    })();
}

for (let i = 0; i < ds.length; i += 32) {
    const d = ds.slice(i, i + 32);
    console.log(d.map(x => x.id));
    await updateHash(d);
}
db.close();