/*
 *  This file is part of goboru. (https://git.redxen.eu/caskd/goboru)
 *  Copyright (c) 2022 Alex-David Denes
 *
 *  goboru 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
 *  any later version.
 *
 *  goboru 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 goboru.  If not, see <https://www.gnu.org/licenses/>.
 */

package gelbooru

import (
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"time"

	. "git.redxen.eu/caskd/goboru"
)

type gelbooru_API struct {
	Attributes struct {
		Limit  float64 `json:"limit"`
		Offset float64 `json:"offset"`
		Count  float64 `json:"count"`
	} `json:"@attributes"`
	Posts []struct {
		Id             uint64 `json:"id"`
		Created_at     string `json:"created_at"`
		Score          int64  `json:"score"`
		Width          uint64 `json:"width"`
		Height         uint64 `json:"height"`
		MD5            string `json:"md5"`
		Directory      string `json:"directory"`
		Image          string `json:"image"`
		Rating         string `json:"rating"`
		Source         string `json:"source"`
		Change         uint64 `json:"change"`
		Owner          string `json:"owner"`
		Creator_id     uint64 `json:"creator_id"`
		Parent_id      uint64 `json:"parent_id"`
		Sample         uint64 `json:"sample"`
		Preview_height uint64 `json:"preview_height"`
		Preview_width  uint64 `json:"preview_width"`
		Tags           string `json:"tags"`
		Title          string `json:"title"`
		Has_notes      string `json:"has_notes"`
		Has_comments   string `json:"has_comments"`
		File_url       string `json:"file_url"`
		Preview_url    string `json:"preview_url"`
		Sample_url     string `json:"sample_url"`
		Sample_height  uint64 `json:"sample_height"`
		Sample_width   uint64 `json:"sample_width"`
		Status         string `json:"status"`
		Post_locked    uint64 `json:"post_locked"`
		Has_children   string `json:"has_children"`
	} `json:"post"`
}

type result struct {
	media []Media
	err   error
	pid   uint
}

func Query(tags Tags, j_max Jobs) (mr []Media, err error) {
	res_chan := make(chan result)
	var r_arr []result

	for pid, rpid, ppid := uint(0), uint(0), uint(0); ; {
		if pid <= 200 { // API only allows to fetch up to 200 pages per query
			go run_job(tags, pid, res_chan)
			pid++
		}

		if pid < uint(j_max) {
			continue
		}

		if rpid < pid {
			r := <-res_chan
			rpid++
			r_arr = append(r_arr, r)
		}

		if ppid < pid {
			sort.Slice(r_arr, func(i, j int) bool {
				return r_arr[i].pid < r_arr[j].pid
			})

			if c := r_arr[0]; c.pid == ppid {
				ppid++
				r_arr = r_arr[1:]
				if c.err != nil {
					err = c.err
					break
				}
				if len(c.media) == 0 {
					break
				}
				mr = append(mr, c.media...)
				log.Print("Added ", len(c.media), "/", len(mr), " elements")
			}
		} else {
			break // Break when no more pages have been fetched
		}
	}
	return
}

func run_job(tags []string, pid uint, res chan result) {
	r := result{pid: pid}
	defer func(x *result, c chan result) { c <- *x }(&r, res)

	var rc io.ReadCloser
	if rc, r.err = fetch(tags, pid); r.err != nil {
		return
	}
	defer rc.Close()

	if r.media, r.err = parse(rc); r.err != nil {
		return
	}
}

func fetch(tags []string, pid uint) (rc io.ReadCloser, err error) {
	client := http.Client{Timeout: 10 * time.Second}
	req := &http.Request{
		URL: &url.URL{
			Scheme: "https",
			Host:   "gelbooru.com",
			Path:   "/index.php",
		},
	}
	query := req.URL.Query()
	query.Add("page", "dapi")
	query.Add("s", "post")
	query.Add("q", "index")
	query.Add("json", "1")
	query.Add("pid", strconv.FormatUint(uint64(pid), 10))
	query.Add("tags", strings.Join(tags, " "))
	req.URL.RawQuery = query.Encode()

	resp, err := client.Do(req)
	if err != nil {
		return
	}
	rc = resp.Body
	return
}

func parse(r io.Reader) (m []Media, err error) {
	var api_resp gelbooru_API

	d := json.NewDecoder(r)
	d.DisallowUnknownFields()
	if err = d.Decode(&api_resp); err != nil {
		err = fmt.Errorf("JSON parse: %s", err)
		return
	}

	if len(api_resp.Posts) == 0 {
		return
	}

	for _, v := range api_resp.Posts {
		cur := Media{
			Source: v.File_url,
			MD5:    v.MD5,
			Tags:   strings.Split(v.Tags, " "),
		}
		m = append(m, cur)
	}
	return
}