// Names and small validators shared by the generators. Pure; no I/O.

/** A usage error: shown to the user as-is, exit code 1, no stack. */
export class UsageError extends Error {}

/** `Hide Trends!` -> `hide-trends` (ASCII letters and digits, dashes between). */
export function slugify(value, max = 64) {
  return String(value)
    .normalize('NFKD')
    .replace(/\p{M}/gu, '')
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, '-')
    .replace(/^-+|-+$/g, '')
    .slice(0, max)
    .replace(/-+$/, '');
}

/** `hide trends 2` -> `HideTrends2`; always a valid JS/Rust type identifier. */
export function pascalCase(value) {
  const words = String(value).normalize('NFKD').replace(/\p{M}/gu, '').replace(/[^A-Za-z0-9]+/g, ' ').trim().split(/\s+/).filter(Boolean);
  const name = words.map(word => word[0].toUpperCase() + word.slice(1)).join('');
  return /^[A-Za-z]/.test(name) ? name : `Plugin${name}`;
}

/** `wayBetter for Kick` -> `wayBetterForKick` (camelCase, for `data-*` keys). */
export function camelCase(value) {
  const name = pascalCase(value);
  return name[0].toLowerCase() + name.slice(1);
}

/**
 * A value for a `@name` / `@description` / ... plugin header line, or a theme string. The plugin
 * store reads each header line up to its end, drops control characters and keeps 300 characters
 * (waybetter-host `plugins::parse_meta`), so values are one line and cannot end the comment.
 */
export function headerValue(label, value, { max = 300, required = false } = {}) {
  const text = String(value ?? '').trim();
  if (required && !text) throw new UsageError(`${label} is required.`);
  if (/[\u0000-\u001f\u007f]/.test(text)) throw new UsageError(`${label} must be one line of text.`);
  if (text.includes('*/')) throw new UsageError(`${label} cannot contain "*/".`);
  if (text.length > max) throw new UsageError(`${label} is longer than ${max} characters.`);
  return text;
}

/** Semver-ish plugin version (`1.0.0`, `0.3.1-beta.2`). */
export function versionValue(value) {
  const text = String(value ?? '1.0.0').trim() || '1.0.0';
  if (!/^\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?$/.test(text)) throw new UsageError(`Version "${text}" is not like 1.0.0.`);
  return text;
}

export const HEX = /^#[0-9a-fA-F]{6}$/;

/** `#abc` / `abc123` / `#ABC123` -> `#aabbcc` style lowercase six-digit hex. */
export function hexValue(label, value) {
  let text = String(value ?? '').trim().toLowerCase();
  if (!text.startsWith('#')) text = `#${text}`;
  const short = /^#([0-9a-f])([0-9a-f])([0-9a-f])$/.exec(text);
  if (short) text = `#${short[1]}${short[1]}${short[2]}${short[2]}${short[3]}${short[3]}`;
  if (!HEX.test(text)) throw new UsageError(`${label} must be a hex color like #1d9bf0 (got "${value}").`);
  return text;
}

/** A JS/TS string literal. */
export const str = value => JSON.stringify(String(value));

/** A Rust string literal (JSON escapes are valid Rust escapes for the characters we allow). */
export function rustStr(value) {
  return JSON.stringify(String(value)).replace(/\\u([0-9a-fA-F]{4})/g, (_, hex) => `\\u{${hex}}`);
}

/** Joins lines with `\n` and ends the file with one newline. */
export const lines = (...parts) => `${parts.flat().join('\n').replace(/\n+$/, '')}\n`;