import { canonicalJson } from '../../src/shared/canonical-json';
import type { AggregatedPolicyState, EnvironmentProfile, StoredPolicySnapshotAggregation } from '../../src/domain/gpo-snapshot-aggregation';
import type { PolicyBaselineState, PolicyComparatorDefinition } from '../../src/domain/policy-evaluation';
import {
  policyEvaluationRulesForContext,
  type PolicyDependencyRule,
  type PolicyEvaluationRule,
  type PolicyEvaluationRuleCatalog
} from '../../src/domain/policy-evaluation-rules';

export interface PolicyRuleResolution {
  baselineState: PolicyBaselineState;
  comparator: PolicyComparatorDefinition;
  ruleIds: string[];
  dependencyRuleIds: string[];
  riskRuleIds: string[];
  notApplicable: boolean;
  diagnosticCodes: string[];
}

function sortedUnique(values: string[]): string[] {
  return [...new Set(values)].sort((left, right) => left.localeCompare(right));
}

function dependencyTarget(
  aggregation: StoredPolicySnapshotAggregation,
  dependency: PolicyDependencyRule
): AggregatedPolicyState | undefined {
  return aggregation.states.find(state => state.identity.id === dependency.identityId
    && state.deliveryMechanism === dependency.deliveryMechanism);
}

function targetIsConfigured(target: AggregatedPolicyState): boolean {
  return target.status === 'configured' && target.completeness === 'complete' && target.targeting === 'none';
}

function dependencyResolution(
  aggregation: StoredPolicySnapshotAggregation,
  dependencies: PolicyDependencyRule[]
): { notApplicable: boolean; diagnosticCodes: string[] } {
  const diagnostics = new Set<string>();
  let notApplicable = false;
  for (const dependency of dependencies) {
    const target = dependencyTarget(aggregation, dependency);
    if (!target) {
      if (!aggregation.snapshot.permitsSetAbsenceConclusions) {
        diagnostics.add('policy-dependency-target-absence-unknown');
      } else if (dependency.kind === 'prerequisite') {
        notApplicable = true;
      }
      continue;
    }
    if (target.status === 'conflicted' || target.status === 'indeterminate'
      || target.completeness !== 'complete' || target.targeting !== 'none') {
      diagnostics.add('policy-dependency-target-indeterminate');
      continue;
    }
    const configured = targetIsConfigured(target);
    if (dependency.kind === 'prerequisite' && !configured) notApplicable = true;
    if (dependency.kind === 'override' && configured) notApplicable = true;
    if (dependency.kind === 'mutual-exclusion' && configured) {
      diagnostics.add('policy-dependency-mutual-exclusion-active');
    }
  }
  return { notApplicable, diagnosticCodes: [...diagnostics].sort() };
}

export function resolvePolicyEvaluationRule(
  catalog: PolicyEvaluationRuleCatalog,
  profile: EnvironmentProfile,
  aggregation: StoredPolicySnapshotAggregation,
  state: AggregatedPolicyState
): PolicyRuleResolution {
  const diagnostics = new Set<string>();
  const selected: PolicyEvaluationRule[] = [];
  for (const contextId of state.applicableContextIds) {
    const context = profile.contexts.find(candidate => candidate.id === contextId);
    if (!context) {
      diagnostics.add('policy-evaluation-context-missing');
      continue;
    }
    const candidates = policyEvaluationRulesForContext(
      catalog, state.identity.id, state.deliveryMechanism, context, state.identity.scope
    );
    if (candidates.length !== 1) {
      diagnostics.add(candidates.length
        ? 'policy-evaluation-rule-ambiguous'
        : 'policy-evaluation-rule-catalog-gap');
      continue;
    }
    selected.push(candidates[0]);
  }
  const rules = [...new Map(selected.map(rule => [rule.id, rule])).values()]
    .sort((left, right) => left.id.localeCompare(right.id));
  const dispositions = new Set(rules.map(rule => rule.baselineDisposition));
  if (dispositions.size > 1) diagnostics.add('policy-evaluation-rule-context-conflict');
  let baselineState: PolicyBaselineState = dispositions.size === 1
    ? rules[0].baselineDisposition
    : 'catalog-gap';
  const recommendationRules = rules.filter(rule => rule.baselineDisposition === 'explicit-recommendation');
  const comparatorSignatures = new Set(recommendationRules.map(rule => canonicalJson(rule.comparator)));
  if (comparatorSignatures.size > 1) diagnostics.add('policy-evaluation-comparator-consensus-conflict');
  const riskSignatures = new Set(recommendationRules.map(rule => canonicalJson(rule.riskRule)));
  if (riskSignatures.size > 1) diagnostics.add('policy-evaluation-risk-consensus-conflict');
  if (baselineState === 'no-recommendation') diagnostics.add('policy-evaluation-no-recommendation');
  const dependencies = [...new Map(rules.flatMap(rule => rule.dependencies).map(rule => [rule.id, rule])).values()]
    .sort((left, right) => left.id.localeCompare(right.id));
  const conflictingDependencyIds = new Set<string>();
  for (const rule of rules) {
    for (const dependency of rule.dependencies) {
      const sameId = dependencies.find(candidate => candidate.id === dependency.id);
      if (sameId && canonicalJson(sameId) !== canonicalJson(dependency)) conflictingDependencyIds.add(dependency.id);
    }
  }
  if (conflictingDependencyIds.size) diagnostics.add('policy-evaluation-dependency-definition-conflict');
  const dependency = dependencyResolution(aggregation, dependencies);
  dependency.diagnosticCodes.forEach(code => diagnostics.add(code));
  let notApplicable = baselineState === 'explicitly-not-applicable' || dependency.notApplicable;
  if (dependency.notApplicable) baselineState = 'explicitly-not-applicable';
  if (diagnostics.size) notApplicable = false;
  const comparator = recommendationRules[0]?.comparator ?? { kind: 'equality' as const };
  return {
    baselineState,
    comparator,
    ruleIds: rules.map(rule => rule.id),
    dependencyRuleIds: dependencies.map(rule => rule.id),
    riskRuleIds: sortedUnique(recommendationRules.flatMap(rule => rule.riskRule ? [rule.riskRule.id] : [])),
    notApplicable,
    diagnosticCodes: [...diagnostics].sort()
  };
}