package main

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"sort"
	"strings"

	"golang.org/x/sys/unix"
)

func main() {
	if len(os.Args) != 2 && len(os.Args) != 3 {
		fmt.Fprintf(os.Stderr, "Usage: %s <submission id/url> [direct url to download instead of inferring from the post]\n", os.Args[0])
		os.Exit(1)
	}
	LoadMimetypes()
	submissionUrl, err := url.Parse(os.Args[1])
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error when parsing submission url: %s\n", err)
		os.Exit(1)
	}
	submissionJsonUrl := ""
	submissionId := os.Args[1]
	if submissionUrl.Hostname() == "redd.it" {
		submissionJsonUrl = "https://old.reddit.com" + submissionUrl.EscapedPath() + ".json?raw_json=1&limit=1"
		submissionId = submissionUrl.EscapedPath()[1:]
	} else if submissionUrl.Hostname() == "" {
		submissionJsonUrl = "https://old.reddit.com/" + os.Args[1] + ".json?raw_json=1&limit=1"
	} else {
		submissionJsonUrl = "https://old.reddit.com" + submissionUrl.EscapedPath() + "/.json?raw_json=1&limit=1"
		split := strings.SplitN(submissionUrl.EscapedPath(), "/", 6)
		if len(split) < 5 {
			fmt.Fprintln(os.Stderr, "URL passed does not have enough path seperators")
			os.Exit(1)
		}
		submissionId = split[4]
	}
	client := &http.Client{}
	submission, err := GetSubmission(client, submissionJsonUrl)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to get submission: %s\n", err)
		os.Exit(1)
	}
	filename := strings.ReplaceAll(submission.Title, "/", "_") + "-" + submissionId
	if filename[0] == '.' {
		filename = "_" + filename[1:]
	}
	if submission.CrosspostParent != "" && len(submission.CrosspostParentList) > 0 {
		submission, err = GetSubmission(client, "https://old.reddit.com"+submission.CrosspostParentList[0].Permalink+".json?raw_json=1&limit=1")
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to get original submission: %s\n", err)
			os.Exit(1)
		}
	}
	if submission.IsSelf {
		fmt.Fprintln(os.Stderr, "Cannot download selfposts")
		os.Exit(1)
	}
	urls := make([]string, 1)
	urls[0] = submission.Url
	if submission.IsVideo {
		ffmpegPath, err := exec.LookPath("ffmpeg")
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to find ffmpeg: %s\n", err)
			os.Exit(1)
		}
		ffmpegUrl := submission.SecureMedia.RedditVideo.HlsUrl
		if ffmpegUrl == "" {
			ffmpegUrl = submission.SecureMedia.RedditVideo.DashUrl
		}
		if ffmpegUrl != "" {
			client.CloseIdleConnections()
			err = unix.Exec(ffmpegPath, []string{"ffmpeg", "-nostdin", "-i", ffmpegUrl, "-c", "copy", "--", filename + ".mp4"}, os.Environ())
			fmt.Fprintf(os.Stderr, "Failed to exec as ffmpeg: %s\n", err)
			os.Exit(1)
		}
		fallbackUrl := submission.SecureMedia.RedditVideo.FallbackUrl
		if fallbackUrl != "" {
			urls[0] = fallbackUrl
		}
	} else if submission.IsGallery {
		var galleryKeys []string
		if submission.GalleryData != nil {
			sort.Sort(submission.GalleryData)
			for _, i := range submission.GalleryData.Items {
				galleryKeys = append(galleryKeys, i.MediaId)
			}
		} else {
			for i, _ := range submission.MediaMetadata {
				galleryKeys = append(galleryKeys, i)
			}
		}
		urls = nil
		for _, i := range galleryKeys {
			mediaMetadataItem := submission.MediaMetadata[i]
			if mediaMetadataItem.Status != "valid" {
				continue
			}
			if mediaMetadataItem.S.U != "" {
				urls = append(urls, mediaMetadataItem.S.U)
			} else if mediaMetadataItem.S.Mp4 != "" {
				urls = append(urls, mediaMetadataItem.S.Mp4)
			} else if mediaMetadataItem.S.Gif != "" {
				urls = append(urls, mediaMetadataItem.S.Gif)
			}
		}
	}
	stdin := bufio.NewReader(os.Stdin)
	i, err := InteractivelyAskIndex(stdin, urls)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to get index: %s\n", err)
		os.Exit(1)
	}
	if len(urls) > 1 {
		filename = fmt.Sprintf("%s_%03d", filename, i)
	}
	unparsedUrl := urls[i]
	parsedUrl, err := url.Parse(unparsedUrl)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to parse url: %s\n", err)
		os.Exit(1)
	}
	domain := submission.Domain
	if domain == "" {
		domain = parsedUrl.Hostname()
	}
	path := parsedUrl.EscapedPath()
	pathExtless, pathExt := SplitExt(path)
	urls = make([]string, 1)
	urls[0] = unparsedUrl
	if domain == "imgur.com" || strings.HasSuffix(domain, ".imgur.com") {
		parsedUrl.Host = "i.imgur.com"
		if strings.HasPrefix(path, "/a/") || strings.HasPrefix(path, "/gallery/") {
			albumId := strings.SplitN(strings.SplitN(path, "/", 4)[2], ".", 2)[0]
			imgurImages, err := GetImgurAlbum(client, albumId)
			if err != nil {
				fmt.Fprintf(os.Stderr, "Failed to get imgur album: %s\n", err)
				os.Exit(1)
			}
			urls = nil
			for _, i := range imgurImages {
				urls = append(urls, "https://i.imgur.com/"+i.Hash+i.Ext)
			}
		} else {
			if pathExt == ".gifv" {
				parsedUrl.RawPath = pathExtless + ".mp4"
			}
			urls[0] = parsedUrl.String()
		}
	} else if domain == "gfycat.com" {
		gfyMp4, err := GetGfycat(client, pathExtless)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to get gfycat video: %s\n", err)
			os.Exit(1)
		}
		if gfyMp4 != "" {
			urls[0] = gfyMp4
		}
	} else if submission.IsRedditMediaDomain && submission.Preview != nil {
		preview := submission.Preview.Images[0]
		if pathExt == ".gif" {
			if preview.Variants.Mp4.Source != nil {
				urls[0] = preview.Variants.Mp4.Source.Url
			} else if preview.Variants.Gif.Source != nil {
				urls[0] = preview.Variants.Gif.Source.Url
			}
		} else if submission.IsVideo {
			urls[0] = preview.Source.Url
		}
	}
	i, err = InteractivelyAskIndex(stdin, urls)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to get index: %s\n", err)
		os.Exit(1)
	}
	if len(urls) > 1 {
		filename = fmt.Sprintf("%s_%03d", filename, i)
	}
	files, err := os.ReadDir(".")
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to list files: %s\n", err)
		os.Exit(1)
	}
	for _, i := range files {
		if strings.HasPrefix(i.Name(), filename) {
			fmt.Printf("A file that starts with %s exists (%s), potentially overwrite (y/N)? ", filename, i.Name())
			b, err := stdin.ReadByte()
			if err != nil {
				fmt.Fprintf(os.Stderr, "Error when reading stdin: %s\n", err)
				os.Exit(1)
			}
			if b != 'y' && b != 'Y' {
				fmt.Println("Not overwriting")
				os.Exit(1)
			}
			break
		}
	}
	if len(os.Args) == 3 {
		unparsedUrl = os.Args[2]
	} else {
		unparsedUrl = urls[i]
	}
	response, err := client.Get(unparsedUrl)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to get response: %s\n", err)
		os.Exit(1)
	}
	defer response.Body.Close()
	ext, err := GetExtension(response.Header.Get("Content-Type"))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Warning: Failed to get file extension: %s\n", err)
	} else {
		filename = filename + ext
	}
	fmt.Printf("Downloading to %s\n", filename)
	file, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE, 0o664)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to open file for writing: %s\n", err)
		os.Exit(1)
	}
	writer := bufio.NewWriter(file)
	defer writer.Flush()
	reader := bufio.NewReader(response.Body)
	lastOutputLength := 0
	bytesDownloaded := 0
	toWrite := make([]byte, 1024*1024)
	for {
		lastOutputLength = PrintStatus(float64(bytesDownloaded), float64(response.ContentLength), lastOutputLength)
		n, err := reader.Read(toWrite)
		if n > 0 {
			_, writeErr := writer.Write(toWrite[:n])
			if writeErr != nil {
				fmt.Fprintf(os.Stderr, "Failed to write response: %s\n", writeErr)
				os.Exit(1)
			}
			bytesDownloaded += n
			lastOutputLength = PrintStatus(float64(bytesDownloaded), float64(response.ContentLength), lastOutputLength)
		}
		if errors.Is(err, io.EOF) {
			break
		}
		if err != nil {
			fmt.Fprintf(os.Stderr, "Failed to read response: %s\n", err)
			os.Exit(1)
		}
	}
	fmt.Println()
}