/**
 * Performance budget presets and classification utilities.
 *
 * ESLint model: global defaults, zero-config, auto-measurement.
 * Users configure 0-3 numbers. Per-component overrides are the `eslint-disable` equivalent.
 */

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

export interface PerformanceBudgets {
  /** Maximum gzipped bundle size in bytes */
  bundleSize: number;
}

export interface PerformanceConfig {
  preset: string;
  budgets: PerformanceBudgets;
}

export type ComplexityTier = 'lightweight' | 'moderate' | 'heavy';

export interface PerformanceData {
  /** Gzipped bundle size in bytes */
  bundleSize: number;
  /** Raw (minified, not gzipped) bundle size in bytes */
  rawSize: number;
  /** Complexity classification */
  complexity: ComplexityTier;
  /** Percentage of budget used (0-100+) */
  budgetPercent: number;
  /** Whether the component exceeds its budget */
  overBudget: boolean;
  /** ISO timestamp when measured */
  measuredAt: string;
}

export interface PerformanceSummary {
  /** Preset name used */
  preset: string;
  /** Budget applied in bytes */
  budget: number;
  /** Total components measured */
  total: number;
  /** Number of components over budget */
  overBudget: number;
  /** Distribution by tier */
  tiers: Record<ComplexityTier, number>;
}

// ---------------------------------------------------------------------------
// Presets
// ---------------------------------------------------------------------------

const PRESETS: Record<string, PerformanceBudgets> = {
  strict: { bundleSize: 8 * 1024 },     // 8KB gzipped
  standard: { bundleSize: 15 * 1024 },   // 15KB gzipped
  relaxed: { bundleSize: 30 * 1024 },    // 30KB gzipped
};

export const PRESET_NAMES = Object.keys(PRESETS) as readonly string[];

// ---------------------------------------------------------------------------
// Resolution
// ---------------------------------------------------------------------------

/**
 * Resolve a performance config from user input.
 * Accepts a preset name string or a custom config object.
 */
export function resolvePerformanceConfig(
  input: string | { preset?: string; budgets?: Partial<PerformanceBudgets> } | undefined
): PerformanceConfig {
  if (!input) {
    return { preset: 'standard', budgets: PRESETS.standard };
  }

  if (typeof input === 'string') {
    const budgets = PRESETS[input];
    if (!budgets) {
      throw new Error(
        `Unknown performance preset "${input}". Available: ${PRESET_NAMES.join(', ')}`
      );
    }
    return { preset: input, budgets };
  }

  const presetName = input.preset ?? 'standard';
  const baseBudgets = PRESETS[presetName];
  if (!baseBudgets) {
    throw new Error(
      `Unknown performance preset "${presetName}". Available: ${PRESET_NAMES.join(', ')}`
    );
  }

  return {
    preset: presetName,
    budgets: {
      bundleSize: input.budgets?.bundleSize ?? baseBudgets.bundleSize,
    },
  };
}

// ---------------------------------------------------------------------------
// Classification
// ---------------------------------------------------------------------------

/**
 * Classify a component's complexity based on gzipped bundle size.
 *
 * - lightweight: < 5KB — simple, leaf components
 * - moderate: < 15KB — typical composed components
 * - heavy: >= 15KB — complex widgets with dependencies
 */
export function classifyComplexity(gzipBytes: number): ComplexityTier {
  if (gzipBytes < 5 * 1024) return 'lightweight';
  if (gzipBytes < 15 * 1024) return 'moderate';
  return 'heavy';
}

// ---------------------------------------------------------------------------
// Formatting helpers
// ---------------------------------------------------------------------------

/**
 * Format bytes to a human-readable string (e.g. "2.1KB", "15.3KB").
 */
export function formatBytes(bytes: number): string {
  if (bytes < 1024) return `${bytes}B`;
  const kb = bytes / 1024;
  return kb < 10 ? `${kb.toFixed(1)}KB` : `${Math.round(kb)}KB`;
}

/**
 * Create a visual budget bar for terminal output.
 */
export function budgetBar(percent: number, width = 20): string {
  const filled = Math.min(Math.round((percent / 100) * width), width);
  const bar = '█'.repeat(filled) + '░'.repeat(width - filled);
  return percent > 100 ? `\x1b[31m${bar}\x1b[0m` : `\x1b[32m${bar}\x1b[0m`;
}