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 = "1.81.0"
	defaultBaseURL = "https://service.greenhost.net/"
	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
	Actions           ActionsService
	Droplets          DropletsService
	DropletActions    DropletActionsService
	Images            ImagesService
	ImageActions      ImageActionsService
	Keys              KeysService
	Regions           RegionsService

	// 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"`
}

// TokenListOptions specifies the optional parameters to various List methods that support token pagination.
type TokenListOptions 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"`

	// For paginated result sets which support tokens, the token provided by the last set
	// of results in order to retrieve the next set of results. This is expected to be faster
	// than incrementing or decrementing the page number.
	Token string `url:"page_token,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 []*LinkAction

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

	// Monitoring URI
	// Deprecated: This field is not populated. To poll for the status of a
	// newly created Droplet, use Links.Actions[0].HREF
	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.Actions = &ActionsServiceOp{client: c}
	c.Droplets = &DropletsServiceOp{client: c}
	c.DropletActions = &DropletActionsServiceOp{client: c}
	c.Images = &ImagesServiceOp{client: c}
	c.ImageActions = &ImageActionsServiceOp{client: c}
	c.Keys = &KeysServiceOp{client: c}
	c.Regions = &RegionsServiceOp{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.
// If the API error response does not include the request ID in its body, the one from its header will be used.
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)
		}
	}

	if errorResponse.RequestID == "" {
		errorResponse.RequestID = r.Header.Get("x-request-id")
	}

	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()
}