/**
 * Unit tests for ShareableURL logic
 * Validates: Requirements 25.1, 25.2, 25.3, 25.4, 25.5
 */

import { describe, it, expect, beforeEach } from 'vitest';

// ─── Pure logic extracted from ShareableURL for testability ─────────────

const HASH_PREFIX = '#model=';

/**
 * Parse a hash string and return the model ID, or null.
 * @param {string} hash - e.g. "#model=ppe"
 * @returns {string|null}
 */
function parseHash(hash) {
  if (!hash || !hash.startsWith(HASH_PREFIX)) {
    return null;
  }
  const raw = hash.substring(HASH_PREFIX.length);
  const decoded = decodeURIComponent(raw).trim();
  return decoded || null;
}

/**
 * Build a hash string from a model ID.
 * @param {string} modelId
 * @returns {string}
 */
function buildHash(modelId) {
  return HASH_PREFIX + encodeURIComponent(modelId);
}

/**
 * Find a model by ID in a list.
 * @param {Array<{id: string}>} modelList
 * @param {string} modelId
 * @returns {object|null}
 */
function findModelById(modelList, modelId) {
  if (!modelList || !modelId) return null;
  return modelList.find((m) => m.id === modelId) || null;
}

/**
 * Validate a hash against a model list. Returns the model or an error.
 * @param {string} hash
 * @param {Array<{id: string}>} modelList
 * @returns {{ model: object|null, error: string|null }}
 */
function validateHash(hash, modelList) {
  const modelId = parseHash(hash);
  if (!modelId) {
    return { model: null, error: null };
  }
  const model = findModelById(modelList, modelId);
  if (!model) {
    return {
      model: null,
      error: `Model "${modelId}" not found. The shared link may be outdated or invalid.`
    };
  }
  return { model, error: null };
}

// ─── Test Data ──────────────────────────────────────────────────────────

const SAMPLE_MODELS = [
  { id: 'jsl', name: 'JSL Model', path: 'models/jsl/model.onnx' },
  { id: 'ppe', name: 'PPE Detection Model', path: 'models/ppe/model.onnx' },
  { id: 'vsl', name: 'VSL Model', path: 'models/vsl/model.onnx' },
];

// ─── Tests ──────────────────────────────────────────────────────────────

describe('ShareableURL - parseHash', () => {
  it('should return null for empty hash', () => {
    expect(parseHash('')).toBeNull();
    expect(parseHash(null)).toBeNull();
    expect(parseHash(undefined)).toBeNull();
  });

  it('should return null for hash without model= prefix', () => {
    expect(parseHash('#other=value')).toBeNull();
    expect(parseHash('#')).toBeNull();
    expect(parseHash('#model')).toBeNull();
  });

  it('should parse a valid model hash', () => {
    expect(parseHash('#model=ppe')).toBe('ppe');
    expect(parseHash('#model=jsl')).toBe('jsl');
  });

  it('should decode URI-encoded model IDs', () => {
    expect(parseHash('#model=my%20model')).toBe('my model');
  });

  it('should return null for #model= with empty value', () => {
    expect(parseHash('#model=')).toBeNull();
    expect(parseHash('#model=   ')).toBeNull();
  });
});

describe('ShareableURL - buildHash', () => {
  it('should build a valid hash string', () => {
    expect(buildHash('ppe')).toBe('#model=ppe');
    expect(buildHash('jsl')).toBe('#model=jsl');
  });

  it('should encode special characters', () => {
    const hash = buildHash('my model');
    expect(hash).toBe('#model=my%20model');
  });
});

describe('ShareableURL - round-trip', () => {
  it('should round-trip a model ID through build and parse', () => {
    const ids = ['ppe', 'jsl', 'vsl', 'some-id'];
    ids.forEach((id) => {
      const hash = buildHash(id);
      expect(parseHash(hash)).toBe(id);
    });
  });
});

describe('ShareableURL - findModelById', () => {
  it('should find a model by ID', () => {
    const result = findModelById(SAMPLE_MODELS, 'ppe');
    expect(result).not.toBeNull();
    expect(result.id).toBe('ppe');
  });

  it('should return null for unknown ID', () => {
    expect(findModelById(SAMPLE_MODELS, 'unknown')).toBeNull();
  });

  it('should return null for null/empty inputs', () => {
    expect(findModelById(null, 'ppe')).toBeNull();
    expect(findModelById(SAMPLE_MODELS, null)).toBeNull();
    expect(findModelById(SAMPLE_MODELS, '')).toBeNull();
  });
});

describe('ShareableURL - validateHash', () => {
  it('should return model for valid hash with known ID', () => {
    const { model, error } = validateHash('#model=ppe', SAMPLE_MODELS);
    expect(error).toBeNull();
    expect(model).not.toBeNull();
    expect(model.id).toBe('ppe');
  });

  it('should return error for valid hash with unknown ID (Req 25.4)', () => {
    const { model, error } = validateHash('#model=nonexistent', SAMPLE_MODELS);
    expect(model).toBeNull();
    expect(error).toContain('nonexistent');
    expect(error).toContain('not found');
  });

  it('should return null model and no error for empty hash', () => {
    const { model, error } = validateHash('', SAMPLE_MODELS);
    expect(model).toBeNull();
    expect(error).toBeNull();
  });

  it('should return null model and no error for non-model hash', () => {
    const { model, error } = validateHash('#other=value', SAMPLE_MODELS);
    expect(model).toBeNull();
    expect(error).toBeNull();
  });
});