import { Asset } from "expo-asset";

export type RealWeatherFrame = Readonly<{
  label: "T0" | "T1" | "T2" | "T3";
  cycle: "2026080700" | "2026080706" | "2026080712" | "2026080718";
  metadataJson: string;
  validTime: number;
  generation: number;
  payloadModule: number;
}>;

type CanonicalMetadata = Readonly<{ validTime: number; generation: number }>;

// Static requires register all four raw .f32 assets with Metro/Expo; payload bytes never enter JS memory.
const metadataT0 = require("../assets/weather/ecmwf-hres-wind-20260807/2026080700/metadata.json") as CanonicalMetadata;
const metadataT1 = require("../assets/weather/ecmwf-hres-wind-20260807/2026080706/metadata.json") as CanonicalMetadata;
const metadataT2 = require("../assets/weather/ecmwf-hres-wind-20260807/2026080712/metadata.json") as CanonicalMetadata;
const metadataT3 = require("../assets/weather/ecmwf-hres-wind-20260807/2026080718/metadata.json") as CanonicalMetadata;

function frame(label: RealWeatherFrame["label"], cycle: RealWeatherFrame["cycle"], metadata: CanonicalMetadata, payloadModule: number): RealWeatherFrame {
  return { label, cycle, metadataJson: JSON.stringify(metadata), validTime: metadata.validTime, generation: metadata.generation, payloadModule };
}

export const realWeatherFrames = [
  frame("T0", "2026080700", metadataT0, require("../assets/weather/ecmwf-hres-wind-20260807/2026080700/field.f32")),
  frame("T1", "2026080706", metadataT1, require("../assets/weather/ecmwf-hres-wind-20260807/2026080706/field.f32")),
  frame("T2", "2026080712", metadataT2, require("../assets/weather/ecmwf-hres-wind-20260807/2026080712/field.f32")),
  frame("T3", "2026080718", metadataT3, require("../assets/weather/ecmwf-hres-wind-20260807/2026080718/field.f32")),
] as const;

export async function materializeRealWeatherFrames(): Promise<ReadonlyArray<RealWeatherFrame & { payloadFileUri: string }>> {
  return Promise.all(realWeatherFrames.map(async (weatherFrame) => {
    const asset = Asset.fromModule(weatherFrame.payloadModule);
    await asset.downloadAsync();
    if (asset.localUri == null || !asset.localUri.startsWith("file://")) {
      throw new Error(`${weatherFrame.label} Asset.downloadAsync did not provide a local file:// URI`);
    }
    return { ...weatherFrame, payloadFileUri: asset.localUri };
  }));
}