import { describe, it, expect, afterEach } from 'vitest';
import { mkdirSync, writeFileSync, rmSync, mkdtempSync, existsSync } from 'fs';
import { join } from 'path';
import { tmpdir } from 'os';
import { SkillInstaller } from './installer.js';

describe('SkillInstaller', () => {
  // Objective: verify that the installer correctly copies, upgrades, and
  // removes skill directories in the managed area.

  const tmpDirs: string[] = [];

  /** Create a temp directory and track it for cleanup. */
  function makeTmpDir(): string {
    const dir = mkdtempSync(join(tmpdir(), 'flynn-test-'));
    tmpDirs.push(dir);
    return dir;
  }

  /** Create a minimal source skill directory with SKILL.md and optional manifest. */
  function makeSourceSkill(
    parentDir: string,
    dirName: string,
    options: { manifest?: Record<string, unknown>; instructions?: string } = {},
  ): string {
    const skillDir = join(parentDir, dirName);
    mkdirSync(skillDir, { recursive: true });
    writeFileSync(join(skillDir, 'SKILL.md'), options.instructions ?? `# ${dirName}\nDefault instructions.`);
    if (options.manifest) {
      writeFileSync(join(skillDir, 'manifest.json'), JSON.stringify(options.manifest));
    }
    return skillDir;
  }

  afterEach(() => {
    for (const dir of tmpDirs) {
      rmSync(dir, { recursive: true, force: true });
    }
    tmpDirs.length = 0;
  });

  it('creates managedDir in constructor if it does not exist', () => {
    // Positive: the constructor should ensure the managed directory exists.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed', 'nested');

    new SkillInstaller(managedDir);

    expect(existsSync(managedDir)).toBe(true);
  });

  it('installs a skill from a source directory', () => {
    // Positive: install should copy SKILL.md and return a loaded Skill.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceDir = makeSourceSkill(tmp, 'my-skill', {
      manifest: { name: 'my-skill', description: 'A skill', version: '1.0.0' },
      instructions: '# My Skill\nDo the thing.',
    });

    const installer = new SkillInstaller(managedDir);
    const skill = installer.install(sourceDir);

    expect(skill).not.toBeNull();
    expect(skill!.manifest.name).toBe('my-skill');
    expect(skill!.instructions).toBe('# My Skill\nDo the thing.');
    expect(existsSync(join(managedDir, 'my-skill', 'SKILL.md'))).toBe(true);
  });

  it('installed skill has tier "managed"', () => {
    // Positive: regardless of source manifest, installed skill tier must be 'managed'.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceDir = makeSourceSkill(tmp, 'tier-skill', {
      manifest: { name: 'tier-skill', description: 'Tier test', version: '1.0.0', tier: 'bundled' },
    });

    const installer = new SkillInstaller(managedDir);
    const skill = installer.install(sourceDir);

    expect(skill).not.toBeNull();
    expect(skill!.manifest.tier).toBe('managed');
  });

  it('uses manifest.json name field for the installed directory name', () => {
    // Positive: directory in managed area should match manifest name, not source dirname.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceDir = makeSourceSkill(tmp, 'source-dirname', {
      manifest: { name: 'manifest-name', description: 'Named via manifest', version: '1.0.0' },
    });

    const installer = new SkillInstaller(managedDir);
    installer.install(sourceDir);

    expect(existsSync(join(managedDir, 'manifest-name', 'SKILL.md'))).toBe(true);
    expect(existsSync(join(managedDir, 'source-dirname'))).toBe(false);
  });

  it('falls back to basename when no manifest.json is present', () => {
    // Positive: without manifest.json, directory name should come from source basename.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceDir = makeSourceSkill(tmp, 'fallback-name');
    // No manifest.json written

    const installer = new SkillInstaller(managedDir);
    installer.install(sourceDir);

    expect(existsSync(join(managedDir, 'fallback-name', 'SKILL.md'))).toBe(true);
  });

  it('upgrades an existing skill by replacing it', () => {
    // Positive: re-installing should overwrite the old version.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceV1 = makeSourceSkill(tmp, 'v1-source', {
      manifest: { name: 'upgradable', description: 'Version 1', version: '1.0.0' },
      instructions: '# V1',
    });

    const installer = new SkillInstaller(managedDir);
    installer.install(sourceV1);

    // Create v2 source
    const sourceV2 = makeSourceSkill(tmp, 'v2-source', {
      manifest: { name: 'upgradable', description: 'Version 2', version: '2.0.0' },
      instructions: '# V2',
    });

    const skill = installer.install(sourceV2);

    expect(skill).not.toBeNull();
    expect(skill!.manifest.version).toBe('2.0.0');
    expect(skill!.instructions).toBe('# V2');
  });

  it('throws when source directory does not exist', () => {
    // Negative: install should throw a descriptive error for missing sources.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const installer = new SkillInstaller(managedDir);

    expect(() => installer.install('/tmp/does-not-exist-xyz-abc-123')).toThrow(
      'Source directory does not exist',
    );
  });

  it('throws when source directory has no SKILL.md', () => {
    // Negative: install should throw when SKILL.md is missing.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const emptyDir = join(tmp, 'empty-skill');
    mkdirSync(emptyDir);

    const installer = new SkillInstaller(managedDir);

    expect(() => installer.install(emptyDir)).toThrow('does not contain SKILL.md');
  });

  it('uninstalls a skill', () => {
    // Positive: uninstall should remove the directory and return true.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceDir = makeSourceSkill(tmp, 'removable', {
      manifest: { name: 'removable', description: 'Will be removed', version: '1.0.0' },
    });

    const installer = new SkillInstaller(managedDir);
    installer.install(sourceDir);

    const result = installer.uninstall('removable');

    expect(result).toBe(true);
    expect(existsSync(join(managedDir, 'removable'))).toBe(false);
  });

  it('returns false when uninstalling a nonexistent skill', () => {
    // Negative: uninstalling a name that was never installed should return false.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const installer = new SkillInstaller(managedDir);

    expect(installer.uninstall('ghost')).toBe(false);
  });

  it('listInstalled lists all installed skills', () => {
    // Positive: every installed skill should appear in the list.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceA = makeSourceSkill(tmp, 'skill-a', {
      manifest: { name: 'skill-a', description: 'Skill A', version: '1.0.0' },
    });
    const sourceB = makeSourceSkill(tmp, 'skill-b', {
      manifest: { name: 'skill-b', description: 'Skill B', version: '1.0.0' },
    });

    const installer = new SkillInstaller(managedDir);
    installer.install(sourceA);
    installer.install(sourceB);

    const installed = installer.listInstalled();

    expect(installed).toHaveLength(2);
    expect(installed).toContain('skill-a');
    expect(installed).toContain('skill-b');
  });

  it('isInstalled checks correctly', () => {
    // Positive/Negative: should return true for installed, false for not installed.
    const tmp = makeTmpDir();
    const managedDir = join(tmp, 'managed');
    const sourceDir = makeSourceSkill(tmp, 'check-me', {
      manifest: { name: 'check-me', description: 'Check me', version: '1.0.0' },
    });

    const installer = new SkillInstaller(managedDir);
    installer.install(sourceDir);

    expect(installer.isInstalled('check-me')).toBe(true);
    expect(installer.isInstalled('not-installed')).toBe(false);
  });
});