package core

import (
	"fmt"
	"math"
	"net/http"
	"sort"
	"strconv"

	"codeberg.org/vnpower/pixivfe/v2/i18n"
	"codeberg.org/vnpower/pixivfe/v2/server/session"
	"github.com/goccy/go-json"
)

// pixivfe internal data type. not used by pixiv.
type UserArtCategory string

const (
	UserArt_Any          UserArtCategory = ""
	UserArt_AnyAlt       UserArtCategory = "artworks"
	UserArt_Illustration UserArtCategory = "illustrations"
	UserArt_Manga        UserArtCategory = "manga"
	UserArt_Bookmarks    UserArtCategory = "bookmarks" // what this user has bookmarked; not art by this user
	UserArt_Novel        UserArtCategory = "novels"
)

func (s UserArtCategory) Validate() error {
	if s != UserArt_Any &&
		s != UserArt_AnyAlt &&
		s != UserArt_Illustration &&
		s != UserArt_Manga &&
		s != UserArt_Bookmarks &&
		s != UserArt_Novel {
		return i18n.Errorf(`Invalid work category: %#v. Only "%s", "%s", "%s", "%s", "%s" and "%s" are available`, s, UserArt_Any, UserArt_AnyAlt, UserArt_Illustration, UserArt_Manga, UserArt_Bookmarks, UserArt_Novel)
	} else {
		return nil
	}
}

type FrequentTag struct {
	Name           string `json:"tag"`
	TranslatedName string `json:"tag_translation"`
}

type CountInfo struct {
	All           int
	Illustrations int
	Manga         int
	Novels        int
	Bookmarks     int
}

type User struct {
	ID                string          `json:"userId"`
	Name              string          `json:"name"`
	Avatar            string          `json:"imageBig"`
	Following         int             `json:"following"`
	MyPixiv           int             `json:"mypixivCount"`
	Comment           HTML            `json:"commentHtml"`
	Webpage           string          `json:"webpage"`
	SocialRaw         json.RawMessage `json:"social"`
	Artworks          []ArtworkBrief  `json:"artworks"` // this slice includes both illustrations and manga, but not novels
	Illustrations     []ArtworkBrief
	Manga             []ArtworkBrief
	Novels            []NovelBrief   `json:"novels"`
	Background        map[string]any `json:"background"`
	CategoryItemCount int
	FrequentTags      []FrequentTag
	Social            map[string]map[string]string
	BackgroundImage   string
	NovelSeries       []NovelSeries
	MangaSeries       []MangaSeries

	IsFollowed bool `json:"isFollowed"` // Denotes whether the logged in user currently following the given user

	// The following fields are internal to PixivFE, used to display the number of works for a given category
	CountInfo CountInfo
}

// IntStringMap is a custom type that can handle both JSON objects and empty arrays.
//
// Required as the Pixiv API returns empty arrays for work types that
// don't exist for a user.
type IntStringMap map[int]string

// UnmarshalJSON implements custom unmarshalling for IntStringMap.
func (m *IntStringMap) UnmarshalJSON(data []byte) error {
	// Check if the data is an empty array.
	if string(data) == "[]" {
		*m = make(map[int]string)
		return nil
	}

	// Otherwise, expect an object.
	var temp map[string]*string
	if err := json.Unmarshal(data, &temp); err != nil {
		return err
	}

	result := make(map[int]string)
	for keyStr, value := range temp {
		key, err := strconv.Atoi(keyStr)
		if err != nil {
			return fmt.Errorf("invalid key '%s': %v", keyStr, err)
		}
		if value != nil {
			result[key] = *value
		} else {
			result[key] = ""
		}
	}

	*m = result
	return nil
}

// GetUserArtworksIDAndSeries retrieves artwork IDs and series information for a user.
func GetUserArtworksIDAndSeries(r *http.Request, id string, category UserArtCategory, page int) (idsString string, count int, illustCount int, mangaCount int, novelCount int, series json.RawMessage, err error) {
	URL := GetUserArtworksURL(id)

	resp, err := API_GET_UnwrapJson(r.Context(), URL, "", r.Header)
	if err != nil {
		return "", -1, -1, -1, -1, nil, err
	}

	resp = session.ProxyImageUrl(r, resp)

	var body struct {
		// *json.RawMessage allows us to easily check whether
		// a field exists by verifying if pointer != nil
		Illusts     *json.RawMessage `json:"illusts"`
		Manga       *json.RawMessage `json:"manga"`
		MangaSeries *json.RawMessage `json:"mangaSeries"`
		Novels      *json.RawMessage `json:"novels"`
		NovelSeries *json.RawMessage `json:"novelSeries"`
	}

	err = json.Unmarshal([]byte(resp), &body)
	if err != nil {
		return "", -1, -1, -1, -1, nil, fmt.Errorf("failed to unmarshal response body: %w", err)
	}

	var ids []int

	var illusts IntStringMap
	var manga IntStringMap
	var novels IntStringMap

	if category == UserArt_Illustration || category == UserArt_Any || category == UserArt_AnyAlt {
		if body.Illusts != nil && len(*body.Illusts) > 0 {
			if err = json.Unmarshal(*body.Illusts, &illusts); err != nil {
				fmt.Printf("Error unmarshalling illusts: %v\n", err)
				illusts = make(IntStringMap)
			}
			for k := range illusts {
				ids = append(ids, k)
				count++
			}
			illustCount = len(illusts)
		}
	}

	if category == UserArt_Manga || category == UserArt_Any {
		if body.Manga != nil && len(*body.Manga) > 0 {
			if err = json.Unmarshal(*body.Manga, &manga); err != nil {
				fmt.Printf("Error unmarshalling manga: %v\n", err)
				manga = make(IntStringMap)
			}
			for k := range manga {
				ids = append(ids, k)
				count++
			}
			mangaCount = len(manga)
			if body.MangaSeries != nil {
				series = *body.MangaSeries
			}
		}
	}

	if category == UserArt_Novel {
		if body.Novels != nil && len(*body.Novels) > 0 {
			if err = json.Unmarshal(*body.Novels, &novels); err != nil {
				fmt.Printf("Error unmarshalling novels: %v\n", err)
				novels = make(IntStringMap)
			}
			for k := range novels {
				ids = append(ids, k)
				count++
			}
			novelCount = len(novels)
			if body.NovelSeries != nil {
				series = *body.NovelSeries
			}
		}
	}

	sort.Sort(sort.Reverse(sort.IntSlice(ids)))

	worksPerPage := 30.0

	start, end, err := computeSliceBounds(page, worksPerPage, len(ids))
	if err != nil {
		return "", -1, -1, -1, -1, nil, err
	}

	// Build the IDs string for the API request
	for _, k := range ids[start:end] {
		idsString += fmt.Sprintf("&ids[]=%d", k)
	}

	return idsString, count, illustCount, mangaCount, novelCount, series, nil
}

func fetchAndProcessArtworks(r *http.Request, id, ids string, category UserArtCategory) ([]ArtworkBrief, []NovelBrief, error) {
	var artworks []ArtworkBrief
	var novels []NovelBrief
	var err error

	if category == UserArt_Novel {
		novels, err = GetUserNovels(r, id, ids)
	} else {
		artworks, err = GetUserArtworkList(r, id, ids)
	}

	if err != nil {
		return nil, nil, err
	}

	// Sort the works
	if category == UserArt_Novel {
		sort.Slice(novels[:], func(i, j int) bool {
			return numberGreaterThan(novels[i].ID, novels[j].ID)
		})
	} else {
		sort.Slice(artworks[:], func(i, j int) bool {
			return numberGreaterThan(artworks[i].ID, artworks[j].ID)
		})
	}

	return artworks, novels, nil
}

func handleSeriesData(series json.RawMessage, category UserArtCategory) ([]NovelSeries, []MangaSeries) {
	var novelSeries []NovelSeries
	var mangaSeries []MangaSeries

	if series != nil {
		if category == UserArt_Novel {
			_ = json.Unmarshal(series, &novelSeries)
		} else {
			_ = json.Unmarshal(series, &mangaSeries)
		}
	}

	return novelSeries, mangaSeries
}

func GetUserProfile(r *http.Request, id string, category UserArtCategory, page int, getTags bool) (User, error) {
	var user User

	token := session.GetUserToken(r)

	URL := GetUserInformationURL(id)

	resp, err := API_GET_UnwrapJson(r.Context(), URL, token, r.Header)
	if err != nil {
		return user, err
	}

	resp = session.ProxyImageUrl(r, resp)

	err = json.Unmarshal([]byte(resp), &user)
	if err != nil {
		return user, err
	}

	// Get counts for illustrations and manga
	_, allCount, illustCount, mangaCount, _, _, err := GetUserArtworksIDAndSeries(r, id, UserArt_Any, 1)
	if err != nil {
		return user, err
	}
	user.CountInfo.All = allCount
	user.CountInfo.Illustrations = illustCount
	user.CountInfo.Manga = mangaCount

	// Get count for novels separately
	_, _, _, _, novelCount, _, err := GetUserArtworksIDAndSeries(r, id, UserArt_Novel, 1)
	if err != nil {
		return user, err
	}
	user.CountInfo.Novels = novelCount

	// Get bookmarks count
	_, bookmarksCount, err := GetUserBookmarks(r, id, "show", 1)
	if err != nil {
		return user, err
	}
	user.CountInfo.Bookmarks = bookmarksCount

	if category == UserArt_Bookmarks {
		// Bookmarks
		works, _, err := GetUserBookmarks(r, id, "show", page)
		if err != nil {
			return user, err
		}

		user.Artworks = works
		user.CategoryItemCount = bookmarksCount
	} else {
		ids, count, _, _, _, series, err := GetUserArtworksIDAndSeries(r, id, category, page)
		if err != nil {
			return user, err
		}

		if count > 0 {
			artworks, novels, err := fetchAndProcessArtworks(r, id, ids, category)
			if err != nil {
				return user, err
			}

			if category == UserArt_Novel {
				user.Novels = novels
			} else {
				user.Artworks = artworks
				user.Illustrations = make([]ArtworkBrief, 0)
				user.Manga = make([]ArtworkBrief, 0)
				for _, artwork := range artworks {
					if artwork.IllustType == 0 {
						user.Illustrations = append(user.Illustrations, artwork)
					} else if artwork.IllustType == 1 {
						user.Manga = append(user.Manga, artwork)
					}
				}
			}

			if getTags {
				user.FrequentTags, err = GetUserFrequentTags(r, ids, category)
				if err != nil {
					return user, err
				}
			}
		}

		user.NovelSeries, user.MangaSeries = handleSeriesData(series, category)
		user.CategoryItemCount = count
	}

	err = user.ParseSocial()
	if err != nil {
		return User{}, err
	}

	if user.Background != nil {
		user.BackgroundImage = user.Background["url"].(string)
	}

	return user, nil
}

// Work is a generic type constraint.
type Work interface{}

// GetUserWorks is a generic helper function to fetch user works.
func GetUserWorks[T Work](r *http.Request, url string) ([]T, error) {
	resp, err := API_GET_UnwrapJson(r.Context(), url, "", r.Header)
	if err != nil {
		return nil, err
	}

	resp = session.ProxyImageUrl(r, resp)

	// Define a generic body structure.
	var body struct {
		Works map[int]json.RawMessage `json:"works"`
	}

	// Unmarshal the response into the body.
	if err := json.Unmarshal([]byte(resp), &body); err != nil {
		return nil, err
	}

	// Initialize the slice to hold the works.
	var works []T

	// Iterate over each work and unmarshal into the specific type.
	for _, v := range body.Works {
		var work T
		if err := json.Unmarshal(v, &work); err != nil {
			return nil, err
		}
		works = append(works, work)
	}

	return works, nil
}

// GetUserFrequentTags retrieves frequent tags for a user based on category.
func GetUserFrequentTags(r *http.Request, ids string, category UserArtCategory) ([]FrequentTag, error) {
	var tags []FrequentTag
	var URL string

	if category != "novels" {
		URL = GetUserFrequentArtworkTagsURL(ids)
	} else {
		URL = GetUserFrequentNovelTagsURL(ids)
	}

	response, err := API_GET_UnwrapJson(r.Context(), URL, "", r.Header)
	if err != nil {
		return nil, err
	}

	err = json.Unmarshal([]byte(response), &tags)
	if err != nil {
		return nil, err
	}

	return tags, nil
}

// GetUserArtworkList fetches the list of artworks for a user.
func GetUserArtworkList(r *http.Request, id, ids string) ([]ArtworkBrief, error) {
	URL := GetUserFullArtworkURL(id, ids)

	works, err := GetUserWorks[ArtworkBrief](r, URL)
	if err != nil {
		return nil, err
	}

	return works, nil
}

// GetUserNovels fetches the list of novels for a user.
func GetUserNovels(r *http.Request, id, ids string) ([]NovelBrief, error) {
	URL := GetUserFullNovelURL(id, ids)

	works, err := GetUserWorks[NovelBrief](r, URL)
	if err != nil {
		return nil, err
	}

	return works, nil
}

func GetUserBookmarks(r *http.Request, id, mode string, page int) ([]ArtworkBrief, int, error) {
	page--

	URL := GetUserBookmarksURL(id, mode, page)

	resp, err := API_GET_UnwrapJson(r.Context(), URL, "", r.Header)
	if err != nil {
		return nil, -1, err
	}
	resp = session.ProxyImageUrl(r, resp)

	var body struct {
		Artworks []json.RawMessage `json:"works"`
		Total    int               `json:"total"`
	}

	err = json.Unmarshal([]byte(resp), &body)
	if err != nil {
		return nil, -1, err
	}

	artworks := make([]ArtworkBrief, len(body.Artworks))

	for index, value := range body.Artworks {
		var artwork ArtworkBrief

		err = json.Unmarshal([]byte(value), &artwork)
		if err != nil {
			artworks[index] = ArtworkBrief{
				ID:        "#",
				Title:     "Deleted or Private",
				Thumbnail: "https://s.pximg.net/common/images/limit_unknown_360.png",
			}
			continue
		}
		artworks[index] = artwork
	}

	return artworks, body.Total, nil
}

func (s *User) ParseSocial() error {
	if string(s.SocialRaw[:]) == "[]" {
		// Fuck Pixiv
		return nil
	}

	err := json.Unmarshal(s.SocialRaw, &s.Social)
	if err != nil {
		return err
	}
	return nil
}

// computeSliceBounds is a utility function to compute slice bounds safely
func computeSliceBounds(page int, worksPerPage float64, totalItems int) (start, end int, err error) {
	if totalItems == 0 {
		return 0, 0, nil
	}

	maxPages := int(math.Ceil(float64(totalItems) / worksPerPage))
	if page < 1 || page > maxPages {
		return 0, 0, i18n.Error("Invalid page number.")
	}

	start = (page - 1) * int(worksPerPage)
	end = min(start+int(worksPerPage), totalItems)

	return start, end, nil
}

func numberGreaterThan(l, r string) bool {
	if len(l) > len(r) {
		return true
	}
	if len(l) < len(r) {
		return false
	}
	return l > r
}