package service

import (
	"github.com/gofiber/fiber/v3"
	"github.com/gofiber/fiber/v3/log"
	"net/url"
	"nysoure/server/config"
	"nysoure/server/dao"
	"nysoure/server/model"
	"nysoure/server/search"
	"nysoure/server/utils"
	"strconv"
	"strings"

	"gorm.io/gorm"
)

const (
	maxSearchQueryLength = 100
)

type ResourceParams struct {
	Title             string       `json:"title" binding:"required"`
	AlternativeTitles []string     `json:"alternative_titles"`
	Links             []model.Link `json:"links"`
	Tags              []uint       `json:"tags"`
	Article           string       `json:"article"`
	Images            []uint       `json:"images"`
}

func CreateResource(uid uint, params *ResourceParams) (uint, error) {
	canUpload, err := checkUserCanUpload(uid)
	if err != nil {
		return 0, err
	}
	if !canUpload {
		return 0, model.NewUnAuthorizedError("You have not permission to upload resources")
	}

	images := make([]model.Image, len(params.Images))
	for i, id := range params.Images {
		images[i] = model.Image{
			Model: gorm.Model{
				ID: id,
			},
		}
	}
	tags := make([]model.Tag, len(params.Tags))
	for i, id := range params.Tags {
		tags[i] = model.Tag{
			Model: gorm.Model{
				ID: id,
			},
		}
	}
	r := model.Resource{
		Title:             params.Title,
		AlternativeTitles: params.AlternativeTitles,
		Article:           params.Article,
		Links:             params.Links,
		Images:            images,
		Tags:              tags,
		UserID:            uid,
	}
	if r, err = dao.CreateResource(r); err != nil {
		return 0, err
	}
	err = updateCachedTagList()
	if err != nil {
		log.Error("Error updating cached tag list:", err)
	}
	err = dao.AddNewResourceActivity(uid, r.ID)
	if err != nil {
		log.Error("AddNewResourceActivity error: ", err)
	}
	return r.ID, nil
}

func findRelatedResources(r model.Resource, host string) []model.ResourceView {
	lines := strings.Split(r.Article, "\n")
	var relatedResources []model.ResourceView
	for _, line := range lines {
		r := parseResourceIfPresent(line, host)
		if r != nil {
			relatedResources = append(relatedResources, *r)
		}
	}
	return relatedResources
}

func parseResourceIfPresent(line string, host string) *model.ResourceView {
	if len(line) < 4 {
		return nil
	}
	if !strings.HasPrefix(line, "[") || !strings.HasSuffix(line, ")") {
		return nil
	}
	if !strings.Contains(line, "](") {
		return nil
	}
	splites := strings.Split(line, "(")
	if len(splites) != 2 {
		return nil
	}
	u := strings.TrimSuffix(splites[1], ")")
	u = strings.TrimSpace(u)
	parsed, err := url.Parse(u)
	if err != nil {
		return nil
	}
	if parsed.IsAbs() && parsed.Hostname() != host {
		return nil
	}
	path := parsed.Path
	if !strings.HasPrefix(path, "/resources/") {
		return nil
	}
	idStr := strings.TrimPrefix(path, "/resources/")
	id, err := strconv.Atoi(idStr)
	if err != nil {
		return nil
	}
	r, err := dao.GetResourceByID(uint(id))
	if err != nil {
		return nil
	}
	v := r.ToView()
	return &v
}

func GetResource(id uint, host string, ctx fiber.Ctx) (*model.ResourceDetailView, error) {
	r, err := dao.GetResourceByID(id)
	if err != nil {
		return nil, err
	}
	if ctx != nil && ctx.Locals("real_user") == true {
		err = dao.AddResourceViewCount(id)
		if err != nil {
			log.Error("AddResourceViewCount error: ", err)
		}
	}
	v := r.ToDetailView()
	if host != "" {
		related := findRelatedResources(r, host)
		v.Related = related
	}
	return &v, nil
}

func GetResourceList(page int, sort model.RSort) ([]model.ResourceView, int, error) {
	resources, totalPages, err := dao.GetResourceList(page, pageSize, sort)
	if err != nil {
		return nil, 0, err
	}
	var views []model.ResourceView
	for _, r := range resources {
		views = append(views, r.ToView())
	}
	return views, totalPages, nil
}

// splitQuery splits the input query string into keywords, treating quoted substrings (single or double quotes)
// as single keywords and supporting escape characters for quotes. Spaces outside quotes are used as separators.
func splitQuery(query string) []string {
	var keywords []string

	query = strings.TrimSpace(query)
	if query == "" {
		return keywords
	}

	l, r := 0, 0
	inQuote := false
	quoteChar := byte(0)

	for r < len(query) {
		if (query[r] == '"' || query[r] == '\'') && (r == 0 || query[r-1] != '\\') {
			if !inQuote {
				inQuote = true
				quoteChar = query[r]
				l = r + 1
			} else if query[r] == quoteChar {
				if r > l {
					keywords = append(keywords, strings.TrimSpace(query[l:r]))
				}
				inQuote = false
				r++
				l = r
				continue
			}
		} else if !inQuote && query[r] == ' ' {
			if r > l {
				keywords = append(keywords, strings.TrimSpace(query[l:r]))
			}
			for r < len(query) && query[r] == ' ' {
				r++
			}
			l = r
			continue
		}

		r++
	}

	if l < len(query) {
		keywords = append(keywords, strings.TrimSpace(query[l:r]))
	}

	return keywords
}

func searchWithKeyword(keyword string) ([]uint, error) {
	resources := make([]uint, 0)

	if len([]rune(keyword)) <= maxTagLength {
		exists, err := dao.ExistsTag(keyword)
		if err != nil {
			return nil, err
		}
		if exists {
			t, err := dao.GetTagByName(keyword)
			if err != nil {
				return nil, err
			}
			res, err := dao.GetResourcesIdWithTag(t.ID)
			if err != nil {
				return nil, err
			}
			resources = append(resources, res...)
		}
	}

	searchResult, err := search.SearchResource(keyword)
	if err != nil {
		return nil, err
	}

	resources = append(resources, searchResult...)

	return resources, nil
}

func SearchResource(query string, page int) ([]model.ResourceView, int, error) {
	if len([]rune(query)) > maxSearchQueryLength {
		return nil, 0, model.NewRequestError("Search query is too long")
	}

	start := (page - 1) * pageSize
	end := start + pageSize
	resources := make([]uint, 0)

	checkTag := func(tag string) error {
		if len([]rune(tag)) > maxTagLength {
			return nil
		}
		exists, err := dao.ExistsTag(tag)
		if err != nil {
			return err
		}
		if exists {
			t, err := dao.GetTagByName(tag)
			if err != nil {
				return err
			}
			res, err := dao.GetResourcesIdWithTag(t.ID)
			if err != nil {
				return err
			}
			resources = append(resources, res...)
		}
		return nil
	}

	// check tag
	if err := checkTag(query); err != nil {
		return nil, 0, err
	}

	// check tag after removing spaces
	trimmed := utils.RemoveSpaces(query)
	if trimmed != query {
		if err := checkTag(trimmed); err != nil {
			return nil, 0, err
		}
	}

	// split query to search
	keywords := splitQuery(query)
	var temp []uint
	first := true
	for _, keyword := range keywords {
		if keyword == "" {
			continue
		}
		res, err := searchWithKeyword(keyword)
		if err != nil {
			return nil, 0, err
		}
		if first {
			for _, id := range res {
				found := false
				for _, id2 := range temp {
					if id == id2 {
						found = true
						break
					}
				}
				if !found {
					temp = append(temp, id)
				}
			}
			first = false
		} else {
			temp1 := make([]uint, 0)
			for _, id := range temp {
				for _, id2 := range res {
					if id == id2 {
						temp1 = append(temp1, id)
						break
					}
				}
			}
			temp = temp1
		}
	}
	resources = append(resources, temp...)

	// remove duplicates
	temp = make([]uint, 0)
	for _, id := range resources {
		found := false
		for _, id2 := range temp {
			if id == id2 {
				found = true
				break
			}
		}
		if !found {
			temp = append(temp, id)
		}
	}

	if start >= len(resources) {
		return []model.ResourceView{}, 0, nil
	}

	total := len(resources)
	totalPages := (total + pageSize - 1) / pageSize
	if start >= total {
		return []model.ResourceView{}, totalPages, nil
	}
	if end > total {
		end = total
	}
	idsPage := resources[start:end]

	resourcesPage, err := dao.BatchGetResources(idsPage)
	if err != nil {
		return nil, 0, err
	}
	var views []model.ResourceView
	for _, r := range resourcesPage {
		views = append(views, r.ToView())
	}
	return views, totalPages, nil
}

func DeleteResource(uid, id uint) error {
	isAdmin, err := CheckUserIsAdmin(uid)
	if err != nil {
		return err
	}
	if !isAdmin {
		r, err := dao.GetResourceByID(id)
		if err != nil {
			return err
		}
		if r.UserID != uid {
			return model.NewUnAuthorizedError("You have not permission to delete this resource")
		}
	}
	r, err := GetResource(id, "", nil)
	if err != nil {
		return err
	}
	if len(r.Files) > 0 {
		return model.NewRequestError("This resource has files, please delete them first")
	}
	if err := dao.DeleteResource(id); err != nil {
		return err
	}
	err = updateCachedTagList()
	if err != nil {
		log.Error("Error updating cached tag list:", err)
	}
	return nil
}

func GetResourcesWithTag(tag string, page int) ([]model.ResourceView, int, error) {
	t, err := dao.GetTagByName(tag)
	if err != nil {
		return nil, 0, err
	}
	tagID := t.ID
	resources, totalPages, err := dao.GetResourceByTag(tagID, page, pageSize)
	if err != nil {
		return nil, 0, err
	}
	var views []model.ResourceView
	for _, r := range resources {
		views = append(views, r.ToView())
	}
	return views, totalPages, nil
}

func GetResourcesWithUser(username string, page int) ([]model.ResourceView, int, error) {
	resources, totalPages, err := dao.GetResourcesByUsername(username, page, pageSize)
	if err != nil {
		return nil, 0, err
	}
	var views []model.ResourceView
	for _, r := range resources {
		views = append(views, r.ToView())
	}
	return views, totalPages, nil
}

func EditResource(uid, rid uint, params *ResourceParams) error {
	isAdmin, err := checkUserCanUpload(uid)
	if err != nil {
		log.Error("checkUserCanUpload error: ", err)
		return model.NewInternalServerError("Failed to check user permission")
	}
	r, err := dao.GetResourceByID(rid)
	if err != nil {
		return err
	}
	if r.UserID != uid && !isAdmin {
		return model.NewUnAuthorizedError("You have not permission to edit this resource")
	}

	r.Title = params.Title
	r.AlternativeTitles = params.AlternativeTitles
	r.Article = params.Article
	r.Links = params.Links

	images := make([]model.Image, len(params.Images))
	for i, id := range params.Images {
		images[i] = model.Image{
			Model: gorm.Model{
				ID: id,
			},
		}
	}
	tags := make([]model.Tag, len(params.Tags))
	for i, id := range params.Tags {
		tags[i] = model.Tag{
			Model: gorm.Model{
				ID: id,
			},
		}
	}
	r.Images = images
	r.Tags = tags
	if err := dao.UpdateResource(r); err != nil {
		log.Error("UpdateResource error: ", err)
		return model.NewInternalServerError("Failed to update resource")
	}
	err = updateCachedTagList()
	if err != nil {
		log.Error("Error updating cached tag list:", err)
	}
	err = dao.AddUpdateResourceActivity(uid, r.ID)
	if err != nil {
		log.Error("AddUpdateResourceActivity error: ", err)
	}
	return nil
}

func RandomResource(host string) (*model.ResourceDetailView, error) {
	r, err := dao.RandomResource()
	if err != nil {
		return nil, err
	}
	v := r.ToDetailView()
	if host != "" {
		related := findRelatedResources(r, host)
		v.Related = related
	}
	return &v, nil
}

var lastSuccessCover uint

func RandomCover() (uint, error) {
	for retries := 0; retries < 5; retries++ {
		v, err := dao.RandomResource()
		if err != nil {
			return 0, err
		}
		if len(v.Images) > 0 {
			lastSuccessCover = v.Images[0].ID
			return v.Images[0].ID, nil
		}
	}
	return lastSuccessCover, nil
}

func GetPinnedResources() ([]model.ResourceView, error) {
	ids := config.PinnedResources()
	var views []model.ResourceView
	for _, id := range ids {
		r, err := dao.GetResourceByID(id)
		if err != nil {
			continue
		}
		views = append(views, r.ToView())
	}
	return views, nil
}