export interface CssTokenAudit {
  declared: string[];
  used: string[];
  missing: string[];
  unused: string[];
}

/** Audit framework design-token declarations and var() references. */
export function auditWrnTokens(css: string): CssTokenAudit {
  const declared = new Set<string>();
  const used = new Set<string>();
  for (const match of css.matchAll(/(--wrn-[A-Za-z0-9_-]+)\s*:/g)) declared.add(match[1]!);
  for (const match of css.matchAll(/var\(\s*(--wrn-[A-Za-z0-9_-]+)/g)) used.add(match[1]!);
  return {
    declared: [...declared].sort(),
    used: [...used].sort(),
    missing: [...used].filter((token) => !declared.has(token)).sort(),
    unused: [...declared].filter((token) => !used.has(token)).sort(),
  };
}

export interface StyleSource {
  path: string;
  reason?: string;
}

/** Normalize/dedupe Tailwind scan sources without allowing line injection. */
export function normalizeStyleSources(values: readonly (string | StyleSource)[]): StyleSource[] {
  const result = new Map<string, StyleSource>();
  for (const value of values) {
    const source = typeof value === "string" ? { path: value } : value;
    const path = source.path.trim();
    if (!path || /[\r\n]/.test(path)) continue;
    result.set(path, { path, reason: source.reason });
  }
  return [...result.values()];
}

export function tailwindSourceDirectives(values: readonly (string | StyleSource)[]): string {
  return normalizeStyleSources(values)
    .map(({ path }) => `@source ${JSON.stringify(path)};`)
    .join("\n");
}

export interface ContrastResult {
  ratio: number;
  level: "fail" | "aa-large" | "aa" | "aaa";
}

function hexRgb(value: string): [number, number, number] | null {
  const hex = value.trim().replace(/^#/, "");
  const normalized = hex.length === 3 ? [...hex].map((part) => part + part).join("") : hex;
  if (!/^[0-9a-f]{6}$/i.test(normalized)) return null;
  return [0, 2, 4].map((offset) => Number.parseInt(normalized.slice(offset, offset + 2), 16)) as [
    number,
    number,
    number,
  ];
}

function luminance(value: string): number | null {
  const rgb = hexRgb(value);
  if (!rgb) return null;
  const channels = rgb.map((channel) => {
    const scaled = channel / 255;
    return scaled <= 0.03928 ? scaled / 12.92 : ((scaled + 0.055) / 1.055) ** 2.4;
  });
  return 0.2126 * channels[0]! + 0.7152 * channels[1]! + 0.0722 * channels[2]!;
}

export function contrast(foreground: string, background: string): ContrastResult | null {
  const left = luminance(foreground);
  const right = luminance(background);
  if (left === null || right === null) return null;
  const ratio = (Math.max(left, right) + 0.05) / (Math.min(left, right) + 0.05);
  return {
    ratio: Math.round(ratio * 100) / 100,
    level: ratio >= 7 ? "aaa" : ratio >= 4.5 ? "aa" : ratio >= 3 ? "aa-large" : "fail",
  };
}

export interface CssPerformanceAuditIssue {
  code: string;
  severity: "error" | "warning" | "info";
  message: string;
  line?: number;
}

function cssLineAt(source: string, offset: number): number {
  return source.slice(0, offset).split(/\r?\n/).length;
}

/** Detect CSS patterns that commonly increase style, paint, or compositing cost. */
export function auditCssPerformance(source: string): CssPerformanceAuditIssue[] {
  const issues: CssPerformanceAuditIssue[] = [];
  const checks: Array<{
    pattern: RegExp;
    code: string;
    severity: CssPerformanceAuditIssue["severity"];
    message: string;
  }> = [
    {
      pattern: /transition\s*:\s*all\b/gi,
      code: "WRN-CSS-TRANSITION-ALL",
      severity: "warning",
      message: "Avoid transition: all; list only properties that should animate.",
    },
    {
      pattern: /backdrop-filter\s*:\s*[^;]*(?:blur\((?:[3-9]\d|\d{3,})px\))/gi,
      code: "WRN-CSS-BACKDROP-BLUR",
      severity: "warning",
      message: "Large backdrop blur areas can be expensive to composite.",
    },
    {
      pattern: /box-shadow\s*:[^;]*(?:,\s*[^;]+){4,}/gi,
      code: "WRN-CSS-MANY-SHADOWS",
      severity: "warning",
      message: "Many layered shadows can increase paint cost.",
    },
    {
      pattern: /(?:^|[},])\s*\*\s*(?:[,{])/gm,
      code: "WRN-CSS-UNIVERSAL-SELECTOR",
      severity: "info",
      message: "Review universal selectors used in large DOM subtrees.",
    },
  ];
  for (const check of checks) {
    for (const match of source.matchAll(check.pattern)) {
      issues.push({
        code: check.code,
        severity: check.severity,
        message: check.message,
        line: cssLineAt(source, match.index ?? 0),
      });
    }
  }

  const keyframes = new Map<string, number>();
  for (const match of source.matchAll(/@keyframes\s+([A-Za-z_][\w-]*)/g)) {
    const name = match[1]!;
    keyframes.set(name, (keyframes.get(name) ?? 0) + 1);
  }
  for (const [name, count] of keyframes) {
    if (count > 1) {
      issues.push({
        code: "WRN-CSS-DUPLICATE-KEYFRAMES",
        severity: "warning",
        message: `@keyframes ${name} is declared ${count} times.`,
      });
    }
  }
  return issues;
}