import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
import { join, resolve } from "node:path";
import { type IronRainConfig, parseConfig } from "./schema.js";

const CONFIG_FILENAMES = [
  ".iron-rain/config.json",
  ".iron-rain/config.jsonc",
  "iron-rain.json",
  "iron-rain.jsonc",
  ".iron-rainrc.json",
];

function stripJsoncComments(text: string): string {
  let result = "";
  let inString = false;
  let escaped = false;

  for (let i = 0; i < text.length; i++) {
    const ch = text[i];

    if (escaped) {
      result += ch;
      escaped = false;
      continue;
    }

    if (inString) {
      if (ch === "\\") escaped = true;
      else if (ch === '"') inString = false;
      result += ch;
      continue;
    }

    if (ch === '"') {
      inString = true;
      result += ch;
      continue;
    }

    if (ch === "/" && text[i + 1] === "/") {
      // Skip to end of line
      while (i < text.length && text[i] !== "\n") i++;
      result += "\n";
      continue;
    }

    if (ch === "/" && text[i + 1] === "*") {
      i += 2;
      while (i < text.length && !(text[i] === "*" && text[i + 1] === "/")) i++;
      i++; // skip closing /
      continue;
    }

    result += ch;
  }

  return result;
}

export function findConfigFile(cwd?: string): string | null {
  const dir = cwd ?? process.cwd();

  for (const name of CONFIG_FILENAMES) {
    const path = resolve(dir, name);
    if (existsSync(path)) return path;
  }

  // Walk up to find project-level config
  const home = process.env.HOME ?? process.env.USERPROFILE ?? "";
  let current = dir;
  while (current !== home && current !== "/") {
    for (const name of CONFIG_FILENAMES) {
      const path = join(current, name);
      if (existsSync(path)) return path;
    }
    current = resolve(current, "..");
  }

  return null;
}

export function writeConfig(
  config: Partial<IronRainConfig>,
  cwd?: string,
): string {
  const dir = cwd ?? process.cwd();
  const configPath =
    findConfigFile(dir) ?? resolve(dir, ".iron-rain/config.json");

  // Ensure .iron-rain/ directory exists when writing to new canonical path
  const configDir = resolve(configPath, "..");
  mkdirSync(configDir, { recursive: true });

  const output: Record<string, unknown> = {};
  if (config.slots) output.slots = config.slots;
  if (config.providers) output.providers = config.providers;
  if (config.permission) output.permission = config.permission;
  if (config.cliPermissions) output.cliPermissions = config.cliPermissions;
  if (config.agent && config.agent !== "build") output.agent = config.agent;
  if (config.lcm) output.lcm = config.lcm;
  if (config.theme && config.theme !== "default") output.theme = config.theme;

  writeFileSync(configPath, `${JSON.stringify(output, null, 2)}\n`, "utf-8");
  return configPath;
}

export function loadConfig(cwd?: string): IronRainConfig {
  const configPath = findConfigFile(cwd);

  if (!configPath) {
    return parseConfig({});
  }

  try {
    const raw = readFileSync(configPath, "utf-8");
    // Always strip JSONC comments — users may add comments to any config file
    return parseConfig(JSON.parse(stripJsoncComments(raw)));
  } catch (err) {
    throw new Error(
      `Failed to parse config at ${configPath}: ${err instanceof Error ? err.message : String(err)}`,
    );
  }
}