package handlers

import (
	vimeopkg "Yimaru-Backend/internal/pkgs/vimeo"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"mime"
	"net/http"
	"net/url"
	"path"
	"sort"
	"strings"
	"time"
)

type sourceFetchResult struct {
	FileName    string
	ContentType string
	Data        []byte
}

func normalizeSourceURL(raw string, mediaType string) (string, error) {
	u, err := url.Parse(strings.TrimSpace(raw))
	if err != nil {
		return "", fmt.Errorf("invalid source URL: %w", err)
	}
	if u.Scheme != "http" && u.Scheme != "https" {
		return "", fmt.Errorf("source URL must use http or https")
	}

	host := strings.ToLower(u.Hostname())

	if strings.Contains(host, "drive.google.com") {
		parts := strings.Split(strings.Trim(u.Path, "/"), "/")
		// Convert /file/d/{id}/view links to a direct-download endpoint.
		if len(parts) >= 3 && parts[0] == "file" && parts[1] == "d" {
			fileID := parts[2]
			return "https://drive.google.com/uc?export=download&id=" + fileID, nil
		}
	}

	if mediaType == "video" && (strings.Contains(host, "vimeo.com") || strings.Contains(host, "player.vimeo.com")) {
		directURL, err := resolveVimeoDirectFileURL(u.String())
		if err != nil {
			return "", err
		}
		if directURL != "" {
			return directURL, nil
		}
	}

	return u.String(), nil
}

func resolveVimeoDirectFileURL(vimeoURL string) (string, error) {
	videoID := vimeopkg.ExtractVideoID(vimeoURL)
	if videoID == "" {
		return "", fmt.Errorf("failed to extract Vimeo video id from source URL")
	}

	src, err := url.Parse(vimeoURL)
	if err != nil {
		return "", fmt.Errorf("invalid Vimeo source URL: %w", err)
	}

	configURL := "https://player.vimeo.com/video/" + videoID + "/config"
	if hash := src.Query().Get("h"); hash != "" {
		configURL += "?h=" + url.QueryEscape(hash)
	}

	req, err := http.NewRequest(http.MethodGet, configURL, nil)
	if err != nil {
		return "", fmt.Errorf("failed to build Vimeo config request: %w", err)
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("User-Agent", "Yimaru-Backend/1.0")

	client := &http.Client{Timeout: 30 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("failed to fetch Vimeo config: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("Vimeo config fetch failed with status %d", resp.StatusCode)
	}

	var payload struct {
		Request struct {
			Files struct {
				Progressive []struct {
					URL      string `json:"url"`
					Height   int    `json:"height"`
					MimeType string `json:"mime"`
				} `json:"progressive"`
			} `json:"files"`
		} `json:"request"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
		return "", fmt.Errorf("failed to decode Vimeo config payload: %w", err)
	}

	if len(payload.Request.Files.Progressive) == 0 {
		return "", fmt.Errorf("no downloadable Vimeo progressive stream found; provide a Vimeo URL with a valid '?h=' hash or a direct file URL")
	}

	sort.Slice(payload.Request.Files.Progressive, func(i, j int) bool {
		return payload.Request.Files.Progressive[i].Height > payload.Request.Files.Progressive[j].Height
	})

	return payload.Request.Files.Progressive[0].URL, nil
}

func fetchMediaFromSourceURL(ctx context.Context, rawSourceURL string, mediaType string, maxSize int64) (*sourceFetchResult, error) {
	sourceURL, err := normalizeSourceURL(rawSourceURL, mediaType)
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, sourceURL, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create source request: %w", err)
	}
	req.Header.Set("User-Agent", "Yimaru-Backend/1.0")
	req.Header.Set("Accept", "*/*")

	client := &http.Client{
		Timeout: 2 * time.Minute,
	}

	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch source URL: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode > 299 {
		return nil, fmt.Errorf("source URL returned status %d", resp.StatusCode)
	}

	limited := io.LimitReader(resp.Body, maxSize+1)
	data, err := io.ReadAll(limited)
	if err != nil {
		return nil, fmt.Errorf("failed to read source content: %w", err)
	}
	if int64(len(data)) > maxSize {
		return nil, fmt.Errorf("source file exceeds size limit for media type '%s'", mediaType)
	}
	if len(data) == 0 {
		return nil, fmt.Errorf("source URL returned empty content")
	}

	contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
	if contentType != "" {
		contentType = strings.ToLower(strings.TrimSpace(strings.Split(contentType, ";")[0]))
	}
	if contentType == "" || contentType == "application/octet-stream" {
		sampleLen := 512
		if len(data) < sampleLen {
			sampleLen = len(data)
		}
		contentType = http.DetectContentType(data[:sampleLen])
	}

	fileName := "source-upload"
	if cd := resp.Header.Get("Content-Disposition"); cd != "" {
		if _, params, parseErr := mime.ParseMediaType(cd); parseErr == nil {
			if fn := strings.TrimSpace(params["filename"]); fn != "" {
				fileName = fn
			}
		}
	}
	if fileName == "source-upload" {
		if parsedURL, parseErr := url.Parse(sourceURL); parseErr == nil {
			base := path.Base(parsedURL.Path)
			if base != "" && base != "." && base != "/" {
				fileName = base
			}
		}
	}

	return &sourceFetchResult{
		FileName:    fileName,
		ContentType: contentType,
		Data:        data,
	}, nil
}