/**
 * Content Item Fixture Generator
 *
 * Provides type-safe helpers for creating ContentItem objects in tests.
 */

import type { ContentItem } from '@wavespec/types';

/**
 * Content type discriminator
 */
export type ContentType = 'text' | 'image' | 'resource';

/**
 * Creates a ContentItem with type-specific defaults
 *
 * Generates a complete ContentItem object with sensible defaults based on the content type.
 * Override any field via the overrides parameter.
 *
 * @param type - Content type (text, image, resource)
 * @param overrides - Partial ContentItem to override defaults
 * @returns Complete ContentItem object
 *
 * @example
 * ```typescript
 * // Text content
 * const text = createContentItem('text', {
 *   text: 'Hello, world!',
 *   mimeType: 'text/plain'
 * });
 *
 * // Image content with base64 data
 * const image = createContentItem('image', {
 *   data: 'iVBORw0KGgoAAAANSUhEUgA...',
 *   mimeType: 'image/png'
 * });
 *
 * // Resource content
 * const resource = createContentItem('resource', {
 *   data: 'eyJuYW1lIjoiQWxpY2UifQ==',
 *   mimeType: 'application/json'
 * });
 * ```
 */
export function createContentItem(
	type: ContentType,
	overrides: Partial<ContentItem> = {}
): ContentItem {
	const base: ContentItem = {
		type,
		...overrides,
	};

	// Apply type-specific defaults if fields not provided
	switch (type) {
		case 'text':
			return {
				...base,
				text: overrides.text ?? 'Sample text content',
				mimeType: overrides.mimeType ?? 'text/plain',
			};

		case 'image':
			return {
				...base,
				data: overrides.data ?? 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==', // 1x1 transparent PNG
				mimeType: overrides.mimeType ?? 'image/png',
			};

		case 'resource':
			return {
				...base,
				data: overrides.data ?? 'eyJzYW1wbGUiOiJkYXRhIn0=', // {"sample":"data"} in base64
				mimeType: overrides.mimeType ?? 'application/octet-stream',
			};

		default:
			// TypeScript exhaustiveness check
			const _exhaustive: never = type;
			throw new Error(`Unknown content type: ${_exhaustive}`);
	}
}

/**
 * Helper: Creates a text ContentItem
 *
 * @param text - Text content
 * @param mimeType - MIME type (default: "text/plain")
 * @returns Text ContentItem
 *
 * @example
 * ```typescript
 * const text = text('Hello, world!');
 * const markdown = text('# Title', 'text/markdown');
 * const json = text('{"key": "value"}', 'application/json');
 * ```
 */
export function text(text: string, mimeType = 'text/plain'): ContentItem {
	return createContentItem('text', { text, mimeType });
}

/**
 * Helper: Creates an image ContentItem
 *
 * @param data - Base64-encoded image data
 * @param mimeType - MIME type (default: "image/png")
 * @returns Image ContentItem
 *
 * @example
 * ```typescript
 * const png = image('iVBORw0KGgoAAAANSUhEUgA...');
 * const jpg = image('data...', 'image/jpeg');
 * ```
 */
export function image(data: string, mimeType = 'image/png'): ContentItem {
	return createContentItem('image', { data, mimeType });
}

/**
 * Helper: Creates a resource ContentItem
 *
 * @param data - Base64-encoded resource data
 * @param mimeType - MIME type (default: "application/octet-stream")
 * @returns Resource ContentItem
 *
 * @example
 * ```typescript
 * const binary = resource('SGVsbG8gV29ybGQh'); // "Hello World!" in base64
 * const json = resource('eyJrZXkiOiJ2YWx1ZSJ9', 'application/json');
 * ```
 */
export function resource(data: string, mimeType = 'application/octet-stream'): ContentItem {
	return createContentItem('resource', { data, mimeType });
}

/**
 * Helper: Creates a JSON text ContentItem from an object
 *
 * @param obj - Object to serialize as JSON
 * @returns Text ContentItem with JSON MIME type
 *
 * @example
 * ```typescript
 * const jsonContent = json({ name: 'Alice', age: 30 });
 * // Returns: { type: 'text', text: '{"name":"Alice","age":30}', mimeType: 'application/json' }
 * ```
 */
export function json(obj: unknown): ContentItem {
	return text(JSON.stringify(obj), 'application/json');
}