/*

Copyright 2017 Ollivier Robert

Copyright 2017 Mikael Berthe

Licensed under the MIT license.  Please see the LICENSE file is this directory.

*/

package madon

import (

	"bytes"

	"encoding/json"

	"fmt"

	"net/http"

	"net/url"

	"regexp"

	"strconv"

	"strings"

	"github.com/sendgrid/rest"

)

type apiLinks struct {

	next, prev *LimitParams

}

func parseLink(links []string) (*apiLinks, error) {

	if len(links) == 0 {

		return nil, nil

	}

	al := new(apiLinks)

	linkRegex := regexp.MustCompile(`<([^>]+)>; rel="([^"]+)`)

	for _, l := range links {

		m := linkRegex.FindAllStringSubmatch(l, -1)

		for _, submatch := range m {

			if len(submatch) != 3 {

				continue

			}

			// Parse URL

			u, err := url.Parse(submatch[1])

			if err != nil {

				return al, err

			}

			var lp *LimitParams

			since := u.Query().Get("since_id")

			max := u.Query().Get("max_id")

			lim := u.Query().Get("limit")

			if since == "" && max == "" {

				continue

			}

			lp = new(LimitParams)

			if since != "" {

				lp.SinceID, err = strconv.Atoi(since)

				if err != nil {

					return al, err

				}

			}

			if max != "" {

				lp.MaxID, err = strconv.Atoi(max)

				if err != nil {

					return al, err

				}

			}

			if lim != "" {

				lp.Limit, err = strconv.Atoi(lim)

				if err != nil {

					return al, err

				}

			}

			switch submatch[2] {

			case "prev":

				al.prev = lp

			case "next":

				al.next = lp

			}

		}

	}

	return al, nil

}

// restAPI actually does the HTTP query

// It is a copy of rest.API with better handling of parameters with multiple values

func restAPI(request rest.Request) (*rest.Response, error) {

	c := &rest.Client{HTTPClient: http.DefaultClient}

	// Build the HTTP request object.

	if len(request.QueryParams) != 0 {

		// Add parameters to the URL

		request.BaseURL += "?"

		urlp := url.Values{}

		for key, value := range request.QueryParams {

			// It seems Mastodon doesn't like parameters with index

			// numbers, but it needs the brackets.

			// Let's check if the key matches '^.+\[.*\]$'

			klen := len(key)

			if klen == 0 {

				continue

			}

			i := strings.Index(key, "[")

			if key[klen-1] == ']' && i > 0 {

				// This is an array, let's remove the index number

				key = key[:i] + "[]"

			}

			urlp.Add(key, value)

		}

		urlpstr := urlp.Encode()

		request.BaseURL += urlpstr

	}

	req, err := http.NewRequest(string(request.Method), request.BaseURL, bytes.NewBuffer(request.Body))

	if err != nil {

		return nil, err

	}

	for key, value := range request.Headers {

		req.Header.Set(key, value)

	}

	_, exists := req.Header["Content-Type"]

	if len(request.Body) > 0 && !exists {

		req.Header.Set("Content-Type", "application/json")

	}

	// Build the HTTP client and make the request.

	res, err := c.MakeRequest(req)

	if err != nil {

		return nil, err

	}

	// Build Response object.

	response, err := rest.BuildResponse(res)

	if err != nil {

		return nil, err

	}

	return response, nil

}

// prepareRequest inserts all pre-defined stuff

func (mc *Client) prepareRequest(target string, method rest.Method, params apiCallParams) (rest.Request, error) {

	var req rest.Request

	if mc == nil {

		return req, ErrUninitializedClient

	}

	endPoint := mc.APIBase + "/" + target

	// Request headers

	hdrs := make(map[string]string)

	hdrs["User-Agent"] = fmt.Sprintf("madon/%s", MadonVersion)

	if mc.UserToken != nil {

		hdrs["Authorization"] = fmt.Sprintf("Bearer %s", mc.UserToken.AccessToken)

	}

	req = rest.Request{

		BaseURL:     endPoint,

		Headers:     hdrs,

		Method:      method,

		QueryParams: params,

	}

	return req, nil

}

// apiCall makes a call to the Mastodon API server

// If links is not nil, the prev/next links from the API response headers

// will be set (if they exist) in the structure.

func (mc *Client) apiCall(endPoint string, method rest.Method, params apiCallParams, limitOptions *LimitParams, links *apiLinks, data interface{}) error {

	if mc == nil {

		return fmt.Errorf("use of uninitialized madon client")

	}

	if limitOptions != nil {

		if params == nil {

			params = make(apiCallParams)

		}

		if limitOptions.Limit > 0 {

			params["limit"] = strconv.Itoa(limitOptions.Limit)

		}

		if limitOptions.SinceID > 0 {

			params["since_id"] = strconv.Itoa(limitOptions.SinceID)

		}

		if limitOptions.MaxID > 0 {

			params["max_id"] = strconv.Itoa(limitOptions.MaxID)

		}

	}

	// Prepare query

	req, err := mc.prepareRequest(endPoint, method, params)

	if err != nil {

		return err

	}

	// Make API call

	r, err := restAPI(req)

	if err != nil {

		return fmt.Errorf("API query (%s) failed: %s", endPoint, err.Error())

	}

	if links != nil {

		pLinks, err := parseLink(r.Headers["Link"])

		if err != nil {

			return fmt.Errorf("cannot decode header links (%s): %s", method, err.Error())

		}

		if pLinks != nil {

			*links = *pLinks

		}

	}

	// Check for error reply

	var errorResult Error

	if err := json.Unmarshal([]byte(r.Body), &errorResult); err == nil {

		// The empty object is not an error

		if errorResult.Text != "" {

			return fmt.Errorf("%s", errorResult.Text)

		}

	}

	// Not an error reply; let's unmarshal the data

	err = json.Unmarshal([]byte(r.Body), &data)

	if err != nil {

		return fmt.Errorf("cannot decode API response (%s): %s", method, err.Error())

	}

	return nil

}