import type { ScenarioValue } from "./ast.ts";
export class CanonicalizeError extends Error {
  readonly code = "CANONICALIZE_UNSUPPORTED";
  constructor(
    message: string,
    readonly details?: unknown,
  ) {
    super(message);
    this.name = "CanonicalizeError";
  }
}
const encode = (value: unknown, path = "$", seen = new Set<unknown>()): string => {
  if (value === null || typeof value === "boolean" || typeof value === "string") return JSON.stringify(value);
  if (typeof value === "number") {
    if (!Number.isFinite(value)) throw new CanonicalizeError("Unsupported value at " + path);
    return JSON.stringify(value);
  }
  if (typeof value !== "object") throw new CanonicalizeError("Unsupported value at " + path);
  if (seen.has(value)) throw new CanonicalizeError("Circular value at " + path);
  seen.add(value);
  const result = Array.isArray(value)
    ? "[" + value.map((item, i) => encode(item, path + "[" + i + "]", seen)).join(",") + "]"
    : "{" +
      Object.keys(value as object)
        .sort()
        .map(
          (key) => JSON.stringify(key) + ":" + encode((value as Record<string, unknown>)[key], path + "." + key, seen),
        )
        .join(",") +
      "}";
  seen.delete(value);
  return result;
};
export const canonicalize = (value: ScenarioValue | object): string => encode(value);