/**
 * CSS Custom Properties Generator
 *
 * Converts a ThemeInterface into a flat map of CSS custom properties.
 * Enables theme values to be consumed via var(--theme-*) in plain CSS,
 * CSS modules, or non-styled-components contexts.
 */
/**
 * Section aliases map ThemeInterface top-level keys to cleaner CSS var prefixes.
 * Keys not listed here use the default kebab-case conversion.
 */
const SECTION_ALIASES = {
    colors: 'color',
    shadows: 'shadow',
    borderRadius: 'radius',
    transitions: 'transition',
    typography: 'type',
    spacing: 'spacing',
    zIndex: 'z',
    duration: 'duration',
    easing: 'easing',
    opacity: 'opacity',
    letterSpacing: 'letter-spacing',
    borderWidth: 'border-width',
};
/**
 * Keys to skip during recursive traversal.
 * - extensions: theme-specific, not suitable for generic CSS vars
 * - breakpoints: typically used in media queries, not as var values
 */
const SKIP_KEYS = new Set(['extensions', 'breakpoints']);
/**
 * Convert a camelCase or PascalCase string to kebab-case.
 */
function toKebab(str) {
    return str.replace(/([a-z0-9])([A-Z])/g, '$1-$2').toLowerCase();
}
/**
 * Recursively flatten an object into CSS variable entries.
 */
function flatten(obj, prefix, result) {
    for (const [key, value] of Object.entries(obj)) {
        if (value === undefined || value === null)
            continue;
        if (typeof value === 'function')
            continue;
        if (SKIP_KEYS.has(key))
            continue;
        const kebabKey = toKebab(key);
        const varName = `${prefix}-${kebabKey}`;
        if (typeof value === 'string') {
            result[varName] = value;
        }
        else if (typeof value === 'number') {
            result[varName] = String(value);
        }
        else if (typeof value === 'object' && !Array.isArray(value)) {
            flatten(value, varName, result);
        }
    }
}
/**
 * Flatten a ThemeInterface into a Record of CSS custom property names to values.
 *
 * @param theme - The theme adapter to flatten
 * @param prefix - CSS var prefix (default: 'theme')
 * @returns Record mapping `--{prefix}-{section}-{path}` to string values
 *
 * @example
 * ```typescript
 * const vars = flattenThemeToCssVars(cyberpunkAdapter)
 * // vars['--theme-color-primary-main'] === '#ff00ff'
 * // vars['--theme-spacing-md'] === '1rem'
 * // vars['--theme-type-font-family-heading'] === '"Courier New", ...'
 * ```
 */
export function flattenThemeToCssVars(theme, prefix = 'theme') {
    const result = {};
    for (const [section, value] of Object.entries(theme)) {
        if (value === undefined || value === null)
            continue;
        if (typeof value === 'function')
            continue;
        if (SKIP_KEYS.has(section))
            continue;
        const sectionPrefix = SECTION_ALIASES[section] ?? toKebab(section);
        const varPrefix = `--${prefix}-${sectionPrefix}`;
        if (typeof value === 'string') {
            result[varPrefix] = value;
        }
        else if (typeof value === 'number') {
            result[varPrefix] = String(value);
        }
        else if (typeof value === 'object' && !Array.isArray(value)) {
            flatten(value, varPrefix, result);
        }
    }
    return result;
}
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