// fetch.ts
// Copyright (C) 2020  Dwayne Harris

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

import {
    UnauthorizedError,
    BadRequestError,
    NotFoundError,
    ServerError,
} from './errors'

import { pathJoin } from '../utils'

import {
    LOCAL_STORAGE_ACCESS_TOKEN_KEY,
    LOCAL_STORAGE_ACCESS_TOKEN_EXPIRES_AT_KEY,
    LOCAL_STORAGE_REFRESH_TOKEN_KEY,
} from '../constants'

import { FetchOptions, FormNotification, NotificationType } from '../types'

interface RefreshResponse {
    id: string
    access: string
    refresh: string
    expires: number
}

interface FormError {
    field?: string
    message: string
}

interface ErrorResponse {
    message: string
    errors?: FormError[]
}

type APIFetch = <T = void>(options: FetchOptions) => Promise<T>

const mapErrorsToFormNotifications = (errors?: FormError[]): FormNotification[] => {
    if (!errors) return []
    
    return errors.map(e => ({
        field: e.field,
        type: NotificationType.Error,
        message: e.message,
    }))
}

const checkResponse = async (response: Response, retry?: () => Promise<void>) => {
    switch (response.status) {
        case 400: {
            const { message, errors } = await response.json() as ErrorResponse
            throw new BadRequestError(message, mapErrorsToFormNotifications(errors))
        }
        case 401: {
            if (retry) return await retry()
            throw new UnauthorizedError()
        }
        case 404: throw new NotFoundError()
        default: {
            throw new ServerError()
        }
    }
}

const getResponseData = async (response: Response) => {
    try {
        return await response.json()
    } catch (err) {
        return {}
    }
}

export const apiFetch: APIFetch = async (options: FetchOptions) => {
    const { path, method = 'get', body } = options
    const contentType = 'application/json'

    const doFetch = async () => {
        const headers = new Headers({
            ...options.headers,
            'Accept': contentType,
        })

        if (body) headers.append('Content-Type', contentType)

        const accessToken = localStorage.getItem(LOCAL_STORAGE_ACCESS_TOKEN_KEY)
        if (accessToken) headers.append('Authorization', `Bearer ${accessToken}`)

        return await fetch(`/${pathJoin('api', path)}`, {
            headers,
            method,
            body: body ? JSON.stringify(body) : undefined,
        })
    }

    const doRefresh = async () => {
        const accessToken = localStorage.getItem(LOCAL_STORAGE_ACCESS_TOKEN_KEY)
        const refreshToken = localStorage.getItem(LOCAL_STORAGE_REFRESH_TOKEN_KEY)

        if (accessToken && refreshToken) {
            const refreshResponse = await fetch('/api/v1/refresh', {
                headers: new Headers({
                    'Content-Type': contentType,
                    'Authorization': `Bearer ${accessToken}`
                }),
                method: 'post',
                body: JSON.stringify({
                    refresh: refreshToken,
                }),
            })

            if (refreshResponse.status !== 201) {
                throw new UnauthorizedError()
            }

            const data = await getResponseData(refreshResponse) as RefreshResponse

            localStorage.setItem(LOCAL_STORAGE_ACCESS_TOKEN_KEY, data.access)
            localStorage.setItem(LOCAL_STORAGE_ACCESS_TOKEN_EXPIRES_AT_KEY, data.expires.toString())
            localStorage.setItem(LOCAL_STORAGE_REFRESH_TOKEN_KEY, data.refresh)

            const secondResponse = await doFetch()
            if (secondResponse.ok) {
                return await getResponseData(secondResponse)
            }

            await checkResponse(secondResponse)
        }
    }

    const accessTokenExpiresAt = localStorage.getItem(LOCAL_STORAGE_ACCESS_TOKEN_EXPIRES_AT_KEY)
    if (accessTokenExpiresAt && Date.now() >= parseInt(accessTokenExpiresAt, 10)) {
        return await doRefresh()
    }

    const response = await doFetch()
    if (response.ok) {
        return await getResponseData(response)
    }

    return await checkResponse(response, doRefresh)
}