import type { DriveStorage } from "@suaveplan/drive";
import type { ChunkLayout } from "../types/chunks.types.js";

export function createChunkKeysLayout(storage: DriveStorage): ChunkLayout {
    return {
        name: "chunk-keys",
        async putChunk(fileId, chunkId, rawBytes) {
            const key = chunkKey(fileId, chunkId);
            await storage.set(key, rawBytes);
        },
        async getChunk(fileId, chunkId) {
            const key = chunkKey(fileId, chunkId);
            return storage.get(key);
        },
        async hasChunks(fileId) {
            const prefix = `chunks/${hex(fileId)}/`;
            const result = await storage.list({ prefix });
            const maxChunkId = result.keys.reduce(
                (max: number, key: string) => {
                    const id = Number.parseInt(key.slice(prefix.length), 10);
                    return Math.max(max, id);
                },
                -1
            );
            const bits = new Array(maxChunkId + 1).fill(false);
            for (const key of result.keys) {
                const id = Number.parseInt(key.slice(prefix.length), 10);
                bits[id] = true;
            }
            return bits;
        },
        async availableChunks(fileId) {
            const bits = await this.hasChunks(fileId);
            const ids: number[] = [];
            for (let i = 0; i < bits.length; i++) {
                if (bits[i]) ids.push(i);
            }
            return ids;
        },
    };
}

function chunkKey(fileId: Uint8Array, chunkId: number): string {
    return `chunks/${hex(fileId)}/${chunkId}`;
}

function hex(bytes: Uint8Array): string {
    return Array.from(bytes, (b) => b.toString(16).padStart(2, "0")).join("");
}