/**
 * Spec Validator - Validate AtomizerSpec v2.0 before running optimization
 * 
 * This validator checks the spec for completeness and correctness,
 * returning structured errors that can be displayed in the ValidationPanel.
 */

import { AtomizerSpec } from '../../types/atomizer-spec';
import { ValidationError, ValidationData } from '../../hooks/usePanelStore';

// ============================================================================
// Validation Rules
// ============================================================================

interface ValidationRule {
  code: string;
  check: (spec: AtomizerSpec) => ValidationError | null;
}

const validationRules: ValidationRule[] = [
  // ---- Critical Errors (must fix) ----
  
  {
    code: 'NO_DESIGN_VARS',
    check: (spec) => {
      const enabledDVs = spec.design_variables.filter(dv => dv.enabled !== false);
      if (enabledDVs.length === 0) {
        return {
          code: 'NO_DESIGN_VARS',
          severity: 'error',
          path: 'design_variables',
          message: 'No design variables defined',
          suggestion: 'Add at least one design variable from the introspection panel or drag from the palette.',
        };
      }
      return null;
    },
  },
  
  {
    code: 'NO_OBJECTIVES',
    check: (spec) => {
      if (spec.objectives.length === 0) {
        return {
          code: 'NO_OBJECTIVES',
          severity: 'error',
          path: 'objectives',
          message: 'No objectives defined',
          suggestion: 'Add at least one objective to define what to optimize (minimize mass, maximize stiffness, etc.).',
        };
      }
      return null;
    },
  },
  
  {
    code: 'NO_EXTRACTORS',
    check: (spec) => {
      if (spec.extractors.length === 0) {
        return {
          code: 'NO_EXTRACTORS',
          severity: 'error',
          path: 'extractors',
          message: 'No extractors defined',
          suggestion: 'Add extractors to pull physics values (displacement, stress, frequency) from FEA results.',
        };
      }
      return null;
    },
  },
  
  {
    code: 'NO_MODEL',
    check: (spec) => {
      if (!spec.model.sim?.path) {
        return {
          code: 'NO_MODEL',
          severity: 'error',
          path: 'model.sim.path',
          message: 'No simulation file configured',
          suggestion: 'Select a .sim file in the study\'s model directory.',
        };
      }
      return null;
    },
  },
  
  // ---- Design Variable Validation ----
  
  {
    code: 'DV_INVALID_BOUNDS',
    check: (spec) => {
      for (const dv of spec.design_variables) {
        if (dv.enabled === false) continue;
        if (dv.bounds.min >= dv.bounds.max) {
          return {
            code: 'DV_INVALID_BOUNDS',
            severity: 'error',
            path: `design_variables.${dv.id}`,
            message: `Design variable "${dv.name}" has invalid bounds (min >= max)`,
            suggestion: `Set min (${dv.bounds.min}) to be less than max (${dv.bounds.max}).`,
            nodeId: dv.id,
          };
        }
      }
      return null;
    },
  },
  
  {
    code: 'DV_NO_EXPRESSION',
    check: (spec) => {
      for (const dv of spec.design_variables) {
        if (dv.enabled === false) continue;
        if (!dv.expression_name || dv.expression_name.trim() === '') {
          return {
            code: 'DV_NO_EXPRESSION',
            severity: 'error',
            path: `design_variables.${dv.id}`,
            message: `Design variable "${dv.name}" has no NX expression name`,
            suggestion: 'Set the expression_name to match an NX expression in the model.',
            nodeId: dv.id,
          };
        }
      }
      return null;
    },
  },
  
  // ---- Extractor Validation ----
  
  {
    code: 'EXTRACTOR_NO_TYPE',
    check: (spec) => {
      for (const ext of spec.extractors) {
        if (!ext.type || ext.type.trim() === '') {
          return {
            code: 'EXTRACTOR_NO_TYPE',
            severity: 'error',
            path: `extractors.${ext.id}`,
            message: `Extractor "${ext.name}" has no type selected`,
            suggestion: 'Select an extractor type (displacement, stress, frequency, etc.).',
            nodeId: ext.id,
          };
        }
      }
      return null;
    },
  },
  
  {
    code: 'CUSTOM_EXTRACTOR_NO_CODE',
    check: (spec) => {
      for (const ext of spec.extractors) {
        if (ext.type === 'custom_function' && (!ext.function?.source_code || ext.function.source_code.trim() === '')) {
          return {
            code: 'CUSTOM_EXTRACTOR_NO_CODE',
            severity: 'error',
            path: `extractors.${ext.id}`,
            message: `Custom extractor "${ext.name}" has no code defined`,
            suggestion: 'Open the code editor and write the extraction function.',
            nodeId: ext.id,
          };
        }
      }
      return null;
    },
  },
  
  // ---- Objective Validation ----
  
  {
    code: 'OBJECTIVE_NO_SOURCE',
    check: (spec) => {
      for (const obj of spec.objectives) {
        // Check if objective is connected to an extractor via canvas edges
        const hasSource = spec.canvas?.edges?.some(
          edge => edge.target === obj.id && edge.source.startsWith('ext_')
        );
        
        // Also check if source.extractor_id is set
        const hasDirectSource = obj.source?.extractor_id && 
          spec.extractors.some(e => e.id === obj.source.extractor_id);
        
        if (!hasSource && !hasDirectSource) {
          return {
            code: 'OBJECTIVE_NO_SOURCE',
            severity: 'error',
            path: `objectives.${obj.id}`,
            message: `Objective "${obj.name}" has no connected extractor`,
            suggestion: 'Connect an extractor to this objective or set source_extractor_id.',
            nodeId: obj.id,
          };
        }
      }
      return null;
    },
  },
  
  // ---- Constraint Validation ----
  
  {
    code: 'CONSTRAINT_NO_THRESHOLD',
    check: (spec) => {
      for (const con of spec.constraints || []) {
        if (con.threshold === undefined || con.threshold === null) {
          return {
            code: 'CONSTRAINT_NO_THRESHOLD',
            severity: 'error',
            path: `constraints.${con.id}`,
            message: `Constraint "${con.name}" has no threshold value`,
            suggestion: 'Set a threshold value for the constraint.',
            nodeId: con.id,
          };
        }
      }
      return null;
    },
  },
  
  // ---- Warnings (can proceed but risky) ----
  
  {
    code: 'HIGH_TRIAL_COUNT',
    check: (spec) => {
      const maxTrials = spec.optimization.budget?.max_trials || 100;
      if (maxTrials > 500) {
        return {
          code: 'HIGH_TRIAL_COUNT',
          severity: 'warning',
          path: 'optimization.budget.max_trials',
          message: `High trial count (${maxTrials}) may take several hours to complete`,
          suggestion: 'Consider starting with fewer trials (50-100) to validate the setup.',
        };
      }
      return null;
    },
  },
  
  {
    code: 'SINGLE_TRIAL',
    check: (spec) => {
      const maxTrials = spec.optimization.budget?.max_trials || 100;
      if (maxTrials === 1) {
        return {
          code: 'SINGLE_TRIAL',
          severity: 'warning',
          path: 'optimization.budget.max_trials',
          message: 'Only 1 trial configured - this will just run a single evaluation',
          suggestion: 'Increase max_trials to explore the design space.',
        };
      }
      return null;
    },
  },
  
  {
    code: 'DV_NARROW_BOUNDS',
    check: (spec) => {
      for (const dv of spec.design_variables) {
        if (dv.enabled === false) continue;
        const range = dv.bounds.max - dv.bounds.min;
        const baseline = dv.baseline || (dv.bounds.min + dv.bounds.max) / 2;
        const relativeRange = range / Math.abs(baseline || 1);
        
        if (relativeRange < 0.01) { // Less than 1% variation
          return {
            code: 'DV_NARROW_BOUNDS',
            severity: 'warning',
            path: `design_variables.${dv.id}`,
            message: `Design variable "${dv.name}" has very narrow bounds (<1% range)`,
            suggestion: 'Consider widening the bounds for more meaningful exploration.',
            nodeId: dv.id,
          };
        }
      }
      return null;
    },
  },
  
  {
    code: 'MANY_DESIGN_VARS',
    check: (spec) => {
      const enabledDVs = spec.design_variables.filter(dv => dv.enabled !== false);
      if (enabledDVs.length > 10) {
        return {
          code: 'MANY_DESIGN_VARS',
          severity: 'warning',
          path: 'design_variables',
          message: `${enabledDVs.length} design variables - high-dimensional space may need more trials`,
          suggestion: 'Consider enabling neural surrogate acceleration or increasing trial budget.',
        };
      }
      return null;
    },
  },
  
  {
    code: 'MULTI_OBJECTIVE_NO_WEIGHTS',
    check: (spec) => {
      if (spec.objectives.length > 1) {
        const hasWeights = spec.objectives.every(obj => obj.weight !== undefined && obj.weight !== null);
        if (!hasWeights) {
          return {
            code: 'MULTI_OBJECTIVE_NO_WEIGHTS',
            severity: 'warning',
            path: 'objectives',
            message: 'Multi-objective optimization without explicit weights',
            suggestion: 'Consider setting weights to control the trade-off between objectives.',
          };
        }
      }
      return null;
    },
  },
];

// ============================================================================
// Main Validation Function
// ============================================================================

export function validateSpec(spec: AtomizerSpec): ValidationData {
  const errors: ValidationError[] = [];
  const warnings: ValidationError[] = [];
  
  for (const rule of validationRules) {
    const result = rule.check(spec);
    if (result) {
      if (result.severity === 'error') {
        errors.push(result);
      } else {
        warnings.push(result);
      }
    }
  }
  
  return {
    valid: errors.length === 0,
    errors,
    warnings,
    checkedAt: Date.now(),
  };
}

// ============================================================================
// Quick Validation (just checks if can run)
// ============================================================================

export function canRunOptimization(spec: AtomizerSpec): { canRun: boolean; reason?: string } {
  // Check critical requirements only
  if (!spec.model.sim?.path) {
    return { canRun: false, reason: 'No simulation file configured' };
  }
  
  const enabledDVs = spec.design_variables.filter(dv => dv.enabled !== false);
  if (enabledDVs.length === 0) {
    return { canRun: false, reason: 'No design variables defined' };
  }
  
  if (spec.objectives.length === 0) {
    return { canRun: false, reason: 'No objectives defined' };
  }
  
  if (spec.extractors.length === 0) {
    return { canRun: false, reason: 'No extractors defined' };
  }
  
  // Check for invalid bounds
  for (const dv of enabledDVs) {
    if (dv.bounds.min >= dv.bounds.max) {
      return { canRun: false, reason: `Invalid bounds for "${dv.name}"` };
    }
  }
  
  return { canRun: true };
}

// ============================================================================
// Export validation result type for backward compatibility
// ============================================================================

export interface LegacyValidationResult {
  valid: boolean;
  errors: string[];
  warnings: string[];
}

export function toLegacyValidationResult(data: ValidationData): LegacyValidationResult {
  return {
    valid: data.valid,
    errors: data.errors.map(e => e.message),
    warnings: data.warnings.map(w => w.message),
  };
}