import { readFileSync } from 'node:fs';
import { homedir } from 'node:os';
import { join } from 'node:path';
import { parse as parseToml } from 'smol-toml';
import type { RepoRef } from './reader.ts';

export interface BoardConfig {
  baseUrl: string;
  token: string;
  repos: RepoRef[];
}

export function defaultConfigPath(): string {
  return join(homedir(), '.config', 'projects-mcp', 'auth.toml');
}

export function loadConfig(path: string = defaultConfigPath()): BoardConfig {
  const raw = readFileSync(path, 'utf8');
  const data = parseToml(raw) as Record<string, unknown>;

  const baseUrl = stringField(data, 'gitea_url');
  const token = stringField(data, 'gitea_token');
  const repos = parseRepos(data['board_viewer_repos']);

  return { baseUrl, token, repos };
}

function stringField(data: Record<string, unknown>, key: string): string {
  const value = data[key];
  if (typeof value !== 'string' || value.length === 0) {
    throw new Error(`config: missing or empty string field "${key}"`);
  }
  return value;
}

function parseRepos(value: unknown): RepoRef[] {
  if (!Array.isArray(value)) {
    throw new Error('config: missing or invalid "board_viewer_repos" (expected array of "owner/repo")');
  }
  return value.map((entry) => {
    if (typeof entry !== 'string') {
      throw new Error(`config: board_viewer_repos entry must be string, got ${typeof entry}`);
    }
    const parts = entry.split('/');
    if (parts.length !== 2 || parts[0] === '' || parts[1] === '') {
      throw new Error(`config: board_viewer_repos entry "${entry}" is not "owner/repo"`);
    }
    return { owner: parts[0]!, repo: parts[1]! };
  });
}