import { createToolcraftModuleDefinition } from "../../contract/module-definition";
import type { ToolcraftModuleRecord } from "../../contract/module-protocol";
import { snapshotToolcraftModuleData } from "../../contract/module-data";
import { toolcraftFileSourceAssetHandler } from "../../../source-assets/file-source-asset-handler";
import { readToolcraftFileBytes } from "../../../source-assets/media-file";
import { createToolcraftMediaResourceRef } from "../../../source-assets/media-resource-ref";
import type { ToolcraftSourceAssetHandler, ToolcraftPreparedSourceAssetRecord } from "../../../source-assets/source-asset-types";

type Palette = Readonly<{ version: 1; colors: readonly string[]; }>;
export function decodePalette(bytes: Uint8Array): Palette {
  const value: unknown = JSON.parse(new TextDecoder().decode(bytes));
  if (!value || typeof value !== "object" || !("version" in value) || value.version !== 1 ||
    !("colors" in value) || !Array.isArray(value.colors) || !value.colors.every(color => typeof color === "string" && /^#[0-9a-f]{6}$/i.test(color))) {
    throw new Error("Invalid palette payload");
  }
  return Object.freeze({ version: 1, colors: Object.freeze([...value.colors]) });
}

export const paletteModule = () => createToolcraftModuleDefinition<ToolcraftModuleRecord>({
  id: "palette-source", provides: ["palette.source"], requires: [], defaultProviders: [], portRequirements: [],
  contributions: [{ id: "palette-source.policy", moduleId: "palette-source", kind: "source-workflow" }],
}, snapshotToolcraftModuleData);

export function createPaletteHandler(afterStage: () => Promise<void> = async () => { }): ToolcraftSourceAssetHandler<"file", ToolcraftPreparedSourceAssetRecord<"file">> {
  return {
    ...toolcraftFileSourceAssetHandler,
    prepare: async context => {
      const file = context.batch.files[0]!;
      const bytes = await readToolcraftFileBytes(file, context.signal);
      decodePalette(bytes);
      const resourceRef = createToolcraftMediaResourceRef("file", bytes);
      await context.stageResource(resourceRef, bytes, { contentType: "application/x-palette", durable: true });
      await afterStage();
      return {
        assets: [{ assetKind: "file", fileName: file.name, lifecycle: "ready", mimeType: "application/x-palette", position: { x: 0, y: 0 }, resourceRef }],
        stagedResourceRefs: [resourceRef],
      };
    },
  };
}