import type { ProposedShard } from "../types.js";

export interface ShardRejection { shard: ProposedShard; reason: string }
export interface DecompositionResult { accepted: ProposedShard[]; rejected: ShardRejection[] }

const norm = (value: string) => value.trim().toLowerCase().replace(/\s+/g, " ");
const overlaps = (left: string, right: string) => {
  const a = left.replace(/\/+$/, "");
  const b = right.replace(/\/+$/, "");
  return a === b || a.startsWith(`${b}/`) || b.startsWith(`${a}/`);
};

export function validateDecomposition(shards: ProposedShard[], remainingAgentBudget: number): DecompositionResult {
  const accepted: ProposedShard[] = [];
  const rejected: ShardRejection[] = [];
  const questions = new Set<string>();
  const evidence = new Set<string>();
  for (const shard of shards) {
    const missing = !shard.id || !shard.objective || !shard.lens || !shard.evidenceTarget || !shard.expectedOutput || shard.scope.length === 0;
    const duplicate = questions.has(norm(shard.objective)) || evidence.has(norm(shard.evidenceTarget));
    const overlapsWriter = shard.writeIntent && accepted.some((other) => other.writeIntent && shard.scope.some((path) => other.scope.some((otherPath) => overlaps(path, otherPath))));
    const invalid = missing ? "missing-required-field"
      : duplicate ? "duplicate-question-or-evidence"
      : !shard.canChangeFinalDecision ? "cannot-change-decision"
      : !shard.canRunIndependently ? "not-independent"
      : overlapsWriter ? "writer-scope-overlap"
      : accepted.length >= remainingAgentBudget ? "budget-exhausted"
      : undefined;
    if (invalid) { rejected.push({ shard, reason: invalid }); continue; }
    questions.add(norm(shard.objective));
    evidence.add(norm(shard.evidenceTarget));
    accepted.push(shard);
  }
  return { accepted, rejected };
}