import { describe, it, expect, beforeEach, afterEach } from "vitest";
import { MetadataCache } from "../../src/server/services/metadata-cache.js";
import type { CacheEntry } from "../../src/server/services/metadata-cache.js";
import fs from "fs/promises";
import path from "path";
import os from "os";

function makeCacheEntry(overrides: Partial<CacheEntry> = {}): CacheEntry {
  return {
    mtimeMs: 1700000000000,
    size: 1024,
    messageCount: 5,
    firstPrompt: "Hello",
    summary: "Session summary",
    firstTimestamp: "2025-01-01T10:00:00Z",
    lastTimestamp: "2025-01-01T11:00:00Z",
    ...overrides,
  };
}

describe("MetadataCache", () => {
  let tmpDir: string;
  let cachePath: string;

  beforeEach(async () => {
    tmpDir = path.join(os.tmpdir(), `sv-cache-test-${Date.now()}`);
    await fs.mkdir(tmpDir, { recursive: true });
    cachePath = path.join(tmpDir, "metadata.json");
  });

  afterEach(async () => {
    await fs.rm(tmpDir, { recursive: true, force: true });
  });

  it("returns null for unknown file path", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();
    expect(cache.get("/unknown/path.jsonl", 1000, 500)).toBeNull();
  });

  it("returns entry when mtimeMs and size match", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();

    const entry = makeCacheEntry({ mtimeMs: 1000, size: 500 });
    cache.set("/test/session.jsonl", entry);

    const result = cache.get("/test/session.jsonl", 1000, 500);
    expect(result).not.toBeNull();
    expect(result!.messageCount).toBe(5);
    expect(result!.firstPrompt).toBe("Hello");
  });

  it("returns null when mtimeMs differs", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();

    const entry = makeCacheEntry({ mtimeMs: 1000, size: 500 });
    cache.set("/test/session.jsonl", entry);

    expect(cache.get("/test/session.jsonl", 2000, 500)).toBeNull();
  });

  it("returns null when size differs", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();

    const entry = makeCacheEntry({ mtimeMs: 1000, size: 500 });
    cache.set("/test/session.jsonl", entry);

    expect(cache.get("/test/session.jsonl", 1000, 999)).toBeNull();
  });

  it("save is no-op when not dirty", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();
    await cache.save();

    // File should not exist since nothing was set
    await expect(fs.access(cachePath)).rejects.toThrow();
  });

  it("save writes to disk when dirty", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();

    cache.set("/test/session.jsonl", makeCacheEntry());
    await cache.save();

    const raw = await fs.readFile(cachePath, "utf-8");
    const parsed = JSON.parse(raw);
    expect(parsed.version).toBe(1);
    expect(parsed.entries["/test/session.jsonl"]).toBeDefined();
    expect(parsed.entries["/test/session.jsonl"].messageCount).toBe(5);
  });

  it("save prunes entries not in existingPaths", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();

    cache.set("/test/a.jsonl", makeCacheEntry());
    cache.set("/test/b.jsonl", makeCacheEntry());
    cache.set("/test/c.jsonl", makeCacheEntry());

    const existingPaths = new Set(["/test/a.jsonl", "/test/c.jsonl"]);
    await cache.save(existingPaths);

    const raw = await fs.readFile(cachePath, "utf-8");
    const parsed = JSON.parse(raw);
    expect(Object.keys(parsed.entries)).toHaveLength(2);
    expect(parsed.entries["/test/b.jsonl"]).toBeUndefined();
  });

  it("load handles missing cache file", async () => {
    const cache = new MetadataCache(
      path.join(tmpDir, "nonexistent", "cache.json")
    );
    await cache.load();
    expect(cache.get("/test/session.jsonl", 1000, 500)).toBeNull();
  });

  it("load handles corrupt cache file", async () => {
    await fs.writeFile(cachePath, "not valid json {{{");
    const cache = new MetadataCache(cachePath);
    await cache.load();
    expect(cache.get("/test/session.jsonl", 1000, 500)).toBeNull();
  });

  it("persists and reloads across instances", async () => {
    const cache1 = new MetadataCache(cachePath);
    await cache1.load();
    cache1.set("/test/session.jsonl", makeCacheEntry({ mtimeMs: 42, size: 100 }));
    await cache1.save();

    const cache2 = new MetadataCache(cachePath);
    await cache2.load();
    const result = cache2.get("/test/session.jsonl", 42, 100);
    expect(result).not.toBeNull();
    expect(result!.messageCount).toBe(5);
  });

  it("isDirty returns false initially, true after set", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();
    expect(cache.isDirty()).toBe(false);

    cache.set("/test/session.jsonl", makeCacheEntry());
    expect(cache.isDirty()).toBe(true);
  });

  it("isDirty resets to false after save", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();
    cache.set("/test/session.jsonl", makeCacheEntry());
    expect(cache.isDirty()).toBe(true);

    await cache.save();
    expect(cache.isDirty()).toBe(false);
  });

  it("flush writes without pruning", async () => {
    const cache = new MetadataCache(cachePath);
    await cache.load();

    cache.set("/test/a.jsonl", makeCacheEntry());
    cache.set("/test/b.jsonl", makeCacheEntry());
    await cache.flush();

    const raw = await fs.readFile(cachePath, "utf-8");
    const parsed = JSON.parse(raw);
    // Both should be present (no pruning on flush)
    expect(Object.keys(parsed.entries)).toHaveLength(2);
  });
});