package godo

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/google/go-querystring/query"
	"golang.org/x/oauth2"
)

const (
	libraryVersion = "1.60.0"
	defaultBaseURL = "https://api.digitalocean.com/"
	userAgent      = "godo/" + libraryVersion
	mediaType      = "application/json"

	headerRateLimit     = "RateLimit-Limit"
	headerRateRemaining = "RateLimit-Remaining"
	headerRateReset     = "RateLimit-Reset"
)

// Client manages communication with DigitalOcean V2 API.
type Client struct {
	// HTTP client used to communicate with the DO API.
	client *http.Client

	// Base URL for API requests.
	BaseURL *url.URL

	// User agent for client
	UserAgent string

	// Rate contains the current rate limit for the client as determined by the most recent
	// API call. It is not thread-safe. Please consider using GetRate() instead.
	Rate    Rate
	ratemtx sync.Mutex

	// Services used for communicating with the API
	Account           AccountService
	Actions           ActionsService
	Apps              AppsService
	Balance           BalanceService
	BillingHistory    BillingHistoryService
	CDNs              CDNService
	Domains           DomainsService
	Droplets          DropletsService
	DropletActions    DropletActionsService
	Images            ImagesService
	ImageActions      ImageActionsService
	Invoices          InvoicesService
	Keys              KeysService
	Regions           RegionsService
	Sizes             SizesService
	FloatingIPs       FloatingIPsService
	FloatingIPActions FloatingIPActionsService
	Snapshots         SnapshotsService
	Storage           StorageService
	StorageActions    StorageActionsService
	Tags              TagsService
	LoadBalancers     LoadBalancersService
	Certificates      CertificatesService
	Firewalls         FirewallsService
	Projects          ProjectsService
	Kubernetes        KubernetesService
	Registry          RegistryService
	Databases         DatabasesService
	VPCs              VPCsService
	OneClick          OneClickService

	// Optional function called after every successful request made to the DO APIs
	onRequestCompleted RequestCompletionCallback

	// Optional extra HTTP headers to set on every request to the API.
	headers map[string]string
}

// RequestCompletionCallback defines the type of the request callback function
type RequestCompletionCallback func(*http.Request, *http.Response)

// ListOptions specifies the optional parameters to various List methods that
// support pagination.
type ListOptions struct {
	// For paginated result sets, page of results to retrieve.
	Page int `url:"page,omitempty"`

	// For paginated result sets, the number of results to include per page.
	PerPage int `url:"per_page,omitempty"`
}

// Response is a DigitalOcean response. This wraps the standard http.Response returned from DigitalOcean.
type Response struct {
	*http.Response

	// Links that were returned with the response. These are parsed from
	// request body and not the header.
	Links *Links

	// Meta describes generic information about the response.
	Meta *Meta

	// Monitoring URI
	Monitor string

	Rate
}

// An ErrorResponse reports the error caused by an API request
type ErrorResponse struct {
	// HTTP response that caused this error
	Response *http.Response

	// Error message
	Message string `json:"message"`

	// RequestID returned from the API, useful to contact support.
	RequestID string `json:"request_id"`
}

// Rate contains the rate limit for the current client.
type Rate struct {
	// The number of request per hour the client is currently limited to.
	Limit int `json:"limit"`

	// The number of remaining requests the client can make this hour.
	Remaining int `json:"remaining"`

	// The time at which the current rate limit will reset.
	Reset Timestamp `json:"reset"`
}

func addOptions(s string, opt interface{}) (string, error) {
	v := reflect.ValueOf(opt)

	if v.Kind() == reflect.Ptr && v.IsNil() {
		return s, nil
	}

	origURL, err := url.Parse(s)
	if err != nil {
		return s, err
	}

	origValues := origURL.Query()

	newValues, err := query.Values(opt)
	if err != nil {
		return s, err
	}

	for k, v := range newValues {
		origValues[k] = v
	}

	origURL.RawQuery = origValues.Encode()
	return origURL.String(), nil
}

// NewFromToken returns a new DigitalOcean API client with the given API
// token.
func NewFromToken(token string) *Client {
	cleanToken := strings.Trim(strings.TrimSpace(token), "'")
	ctx := context.Background()
	ts := oauth2.StaticTokenSource(&oauth2.Token{AccessToken: cleanToken})
	return NewClient(oauth2.NewClient(ctx, ts))
}

// NewClient returns a new DigitalOcean API client, using the given
// http.Client to perform all requests.
//
// Users who wish to pass their own http.Client should use this method. If
// you're in need of further customization, the godo.New method allows more
// options, such as setting a custom URL or a custom user agent string.
func NewClient(httpClient *http.Client) *Client {
	if httpClient == nil {
		httpClient = http.DefaultClient
	}

	baseURL, _ := url.Parse(defaultBaseURL)

	c := &Client{client: httpClient, BaseURL: baseURL, UserAgent: userAgent}
	c.Account = &AccountServiceOp{client: c}
	c.Actions = &ActionsServiceOp{client: c}
	c.Apps = &AppsServiceOp{client: c}
	c.Balance = &BalanceServiceOp{client: c}
	c.BillingHistory = &BillingHistoryServiceOp{client: c}
	c.CDNs = &CDNServiceOp{client: c}
	c.Certificates = &CertificatesServiceOp{client: c}
	c.Domains = &DomainsServiceOp{client: c}
	c.Droplets = &DropletsServiceOp{client: c}
	c.DropletActions = &DropletActionsServiceOp{client: c}
	c.Firewalls = &FirewallsServiceOp{client: c}
	c.FloatingIPs = &FloatingIPsServiceOp{client: c}
	c.FloatingIPActions = &FloatingIPActionsServiceOp{client: c}
	c.Images = &ImagesServiceOp{client: c}
	c.ImageActions = &ImageActionsServiceOp{client: c}
	c.Invoices = &InvoicesServiceOp{client: c}
	c.Keys = &KeysServiceOp{client: c}
	c.LoadBalancers = &LoadBalancersServiceOp{client: c}
	c.Projects = &ProjectsServiceOp{client: c}
	c.Regions = &RegionsServiceOp{client: c}
	c.Sizes = &SizesServiceOp{client: c}
	c.Snapshots = &SnapshotsServiceOp{client: c}
	c.Storage = &StorageServiceOp{client: c}
	c.StorageActions = &StorageActionsServiceOp{client: c}
	c.Tags = &TagsServiceOp{client: c}
	c.Kubernetes = &KubernetesServiceOp{client: c}
	c.Registry = &RegistryServiceOp{client: c}
	c.Databases = &DatabasesServiceOp{client: c}
	c.VPCs = &VPCsServiceOp{client: c}
	c.OneClick = &OneClickServiceOp{client: c}

	c.headers = make(map[string]string)

	return c
}

// ClientOpt are options for New.
type ClientOpt func(*Client) error

// New returns a new DigitalOcean API client instance.
func New(httpClient *http.Client, opts ...ClientOpt) (*Client, error) {
	c := NewClient(httpClient)
	for _, opt := range opts {
		if err := opt(c); err != nil {
			return nil, err
		}
	}

	return c, nil
}

// SetBaseURL is a client option for setting the base URL.
func SetBaseURL(bu string) ClientOpt {
	return func(c *Client) error {
		u, err := url.Parse(bu)
		if err != nil {
			return err
		}

		c.BaseURL = u
		return nil
	}
}

// SetUserAgent is a client option for setting the user agent.
func SetUserAgent(ua string) ClientOpt {
	return func(c *Client) error {
		c.UserAgent = fmt.Sprintf("%s %s", ua, c.UserAgent)
		return nil
	}
}

// SetRequestHeaders sets optional HTTP headers on the client that are
// sent on each HTTP request.
func SetRequestHeaders(headers map[string]string) ClientOpt {
	return func(c *Client) error {
		for k, v := range headers {
			c.headers[k] = v
		}
		return nil
	}
}

// NewRequest creates an API request. A relative URL can be provided in urlStr, which will be resolved to the
// BaseURL of the Client. Relative URLS should always be specified without a preceding slash. If specified, the
// value pointed to by body is JSON encoded and included in as the request body.
func (c *Client) NewRequest(ctx context.Context, method, urlStr string, body interface{}) (*http.Request, error) {
	u, err := c.BaseURL.Parse(urlStr)
	if err != nil {
		return nil, err
	}

	var req *http.Request
	switch method {
	case http.MethodGet, http.MethodHead, http.MethodOptions:
		req, err = http.NewRequest(method, u.String(), nil)
		if err != nil {
			return nil, err
		}

	default:
		buf := new(bytes.Buffer)
		if body != nil {
			err = json.NewEncoder(buf).Encode(body)
			if err != nil {
				return nil, err
			}
		}

		req, err = http.NewRequest(method, u.String(), buf)
		if err != nil {
			return nil, err
		}
		req.Header.Set("Content-Type", mediaType)
	}

	for k, v := range c.headers {
		req.Header.Add(k, v)
	}

	req.Header.Set("Accept", mediaType)
	req.Header.Set("User-Agent", c.UserAgent)

	return req, nil
}

// OnRequestCompleted sets the DO API request completion callback
func (c *Client) OnRequestCompleted(rc RequestCompletionCallback) {
	c.onRequestCompleted = rc
}

// GetRate returns the current rate limit for the client as determined by the most recent
// API call. It is thread-safe.
func (c *Client) GetRate() Rate {
	c.ratemtx.Lock()
	defer c.ratemtx.Unlock()
	return c.Rate
}

// newResponse creates a new Response for the provided http.Response
func newResponse(r *http.Response) *Response {
	response := Response{Response: r}
	response.populateRate()

	return &response
}

// populateRate parses the rate related headers and populates the response Rate.
func (r *Response) populateRate() {
	if limit := r.Header.Get(headerRateLimit); limit != "" {
		r.Rate.Limit, _ = strconv.Atoi(limit)
	}
	if remaining := r.Header.Get(headerRateRemaining); remaining != "" {
		r.Rate.Remaining, _ = strconv.Atoi(remaining)
	}
	if reset := r.Header.Get(headerRateReset); reset != "" {
		if v, _ := strconv.ParseInt(reset, 10, 64); v != 0 {
			r.Rate.Reset = Timestamp{time.Unix(v, 0)}
		}
	}
}

// Do sends an API request and returns the API response. The API response is JSON decoded and stored in the value
// pointed to by v, or returned as an error if an API error has occurred. If v implements the io.Writer interface,
// the raw response will be written to v, without attempting to decode it.
func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*Response, error) {
	resp, err := DoRequestWithClient(ctx, c.client, req)
	if err != nil {
		return nil, err
	}
	if c.onRequestCompleted != nil {
		c.onRequestCompleted(req, resp)
	}

	defer func() {
		// Ensure the response body is fully read and closed
		// before we reconnect, so that we reuse the same TCPconnection.
		// Close the previous response's body. But read at least some of
		// the body so if it's small the underlying TCP connection will be
		// re-used. No need to check for errors: if it fails, the Transport
		// won't reuse it anyway.
		const maxBodySlurpSize = 2 << 10
		if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize {
			io.CopyN(ioutil.Discard, resp.Body, maxBodySlurpSize)
		}

		if rerr := resp.Body.Close(); err == nil {
			err = rerr
		}
	}()

	response := newResponse(resp)
	c.ratemtx.Lock()
	c.Rate = response.Rate
	c.ratemtx.Unlock()

	err = CheckResponse(resp)
	if err != nil {
		return response, err
	}

	if v != nil {
		if w, ok := v.(io.Writer); ok {
			_, err = io.Copy(w, resp.Body)
			if err != nil {
				return nil, err
			}
		} else {
			err = json.NewDecoder(resp.Body).Decode(v)
			if err != nil {
				return nil, err
			}
		}
	}

	return response, err
}

// DoRequest submits an HTTP request.
func DoRequest(ctx context.Context, req *http.Request) (*http.Response, error) {
	return DoRequestWithClient(ctx, http.DefaultClient, req)
}

// DoRequestWithClient submits an HTTP request using the specified client.
func DoRequestWithClient(
	ctx context.Context,
	client *http.Client,
	req *http.Request) (*http.Response, error) {
	req = req.WithContext(ctx)
	return client.Do(req)
}

func (r *ErrorResponse) Error() string {
	if r.RequestID != "" {
		return fmt.Sprintf("%v %v: %d (request %q) %v",
			r.Response.Request.Method, r.Response.Request.URL, r.Response.StatusCode, r.RequestID, r.Message)
	}
	return fmt.Sprintf("%v %v: %d %v",
		r.Response.Request.Method, r.Response.Request.URL, r.Response.StatusCode, r.Message)
}

// CheckResponse checks the API response for errors, and returns them if present. A response is considered an
// error if it has a status code outside the 200 range. API error responses are expected to have either no response
// body, or a JSON response body that maps to ErrorResponse. Any other response body will be silently ignored.
func CheckResponse(r *http.Response) error {
	if c := r.StatusCode; c >= 200 && c <= 299 {
		return nil
	}

	errorResponse := &ErrorResponse{Response: r}
	data, err := ioutil.ReadAll(r.Body)
	if err == nil && len(data) > 0 {
		err := json.Unmarshal(data, errorResponse)
		if err != nil {
			errorResponse.Message = string(data)
		}
	}

	return errorResponse
}

func (r Rate) String() string {
	return Stringify(r)
}

// String is a helper routine that allocates a new string value
// to store v and returns a pointer to it.
func String(v string) *string {
	p := new(string)
	*p = v
	return p
}

// Int is a helper routine that allocates a new int32 value
// to store v and returns a pointer to it, but unlike Int32
// its argument value is an int.
func Int(v int) *int {
	p := new(int)
	*p = v
	return p
}

// Bool is a helper routine that allocates a new bool value
// to store v and returns a pointer to it.
func Bool(v bool) *bool {
	p := new(bool)
	*p = v
	return p
}

// StreamToString converts a reader to a string
func StreamToString(stream io.Reader) string {
	buf := new(bytes.Buffer)
	_, _ = buf.ReadFrom(stream)
	return buf.String()
}
