import { readFile, writeFile } from "node:fs/promises";
import { dirname, resolve } from "node:path";
import { fileURLToPath } from "node:url";

// The runtime context parser rejects unknown fields. Its accepted field lists
// come from the schema so the pack contract digest, which fingerprints the
// schema, changes whenever the parser's contract does.
const root = resolve(dirname(fileURLToPath(import.meta.url)), "..");
const schema = JSON.parse(
  await readFile(resolve(root, "protocol/provider-schemas/runtime-context.schema.json"), "utf8"),
);
const objects = ["runtimeContext", "prompt", "instructions", "workingCopy", "skill", "mcp", "connectionInstructions", "asset"];
const fields = objects.map((name) => {
  const definition = schema.$defs?.[name];
  if (definition?.type !== "object" || definition.additionalProperties !== false || !definition.properties) {
    throw new Error(`runtime context ${name} must be a closed object schema`);
  }
  return [name, Object.keys(definition.properties)];
});

const typescript = `// Generated by scripts/generate-runtime-context-contract.mjs. Do not edit.

export const GENERATED_RUNTIME_CONTEXT_FIELDS = {
${fields.map(([name, keys]) => `  ${name}: [${keys.map((key) => JSON.stringify(key)).join(", ")}],`).join("\n")}
} as const;
`;

const output = resolve(root, "src/contracts/generated-runtime-context-contract.ts");
if (process.argv.includes("--check")) {
  if ((await readFile(output, "utf8").catch(() => "")) !== typescript) {
    process.stderr.write(`Generated runtime context contract is stale: ${output}\n`);
    process.exitCode = 1;
  } else process.stdout.write("Generated runtime context contract matches the schema.\n");
} else {
  await writeFile(output, typescript);
  process.stdout.write("Generated runtime context contract.\n");
}