import type {
    BitPackerSchema,
    PackingContext,
    PackingStrategy,
} from "@suaveplan/bitpacker";
import { BITPACKER_CODES, BitpackerError } from "@suaveplan/bitpacker";

const DATETIME_TOKENS: readonly string[] = [
    "timestamp",
    "timestamp-ms",
    "timestamp-s",
    "timespan",
    "timespan-ms",
    "date-only",
];

export class DateTimePackingStrategy implements PackingStrategy {
    canHandle(schema: BitPackerSchema): boolean {
        return typeof schema === "string" && DATETIME_TOKENS.includes(schema);
    }

    pack(
        data: unknown,
        schema: BitPackerSchema,
        context: PackingContext
    ): void {
        const token = schema as string;
        let ms: number;

        if (data instanceof Date) {
            ms = data.getTime();
        } else if (typeof data === "number") {
            ms = data;
        } else {
            throw new BitpackerError(
                BITPACKER_CODES.INVALID_SCHEMA,
                `Expected Date or number for datetime schema "${token}", got ${typeof data}`,
                { context: { token, data } }
            );
        }

        switch (token) {
            case "timestamp":
            case "timestamp-ms":
            case "date-only":
                context.writer.writeInt(ms, 53);
                break;
            case "timestamp-s":
                context.writer.writeInt(Math.floor(ms / 1000), 32);
                break;
            case "timespan":
                context.writer.writeInt(ms, 53);
                break;
            case "timespan-ms":
                context.writer.writeInt(ms, 53);
                break;
        }
    }

    unpack(schema: BitPackerSchema, context: PackingContext): unknown {
        const token = schema as string;

        switch (token) {
            case "timestamp":
            case "timestamp-ms":
            case "date-only":
                return context.reader.readInt(53);
            case "timestamp-s":
                return context.reader.readInt(32) * 1000;
            case "timespan":
            case "timespan-ms":
                return context.reader.readInt(53);
            default:
                return 0;
        }
    }
}