export class API {
	// query resolves into the JSON data produced by the application, or an exception with 'type' and 'error' properties.
	static async query(method, path, request) {
		try {
			const body = JSON.stringify(request)
			const headers = {}

			// Authentication is done with a bearer token.
			// Here provided to the backend if set.
			const token = localStorage.getItem('token')
			if (token) {
				headers.Authorization = `Bearer ${token}`
			}

			const res = await fetch(path, { method, headers, body })
			// An HTTP communication level error occured.
			if (!res.ok || res.status != 200)
				throw new Error('HTTP error', { cause: { type: 'http', error: res, }})

			// Application level response are handled here.
			const json = await res.json()
			if (!json.OK)
				throw new Error(json.Error, { cause: { type: 'application', application: json, }})

			return json

		} catch (err) {
			// Catch any other errors from fetch.
			throw new Error(err.message, { cause: { type: 'http', error: err, }})
		}
	}

	static hasAuthenticationToken() {//{{{
		const token = localStorage.getItem('token')
		return token !== null && token !== ''
	}//}}}
	static authenticate(username, password) {//{{{
		return new Promise((resolve, reject) => {
			const req = { username, password }
			API.query('POST', '/user/authenticate', req)
				.then(response => {
					localStorage.setItem('token', response.Token)
					localStorage.setItem('user', JSON.stringify(response.User))
					resolve(response.User)
				})
				.catch(e => {
					console.log(e.type, e.error)
					reject(e.error)
				})
		})
	}//}}}
	static logout() {//{{{
		localStorage.removeItem('token')
		location.href = '/'
	}//}}}
}