require 'base64'
require 'openssl'
require 'net/http'
require 'json'

module Zzlink
  # Error.
  class Error < StandardError
    def initialize(code, error)
      super("#{code}: #{error}")
    end
  end

  # The HTTP client.
  module Client
    class << self
      attr_accessor :access_key, :secret_key, :api_url
    end

    # Do a GET request.
    def get(path, query_params = {})
      uri = uri_of(path, query_params)
      resp = Net::HTTP.start(uri.host, uri.port, nil, nil, nil, nil, use_ssl: (uri.scheme == 'https')) do |http|
        req = Net::HTTP::Get.new(uri.request_uri)
        set_request_headers(req)
        http.request(req)
      end
      check_and_return(resp)
    end

    def post(path, data = {})
      uri = uri_of(path)
      resp = Net::HTTP.start(uri.host, uri.port, nil, nil, nil, nil, use_ssl: (uri.scheme == 'https')) do |http|
        req = Net::HTTP::Post.new(uri.request_uri)
        set_request_headers(req)
        unless data.empty?
          req['Content-Type'] = 'application/json'
          req.body = data.to_json
        end
        http.request(req)
      end
      check_and_return(resp)
    end

    def put(path, data = {})
      uri = uri_of(path)
      resp = Net::HTTP.start(uri.host, uri.port, nil, nil, nil, nil, use_ssl: (uri.scheme == 'https')) do |http|
        req = Net::HTTP::Put.new(uri.request_uri)
        set_request_headers(req)
        unless data.empty?
          req['Content-Type'] = 'application/json'
          req.body = data.to_json
        end
        http.request(req)
      end
      check_and_return(resp)
    end

    def delete(path, query_params = {})
      uri = uri_of(path, query_params)
      resp = Net::HTTP.start(uri.host, uri.port, nil, nil, nil, nil, use_ssl: (uri.scheme == 'https')) do |http|
        req = Net::HTTP::Delete.new(uri.request_uri)
        set_request_headers(req)
        http.request(req)
      end
      check_and_return(resp)
    end

    private

    # Make URI object from request path and query parameters.
    # @param path [String] request path (without scheme, host and port).
    # @param query_params [Hash] optional query parameters.
    # @return the URI object.
    def uri_of(path, query_params = {})
      url = Client.api_url + path
      if query_params.empty?
        URI(url)
      else
        queries = URI.encode_www_form(query_params)
        url.include?('?') ? URI(url + '&' + queries) : URI(url + '?' + queries)
      end
    end

    # Set headers for the HTTP request.
    # @param request [HttpRequest] the request object.
    def set_request_headers(request)
      host = self.name + '.' + self.version
      date = Time.now().gmtime.strftime('%a, %d %b %Y %H:%M:%S %Z')
      signing_string = "host: #{host}\n#{request.method} #{request.path} HTTP/1.1\ndate: #{date}"
      signature = Base64.strict_encode64(OpenSSL::HMAC.digest("SHA256", Client.secret_key, signing_string))
      request['Accept'] = 'application/json'
      request['Host'] = host
      request['Date'] = date
      request['Authorization'] = "hmac username=\"#{Client.access_key}\", algorithm=\"hmac-sha256\", headers=\"host request-line date\", signature=\"#{signature}\""
    end

    def check_and_return(response)
      if response.is_a?(Net::HTTPSuccess)
        response.body
      else
        raise Error.new(response.code, response.body)
      end
    end
  end

  class << self
    # Initialize the ZzLink client.
    # @param access_key [String] developer's access key.
    # @param secret_key [String] developer's secret key.
    # @param api_url [String] URL of zzLink API service. Default to 'https://api.zhizhi.link'.
    def init(access_key, secret_key, api_url = nil)
      Client.access_key = access_key
      Client.secret_key = secret_key
      Client.api_url = (api_url.nil? || api_url.empty?) ? 'https://api.zhizhi.link' : api_url.delete_suffix('/')
    end
  end
end