/*
 *   Copyright (C) 2021 Arsen Musayelyan
 *
 *   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/>.
 */

// wolframalpha is a Trident plugin that queries the WolframAlpha API and says the result
package wolframalpha

import (
	"encoding/xml"
	"fmt"
	"log"
	"net/http"
	"net/url"
	"strings"
	"trident"
)

// Result stores the result of the WolframAlpha query
type Result struct {
	Pods []Pod `xml:"pod"`
}

// Pod stores pod tags from result
type Pod struct {
	XMLName xml.Name `xml:"pod"`
	ID      string   `xml:"id,attr"`
	SubPods []SubPod `xml:"subpod"`
}

// SubPod stores subpod tags from pod
type SubPod struct {
	XMLName   xml.Name   `xml:"subpod,omitempty"`
	Plaintext *Plaintext `xml:"plaintext,omitempty"`
}

// Plaintext stores plaintext tags from subpod
type Plaintext struct {
	XMLName xml.Name `xml:"plaintext"`
	String  string   `xml:",chardata"`
}

func RunPlugin(query string, data map[string]interface{}) {
	// Escape query for inclusion in URL
	escapedQuery := url.QueryEscape(query)
	// Query WolframAlpha API
	res, err := http.Get(fmt.Sprintf("https://api.wolframalpha.com/v2/query?input=%s&appid=%s", escapedQuery, data["appid"].(string)))
	if err != nil {
		log.Fatalln(err)
	}
	// Close response body at end of function
	defer res.Body.Close()
	// Create new nil struct to store query results
	var resStruct Result
	// Create new XML decoder reading from API response body
	dec := xml.NewDecoder(res.Body)
	// Decode contents of response body into struct
	err = dec.Decode(&resStruct)
	if err != nil {
		log.Fatalln(err)
	}

	// Create string builder to combine results
	all := strings.Builder{}
	for _, pod := range resStruct.Pods {
		switch pod.ID {
		case "Result", "RealSolution", "Solution":
			// If pod ID is one of the above cases, write it to builder
			all.WriteString(pod.ID)
			for _, subpod := range pod.SubPods {
				// Write string from subpod plaintext tag to builder
				all.WriteString(subpod.Plaintext.String)
			}
		}
	}
	// Use voice to say built string
	trident.Say(all.String())
}