import { format, addHours } from "date-fns";
import { TZDate } from "@date-fns/tz";
import { UTCDate, utc } from "@date-fns/utc";
import spacetime from "spacetime";

export function dateFromInput(input: { dateQuery: string, timezone: string }) {
    let t: string;
    try {
        t = format(new UTCDate(input.dateQuery), "yyyy-MM-dd", { in: utc });
    }
    catch (e) {
        const now_here = spacetime.now(input.timezone);
        switch (input.dateQuery) {
            case "today":
                t = now_here.format("yyyy-MM-dd");
                break;
            case "yesterday":
                t = now_here.subtract(1, "day").format("yyyy-MM-dd");
                break;
            case "tomorrow":
                t = now_here.add(1, "day").format("yyyy-MM-dd");
                break;
            default:
                throw new Error("Invalid dateQuery");
        }
    }
    // console.log(`dateFromInput(${input.dateQuery}, ${input.timezone}) = ${t}`);
    return t;
}

function generateHour(d, t) {
    const dt: TZDate = addHours(d, t);
    console.log(dt);
    return {
        date: format(dt, 'yyyy-MM-dd'),
        time: parseInt(format(dt, 'H')),
    };
}

export function hoursListInUTC(input: { dateQuery: string, timezone: string }) {
    const localMidnight = spacetime(input.dateQuery, input.timezone).startOf("day");
    return Array.from({ length: 24 }).map((_, i) => {
        const utcTime = localMidnight.goto("UTC").add(i, "hours");
        return {
            time: utcTime.hour(),
            date: utcTime.format("iso-short"),
        };
    });
}