import type { ComputeAppConfig, ComputeConfig } from "./types.ts";

/**
 * Renders a `prisma.compute.ts` source file for a config — the scaffolding
 * counterpart of `loadComputeConfig`. Output round-trips through
 * `normalizeComputeConfig` and is stable for committing to a repository.
 */
export function serializeComputeConfig(
  config: ComputeConfig,
  options?: {
    /** Import specifier for the typed helper. Defaults to this SDK. */
    importFrom?: string;
  },
): string {
  const importFrom = options?.importFrom ?? "@prisma/compute-sdk/config";
  const body =
    "app" in config && config.app !== undefined
      ? `{\n  app: ${renderValue(config.app, 1)},\n}`
      : `{\n  apps: ${renderValue((config as { apps: Record<string, ComputeAppConfig> }).apps, 1)},\n}`;

  return [
    `import { defineComputeConfig } from ${JSON.stringify(importFrom)};`,
    "",
    `export default defineComputeConfig(${body});`,
    "",
  ].join("\n");
}

const IDENTIFIER_KEY = /^[A-Za-z_$][A-Za-z0-9_$]*$/;

function renderValue(value: unknown, depth: number): string {
  if (value === null) {
    return "null";
  }

  switch (typeof value) {
    case "string":
      return JSON.stringify(value);
    case "number":
    case "boolean":
      return String(value);
    case "object":
      break;
    default:
      throw new Error(
        `Cannot serialize a ${typeof value} value in a compute config.`,
      );
  }

  if (Array.isArray(value)) {
    return `[${value.map((entry) => renderValue(entry, depth)).join(", ")}]`;
  }

  const entries = Object.entries(value as Record<string, unknown>).filter(
    ([, entry]) => entry !== undefined,
  );
  if (entries.length === 0) {
    return "{}";
  }

  const indent = "  ".repeat(depth + 1);
  const closingIndent = "  ".repeat(depth);
  const rendered = entries.map(([key, entry]) => {
    // "__proto__" needs a computed key: in an object literal both the bare
    // and the quoted form set the prototype instead of defining a property.
    const renderedKey =
      key === "__proto__"
        ? '["__proto__"]'
        : IDENTIFIER_KEY.test(key)
          ? key
          : JSON.stringify(key);
    return `${indent}${renderedKey}: ${renderValue(entry, depth + 1)},`;
  });

  return `{\n${rendered.join("\n")}\n${closingIndent}}`;
}