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

import Ajv2020 from "ajv/dist/2020.js";
import standaloneCode from "ajv/dist/standalone/index.js";

const packageRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..");
const schemaDirectory = resolve(packageRoot, "protocol/schemas");
const outputPath = resolve(packageRoot, "src/protocol/generated/schema-bundle.ts");
const validatorsOutputPath = resolve(
  packageRoot,
  "src/protocol/generated/standalone-validators.ts",
);
const schemaNames = [
  "identity",
  "capabilities",
  "capabilities-v2",
  "command",
  "command-v2",
  "provider-descriptor",
  "provider-event",
  "workspace-diff",
  "workspace-file-reference",
  "semantic-tool",
  "usage",
  "stop-reason",
  "terminal",
  "question-set",
  "question-response",
  "question-adapter-fixture",
  "request",
  "result",
  "event",
  "event-v2",
  "session-goal",
  "fixture",
];

const schemas = await Promise.all(
  schemaNames.map(async (name) => ({
    name,
    value: JSON.parse(await readFile(resolve(schemaDirectory, `${name}.schema.json`), "utf8")),
  })),
);

const identifier = (name) => name.replace(/-([a-z])/g, (_match, letter) => letter.toUpperCase());
const declarations = schemas
  .map(({ name, value }) => `export const ${identifier(name)}Schema = ${JSON.stringify(value, null, 2)} as const;`)
  .join("\n\n");
const bundle = schemaNames.map((name) => `  ${JSON.stringify(name)}: ${identifier(name)}Schema,`).join("\n");
const generated = `// Generated by scripts/generate-protocol-schema-module.mjs. Do not edit.\n\n${declarations}\n\nexport const prpSchemaBundle = {\n${bundle}\n} as const;\n`;

const schemaByName = Object.fromEntries(schemas.map(({ name, value }) => [name, value]));
const ajv = new Ajv2020({
  allErrors: true,
  strict: true,
  strictRequired: false,
  code: { esm: true, source: true },
  formats: {
    "date-time": /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d{3})?Z$/,
  },
});
for (const { value } of schemas) ajv.addSchema(value);
const standaloneValidators = standaloneCode(ajv, {
  fixtureValidator: schemaByName.fixture.$id,
  eventValidator: schemaByName.event.$id,
  eventV2Validator: schemaByName["event-v2"].$id,
  resultValidator: schemaByName.result.$id,
});
const ucs2RuntimePattern = /const (func\d+) = require\("ajv\/dist\/runtime\/ucs2length"\)\.default;/;
if (!ucs2RuntimePattern.test(standaloneValidators)) {
  throw new Error("Ajv standalone output no longer has the expected ucs2length runtime binding");
}
const equalRuntimePattern = /const (func\d+) = require\("ajv\/dist\/runtime\/equal"\)\.default;/;
if (!equalRuntimePattern.test(standaloneValidators)) {
  throw new Error("Ajv standalone output no longer has the expected equal runtime binding");
}
const validatorsWithRuntimeImports = standaloneValidators.replace(
  ucs2RuntimePattern,
  "const $1 = typeof ucs2LengthModule === \"function\" ? ucs2LengthModule : ucs2LengthModule.default;",
).replace(
  equalRuntimePattern,
  "const $1 = typeof equalModule === \"function\" ? equalModule : equalModule.default;",
);
const validatorExportPattern = /export const (fixtureValidator|eventValidator|resultValidator) =/g;
const validatorExports = [...validatorsWithRuntimeImports.matchAll(validatorExportPattern)];
if (validatorExports.length !== 3) {
  throw new Error("Ajv standalone output no longer has the expected validator exports");
}
// Ajv's generated functions are intentionally unchecked runtime JavaScript.
// Bound their exported types so TypeScript does not infer the full generated
// implementation graph. replay-contract.ts applies the checked public types.
const validators = validatorsWithRuntimeImports.replace(
  validatorExportPattern,
  "export const $1: unknown =",
);
const generatedValidators = `// Generated by scripts/generate-protocol-schema-module.mjs. Do not edit.\n// @ts-nocheck -- Ajv standalone output is JavaScript compiled from the checked-in schemas.\n\nimport equalModule from "ajv/dist/runtime/equal.js";\nimport ucs2LengthModule from "ajv/dist/runtime/ucs2length.js";\n\n${validators}\n`;

if (process.argv.includes("--check")) {
  const current = await readFile(outputPath, "utf8").catch(() => "");
  const currentValidators = await readFile(validatorsOutputPath, "utf8").catch(() => "");
  if (current !== generated || currentValidators !== generatedValidators) {
    process.stderr.write("Generated PRP schema modules are stale. Run pnpm generate:protocol-types.\n");
    process.exitCode = 1;
  } else {
    process.stdout.write("Generated PRP schema modules match the JSON Schema sources.\n");
  }
} else {
  await Promise.all([
    writeFile(outputPath, generated),
    writeFile(validatorsOutputPath, generatedValidators),
  ]);
  process.stdout.write("Generated PRP schema and standalone validator modules.\n");
}