import { describe, test } from 'node:test';
import assert from 'node:assert/strict';
import fs from 'node:fs';
import os from 'node:os';
import path from 'node:path';
import { CondensedGraph } from '../../src/core/CondensedGraph.js';
import { ShardedSnapshotBuilder } from '../../src/core/shards/ShardedSnapshotBuilder.js';
import { ShardedSnapshot } from '../../src/core/shards/ShardedSnapshot.js';
import { FileShardStorage } from '../../src/core/shards/FileShardStorage.js';
import { DeltaShardBinary } from '../../src/core/shards/DeltaShardBinary.js';
import { WaveletShardBinary } from '../../src/core/shards/WaveletShardBinary.js';

function buildSnapshot(bucketSize = 4) {
  const graph = new CondensedGraph();
  const nodes = [];
  for (let i = 0; i < 6; i++) {
    nodes.push(graph._ensureNode(`node:${i}`));
  }

  graph.addEdge(nodes[0], 'risk_score', nodes[1], 1.0, { value: 0.4 });
  graph.addEdge(nodes[0], 'risk_score', nodes[2], 1.0, { value: 0.9 });
  graph.addEdge(nodes[3], 'risk_score', nodes[4], 1.0, { value: 0.5 });
  graph.addEdge(nodes[1], 'risk_limit', nodes[1], 1.0, { value: 0.6 });
  graph.addEdge(nodes[2], 'risk_limit', nodes[2], 1.0, { value: 0.6 });
  graph.addEdge(nodes[4], 'risk_limit', nodes[4], 1.0, { value: 0.6 });

  graph.finalizePerfectHash();
  graph.finalizeWaveletAdjacency({ dropAdjacencyList: true });

  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'sharded-delta-comp-'));
  const builder = new ShardedSnapshotBuilder({ bucketSize, includeDirections: ['out', 'in'] });
  const manifest = builder.build(graph, dir);
  const storage = new FileShardStorage(dir);
  const snapshot = new ShardedSnapshot(manifest, storage, { cacheLimit: 8 });
  snapshot.initializeSync();

  return { snapshot, manifest, dir, nodes };
}

function writeDeltaLayer(snapshot, dir, entries, mode = 'override') {
  fs.mkdirSync(dir, { recursive: true });
  const merged = new Map();
  for (const entry of entries) {
    const shardMeta = snapshot._selectShardMeta(entry.relationId, entry.direction, entry.srcId);
    assert.ok(shardMeta, 'Missing shard meta for delta entry');
    const localSource = snapshot._localSource(entry.srcId, shardMeta);
    const key = shardMeta.cacheKey;
    let bucket = merged.get(key);
    if (!bucket) {
      bucket = { shardMeta, additions: [], removals: [] };
      merged.set(key, bucket);
    }
    for (const add of entry.additions) {
      bucket.additions.push({
        srcLocal: localSource,
        otherId: add.dstId,
        possBits: add.possBits,
        relBits: add.relBits
      });
    }
    for (const rem of entry.removals) {
      bucket.removals.push({
        srcLocal: localSource,
        otherId: rem.dstId
      });
    }
  }

  const shards = [];
  for (const bucket of merged.values()) {
    const shardMeta = bucket.shardMeta;
    const buffer = DeltaShardBinary.serialize({
      relationId: shardMeta.relationId,
      direction: shardMeta.direction,
      rangeStart: shardMeta.rangeStart,
      rangeEnd: shardMeta.rangeEnd,
      nodeCount: snapshot.nodeCount,
      additions: bucket.additions,
      removals: bucket.removals
    });
    const shardKey = `delta-${shardMeta.key}`;
    fs.writeFileSync(path.join(dir, shardKey), new Uint8Array(buffer));
    shards.push({
      key: shardKey,
      relationId: shardMeta.relationId,
      direction: shardMeta.direction,
      rangeStart: shardMeta.rangeStart,
      rangeEnd: shardMeta.rangeEnd,
      cacheKey: shardMeta.cacheKey
    });
  }

  return { shards, storage: new FileShardStorage(dir), mode };
}

function compactLayer(snapshot, layer, manifest, outputDir, baseDir) {
  fs.rmSync(outputDir, { recursive: true, force: true });
  fs.mkdirSync(outputDir, { recursive: true });

  if (manifest.nodeTableKey) {
    fs.copyFileSync(path.join(baseDir, manifest.nodeTableKey), path.join(outputDir, manifest.nodeTableKey));
  }
  if (manifest.componentKey) {
    fs.copyFileSync(path.join(baseDir, manifest.componentKey), path.join(outputDir, manifest.componentKey));
  }

  for (const shard of manifest.shards || []) {
    const basePath = path.join(baseDir, shard.key);
    fs.copyFileSync(basePath, path.join(outputDir, shard.key));
  }

  for (const shardMeta of layer.shards) {
    const base = snapshot._cacheIndex.get(shardMeta.cacheKey);
    if (!base) continue;
    const shard = snapshot._loadShardSync(base.relationId, base.direction, base.rangeStart);
    if (!shard) continue;

    const deltaBuffer = layer.storage.getSync(shardMeta.key);
    if (!deltaBuffer) continue;
    const deltaShard = DeltaShardBinary.deserialize(deltaBuffer);
    const rangeSize = shard.rangeEnd - shard.rangeStart;
    const sources = new Array(rangeSize);
    for (let localSource = 0; localSource < rangeSize; localSource++) {
      const range = snapshot._rangeForSource(shard, localSource);
      const list = [];
      if (range) {
        for (let pos = range.start; pos < range.end; pos++) {
          list.push({ otherId: shard.dstIds[pos], possBits: shard.possBits[pos], relBits: shard.relBits[pos] });
        }
      }
      sources[localSource] = list;
    }

    for (const removal of deltaShard.removals) {
      const list = sources[removal.srcLocal];
      if (!list) continue;
      const idx = list.findIndex((item) => item.otherId === removal.otherId);
      if (idx !== -1) list.splice(idx, 1);
    }

    for (const addition of deltaShard.additions) {
      const list = sources[addition.srcLocal] || (sources[addition.srcLocal] = []);
      list.push({ otherId: addition.otherId, possBits: addition.possBits, relBits: addition.relBits });
    }

    const buffer = WaveletShardBinary.serialize({
      relationId: shard.relationId,
      direction: shard.direction,
      rangeStart: shard.rangeStart,
      rangeEnd: shard.rangeEnd,
      nodeCount: snapshot.nodeCount,
      sources
    });
    fs.writeFileSync(path.join(outputDir, base.key), new Uint8Array(buffer));
  }
}

function evaluateRisk(snapshot, relScore, relLimit, userId, docId) {
  const scoreEdge = snapshot.findEdgeSync(userId, relScore, docId);
  if (!scoreEdge || scoreEdge.value === undefined) return false;
  const limitEdge = snapshot.findEdgeSync(docId, relLimit, docId);
  if (!limitEdge || limitEdge.value === undefined) return false;
  return scoreEdge.value <= limitEdge.value;
}

// ADR-003: sharded snapshots are stubs in src/core/shards/ — tests are the spec for when the subsystem is implemented.
describe.skip('Sharded delta comparator equivalence', () => {
  test('overlay and compacted base agree on comparator outcomes', () => {
    const { snapshot, manifest, dir, nodes } = buildSnapshot(4);
    const relIdScore = snapshot.relationIdToName.indexOf('risk_score');
    const relIdLimit = snapshot.relationIdToName.indexOf('risk_limit');

    const deltaDir = path.join(dir, 'delta');
    const layer = writeDeltaLayer(snapshot, deltaDir, [
      { relationId: relIdScore, direction: 'out', srcId: nodes[0], additions: [{ dstId: nodes[3], possBits: 65535, relBits: 65535 }], removals: [] },
      { relationId: relIdLimit, direction: 'out', srcId: nodes[3], additions: [{ dstId: nodes[3], possBits: 65535, relBits: 65535 }], removals: [] }
    ], 'override');

    snapshot.setDeltaLayers([layer]);

    const compactDir = path.join(dir, 'compact');
    compactLayer(snapshot, layer, manifest, compactDir, dir);
    const compactSnapshot = new ShardedSnapshot(manifest, new FileShardStorage(compactDir), { cacheLimit: 8 });
    compactSnapshot.initializeSync();

    const overlayResult = evaluateRisk(snapshot, relIdScore, relIdLimit, nodes[0], nodes[3]);
    const compactResult = evaluateRisk(compactSnapshot, relIdScore, relIdLimit, nodes[0], nodes[3]);
    assert.strictEqual(overlayResult, compactResult);

    fs.rmSync(dir, { recursive: true, force: true });
  });
});