import { Readable } from 'node:stream';
import { createInterface } from 'node:readline';
import XXH from 'xxhashjs';
import { log } from './logger.js';
import { DataIngressPisData } from '@owlboard/backend-data-contracts';
import type { GeneralConfig } from './config.js';

const BASE_URL = process.env.BASEURL || 'https://owlboard.info'

// Local cache crs, tiploc mappings to reduce API hits to once per CRS
const tiplocCache = new Map<string, string>();

// To align with generating the hash in Go if needed for lookups
const SEED = 0;

// Type for the data input
interface InputRecord {
    code: string;
    stops: string[];
}

export async function* processPisStream(cfg: GeneralConfig, inputStream: Readable) {
    const TOC = cfg.TOC;
    if (!TOC) {
        log('ERROR', "TOC not set: Exit code 19");
        process.exit(19);
    }
    log('DEBUG', `TOC set to: ${TOC}`)

    const rl = createInterface({
        input: inputStream,
        terminal: false,
    });

    for await (const line of rl) {
        if (!line.trim()) continue;

        const record = JSON.parse(line) as InputRecord;
        log('DEBUG', `JSON Line Parsed: ${JSON.stringify(record)}`)

        const crsHash = XXH.h64(record.stops.join('|'), SEED);
        const tiplocStops = await mapStopsToTiploc(record.stops);
        const tiplocHash = XXH.h64(tiplocStops.join('|'), SEED);

        const data: DataIngressPisData.PisObjects = {
            code: record.code,
            toc: TOC.toLowerCase(),
            crsStops: record.stops,
            crsHash: crsHash.toString(),
            tiplocStops: tiplocStops,
            tiplocHash: tiplocHash.toString(),
        }
        yield data;
    
    }
}

async function mapStopsToTiploc(crsStops: string[]): Promise<string[]> {
    return Promise.all(crsStops.map(async (crs) => {
        if (tiplocCache.has(crs)) {
            return tiplocCache.get(crs)!;
        }

        // Cache Miss
        try {
            const tiploc = await fetchTiplocFromApi(crs);
            tiplocCache.set(crs, tiploc);
            return tiploc;
        } catch (err) {
            log('ERROR', `Failed lookup for: ${crs}`, err);
            process.exit(99);
        }
    }))
}

async function fetchTiplocFromApi(crs: string): Promise<string> {
    const apiUrl = `${BASE_URL}/api/v2/ref/locationCode/crs/${crs}`;
    const response = await fetch(apiUrl, {
        headers: { 'Accept': 'application/json' },
    });

    if (!response.ok) {
        throw new Error(`API Error: ${response.status}`);
    }

    const data = await response.json();
    return data[0].TIPLOC;
}