package services

import (
	"encoding/json"
	"fmt"
	"io"
	"mime"
	"net/http"
	neturl "net/url"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"
)

const (
	defaultGiphyAPIBaseURL = "https://api.giphy.com"
	defaultGiphyMaxResults = 100
	giphyBatchSize         = 20
	giphyDownloadSizeLimit = 50 * 1024 * 1024
)

type GiphyConfig struct {
	Enabled     bool
	APIKey      string
	MaxResults  int
	Rating      string
	Lang        string
	DownloadDir string
	BaseURL     string
}

type GiphyService struct {
	Config  GiphyConfig
	Client  *http.Client
	Gemini  *GeminiService
	Debug   func(message string, data any)
	BaseURL string
}

type GiphyResult struct {
	Provider               string         `json:"provider"`
	ProviderID             string         `json:"providerId"`
	Link                   string         `json:"link,omitempty"`
	Title                  string         `json:"title"`
	SearchQuery            string         `json:"searchQuery"`
	OriginalQuery          string         `json:"originalQuery,omitempty"`
	PreviewURL             string         `json:"previewUrl"`
	PreviewStillURL        string         `json:"previewStillUrl"`
	FullURL                string         `json:"fullUrl"`
	DownloadURL            string         `json:"downloadUrl"`
	Width                  int            `json:"width"`
	Height                 int            `json:"height"`
	Rating                 string         `json:"rating"`
	SourcePageURL          string         `json:"sourcePageUrl"`
	OpenURL                string         `json:"openUrl,omitempty"`
	Source                 string         `json:"source,omitempty"`
	ActionLabel            string         `json:"actionLabel,omitempty"`
	ActionType             string         `json:"actionType,omitempty"`
	SecondaryActionLabel   string         `json:"secondaryActionLabel,omitempty"`
	PreviewBlockedReason   string         `json:"previewBlockedReason,omitempty"`
	Raw                    map[string]any `json:"raw,omitempty"`
}

type GiphySearchResponse struct {
	Provider        string        `json:"provider"`
	OriginalQuery   string        `json:"originalQuery"`
	ExpandedQueries []string      `json:"expandedQueries"`
	Total           int           `json:"total"`
	Items           []GiphyResult `json:"items"`
	Warning         string        `json:"warning,omitempty"`
}

type GiphyDownloadRequest struct {
	ProviderID             string `json:"providerId"`
	Title                  string `json:"title"`
	DownloadURL            string `json:"downloadUrl"`
	OriginalQuery          string `json:"originalQuery"`
	SelectedExpansionQuery string `json:"selectedExpansionQuery"`
}

type GiphyDownloadResponse struct {
	OK        bool   `json:"ok"`
	FileName  string `json:"fileName,omitempty"`
	SavedPath string `json:"savedPath,omitempty"`
	Error     string `json:"error,omitempty"`
	Message   string `json:"message,omitempty"`
}

type giphySearchAPIResponse struct {
	Data []giphyAPIItem `json:"data"`
}

type giphyAPIItem struct {
	ID     string `json:"id"`
	Title  string `json:"title"`
	Slug   string `json:"slug"`
	Rating string `json:"rating"`
	URL    string `json:"url"`
	Images struct {
		Original             giphyRendition `json:"original"`
		OriginalStill        giphyRendition `json:"original_still"`
		FixedWidth           giphyRendition `json:"fixed_width"`
		FixedWidthStill      giphyRendition `json:"fixed_width_still"`
		FixedWidthDownsample giphyRendition `json:"fixed_width_downsampled"`
		FixedHeight          giphyRendition `json:"fixed_height"`
		PreviewGIF           giphyRendition `json:"preview_gif"`
		Downsized            giphyRendition `json:"downsized"`
		DownsizedLarge       giphyRendition `json:"downsized_large"`
	} `json:"images"`
}

type giphyRendition struct {
	URL    string `json:"url"`
	MP4    string `json:"mp4"`
	WebP   string `json:"webp"`
	Width  string `json:"width"`
	Height string `json:"height"`
}

func NewGiphyService(config GiphyConfig, gemini *GeminiService) *GiphyService {
	if config.MaxResults <= 0 {
		config.MaxResults = defaultGiphyMaxResults
	}
	if strings.TrimSpace(config.Rating) == "" {
		config.Rating = "g"
	}
	if strings.TrimSpace(config.Lang) == "" {
		config.Lang = "en"
	}
	if strings.TrimSpace(config.BaseURL) == "" {
		config.BaseURL = defaultGiphyAPIBaseURL
	}
	return &GiphyService{
		Config:  config,
		BaseURL: strings.TrimRight(config.BaseURL, "/"),
		Client:  &http.Client{Timeout: 20 * time.Second},
		Gemini:  gemini,
	}
}

func (s *GiphyService) SearchImages(query string, requestedMax int) (GiphySearchResponse, error) {
	response := GiphySearchResponse{
		Provider:      "giphy",
		OriginalQuery: strings.TrimSpace(query),
	}
	if !s.Config.Enabled {
		return response, fmt.Errorf("giphy is disabled")
	}
	if response.OriginalQuery == "" {
		return response, fmt.Errorf("query is required")
	}
	if strings.TrimSpace(s.Config.APIKey) == "" {
		return response, fmt.Errorf("giphy api key is not configured")
	}

	target := s.Config.MaxResults
	if requestedMax > 0 {
		target = minInt(requestedMax, s.Config.MaxResults)
	}
	if target <= 0 {
		target = minInt(defaultGiphyMaxResults, s.Config.MaxResults)
	}

	expandedQueries, expansionErr := s.expandQueries(response.OriginalQuery)
	response.ExpandedQueries = expandedQueries
	if expansionErr != nil {
		response.Warning = "Query expansion failed, using fallback search terms."
		s.debug("giphy:query_expansion_fallback", map[string]any{
			"query":   response.OriginalQuery,
			"queries": expandedQueries,
			"error":   expansionErr.Error(),
		})
	} else {
		s.debug("giphy:query_expansion", map[string]any{
			"query":   response.OriginalQuery,
			"queries": expandedQueries,
		})
	}

	type queryState struct {
		query   string
		offset  int
		enabled bool
	}

	states := make([]queryState, 0, len(expandedQueries))
	for _, item := range expandedQueries {
		states = append(states, queryState{query: item, enabled: true})
	}

	items := make([]GiphyResult, 0, target)
	seen := map[string]bool{}
	var allErrs []string
	var successfulCalls int

	fetchRound := func(limit int) bool {
		progress := false
		for idx := range states {
			if !states[idx].enabled || len(items) >= target {
				continue
			}
			batchLimit := minInt(limit, target-len(items))
			found, err := s.searchQuery(states[idx].query, batchLimit, states[idx].offset, response.OriginalQuery)
			if err != nil {
				allErrs = append(allErrs, err.Error())
				s.debug("giphy:query_error", map[string]any{
					"query":  states[idx].query,
					"offset": states[idx].offset,
					"error":  err.Error(),
				})
				continue
			}
			successfulCalls++
			s.debug("giphy:query_results", map[string]any{
				"query":  states[idx].query,
				"offset": states[idx].offset,
				"count":  len(found),
			})
			if len(found) == 0 {
				states[idx].enabled = false
				continue
			}
			states[idx].offset += len(found)
			before := len(items)
			for _, item := range found {
				if len(items) >= target {
					break
				}
				if mergeUniqueGiphyResult(&items, item, seen) {
					progress = true
				}
			}
			if len(found) < batchLimit && len(items) == before {
				states[idx].enabled = false
			}
		}
		return progress
	}

	progress := fetchRound(minInt(giphyBatchSize, target))
	for round := 0; len(items) < target && progress && round < 3; round++ {
		progress = fetchRound(minInt(giphyBatchSize, target-len(items)))
	}

	response.Items = items
	response.Total = len(items)
	s.debug("giphy:search_complete", map[string]any{
		"query":        response.OriginalQuery,
		"expanded":     response.ExpandedQueries,
		"total":        response.Total,
		"target":       target,
		"warning":      response.Warning,
		"successCalls": successfulCalls,
	})

	if response.Total == 0 && len(allErrs) > 0 {
		return response, fmt.Errorf("giphy search failed: %s", strings.Join(uniqueStrings(allErrs, 3), "; "))
	}
	if len(allErrs) > 0 && response.Warning == "" {
		response.Warning = "Some GIPHY requests failed, showing partial results."
	}
	return response, nil
}

func (s *GiphyService) DownloadMedia(req GiphyDownloadRequest) (GiphyDownloadResponse, error) {
	if !s.Config.Enabled {
		return GiphyDownloadResponse{OK: false, Error: "GIPHY_DISABLED", Message: "GIPHY is disabled"}, fmt.Errorf("giphy is disabled")
	}
	if strings.TrimSpace(req.ProviderID) == "" || strings.TrimSpace(req.DownloadURL) == "" {
		return GiphyDownloadResponse{OK: false, Error: "INVALID_REQUEST", Message: "providerId and downloadUrl are required"}, fmt.Errorf("providerId and downloadUrl are required")
	}
	if !isAllowedGiphyDownloadURL(req.DownloadURL) {
		return GiphyDownloadResponse{OK: false, Error: "INVALID_DOWNLOAD_URL", Message: "Only approved GIPHY media URLs are allowed"}, fmt.Errorf("download url is not on an approved giphy host")
	}
	if err := os.MkdirAll(s.Config.DownloadDir, 0o755); err != nil {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_DIR_FAILED", Message: "Failed to prepare GIPHY download directory"}, err
	}

	httpReq, err := http.NewRequest(http.MethodGet, req.DownloadURL, nil)
	if err != nil {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_FAILED", Message: "Failed to build GIPHY download request"}, err
	}
	httpReq.Header.Set("User-Agent", "AI-Media-Hub/1.0")
	resp, err := s.Client.Do(httpReq)
	if err != nil {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_FAILED", Message: "Failed to download media from GIPHY"}, err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 300 {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_FAILED", Message: "Failed to download media from GIPHY"}, fmt.Errorf("giphy download returned status %d", resp.StatusCode)
	}
	if resp.ContentLength > giphyDownloadSizeLimit {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_TOO_LARGE", Message: "GIPHY media exceeds the configured size limit"}, fmt.Errorf("giphy download too large: %d", resp.ContentLength)
	}

	contentType, _, _ := mime.ParseMediaType(resp.Header.Get("Content-Type"))
	extension := determineGiphyExtension(req.DownloadURL, contentType)
	fileName := buildGiphyFilename(req.ProviderID, req.Title, extension, time.Now())
	targetPath := filepath.Join(s.Config.DownloadDir, fileName)
	cleanTargetPath := filepath.Clean(targetPath)
	cleanBaseDir := filepath.Clean(s.Config.DownloadDir)
	if !strings.HasPrefix(cleanTargetPath, cleanBaseDir) {
		return GiphyDownloadResponse{OK: false, Error: "INVALID_PATH", Message: "Resolved download path is invalid"}, fmt.Errorf("resolved giphy download path escaped base directory")
	}

	data, err := io.ReadAll(io.LimitReader(resp.Body, giphyDownloadSizeLimit+1))
	if err != nil {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_FAILED", Message: "Failed to read media from GIPHY"}, err
	}
	if int64(len(data)) > giphyDownloadSizeLimit {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_TOO_LARGE", Message: "GIPHY media exceeds the configured size limit"}, fmt.Errorf("giphy download exceeded size limit during read")
	}
	if err := os.WriteFile(cleanTargetPath, data, 0o644); err != nil {
		return GiphyDownloadResponse{OK: false, Error: "DOWNLOAD_FAILED", Message: "Failed to save media from GIPHY"}, err
	}

	s.debug("giphy:download_success", map[string]any{
		"providerId": req.ProviderID,
		"fileName":   fileName,
		"savedPath":  cleanTargetPath,
	})
	return GiphyDownloadResponse{
		OK:        true,
		FileName:  fileName,
		SavedPath: cleanTargetPath,
	}, nil
}

func (s *GiphyService) expandQueries(query string) ([]string, error) {
	if s.Gemini == nil {
		return buildFallbackImageQueries(query, strings.TrimSpace(query)), fmt.Errorf("gemini service is not configured")
	}
	return s.Gemini.ExpandImageQueries(query)
}

func (s *GiphyService) searchQuery(query string, limit, offset int, originalQuery string) ([]GiphyResult, error) {
	endpoint, err := neturl.Parse(s.BaseURL + "/v1/gifs/search")
	if err != nil {
		return nil, err
	}
	params := endpoint.Query()
	params.Set("api_key", s.Config.APIKey)
	params.Set("q", query)
	params.Set("limit", strconv.Itoa(limit))
	params.Set("offset", strconv.Itoa(max(offset, 0)))
	params.Set("rating", s.Config.Rating)
	params.Set("lang", s.Config.Lang)
	endpoint.RawQuery = params.Encode()

	req, err := http.NewRequest(http.MethodGet, endpoint.String(), nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/json")

	resp, err := s.Client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		data, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
		return nil, fmt.Errorf("giphy returned status %d: %s", resp.StatusCode, strings.TrimSpace(string(data)))
	}

	var payload giphySearchAPIResponse
	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
		return nil, err
	}
	items := make([]GiphyResult, 0, len(payload.Data))
	for _, item := range payload.Data {
		mapped := mapGiphyItem(item, query, originalQuery)
		if mapped.ProviderID == "" || mapped.FullURL == "" {
			continue
		}
		items = append(items, mapped)
	}
	return items, nil
}

func mapGiphyItem(item giphyAPIItem, searchQuery, originalQuery string) GiphyResult {
	previewURL := firstNonEmpty(
		item.Images.FixedWidthDownsample.URL,
		item.Images.FixedWidth.URL,
		item.Images.FixedHeight.URL,
		item.Images.PreviewGIF.URL,
		item.Images.Downsized.URL,
		item.Images.Original.URL,
	)
	stillURL := firstNonEmpty(
		item.Images.FixedWidthStill.URL,
		item.Images.OriginalStill.URL,
		item.Images.FixedWidth.URL,
		item.Images.Downsized.URL,
		item.Images.Original.URL,
	)
	fullURL := firstNonEmpty(
		item.Images.Original.URL,
		item.Images.DownsizedLarge.URL,
		item.Images.Downsized.URL,
		item.Images.FixedWidth.URL,
	)
	downloadURL := firstNonEmpty(
		item.Images.Original.URL,
		item.Images.DownsizedLarge.URL,
		item.Images.FixedWidth.URL,
		item.Images.Original.MP4,
	)
	width := atoiOrZero(firstNonEmpty(item.Images.Original.Width, item.Images.FixedWidth.Width, item.Images.DownsizedLarge.Width))
	height := atoiOrZero(firstNonEmpty(item.Images.Original.Height, item.Images.FixedWidth.Height, item.Images.DownsizedLarge.Height))
	title := strings.TrimSpace(item.Title)
	if title == "" {
		title = strings.ReplaceAll(strings.TrimSpace(item.Slug), "-", " ")
	}
	if title == "" {
		title = "Untitled GIPHY"
	}
	return GiphyResult{
		Provider:             "giphy",
		ProviderID:           strings.TrimSpace(item.ID),
		Link:                 strings.TrimSpace(item.URL),
		Title:                title,
		SearchQuery:          searchQuery,
		OriginalQuery:        originalQuery,
		PreviewURL:           previewURL,
		PreviewStillURL:      stillURL,
		FullURL:              fullURL,
		DownloadURL:          downloadURL,
		Width:                width,
		Height:               height,
		Rating:               strings.TrimSpace(item.Rating),
		SourcePageURL:        strings.TrimSpace(item.URL),
		OpenURL:              strings.TrimSpace(item.URL),
		Source:               "GIPHY",
		ActionLabel:          "Download",
		ActionType:           "giphy_download",
		SecondaryActionLabel: "Open Original",
	}
}

func mergeUniqueGiphyResult(items *[]GiphyResult, candidate GiphyResult, seen map[string]bool) bool {
	for _, key := range giphyDedupKeys(candidate) {
		if key == "" {
			continue
		}
		if seen[key] {
			return false
		}
	}
	for _, key := range giphyDedupKeys(candidate) {
		if key != "" {
			seen[key] = true
		}
	}
	*items = append(*items, candidate)
	return true
}

func giphyDedupKeys(item GiphyResult) []string {
	keys := []string{}
	if item.ProviderID != "" {
		keys = append(keys, "id:"+strings.ToLower(item.ProviderID))
	}
	if item.FullURL != "" {
		keys = append(keys, "full:"+strings.ToLower(strings.TrimSpace(item.FullURL)))
	}
	if item.SourcePageURL != "" {
		keys = append(keys, "source:"+strings.ToLower(strings.TrimSpace(item.SourcePageURL)))
	}
	return keys
}

func buildFallbackImageQueries(originalQuery, englishBase string) []string {
	base := strings.TrimSpace(englishBase)
	if base == "" {
		base = strings.TrimSpace(originalQuery)
	}
	candidates := []string{
		base,
		base + " gif",
		base + " reaction gif",
		base + " meme gif",
		base + " animated gif",
		base + " reaction image",
		base + " sticker",
	}
	queries := normalizeImageExpansionQueries(candidates)
	if len(queries) > 5 {
		return queries[:5]
	}
	for len(queries) < 5 {
		queries = append(queries, fmt.Sprintf("%s gif %d", base, len(queries)+1))
	}
	return queries[:5]
}

func normalizeImageExpansionQueries(items []string) []string {
	seen := map[string]bool{}
	queries := make([]string, 0, 5)
	for _, item := range items {
		normalized := sanitizePlainEnglishLine(item)
		normalized = strings.Join(strings.Fields(normalized), " ")
		if normalized == "" {
			continue
		}
		if !looksMostlyASCII(normalized) {
			continue
		}
		key := strings.ToLower(normalized)
		if seen[key] {
			continue
		}
		seen[key] = true
		queries = append(queries, normalized)
	}
	return queries
}

func isAllowedGiphyDownloadURL(rawURL string) bool {
	parsed, err := neturl.Parse(strings.TrimSpace(rawURL))
	if err != nil {
		return false
	}
	host := strings.ToLower(parsed.Hostname())
	if host == "" {
		return false
	}
	if parsed.Scheme != "https" && parsed.Scheme != "http" {
		return false
	}
	return host == "giphy.com" || strings.HasSuffix(host, ".giphy.com")
}

func buildGiphyFilename(providerID, title, extension string, now time.Time) string {
	slug := sanitizeGiphyFilenameComponent(title)
	if slug == "" {
		slug = "untitled"
	}
	providerID = sanitizeGiphyFilenameComponent(providerID)
	if providerID == "" {
		providerID = "unknown"
	}
	ext := extension
	if !strings.HasPrefix(ext, ".") {
		ext = "." + ext
	}
	return fmt.Sprintf("giphy_%s_%s_%s%s", providerID, slug, now.Format("20060102_150405"), ext)
}

func sanitizeGiphyFilenameComponent(value string) string {
	re := regexp.MustCompile(`[^a-z0-9]+`)
	normalized := strings.ToLower(strings.TrimSpace(value))
	normalized = re.ReplaceAllString(normalized, "-")
	return strings.Trim(normalized, "-")
}

func determineGiphyExtension(rawURL, contentType string) string {
	switch strings.ToLower(strings.TrimSpace(contentType)) {
	case "image/gif":
		return ".gif"
	case "video/mp4":
		return ".mp4"
	case "image/webp":
		return ".webp"
	case "image/png":
		return ".png"
	case "image/jpeg":
		return ".jpg"
	}
	parsed, err := neturl.Parse(rawURL)
	if err == nil {
		ext := strings.ToLower(path.Ext(parsed.Path))
		switch ext {
		case ".gif", ".mp4", ".webp", ".png", ".jpg", ".jpeg":
			if ext == ".jpeg" {
				return ".jpg"
			}
			return ext
		}
	}
	return ".gif"
}

func atoiOrZero(value string) int {
	parsed, err := strconv.Atoi(strings.TrimSpace(value))
	if err != nil {
		return 0
	}
	return parsed
}

func uniqueStrings(items []string, limit int) []string {
	seen := map[string]bool{}
	unique := make([]string, 0, minInt(len(items), limit))
	for _, item := range items {
		trimmed := strings.TrimSpace(item)
		if trimmed == "" || seen[trimmed] {
			continue
		}
		seen[trimmed] = true
		unique = append(unique, trimmed)
		if len(unique) >= limit {
			break
		}
	}
	return unique
}

func (s *GiphyService) debug(message string, data any) {
	if s != nil && s.Debug != nil {
		s.Debug(message, data)
	}
}