/**
 * Token JS Compiler -- `TokenDef[]` to JavaScript const + `.d.ts` type declaration.
 *
 * Emits a fully typed `tokens` object grouped by category with const
 * assertion, plus a companion `.d.ts` declaration using `typeof`.
 *
 * @module
 */

import type { Token } from '@czap/core';
import { groupTokensByCategory } from './css-utils.js';

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

/**
 * Output of {@link TokenJSCompiler.compile}.
 *
 * Two parallel artifacts for the same token set: a runtime ES module and
 * a companion ambient declaration. The type declaration uses `typeof` so
 * values round-trip exactly through the compiler without hand-maintained
 * duplication.
 */
export interface TokenJSResult {
  /** Runtime `.ts` source declaring `export const tokens` with const assertion. */
  readonly code: string;
  /** Ambient `.d.ts` declaration exposing the same shape via `typeof`. */
  readonly typeDeclaration: string;
}

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

/**
 * Serialize a token value for JS/TS output.
 * Strings are JSON-quoted, numbers and booleans are plain, everything else
 * falls back to JSON.stringify.  Distinct from stringifyCSSValue which emits
 * raw CSS text without quoting.
 */
function serializeJSValue(value: unknown): string {
  if (typeof value === 'string') return JSON.stringify(value);
  if (typeof value === 'number') return String(value);
  if (typeof value === 'boolean') return String(value);
  return JSON.stringify(value);
}

// ---------------------------------------------------------------------------
// TokenJSCompiler
// ---------------------------------------------------------------------------

/**
 * Compile a list of {@link Token.Shape} into a JS object + companion type
 * declaration, grouped by category.
 */
function compile(tokens: readonly Token.Shape[]): TokenJSResult {
  // Group tokens by category
  const grouped = groupTokensByCategory(tokens);

  // Build the JS object literal
  const categoryBlocks: string[] = [];

  for (const [category, categoryTokens] of grouped) {
    const entries: string[] = [];
    for (const tok of categoryTokens) {
      entries.push(`    ${JSON.stringify(tok.name)}: ${serializeJSValue(tok.fallback)}`);
    }
    categoryBlocks.push(`  ${JSON.stringify(category)}: {\n${entries.join(',\n')}\n  }`);
  }

  const objectLiteral = `{\n${categoryBlocks.join(',\n')}\n}`;

  const code = [
    `// Generated by @czap/compiler -- do not edit manually.`,
    ``,
    `export const tokens = ${objectLiteral} as const;`,
    ``,
    `export type TokenMap = typeof tokens;`,
    ``,
  ].join('\n');

  const typeDeclaration = [
    `// Generated by @czap/compiler -- do not edit manually.`,
    ``,
    `export declare const tokens: ${objectLiteral};`,
    ``,
    `export type TokenMap = typeof tokens;`,
    ``,
  ].join('\n');

  return { code, typeDeclaration };
}

/**
 * Token JS compiler namespace.
 *
 * Serializes a token set to a runtime ES module and an ambient `.d.ts`
 * declaration in parallel so consumers import a single typed object while
 * the build artifact stays 100% generated.
 */
export const TokenJSCompiler = {
  /** Compile a token array into parallel `.ts` source and `.d.ts` declaration. */
  compile,
} as const;