import { mkdirSync, readFileSync, rmSync, writeFileSync } from "fs";
import { tmpdir } from "os";
import { join } from "path";
import { afterEach, beforeEach, describe, expect, it } from "vitest";
import {
  findMostRecentSession,
  loadEntriesFromFile,
  SessionManager,
} from "../../src/core/session-manager.js";

describe("loadEntriesFromFile", () => {
  let tempDir: string;

  beforeEach(() => {
    tempDir = join(tmpdir(), `session-test-${Date.now()}`);
    mkdirSync(tempDir, { recursive: true });
  });

  afterEach(() => {
    rmSync(tempDir, { recursive: true, force: true });
  });

  it("returns empty array for non-existent file", () => {
    const entries = loadEntriesFromFile(join(tempDir, "nonexistent.jsonl"));
    expect(entries).toEqual([]);
  });

  it("returns empty array for empty file", () => {
    const file = join(tempDir, "empty.jsonl");
    writeFileSync(file, "");
    expect(loadEntriesFromFile(file)).toEqual([]);
  });

  it("returns empty array for file without valid session header", () => {
    const file = join(tempDir, "no-header.jsonl");
    writeFileSync(file, '{"type":"message","id":"1"}\n');
    expect(loadEntriesFromFile(file)).toEqual([]);
  });

  it("returns empty array for malformed JSON", () => {
    const file = join(tempDir, "malformed.jsonl");
    writeFileSync(file, "not json\n");
    expect(loadEntriesFromFile(file)).toEqual([]);
  });

  it("loads valid session file", () => {
    const file = join(tempDir, "valid.jsonl");
    writeFileSync(
      file,
      '{"type":"session","id":"abc","timestamp":"2025-01-01T00:00:00Z","cwd":"/tmp"}\n' +
        '{"type":"message","id":"1","parentId":null,"timestamp":"2025-01-01T00:00:01Z","message":{"role":"user","content":"hi","timestamp":1}}\n',
    );
    const entries = loadEntriesFromFile(file);
    expect(entries).toHaveLength(2);
    expect(entries[0].type).toBe("session");
    expect(entries[1].type).toBe("message");
  });

  it("skips malformed lines but keeps valid ones", () => {
    const file = join(tempDir, "mixed.jsonl");
    writeFileSync(
      file,
      '{"type":"session","id":"abc","timestamp":"2025-01-01T00:00:00Z","cwd":"/tmp"}\n' +
        "not valid json\n" +
        '{"type":"message","id":"1","parentId":null,"timestamp":"2025-01-01T00:00:01Z","message":{"role":"user","content":"hi","timestamp":1}}\n',
    );
    const entries = loadEntriesFromFile(file);
    expect(entries).toHaveLength(2);
  });
});

describe("findMostRecentSession", () => {
  let tempDir: string;

  beforeEach(() => {
    tempDir = join(tmpdir(), `session-test-${Date.now()}`);
    mkdirSync(tempDir, { recursive: true });
  });

  afterEach(() => {
    rmSync(tempDir, { recursive: true, force: true });
  });

  it("returns null for empty directory", () => {
    expect(findMostRecentSession(tempDir)).toBeNull();
  });

  it("returns null for non-existent directory", () => {
    expect(findMostRecentSession(join(tempDir, "nonexistent"))).toBeNull();
  });

  it("ignores non-jsonl files", () => {
    writeFileSync(join(tempDir, "file.txt"), "hello");
    writeFileSync(join(tempDir, "file.json"), "{}");
    expect(findMostRecentSession(tempDir)).toBeNull();
  });

  it("ignores jsonl files without valid session header", () => {
    writeFileSync(join(tempDir, "invalid.jsonl"), '{"type":"message"}\n');
    expect(findMostRecentSession(tempDir)).toBeNull();
  });

  it("returns single valid session file", () => {
    const file = join(tempDir, "session.jsonl");
    writeFileSync(
      file,
      '{"type":"session","id":"abc","timestamp":"2025-01-01T00:00:00Z","cwd":"/tmp"}\n',
    );
    expect(findMostRecentSession(tempDir)).toBe(file);
  });

  it("returns most recently modified session", async () => {
    const file1 = join(tempDir, "older.jsonl");
    const file2 = join(tempDir, "newer.jsonl");

    writeFileSync(
      file1,
      '{"type":"session","id":"old","timestamp":"2025-01-01T00:00:00Z","cwd":"/tmp"}\n',
    );
    // Small delay to ensure different mtime
    await new Promise((r) => setTimeout(r, 10));
    writeFileSync(
      file2,
      '{"type":"session","id":"new","timestamp":"2025-01-01T00:00:00Z","cwd":"/tmp"}\n',
    );

    expect(findMostRecentSession(tempDir)).toBe(file2);
  });

  it("skips invalid files and returns valid one", async () => {
    const invalid = join(tempDir, "invalid.jsonl");
    const valid = join(tempDir, "valid.jsonl");

    writeFileSync(invalid, '{"type":"not-session"}\n');
    await new Promise((r) => setTimeout(r, 10));
    writeFileSync(
      valid,
      '{"type":"session","id":"abc","timestamp":"2025-01-01T00:00:00Z","cwd":"/tmp"}\n',
    );

    expect(findMostRecentSession(tempDir)).toBe(valid);
  });
});

describe("SessionManager.setSessionFile with corrupted files", () => {
  let tempDir: string;

  beforeEach(() => {
    tempDir = join(tmpdir(), `session-test-${Date.now()}`);
    mkdirSync(tempDir, { recursive: true });
  });

  afterEach(() => {
    rmSync(tempDir, { recursive: true, force: true });
  });

  it("truncates and rewrites empty file with valid header", () => {
    const emptyFile = join(tempDir, "empty.jsonl");
    writeFileSync(emptyFile, "");

    const sm = SessionManager.open(emptyFile, tempDir);

    // Should have created a new session with valid header
    expect(sm.getSessionId()).toBeTruthy();
    expect(sm.getHeader()).toBeTruthy();
    expect(sm.getHeader()?.type).toBe("session");

    // File should now contain a valid header
    const content = readFileSync(emptyFile, "utf-8");
    const lines = content.trim().split("\n").filter(Boolean);
    expect(lines.length).toBe(1);
    const header = JSON.parse(lines[0]);
    expect(header.type).toBe("session");
    expect(header.id).toBe(sm.getSessionId());
  });

  it("truncates and rewrites file without valid header", () => {
    const noHeaderFile = join(tempDir, "no-header.jsonl");
    // File with messages but no session header (corrupted state)
    writeFileSync(
      noHeaderFile,
      '{"type":"message","id":"abc","parentId":"orphaned","timestamp":"2025-01-01T00:00:00Z","message":{"role":"assistant","content":"test"}}\n',
    );

    const sm = SessionManager.open(noHeaderFile, tempDir);

    // Should have created a new session with valid header
    expect(sm.getSessionId()).toBeTruthy();
    expect(sm.getHeader()).toBeTruthy();
    expect(sm.getHeader()?.type).toBe("session");

    // File should now contain only a valid header (old content truncated)
    const content = readFileSync(noHeaderFile, "utf-8");
    const lines = content.trim().split("\n").filter(Boolean);
    expect(lines.length).toBe(1);
    const header = JSON.parse(lines[0]);
    expect(header.type).toBe("session");
    expect(header.id).toBe(sm.getSessionId());
  });

  it("preserves explicit session file path when recovering from corrupted file", () => {
    const explicitPath = join(tempDir, "my-session.jsonl");
    writeFileSync(explicitPath, "");

    const sm = SessionManager.open(explicitPath, tempDir);

    // The session file path should be preserved
    expect(sm.getSessionFile()).toBe(explicitPath);
  });

  it("subsequent loads of recovered file work correctly", () => {
    const corruptedFile = join(tempDir, "corrupted.jsonl");
    writeFileSync(corruptedFile, "garbage content\n");

    // First open recovers the file
    const sm1 = SessionManager.open(corruptedFile, tempDir);
    const sessionId = sm1.getSessionId();

    // Second open should load the recovered file successfully
    const sm2 = SessionManager.open(corruptedFile, tempDir);
    expect(sm2.getSessionId()).toBe(sessionId);
    expect(sm2.getHeader()?.type).toBe("session");
  });
});
