import { afterEach, describe, expect, it } from 'vitest';
import * as fs from 'fs';
import * as os from 'os';
import * as path from 'path';
import { CodeGraph } from '../src';
import { oversizeStamp, hashContent } from '../src/extraction';
import { hasDriftedOnDisk, readFileShape } from '../src/ui-server/api/source';
import { ToolHandler } from '../src/mcp/tools';
import { validateAnswerFiles } from '../src/mcp/answer-freshness';

/**
 * A file over the size limit is stored as skipped without ever being read
 * (#1910): committed video/blob fixtures used to be decoded in full — and
 * hashed — only to be discarded, costing their size in RSS per file.
 */
describe('oversize files are stat-gated, never read (#1910)', () => {
  let dir: string;
  afterEach(() => { if (dir) fs.rmSync(dir, { recursive: true, force: true }); });

  const big = (bytes: number, fill = 0x41) => Buffer.alloc(bytes, fill);

  it('indexes the neighbours, records the oversize file as skipped with a size-stamp hash, and does not decode it', async () => {
    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-oversize-'));
    fs.writeFileSync(path.join(dir, 'app.ts'), 'export function alpha() { return beta(); }\nexport function beta() { return 1; }\n');
    // 1 MB + 1: over the limit; invalid UTF-8 (0xFF) so any decode would be visible as replacement chars.
    fs.writeFileSync(path.join(dir, 'blob.ts'), big(1024 * 1024 + 1, 0xff));
    const cg = await CodeGraph.init(dir, { index: true });
    try {
      expect(cg.getNodesByKind('function').map(n => n.name).sort()).toEqual(['alpha', 'beta']);
      const rec = cg.getFiles().find(f => f.path === 'blob.ts');
      expect(rec).toBeDefined();
      expect(rec!.contentHash).toBe(hashContent(oversizeStamp(1024 * 1024 + 1)));
      // Nothing from the blob reached the graph.
      expect(cg.getNodesInFile('blob.ts').filter(n => n.kind !== 'file')).toEqual([]);
      // Change detection agrees with what was stored: nothing pending.
      expect(cg.getChangedFiles()).toEqual({ added: [], modified: [], removed: [] });
      // A same-size rewrite is not a change (nothing about it is indexed)...
      fs.writeFileSync(path.join(dir, 'blob.ts'), big(1024 * 1024 + 1, 0xfe));
      expect(cg.getChangedFiles().modified).toEqual([]);
      // ...crossing the limit is: the file becomes ordinary source.
      fs.writeFileSync(path.join(dir, 'blob.ts'), 'export const gamma = 3;\n');
      expect(cg.getChangedFiles().modified).toEqual(['blob.ts']);
      await cg.sync();
      expect(cg.getNodesInFile('blob.ts').some(n => n.name === 'gamma')).toBe(true);
      // ...and growing back over it is a change too, stored as the stamp again.
      fs.writeFileSync(path.join(dir, 'blob.ts'), big(2 * 1024 * 1024, 0xff));
      expect(cg.getChangedFiles().modified).toEqual(['blob.ts']);
      await cg.sync();
      expect(cg.getFiles().find(f => f.path === 'blob.ts')!.contentHash).toBe(hashContent(oversizeStamp(2 * 1024 * 1024)));
      expect(cg.getNodesInFile('blob.ts').some(n => n.name === 'gamma')).toBe(false);
    } finally {
      cg.close();
    }
  });

  it('a 400 MB sparse fixture indexes in well under a second and without growing the heap by its size', async () => {
    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-oversize-big-'));
    fs.writeFileSync(path.join(dir, 'ok.ts'), 'export const one = 1;\n');
    // Sparse: occupies no disk, but stat() reports 400 MB — a read would decode all of it.
    const fd = fs.openSync(path.join(dir, 'huge.ts'), 'w');
    fs.ftruncateSync(fd, 400 * 1024 * 1024);
    fs.closeSync(fd);
    // Warm the engine on a sibling project first, so the grammar and worker
    // start-up cost is not mistaken for the file being read.
    const warm = fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-oversize-warm-'));
    fs.writeFileSync(path.join(warm, 'w.ts'), 'export const w = 1;\n');
    (await CodeGraph.init(warm, { index: true })).close();
    fs.rmSync(warm, { recursive: true, force: true });
    const before = process.memoryUsage().rss;
    const t0 = Date.now();
    const cg = await CodeGraph.init(dir, { index: true });
    try {
      expect(Date.now() - t0).toBeLessThan(5000);
      // Reading 400 MB would show as at least that much RSS; the stamp shows as none.
      expect(process.memoryUsage().rss - before).toBeLessThan(100 * 1024 * 1024);
      expect(cg.getFiles().map(f => f.path).sort()).toEqual(['huge.ts', 'ok.ts']);
      expect(cg.getChangedFiles()).toEqual({ added: [], modified: [], removed: [] });
    } finally {
      cg.close();
    }
  });
});

describe('an unchanged file over the size limit is not reported as drifted (#1910, #1915 review)', () => {
  let dir: string;
  afterEach(() => { if (dir) fs.rmSync(dir, { recursive: true, force: true }); });

  it('reads as current in the viewer and in MCP until its size changes', async () => {
    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'codegraph-oversize-drift-'));
    fs.writeFileSync(path.join(dir, 'app.ts'), 'export function alpha() { return 1; }\n');
    // 1.4 MB of ordinary text: over the index limit, under the viewer's 8 MB read cap.
    // Each line differs: Windows Defender's script scan of a freshly written `.js`
    // made of one statement repeated 110k times takes close to a minute on the
    // first read, so the viewer's read below blew the test timeout there. Real
    // code of the same size is scanned in milliseconds.
    const line = 'const last = 0;\n';
    const lines: string[] = [];
    for (let size = 0, i = 0; size < 1.4 * 1024 * 1024; i++) {
      lines.push(`const x${i} = ${i};\n`);
      size += lines[i]!.length;
    }
    fs.writeFileSync(path.join(dir, 'big.js'), lines.join(''));
    const cg = await CodeGraph.init(dir, { index: true });
    try {
      const record = cg.getFiles().find((f) => f.path === 'big.js')!;
      expect(record).toBeDefined();
      // Touch it: the stat fast path no longer answers, so the hash has to.
      const later = new Date(Date.now() + 5000);
      fs.utimesSync(path.join(dir, 'big.js'), later, later);

      expect(readFileShape(dir, 'big.js', record).drift).toBe(false);
      expect(hasDriftedOnDisk(dir, 'big.js', record)).toBe(false);
      expect((new ToolHandler(cg) as any).isFileStaleOnDisk(cg, 'big.js')).toBe(false);
      const answer = [{ path: 'big.js', contentHash: record.contentHash }];
      expect((await validateAnswerFiles(dir, answer)).stale).toEqual([]);

      // A different size is a different stamp, and that is drift.
      fs.appendFileSync(path.join(dir, 'big.js'), line);
      expect(readFileShape(dir, 'big.js', record).drift).toBe(true);
      expect(hasDriftedOnDisk(dir, 'big.js', record)).toBe(true);
      expect((await validateAnswerFiles(dir, answer)).stale).toEqual(['big.js']);
    } finally {
      cg.close();
    }
  });
});