Imhotep/packages/imhotep-solver/src/predicates.ts

/**
 * Predicate registry and evaluator contracts for the Imhotep logic engine.
 *
 * Predicates are the atomic propositions over which first-order logic
 * formulas are built.  Each predicate declares its name, arity, domain
 * signature, and required geometry facts.
 *
 * Invariant: a predicate evaluator is a pure function from a geometry
 * world and a tuple of bound subject ids to a PredicateTruth result.
 */

import type { DiagnosticCode } from 'imhotep-core'
import type {
  GeometryWorld,
  ClauseResult,
  ClauseStatus,
  TruthValue,
} from './registry.js';

// ---------------------------------------------------------------------------
// Predicate Truth
// ---------------------------------------------------------------------------

export type PredicateTruth = 'true' | 'false' | 'indeterminate';

export interface PredicateResult {
  truth: PredicateTruth;
  metrics?: Record<string, number>;
  witness?: {
    subjectIds: number[];
  };
  diagnostics?: Array<{
    code: DiagnosticCode;
    severity: 'error' | 'warning' | 'info';
    message: string;
  }>;
}

// ---------------------------------------------------------------------------
// Predicate Descriptor
// ---------------------------------------------------------------------------

export interface PredicateDescriptor {
  name: string;
  arity: number;
  domains: string[];
  requiredFacts: string[];
}

// ---------------------------------------------------------------------------
// Predicate Evaluator
// ---------------------------------------------------------------------------

export interface PredicateEvaluator {
  descriptor: PredicateDescriptor;
  evaluateTuple(
    world: GeometryWorld,
    tuple: number[],
    options?: Record<string, unknown>,
  ): PredicateResult;
}

// ---------------------------------------------------------------------------
// Built-in Predicates
// ---------------------------------------------------------------------------

export const BUILTIN_PREDICATES: PredicateDescriptor[] = [
  { name: 'width', arity: 1, domains: ['element'], requiredFacts: ['subject.primaryBox'] },
  { name: 'height', arity: 1, domains: ['element'], requiredFacts: ['subject.primaryBox'] },
  { name: 'above', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'below', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'leftOf', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'rightOf', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'inside', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'contains', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'overlaps', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'alignedWith', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'centeredWithin', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'atLeast', arity: 1, domains: ['element'], requiredFacts: ['subject.primaryBox'] },
  { name: 'atMost', arity: 1, domains: ['element'], requiredFacts: ['subject.primaryBox'] },
  { name: 'between', arity: 1, domains: ['element'], requiredFacts: ['subject.primaryBox'] },
  { name: 'clippedBy', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.clipChain', 'reference.clipChain'] },
  { name: 'inStackingContext', arity: 1, domains: ['element'], requiredFacts: ['topology.stackingContextOf'] },
  { name: 'separatedFrom', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  // Spatial alias predicates
  { name: 'beside', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'nextTo', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'adjacent', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'touching', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'near', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'under', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  { name: 'within', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
];

// ---------------------------------------------------------------------------
// Predicate Registry
// ---------------------------------------------------------------------------

export class PredicateRegistry {
  private registry = new Map<string, PredicateEvaluator>();

  register(evaluator: PredicateEvaluator): void {
    this.registry.set(evaluator.descriptor.name, evaluator);
  }

  get(name: string): PredicateEvaluator | undefined {
    return this.registry.get(name);
  }

  list(): string[] {
    return Array.from(this.registry.keys());
  }

  clear(): void {
    this.registry.clear();
  }

  getDescriptor(name: string): PredicateDescriptor | undefined {
    return this.registry.get(name)?.descriptor;
  }

  getRequiredFacts(name: string): string[] {
    return this.getDescriptor(name)?.requiredFacts ?? [];
  }
}

// Global default instance for backward compatibility.
export const globalPredicateRegistry = new PredicateRegistry();

export function registerPredicate(evaluator: PredicateEvaluator): void {
  globalPredicateRegistry.register(evaluator);
}

export function getPredicateEvaluator(name: string): PredicateEvaluator | undefined {
  return globalPredicateRegistry.get(name);
}

export function listRegisteredPredicates(): string[] {
  return globalPredicateRegistry.list();
}

export function clearPredicateRegistry(): void {
  globalPredicateRegistry.clear();
  defaultPredicatesRegistered = false;
}

export function getPredicateDescriptor(name: string): PredicateDescriptor | undefined {
  return globalPredicateRegistry.getDescriptor(name);
}

export function getRequiredFactsForPredicate(name: string): string[] {
  return globalPredicateRegistry.getRequiredFacts(name);
}

// ---------------------------------------------------------------------------
// Built-in Predicate Evaluators
// ---------------------------------------------------------------------------

function getBorderRect(world: GeometryWorld, subjectId: number) {
  const { boxes } = world;
  // Build a subjectId -> boxIndex map on first use for O(1) lookups.
  // This avoids O(n) linear scans on every predicate evaluation.
  let index = (world as any).__boxIndex as Map<number, number> | undefined;
  if (!index) {
    index = new Map<number, number>();
    for (let i = 0; i < boxes.subjectId.length; i++) {
      index.set(boxes.subjectId[i], i);
    }
    (world as any).__boxIndex = index;
  }
  const i = index.get(subjectId);
  if (i === undefined) {
    return null;
  }
  return {
    left: boxes.borderLeft[i],
    top: boxes.borderTop[i],
    right: boxes.borderRight[i],
    bottom: boxes.borderBottom[i],
  };
}

function makePredicateResult(
  truth: PredicateTruth,
  metrics?: Record<string, number>,
  witness?: number[],
  diagnostics?: PredicateResult['diagnostics'],
): PredicateResult {
  return {
    truth,
    metrics,
    witness: witness ? { subjectIds: witness } : undefined,
    diagnostics,
  };
}

/**
 * Build a diagnostic for a failing predicate that includes observed values.
 */
function makePredicateDiagnostic(
  predicate: string,
  metrics: Record<string, number>,
  subjectIds: number[],
): PredicateResult['diagnostics'] {
  const entries = Object.entries(metrics)
    .map(([k, v]) => `${k}=${typeof v === 'number' ? v.toFixed(2) : String(v)}`)
    .join(', ');
  return [
    {
      code: 'IMH_PREDICATE_FAILED',
      severity: 'error',
      message: `Predicate "${predicate}" failed for subjects [${subjectIds.join(', ')}]. Observed: { ${entries} }`,
    },
  ];
}

function parseLengthOption(raw: unknown): { value: number; unit: string } | null {
  if (typeof raw === 'number') {
    return { value: raw, unit: 'px' };
  }
  if (typeof raw === 'string') {
    const trimmed = raw.trim();
    const m = trimmed.match(/^(-?\d*\.?\d+)\s*([a-z%]+)?$/i);
    if (!m) return null;
    const value = Number.parseFloat(m[1] ?? '');
    if (Number.isNaN(value)) return null;
    return { value, unit: (m[2] ?? 'px').toLowerCase() };
  }
  if (raw && typeof raw === 'object') {
    const obj = raw as Record<string, unknown>;
    if (typeof obj.value === 'number') {
      return {
        value: obj.value,
        unit: typeof obj.unit === 'string' ? obj.unit.toLowerCase() : 'px',
      };
    }
  }
  return null;
}

function getSubjectFontSizePx(world: GeometryWorld, subjectId: number): number {
  const styles = (world as any).styles as { fontSize?: ArrayLike<number> } | undefined;
  const fontSize = styles?.fontSize;
  if (!fontSize) return 16;
  const ids = world.subjects?.ids;
  if (!ids) return 16;
  const idx = ids.indexOf(subjectId);
  if (idx < 0) return 16;
  const fs = Number(fontSize[idx] ?? 16);
  return Number.isFinite(fs) && fs > 0 ? fs : 16;
}

function getRootFontSizePx(world: GeometryWorld): number {
  const styles = (world as any).styles as { fontSize?: ArrayLike<number> } | undefined;
  const fontSize = styles?.fontSize;
  if (!fontSize || fontSize.length === 0) return 16;
  const fs = Number(fontSize[0] ?? 16);
  return Number.isFinite(fs) && fs > 0 ? fs : 16;
}

function getSubjectChWidthPx(world: GeometryWorld, subjectId: number): number {
  const styles = (world as any).styles as {
    subjectId?: ArrayLike<number>
    chWidth?: ArrayLike<number>
  } | undefined;
  const chWidth = styles?.chWidth;
  if (!chWidth || chWidth.length === 0) {
    return getSubjectFontSizePx(world, subjectId) * 0.5;
  }

  const styleSubjectIds = styles?.subjectId;
  if (styleSubjectIds && styleSubjectIds.length > 0) {
    for (let i = 0; i < styleSubjectIds.length; i++) {
      if (Number(styleSubjectIds[i]) !== subjectId) continue;
      const w = Number(chWidth[i]);
      if (Number.isFinite(w) && w > 0) return w;
      break;
    }
  }

  const ids = world.subjects?.ids;
  if (ids) {
    const idx = ids.indexOf(subjectId);
    if (idx >= 0) {
      const w = Number(chWidth[idx]);
      if (Number.isFinite(w) && w > 0) return w;
    }
  }

  return getSubjectFontSizePx(world, subjectId) * 0.5;
}

function resolveLengthToPx(
  world: GeometryWorld,
  subjectId: number,
  raw: unknown,
  dimension: 'width' | 'height',
): number | undefined {
  const parsed = parseLengthOption(raw);
  if (!parsed) return undefined;
  const { value, unit } = parsed;
  switch (unit) {
    case 'px':
      return value;
    case 'vw':
      return value * (world.env.viewportWidth / 100);
    case 'vh':
      return value * (world.env.viewportHeight / 100);
    case '%':
      return value * ((dimension === 'height' ? world.env.viewportHeight : world.env.viewportWidth) / 100);
    case 'rem':
      return value * getRootFontSizePx(world);
    case 'em':
      return value * getSubjectFontSizePx(world, subjectId);
    case 'ch':
      return value * getSubjectChWidthPx(world, subjectId);
    default:
      return value;
  }
}

export const widthPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[0]!,
  evaluateTuple(world, tuple) {
    const subjectId = tuple[0];
    if (subjectId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const rect = getBorderRect(world, subjectId);
    if (!rect) {
      return makePredicateResult('indeterminate');
    }
    const w = rect.right - rect.left;
    return makePredicateResult('true', { width: w, left: rect.left, right: rect.right }, [subjectId]);
  },
};

export const heightPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[1]!,
  evaluateTuple(world, tuple) {
    const subjectId = tuple[0];
    if (subjectId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const rect = getBorderRect(world, subjectId);
    if (!rect) {
      return makePredicateResult('indeterminate');
    }
    const h = rect.bottom - rect.top;
    return makePredicateResult('true', { height: h }, [subjectId]);
  },
};

export const abovePredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[2]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const gap = rRect.top - sRect.bottom;
    const minGap = (options?.minGap as number | undefined) ?? 0;
    const maxGap = (options?.maxGap as number | undefined) ?? Infinity;
    const pass = gap >= minGap && gap <= maxGap;
    const metrics = { gap, observedGap: gap, minGap, maxGap, subjectBottom: sRect.bottom, refTop: rRect.top };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('above', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const belowPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[3]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const gap = sRect.top - rRect.bottom;
    const minGap = (options?.minGap as number | undefined) ?? 0;
    const maxGap = (options?.maxGap as number | undefined) ?? Infinity;
    const pass = gap >= minGap && gap <= maxGap;
    const metrics = { gap, observedGap: gap, minGap, maxGap };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('below', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const leftOfPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[4]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const gap = rRect.left - sRect.right;
    const minGap = (options?.minGap as number | undefined) ?? 0;
    const maxGap = (options?.maxGap as number | undefined) ?? Infinity;
    const pass = gap >= minGap && gap <= maxGap;
    const metrics = { gap, observedGap: gap, minGap, maxGap, subjectRight: sRect.right, refLeft: rRect.left };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('leftOf', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const rightOfPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[5]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const gap = sRect.left - rRect.right;
    const minGap = (options?.minGap as number | undefined) ?? 0;
    const maxGap = (options?.maxGap as number | undefined) ?? Infinity;
    const pass = gap >= minGap && gap <= maxGap;
    const metrics = { gap, observedGap: gap, minGap, maxGap };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('rightOf', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const insidePredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[6]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const tolerance = (options?.tolerance as number | undefined) ?? 0;
    const epsilon = (options?.epsilon as number | undefined) ?? 0.1;
    const effectiveTolerance = tolerance + epsilon;
    const pass =
      sRect.left >= rRect.left - effectiveTolerance &&
      sRect.top >= rRect.top - effectiveTolerance &&
      sRect.right <= rRect.right + effectiveTolerance &&
      sRect.bottom <= rRect.bottom + effectiveTolerance;
    const metrics: Record<string, number> = {
      overflowLeft: Math.max(0, rRect.left - sRect.left),
      overflowTop: Math.max(0, rRect.top - sRect.top),
      overflowRight: Math.max(0, sRect.right - rRect.right),
      overflowBottom: Math.max(0, sRect.bottom - rRect.bottom),
      tolerance,
      epsilon,
      effectiveTolerance,
      subjectLeft: sRect.left,
      subjectTop: sRect.top,
      subjectRight: sRect.right,
      subjectBottom: sRect.bottom,
      refLeft: rRect.left,
      refTop: rRect.top,
      refRight: rRect.right,
      refBottom: rRect.bottom,
    };
    const hasOverflow = metrics.overflowLeft > 0 || metrics.overflowTop > 0
                     || metrics.overflowRight > 0 || metrics.overflowBottom > 0;
    if (hasOverflow && world.clipping?.subjectId) {
      for (let i = 0; i < world.clipping.subjectId.length; i++) {
        if (world.clipping.subjectId[i] === referenceId) {
          metrics.hasClippedOverflow = 1;
          break;
        }
      }
    }
    const diagnostics = pass ? undefined : makePredicateDiagnostic('inside', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const containsPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[7]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const tolerance = (options?.tolerance as number | undefined) ?? 0;
    const pass =
      rRect.left >= sRect.left - tolerance &&
      rRect.top >= sRect.top - tolerance &&
      rRect.right <= sRect.right + tolerance &&
      rRect.bottom <= sRect.bottom + tolerance;
    const metrics: Record<string, number> = {
      tolerance,
      subjectLeft: sRect.left,
      subjectTop: sRect.top,
      subjectRight: sRect.right,
      subjectBottom: sRect.bottom,
      refLeft: rRect.left,
      refTop: rRect.top,
      refRight: rRect.right,
      refBottom: rRect.bottom,
    };
    const overflowLeft = Math.max(0, sRect.left - rRect.left);
    const overflowTop = Math.max(0, sRect.top - rRect.top);
    const overflowRight = Math.max(0, rRect.right - sRect.right);
    const overflowBottom = Math.max(0, rRect.bottom - sRect.bottom);
    if (overflowLeft > 0 || overflowTop > 0 || overflowRight > 0 || overflowBottom > 0) {
      if (world.clipping?.subjectId) {
        for (let i = 0; i < world.clipping.subjectId.length; i++) {
          if (world.clipping.subjectId[i] === subjectId) {
            metrics.hasClippedOverflow = 1;
            break;
          }
        }
      }
    }
    const diagnostics = pass ? undefined : makePredicateDiagnostic('contains', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const overlapsPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[8]!,
  evaluateTuple(world, tuple) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const pass =
      sRect.left < rRect.right &&
      sRect.right > rRect.left &&
      sRect.top < rRect.bottom &&
      sRect.bottom > rRect.top;
    return makePredicateResult(pass ? 'true' : 'false', {}, [subjectId, referenceId]);
  },
};

export const alignedWithPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[9]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const axis = (options?.axis as string | undefined) ?? 'centerY';
    const tolerance = (options?.tolerance as number | undefined) ?? 0;
    let delta = Infinity;
    switch (axis) {
      case 'left':
        delta = Math.abs(sRect.left - rRect.left);
        break;
      case 'right':
        delta = Math.abs(sRect.right - rRect.right);
        break;
      case 'top':
        delta = Math.abs(sRect.top - rRect.top);
        break;
      case 'bottom':
        delta = Math.abs(sRect.bottom - rRect.bottom);
        break;
      case 'centerX':
        delta = Math.abs((sRect.left + sRect.right) / 2 - (rRect.left + rRect.right) / 2);
        break;
      case 'centerY':
        delta = Math.abs((sRect.top + sRect.bottom) / 2 - (rRect.top + rRect.bottom) / 2);
        break;
    }
    const pass = delta <= tolerance;
    const metrics: Record<string, number> = { delta, tolerance };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('alignedWith', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const centeredWithinPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[10]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    const tolerance = (options?.tolerance as number | undefined) ?? 0;
    const sCx = (sRect.left + sRect.right) / 2;
    const sCy = (sRect.top + sRect.bottom) / 2;
    const rCx = (rRect.left + rRect.right) / 2;
    const rCy = (rRect.top + rRect.bottom) / 2;
    const deltaX = Math.abs(sCx - rCx);
    const deltaY = Math.abs(sCy - rCy);
    const pass = deltaX <= tolerance && deltaY <= tolerance;
    const metrics = { deltaX, deltaY, tolerance };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('centeredWithin', metrics, [subjectId, referenceId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId], diagnostics);
  },
};

export const atLeastPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[11]!,
  evaluateTuple(world, tuple, options) {
    const subjectId = tuple[0];
    if (subjectId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const rect = getBorderRect(world, subjectId);
    if (!rect) {
      return makePredicateResult('indeterminate');
    }
    const dimension = options?.dimension as string | undefined;
    const min = resolveLengthToPx(world, subjectId, options?.min, dimension === 'height' ? 'height' : 'width');
    const value = dimension === 'height' ? rect.bottom - rect.top : rect.right - rect.left;
    if (min === undefined) {
      return makePredicateResult('true', { value, left: rect.left, right: rect.right, top: rect.top, bottom: rect.bottom }, [subjectId]);
    }
    const pass = value >= min;
    const metrics = { value, min, left: rect.left, right: rect.right, top: rect.top, bottom: rect.bottom };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('atLeast', metrics, [subjectId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId], diagnostics);
  },
};

export const atMostPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[12]!,
  evaluateTuple(world, tuple, options) {
    const subjectId = tuple[0];
    if (subjectId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const rect = getBorderRect(world, subjectId);
    if (!rect) {
      return makePredicateResult('indeterminate');
    }
    const dimension = options?.dimension as string | undefined;
    const max = resolveLengthToPx(world, subjectId, options?.max, dimension === 'height' ? 'height' : 'width');
    const value = dimension === 'height' ? rect.bottom - rect.top : rect.right - rect.left;
    if (max === undefined) {
      return makePredicateResult('true', { value, left: rect.left, right: rect.right, top: rect.top, bottom: rect.bottom }, [subjectId]);
    }
    const pass = value <= max;
    const metrics = { value, max, left: rect.left, right: rect.right, top: rect.top, bottom: rect.bottom };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('atMost', metrics, [subjectId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId], diagnostics);
  },
};

export const betweenPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[13]!,
  evaluateTuple(world, tuple, options) {
    const subjectId = tuple[0];
    if (subjectId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const rect = getBorderRect(world, subjectId);
    if (!rect) {
      return makePredicateResult('indeterminate');
    }
    const dimension = options?.dimension as string | undefined;
    const min = resolveLengthToPx(world, subjectId, options?.min, dimension === 'height' ? 'height' : 'width');
    const max = resolveLengthToPx(world, subjectId, options?.max, dimension === 'height' ? 'height' : 'width');
    const value = dimension === 'height' ? rect.bottom - rect.top : rect.right - rect.left;
    if (min === undefined && max === undefined) {
      return makePredicateResult('true', { value, left: rect.left, right: rect.right, top: rect.top, bottom: rect.bottom }, [subjectId]);
    }
    const pass = (min === undefined || value >= min) && (max === undefined || value <= max);
    const metrics = { value, min: min ?? -Infinity, max: max ?? Infinity, left: rect.left, right: rect.right, top: rect.top, bottom: rect.bottom };
    const diagnostics = pass ? undefined : makePredicateDiagnostic('between', metrics, [subjectId]);
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId], diagnostics);
  },
};

export const clippedByPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[14]!,
  evaluateTuple(world, tuple) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    // Simplified: check if subject's clipping root is the reference
    const clipRoot = world.topology.clippingRootOf[subjectId - 1] ?? 0;
    const pass = clipRoot === referenceId;
    // Determine clip kind from the clipping table entry for the reference.
    // Encoding: 1=contain:paint, 2=overflow:hidden/scroll/auto
    const metrics: Record<string, number> = {};
    if (referenceId !== undefined) {
      const { clipping } = world;
      for (let i = 0; i < clipping.subjectId.length; i++) {
        if (clipping.subjectId[i] === referenceId) {
          metrics.clipKind = clipping.clipKind[i] === 5 /* Contain */ ? 1 : 2;
          break;
        }
      }
    }
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId]);
  },
};

export const inStackingContextPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[15]!,
  evaluateTuple(world, tuple) {
    const subjectId = tuple[0];
    if (subjectId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sc = world.topology.stackingContextOf[subjectId - 1] ?? 0;
    const pass = sc > 0;
    return makePredicateResult(pass ? 'true' : 'false', { stackingContext: sc }, [subjectId]);
  },
};

// ---------------------------------------------------------------------------
// Spatial Alias Predicate Evaluators
// ---------------------------------------------------------------------------

/**
 * beside(subject, opts) = leftOf(subject, opts) OR rightOf(subject, opts)
 * Tries leftOf first, then rightOf. Returns whichever passes, or fails with both measured values.
 */
export const besidePredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[17]!,
  evaluateTuple(world, tuple, options) {
    const leftResult = leftOfPredicate.evaluateTuple(world, tuple, options);
    if (leftResult.truth === 'true') {
      return makePredicateResult('true', { ...leftResult.metrics, direction: 'left' } as any, tuple);
    }
    const rightResult = rightOfPredicate.evaluateTuple(world, tuple, options);
    if (rightResult.truth === 'true') {
      return makePredicateResult('true', { ...rightResult.metrics, direction: 'right' } as any, tuple);
    }
    const metrics = {
      leftGap: leftResult.metrics?.gap ?? NaN,
      rightGap: rightResult.metrics?.gap ?? NaN,
    };
    return makePredicateResult('false', metrics, tuple, [
      {
        code: 'IMH_RELATION_BESIDE_FAILED',
        severity: 'error',
        message: `Predicate "beside" failed: neither leftOf (gap=${(metrics.leftGap as number).toFixed(2)}) nor rightOf (gap=${(metrics.rightGap as number).toFixed(2)}) satisfied.`,
      },
    ]);
  },
};

/**
 * nextTo(subject, opts) = beside(subject, opts)
 * Synonym for beside — delegates to the beside evaluator.
 */
export const nextToPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[18]!,
  evaluateTuple(world, tuple, options) {
    const besideResult = besidePredicate.evaluateTuple(world, tuple, options);
    if (besideResult.truth === 'true') {
      return makePredicateResult('true', { ...besideResult.metrics, alias: 'nextTo' } as any, tuple);
    }
    // Rewrite diagnostic to mention nextTo
    const diagnostics = besideResult.diagnostics?.map((d) => ({
      ...d,
      code: 'IMH_RELATION_BESIDE_FAILED' as const,
      message: d.message.replace('"beside"', '"nextTo"'),
    }));
    return makePredicateResult('false', besideResult.metrics ?? {}, tuple, diagnostics);
  },
};

/**
 * adjacent(subject, opts) = leftOr(subject, { maxGap: 0 }) OR rightOf(subject, { maxGap: 0 })
 *         OR above(subject, { maxGap: 0 }) OR below(subject, { maxGap: 0 })
 * Checks all four cardinal directions with maxGap: 0. Returns whichever passes, or fails.
 */
export const adjacentPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[19]!,
  evaluateTuple(world, tuple, options) {
    const adjOptions = { ...options, maxGap: 0 };
    const directions = [
      { name: 'leftOf', result: leftOfPredicate.evaluateTuple(world, tuple, adjOptions) },
      { name: 'rightOf', result: rightOfPredicate.evaluateTuple(world, tuple, adjOptions) },
      { name: 'above', result: abovePredicate.evaluateTuple(world, tuple, adjOptions) },
      { name: 'below', result: belowPredicate.evaluateTuple(world, tuple, adjOptions) },
    ];
    for (const dir of directions) {
      if (dir.result.truth === 'true') {
        return makePredicateResult('true', { ...dir.result.metrics, direction: dir.name } as any, tuple);
      }
    }
    const metrics = {
      leftGap: directions[0].result.metrics?.gap ?? NaN,
      rightGap: directions[1].result.metrics?.gap ?? NaN,
      aboveGap: directions[2].result.metrics?.gap ?? NaN,
      belowGap: directions[3].result.metrics?.gap ?? NaN,
    };
    return makePredicateResult('false', metrics, tuple, [
      {
        code: 'IMH_RELATION_ADJACENT_FAILED',
        severity: 'error',
        message: `Predicate "adjacent" failed: no direction satisfied with maxGap=0.`,
      },
    ]);
  },
};

/**
 * touching(subject, opts) = adjacent(subject, opts)
 * Synonym for adjacent — delegates to the adjacent evaluator.
 */
export const touchingPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[20]!,
  evaluateTuple(world, tuple, options) {
    const adjacentResult = adjacentPredicate.evaluateTuple(world, tuple, options);
    if (adjacentResult.truth === 'true') {
      return makePredicateResult('true', { ...adjacentResult.metrics, alias: 'touching' } as any, tuple);
    }
    const diagnostics = adjacentResult.diagnostics?.map((d) => ({
      ...d,
      code: 'IMH_RELATION_ADJACENT_FAILED' as const,
      message: d.message.replace('"adjacent"', '"touching"'),
    }));
    return makePredicateResult('false', adjacentResult.metrics ?? {}, tuple, diagnostics);
  },
};

/**
 * near(subject, opts) = overlaps(subject) OR inside a proximity radius
 * First checks overlaps. If that fails, checks directional proximity using leftOf/rightOf/above/below
 * with a large maxGap (default 100px, overridable via opts.maxGap).
 */
export const nearPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[21]!,
  evaluateTuple(world, tuple, options) {
    const overlapsResult = overlapsPredicate.evaluateTuple(world, tuple);
    if (overlapsResult.truth === 'true') {
      return makePredicateResult('true', { ...overlapsResult.metrics, mode: 'overlaps' } as any, tuple);
    }
    const radius = (options?.maxGap as number | undefined) ?? 100;
    const proximityOptions = { ...options, maxGap: radius };
    const directions = [
      { name: 'leftOf', result: leftOfPredicate.evaluateTuple(world, tuple, proximityOptions) },
      { name: 'rightOf', result: rightOfPredicate.evaluateTuple(world, tuple, proximityOptions) },
      { name: 'above', result: abovePredicate.evaluateTuple(world, tuple, proximityOptions) },
      { name: 'below', result: belowPredicate.evaluateTuple(world, tuple, proximityOptions) },
    ];
    for (const dir of directions) {
      if (dir.result.truth === 'true') {
        return makePredicateResult('true', { ...dir.result.metrics, direction: dir.name, mode: 'proximity', radius } as any, tuple);
      }
    }
    const metrics = {
      radius,
      leftGap: directions[0].result.metrics?.gap ?? NaN,
      rightGap: directions[1].result.metrics?.gap ?? NaN,
      aboveGap: directions[2].result.metrics?.gap ?? NaN,
      belowGap: directions[3].result.metrics?.gap ?? NaN,
    };
    return makePredicateResult('false', metrics, tuple, [
      {
        code: 'IMH_RELATION_NEAR_FAILED',
        severity: 'error',
        message: `Predicate "near" failed: elements neither overlap nor are within proximity radius ${radius}.`,
      },
    ]);
  },
};

/**
 * under(subject, opts) = below(subject, opts)
 * Synonym for below — delegates to the below evaluator.
 */
export const underPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[22]!,
  evaluateTuple(world, tuple, options) {
    return belowPredicate.evaluateTuple(world, tuple, options);
  },
};

/**
 * within(subject, opts) = inside(subject, opts)
 * Synonym for inside — delegates to the inside evaluator.
 */
export const withinPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[23]!,
  evaluateTuple(world, tuple, options) {
    return insidePredicate.evaluateTuple(world, tuple, options);
  },
};

// ---------------------------------------------------------------------------
// Not-Yet-Implemented Predicates
// ---------------------------------------------------------------------------

function makeNotImplementedPredicate(name: string): PredicateEvaluator {
  return {
    descriptor: {
      name,
      arity: 2,
      domains: ['element', 'element'],
      requiredFacts: ['subject.primaryBox', 'reference.primaryBox'],
    },
    evaluateTuple(_world, tuple) {
      const subjectId = tuple[0];
      const referenceId = tuple[1];
      return makePredicateResult('false', {}, [subjectId, referenceId].filter((id): id is number => id !== undefined), [
        {
          code: 'IMH_FEATURE_NOT_YET_IMPLEMENTED',
          severity: 'error',
          message: `Predicate "${name}" is not yet implemented.`,
        },
      ]);
    },
  };
}

export const separatedFromPredicate: PredicateEvaluator = {
  descriptor: BUILTIN_PREDICATES[16]!,
  evaluateTuple(world, tuple, options) {
    const [subjectId, referenceId] = tuple;
    if (subjectId === undefined || referenceId === undefined) {
      return makePredicateResult('indeterminate');
    }
    const sRect = getBorderRect(world, subjectId);
    const rRect = getBorderRect(world, referenceId);
    if (!sRect || !rRect) {
      return makePredicateResult('indeterminate');
    }
    // separatedFrom = NOT overlaps
    const overlaps =
      sRect.left < rRect.right &&
      sRect.right > rRect.left &&
      sRect.top < rRect.bottom &&
      sRect.bottom > rRect.top;
    const pass = !overlaps;
    const metrics: Record<string, number> = {};
    if (!pass) {
      // Calculate overlap area for diagnostics
      const overlapLeft = Math.max(sRect.left, rRect.left);
      const overlapTop = Math.max(sRect.top, rRect.top);
      const overlapRight = Math.min(sRect.right, rRect.right);
      const overlapBottom = Math.min(sRect.bottom, rRect.bottom);
      metrics.overlapWidth = overlapRight - overlapLeft;
      metrics.overlapHeight = overlapBottom - overlapTop;
    }
    return makePredicateResult(pass ? 'true' : 'false', metrics, [subjectId, referenceId]);
  },
};
export const leftAlignedWithPredicate: PredicateEvaluator = {
  descriptor: { name: 'leftAlignedWith', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  evaluateTuple(world, tuple, options) {
    return alignedWithPredicate.evaluateTuple(world, tuple, { ...options as Record<string, unknown>, axis: 'left' });
  },
};

export const rightAlignedWithPredicate: PredicateEvaluator = {
  descriptor: { name: 'rightAlignedWith', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  evaluateTuple(world, tuple, options) {
    return alignedWithPredicate.evaluateTuple(world, tuple, { ...options as Record<string, unknown>, axis: 'right' });
  },
};

export const topAlignedWithPredicate: PredicateEvaluator = {
  descriptor: { name: 'topAlignedWith', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  evaluateTuple(world, tuple, options) {
    return alignedWithPredicate.evaluateTuple(world, tuple, { ...options as Record<string, unknown>, axis: 'top' });
  },
};

export const bottomAlignedWithPredicate: PredicateEvaluator = {
  descriptor: { name: 'bottomAlignedWith', arity: 2, domains: ['element', 'element'], requiredFacts: ['subject.primaryBox', 'reference.primaryBox'] },
  evaluateTuple(world, tuple, options) {
    return alignedWithPredicate.evaluateTuple(world, tuple, { ...options as Record<string, unknown>, axis: 'bottom' });
  },
};

// ---------------------------------------------------------------------------
// Register Defaults
// ---------------------------------------------------------------------------

let defaultPredicatesRegistered = false;

export function registerDefaultPredicates(): void {
  if (defaultPredicatesRegistered) return;
  defaultPredicatesRegistered = true;
  registerPredicate(widthPredicate);
  registerPredicate(heightPredicate);
  registerPredicate(abovePredicate);
  registerPredicate(belowPredicate);
  registerPredicate(leftOfPredicate);
  registerPredicate(rightOfPredicate);
  registerPredicate(insidePredicate);
  registerPredicate(containsPredicate);
  registerPredicate(overlapsPredicate);
  registerPredicate(alignedWithPredicate);
  registerPredicate(centeredWithinPredicate);
  registerPredicate(atLeastPredicate);
  registerPredicate(atMostPredicate);
  registerPredicate(betweenPredicate);
  registerPredicate(clippedByPredicate);
  registerPredicate(inStackingContextPredicate);
  registerPredicate(separatedFromPredicate);
  registerPredicate(leftAlignedWithPredicate);
  registerPredicate(rightAlignedWithPredicate);
  registerPredicate(topAlignedWithPredicate);
  registerPredicate(bottomAlignedWithPredicate);
  registerPredicate(besidePredicate);
  registerPredicate(nextToPredicate);
  registerPredicate(adjacentPredicate);
  registerPredicate(touchingPredicate);
  registerPredicate(nearPredicate);
  registerPredicate(underPredicate);
  registerPredicate(withinPredicate);
}