src/lib/services/api.ts

// Base API client with fetch wrapper
import {
	API_URL,
	API_TIMEOUT,
	HEADER_AUTHORIZATION,
	HEADER_USER_ID,
	HEADER_CONTENT_TYPE,
	MAX_RETRIES,
	RETRY_DELAY
} from '../utils/constants';
import type {
	Session,
	SessionMetadata,
	ListSessionsResponse,
	CreateSessionRequest,
	CreateSessionResponse,
	SendMessageRequest,
	SendMessageResponse,
	UserProfile,
	APIError,
	ComparisonResult
} from '../types/api';
import type { ClientError } from '../types/client';

class APIClient {
	private baseURL: string;
	private token: string | null = null;
	private userId: string | null = null;

	constructor(baseURL: string = API_URL) {
		this.baseURL = baseURL;
	}

	/**
	 * Set authentication token and user ID
	 */
	setAuth(token: string, userId: string): void {
		this.token = token;
		this.userId = userId;
	}

	/**
	 * Clear authentication
	 */
	clearAuth(): void {
		this.token = null;
		this.userId = null;
	}

	/**
	 * Make HTTP request with retry logic and timeout
	 */
	private async request<T>(
		endpoint: string,
		options: RequestInit = {},
		retries: number = MAX_RETRIES
	): Promise<T> {
		const url = `${this.baseURL}${endpoint}`;

		// Add authentication headers
		const headers: Record<string, string> = {
			[HEADER_CONTENT_TYPE]: 'application/json'
		};

		// Merge existing headers
		if (options.headers) {
			Object.entries(options.headers).forEach(([key, value]) => {
				if (typeof value === 'string') {
					headers[key] = value;
				}
			});
		}

		if (this.token) {
			headers[HEADER_AUTHORIZATION] = `Bearer ${this.token}`;
		}

		if (this.userId && !endpoint.includes('/user/profile')) {
			headers[HEADER_USER_ID] = this.userId;
		}

		// Create abort controller for timeout
		const controller = new AbortController();
		const timeoutId = setTimeout(() => controller.abort(), API_TIMEOUT);

		try {
			const response = await fetch(url, {
				...options,
				headers,
				signal: controller.signal
			});

			clearTimeout(timeoutId);

			if (!response.ok) {
				const error: APIError = await response.json();
				throw this.createClientError(error, response.status, false);
			}

			// Handle 204 No Content
			if (response.status === 204) {
				return {} as T;
			}

			return await response.json();
		} catch (error) {
			clearTimeout(timeoutId);

			// Handle abort/timeout
			if (error instanceof Error && error.name === 'AbortError') {
				if (retries > 0) {
					await this.delay(RETRY_DELAY);
					return this.request<T>(endpoint, options, retries - 1);
				}
				throw this.createClientError(
					{ error: 'Request timeout', status: 408 },
					408,
					true
				);
			}

			// Handle network errors
			if (error instanceof TypeError) {
				if (retries > 0) {
					await this.delay(RETRY_DELAY);
					return this.request<T>(endpoint, options, retries - 1);
				}
				throw this.createClientError(
					{ error: 'Network error', status: 0 },
					0,
					true
				);
			}

			// Re-throw client errors
			if (this.isClientError(error)) {
				throw error;
			}

			// Unknown error
			throw this.createClientError({ error: String(error), status: 500 }, 500, false);
		}
	}

	/**
	 * Create typed client error
	 */
	private createClientError(apiError: APIError, status: number, retryable: boolean): ClientError {
		let type: ClientError['type'] = 'unknown';

		if (status === 401 || status === 403) {
			type = 'auth';
		} else if (status >= 400 && status < 500) {
			type = 'validation';
		} else if (status >= 500) {
			type = 'server';
		} else if (status === 0 || status === 408) {
			type = 'network';
		}

		return {
			message: apiError.error,
			type,
			cause: apiError,
			retryable
		};
	}

	/**
	 * Type guard for ClientError
	 */
	private isClientError(error: unknown): error is ClientError {
		return (
			typeof error === 'object' &&
			error !== null &&
			'message' in error &&
			'type' in error &&
			'retryable' in error
		);
	}

	/**
	 * Delay utility for retry logic
	 */
	private delay(ms: number): Promise<void> {
		return new Promise((resolve) => setTimeout(resolve, ms));
	}

	// Session Management Methods
	async createSession(title: string): Promise<CreateSessionResponse> {
		const request: CreateSessionRequest = {
			title,
			user_id: this.userId || ''
		};

		return this.request<CreateSessionResponse>('/v1/sessions', {
			method: 'POST',
			body: JSON.stringify(request)
		});
	}

	async listSessions(): Promise<SessionMetadata[]> {
		const response = await this.request<ListSessionsResponse>('/v1/sessions', {
			method: 'GET'
		});
		return response.sessions;
	}

	async getSession(sessionId: string): Promise<Session> {
		return this.request<Session>(`/v1/sessions/${sessionId}`, {
			method: 'GET'
		});
	}

	async updateSession(sessionId: string, isReference: boolean): Promise<CreateSessionResponse> {
		return this.request<CreateSessionResponse>(`/v1/sessions/${sessionId}`, {
			method: 'PATCH',
			body: JSON.stringify({ is_reference: isReference })
		});
	}

	async deleteSession(sessionId: string): Promise<void> {
		await this.request<void>(`/v1/sessions/${sessionId}`, {
			method: 'DELETE'
		});
	}

	async sendMessage(
		sessionId: string,
		request: SendMessageRequest
	): Promise<SendMessageResponse> {
		return this.request<SendMessageResponse>(`/v1/sessions/${sessionId}/messages`, {
			method: 'POST',
			body: JSON.stringify(request)
		});
	}

	async compareSession(sessionId: string, referenceSessionId: string): Promise<ComparisonResult> {
		return this.request<ComparisonResult>(
			`/v1/sessions/${sessionId}/compare?reference_id=${referenceSessionId}`,
			{
				method: 'GET'
			}
		);
	}

	async getUserProfile(): Promise<UserProfile> {
		return this.request<UserProfile>('/v1/user/profile', {
			method: 'GET'
		});
	}
}

// Export singleton instance
export const apiClient = new APIClient();