/*
 *  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 e621

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

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

type (
	user_id     uint64
	post_id     uint64
	pool_id     uint64
	file_size   uint64
	file_struct struct {
		Width  uint64 `json:"width"`
		Height uint64 `json:"height"`
		URL    string `json:"url"`
	}
	e621_API struct {
		Posts []struct {
			ID        post_id `json:"id"`
			CreatedAt string  `json:"created_at"`
			UpdatedAt string  `json:"updated_at"`
			File      struct {
				file_struct
				Size file_size `json:"size"`
				Ext  string    `json:"ext"`
				Md5  string    `json:"md5"`
			} `json:"file"`
			Preview file_struct `json:"preview"`
			Sample  struct {
				file_struct
				Has        bool `json:"has"`
				Alternates map[string]struct {
					Type   string   `json:"type"`
					Height int      `json:"height"`
					Width  int      `json:"width"`
					Urls   []string `json:"urls"`
				} `json:"alternates"`
			} `json:"sample"`
			Score struct {
				Up    int64 `json:"up"`
				Down  int64 `json:"down"`
				Total int64 `json:"total"`
			} `json:"score"`
			Tags struct {
				General   []string `json:"general"`
				Species   []string `json:"species"`
				Character []string `json:"character"`
				Copyright []string `json:"copyright"`
				Artist    []string `json:"artist"`
				Invalid   []string `json:"invalid"`
				Lore      []string `json:"lore"`
				Meta      []string `json:"meta"`
			} `json:"tags"`
			LockedTags []string `json:"locked_tags"`
			ChangeSeq  uint64   `json:"change_seq"`
			Flags      struct {
				Pending         bool `json:"pending"`
				Flagged         bool `json:"flagged"`
				NoteLocked      bool `json:"note_locked"`
				StatusLocked    bool `json:"status_locked"`
				RatingLocked    bool `json:"rating_locked"`
				CommentDisabled bool `json:"comment_disabled"`
				Deleted         bool `json:"deleted"`
			} `json:"flags"`
			Rating        string    `json:"rating"`
			FavCount      uint64    `json:"fav_count"`
			Sources       []string  `json:"sources"`
			Pools         []pool_id `json:"pools"`
			Relationships struct {
				ParentID          post_id   `json:"parent_id"`
				HasChildren       bool      `json:"has_children"`
				HasActiveChildren bool      `json:"has_active_children"`
				Children          []post_id `json:"children"`
			} `json:"relationships"`
			ApproverID   user_id `json:"approver_id"`
			UploaderID   user_id `json:"uploader_id"`
			Description  string  `json:"description"`
			CommentCount uint64  `json:"comment_count"`
			IsFavorited  bool    `json:"is_favorited"`
			HasNotes     bool    `json:"has_notes"`
			Duration     float32 `json:"duration"`
		} `json:"posts"`
	}
)

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:   "e621.net",
			Path:   "/posts.json",
		},
	}
	query := req.URL.Query()
	query.Add("page", strconv.FormatUint(uint64(pid), 10))
	query.Add("tags", strings.Join(tags, " "))
	req.URL.RawQuery = query.Encode()
	req.Header = make(http.Header)
	req.Header.Set("user-agent", "gomon/1.0 (https://git.redxen.eu/caskd/gomon)")

	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 e621_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 {
		if v.File.URL == "" {
			// Skip posts that require higher priviledges to access
			// - "Some posts cannot be viewed without logging in based on which tags are applied to them."
			// https://e621.net/forum_topics/25717
			continue
		}
		cur := Media{
			Source: v.File.URL,
			MD5:    v.File.Md5,
		}
		for _, tc := range [][]string{
			v.Tags.General,
			v.Tags.Species,
			v.Tags.Character,
			v.Tags.Copyright,
			v.Tags.Artist,
			v.Tags.Lore,
			v.Tags.Meta,
		} {
			cur.Tags = append(cur.Tags, tc...)
		}
		m = append(m, cur)
	}
	return
}