commit 3c9a111ab0ad16653e9eb519612182ba1f882098
Author: OMGeeky <aalaalgmx@gmail.com>
Date:   Sat Oct 14 02:04:43 2023 +0200

    fully implement downloading files

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..aa346cf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/target
+/.idea
+/.cargo
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..01df2e3
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,25 @@
+[package]
+name = "downloader"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+backup-config = {version = "0.1.1",  git = "https://github.com/OMGeeky/backup_config.git" }
+local-db = {version = "0.1",  git = "https://github.com/OMGeeky/twitch_backup.local_db.git"}
+reqwest-backoff = {version = "0.1",  git = "https://github.com/OMGeeky/twba_reqwest_backoff.git"}
+
+
+tracing-subscriber = "0.3"
+tracing = "0.1"
+tokio = { version = "1.33", features = ["rt", "rt-multi-thread", "macros"] }
+
+thiserror = "1.0"
+anyhow = "1.0"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+reqwest = "0.11"
+chrono = "0.4"
+futures = "0.3"
+futures-util = "0.3"
diff --git a/src/errors.rs b/src/errors.rs
new file mode 100644
index 0000000..43849bc
--- /dev/null
+++ b/src/errors.rs
@@ -0,0 +1,75 @@
+use reqwest_backoff::ReqwestBackoffError;
+use std::path::PathBuf;
+
+#[derive(Debug, thiserror::Error)]
+pub enum DownloadError {
+    #[error("Malformed playlist")]
+    MalformedPlaylist(#[from] MalformedPlaylistError),
+
+    #[error("Backoff error")]
+    Backoff(#[from] ReqwestBackoffError),
+    #[error("Database Error")]
+    Database(#[from] local_db::re_exports::sea_orm::errors::DbErr),
+
+    #[error("Reqwest error")]
+    Reqwest(#[from] reqwest::Error),
+
+    #[error("Could not parse json to access token value and signature")]
+    AccessTokenJsonParse(#[source] serde_json::Error),
+    #[error("The server did not provide an access token")]
+    AccessTokenEmpty,
+    #[error("Got an error with the Filesystem")]
+    File(#[from] DownloadFileError),
+    #[error("Error while loading config")]
+    LoadConfig(#[source] anyhow::Error),
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum MalformedPlaylistError {
+    #[error("Playlist was empty/did not contain any useful information")]
+    Empty,
+    #[error("Playlist did not specify any qualities")]
+    NoQualities,
+
+    #[error("Could not parse the playlist")]
+    Parse(#[from] PlaylistParseError),
+    #[error("Could not parse the url/the url did not contain the expected information")]
+    InvalidUrl,
+}
+#[derive(Debug, thiserror::Error)]
+pub enum PlaylistParseError {
+    #[error("Unexpected end of file while parsing playlist")]
+    Eof,
+    #[error("Invalid time format in playlist")]
+    InvalidTimeFormat(#[source] chrono::ParseError),
+}
+#[derive(Debug, thiserror::Error)]
+pub enum DownloadFileError {
+    #[error("The target folder is not empty {0:?}")]
+    TargetFolderIsNotEmpty(PathBuf),
+    #[error("The target folder is not a directory {0:?}")]
+    TargetFolderIsNotADirectory(PathBuf),
+    #[error("The target path already exists: {0:?}")]
+    TargetAlreadyExists(PathBuf),
+    #[error("Could not create the target folder")]
+    CouldNotCreateTargetFolder(#[source] std::io::Error),
+    #[error("Could not create a needed file")]
+    FileCreation(#[source] std::io::Error),
+    #[error("Could not read the folder/file")]
+    Read(#[source] std::io::Error),
+    #[error("Could not write the folder/file")]
+    Write(#[source] std::io::Error),
+    #[error("There was some error during a filesystem operation")]
+    Filesystem(#[source] tokio::io::Error),
+
+    #[error("The ffmpeg command returned an error")]
+    Ffmpeg(#[source] tokio::io::Error),
+
+    #[error("could not canonicalize path: {0:?}")]
+    Canonicalization(#[source] std::io::Error),
+
+    #[error("could not download file: {0:?}")]
+    DownloadBackoff(#[source] ReqwestBackoffError),
+    #[error("Got an Error during a reqwest request (download)")]
+    DownloadReqwest(#[source] reqwest::Error),
+}
diff --git a/src/prelude.rs b/src/prelude.rs
new file mode 100644
index 0000000..d17fa5c
--- /dev/null
+++ b/src/prelude.rs
@@ -0,0 +1,16 @@
+pub use crate::errors::DownloadError;
+// pub(crate) use anyhow::Result;
+pub(crate) use backup_config::prelude::*;
+use std::fmt::Debug;
+pub(crate) use tracing::{debug, error, info, trace, warn};
+
+pub(crate) use std::result::Result as StdResult;
+
+/// Just a wrapper around Into<String> that implements Debug.
+///
+/// This is just for convenience so we dont need to write
+/// '`impl Into<String> + Debug`' everywhere.
+pub trait DIntoString: Into<String> + Debug {}
+impl<T> DIntoString for T where T: Into<String> + Debug {}
+
+pub type Result<T> = StdResult<T, DownloadError>;
diff --git a/src/twitch/access_token.rs b/src/twitch/access_token.rs
new file mode 100644
index 0000000..126c7ae
--- /dev/null
+++ b/src/twitch/access_token.rs
@@ -0,0 +1,18 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct TwitchVideoAccessTokenResponse {
+    pub data: VideoAccessTokenResponseData,
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct VideoAccessTokenResponseData {
+    #[serde(rename = "videoPlaybackAccessToken")]
+    pub video_playback_access_token: Option<VideoAccessTokenResponseDataAccessToken>,
+}
+
+#[derive(Debug, Deserialize, Serialize)]
+pub struct VideoAccessTokenResponseDataAccessToken {
+    pub value: String,
+    pub signature: String,
+}
diff --git a/src/twitch/mod.rs b/src/twitch/mod.rs
new file mode 100644
index 0000000..7b8eb7e
--- /dev/null
+++ b/src/twitch/mod.rs
@@ -0,0 +1,555 @@
+use chrono::{NaiveDateTime, Utc};
+use futures_util::{StreamExt, TryStreamExt};
+use reqwest_backoff::ReqwestClient;
+use serde_json::json;
+use std::collections::HashMap;
+use std::fmt::Debug;
+use std::path::{Path, PathBuf};
+use tokio::fs;
+use tokio::io::AsyncWriteExt;
+use tokio::process::Command;
+use tokio::time::Instant;
+use tracing::instrument;
+
+use crate::errors::{DownloadError, DownloadFileError, MalformedPlaylistError, PlaylistParseError};
+use crate::prelude::*;
+
+mod access_token;
+use access_token::TwitchVideoAccessTokenResponse;
+
+#[derive(Debug)]
+pub struct TwitchClient {
+    client: ReqwestClient,
+    config: Conf,
+}
+//region public functions
+impl TwitchClient {
+    #[tracing::instrument]
+    pub fn new(config: Conf) -> Self {
+        let client = reqwest::Client::new().into();
+        Self { client, config }
+    }
+    #[tracing::instrument(skip(self))]
+    pub async fn download_video<VideoId: DIntoString, QUALITY: DIntoString>(
+        &self,
+        video_id: VideoId,
+        quality: QUALITY,
+        output_folder: &Path,
+    ) -> Result<PathBuf> {
+        let video_id = video_id.into();
+        let folder_path = output_folder.join(&video_id);
+        let final_path = output_folder.join(format!("{}.mp4", video_id));
+        if final_path.exists() {
+            return Err(DownloadFileError::TargetAlreadyExists(final_path).into());
+        }
+        if !folder_path.exists() {
+            std::fs::create_dir_all(&folder_path)
+                .map_err(DownloadFileError::CouldNotCreateTargetFolder)?;
+        } else if !folder_path.is_dir() {
+            return Err(DownloadFileError::TargetFolderIsNotADirectory(folder_path).into());
+        } else {
+            // folder exists and is a directory
+            if folder_path
+                .read_dir()
+                .map_err(DownloadFileError::Read)?
+                .next()
+                .is_some()
+            {
+                // folder is not empty
+                return Err(DownloadFileError::TargetFolderIsNotEmpty(folder_path).into());
+            }
+        }
+
+        let mut parts = self
+            .download_all_parts(quality, &video_id, &folder_path)
+            .await?;
+
+        sort_parts(&mut parts);
+        let mp4_file_path = combine_parts_to_mp4(&parts, &folder_path).await?;
+
+        tokio::fs::rename(&mp4_file_path, &final_path)
+            .await
+            .map_err(DownloadFileError::Filesystem)?;
+        //clean up the leftover parts
+        tokio::fs::remove_dir_all(folder_path)
+            .await
+            .map_err(DownloadFileError::Filesystem)?;
+        Ok(final_path)
+    }
+}
+//endregion
+impl TwitchClient {
+    async fn download_all_parts<QUALITY: DIntoString>(
+        &self,
+        quality: QUALITY,
+        video_id: &String,
+        folder_path: &Path,
+    ) -> Result<Vec<PathBuf>> {
+        let download_info = self.get_download_info(video_id, quality).await?;
+        let parts = download_info.parts;
+        let base_url = download_info.base_url;
+        let age = download_info.vod_age;
+        if parts.is_empty() {
+            return Err(MalformedPlaylistError::Empty.into());
+        }
+        let try_unmute = age.unwrap_or(999) < 24; //hours i think
+        let amount_of_parts = parts.len() as u64;
+        let thread_count = self.config.twitch.downloader_thread_count;
+        let thread_count: u64 = if thread_count < 1 {
+            1
+        } else if thread_count > amount_of_parts {
+            amount_of_parts
+        } else {
+            thread_count
+        };
+
+        // todo!("maybe add a progress bar/indicator?");
+        let it = parts
+            .into_iter()
+            .map(|part| {
+                let folder_path = folder_path.clone();
+                let client = self.client.clone();
+                let url = base_url.clone();
+                async move {
+                    // download
+                    let result = download_part(part, url, folder_path, try_unmute, client).await;
+                    // report progress
+                    trace!("downloaded part: {:?}", result);
+                    // return result
+                    result
+                }
+            })
+            .map(|x| async {
+                x.await.and_then(|x: PathBuf| {
+                    x.canonicalize()
+                        .map_err(DownloadFileError::Canonicalization)
+                })
+            });
+        let x = futures::stream::iter(it)
+            .buffer_unordered(thread_count as usize)
+            .try_collect::<Vec<_>>()
+            .await?;
+
+        Ok(x)
+    }
+    #[tracing::instrument(skip(self))]
+    async fn get_download_info<ID: DIntoString, QUALITY: DIntoString>(
+        &self,
+        video_id: ID,
+        quality: QUALITY,
+    ) -> Result<DownloadInfo> {
+        let playlist = self.get_video_playlist(video_id, quality).await?;
+        let playlist_content = self
+            .client
+            .execute_with_backoff(self.client.get(&playlist).build()?)
+            .await?
+            .text()
+            .await?;
+        let base_url = &playlist[..playlist
+            .rfind('/')
+            .ok_or(MalformedPlaylistError::InvalidUrl)?
+            + 1];
+        let parts = parse_playlist(playlist_content)?;
+        // dbg!(&parts);
+        Ok(DownloadInfo {
+            vod_age: parts.0,
+            parts: parts.1,
+            base_url: base_url.to_string(),
+        })
+    }
+
+    #[tracing::instrument(skip(self))]
+    async fn get_video_token_and_signature<S: DIntoString>(
+        &self,
+        video_id: S,
+    ) -> Result<(String, String)> {
+        let video_id = video_id.into();
+        trace!("Getting access token & signature for video {}", video_id,);
+
+        const URL: &str = "https://gql.twitch.tv/gql";
+        let json = json!({"operationName":"PlaybackAccessToken_Template",
+            "query": "query PlaybackAccessToken_Template($login: String!, $isLive: Boolean!, $vodID: ID!, $isVod: Boolean!, $playerType: String!) {  streamPlaybackAccessToken(channelName: $login, params: {platform: \"web\", playerBackend: \"mediaplayer\", playerType: $playerType}) @include(if: $isLive) {    value    signature    __typename  }  videoPlaybackAccessToken(id: $vodID, params: {platform: \"web\", playerBackend: \"mediaplayer\", playerType: $playerType}) @include(if: $isVod) {    value    signature    __typename  }}",
+            "variables": {
+            "isLive": false,
+            "login": "",
+            "isVod": true,
+            "vodID": video_id,
+            "playerType": "embed"
+            }
+        }).to_string();
+        let request = self
+            .client
+            .post(URL)
+            .header("Client-ID", &self.config.twitch.downloader_id)
+            .body(json)
+            .build()?;
+
+        let response = self.client.execute_with_backoff(request).await?;
+        let json = response.text().await?;
+        // trace!("Got json response: {}", json);
+        let token_response: TwitchVideoAccessTokenResponse =
+            serde_json::from_str(&json).map_err(DownloadError::AccessTokenJsonParse)?;
+        trace!(
+            "Got access token & signature for video {}=>{:?}",
+            video_id,
+            token_response
+        );
+        let access_token = token_response
+            .data
+            .video_playback_access_token
+            .ok_or(DownloadError::AccessTokenEmpty)?;
+
+        Ok((access_token.value, access_token.signature))
+    }
+
+    #[tracing::instrument(skip(self))]
+    async fn get_video_playlist<ID: DIntoString, QUALITY: DIntoString>(
+        &self,
+        video_id: ID,
+        quality: QUALITY,
+    ) -> Result<String> {
+        let video_id = video_id.into();
+        let quality = quality.into();
+
+        trace!(
+            "Getting video playlist with quality for video {} with quality {}",
+            video_id,
+            quality
+        );
+
+        let playlist = self.get_video_playlist_per_quality(&video_id).await?;
+        let playlist = get_playlist_from_quality_list(playlist, &quality)?;
+
+        Ok(playlist)
+    }
+
+    #[tracing::instrument(skip(self))]
+    async fn get_video_playlist_per_quality(&self, video_id: &str) -> Result<String> {
+        let (token, signature) = self.get_video_token_and_signature(video_id).await?;
+
+        let playlist_url = format!(
+            "https://usher.ttvnw.net/vod/{}?nauth={}&nauthsig={}&allow_source=true&player=twitchweb",
+            video_id, token, signature
+        );
+
+        let request = self.client.get(playlist_url).build()?;
+        let playlist = self.client.execute_with_backoff(request).await?;
+        let playlist = playlist.text().await?;
+        Ok(playlist)
+    }
+}
+#[instrument]
+async fn download_part(
+    part: (String, f32),
+    base_url: String,
+    folder_path: &Path,
+    try_unmute: bool,
+    client: ReqwestClient,
+) -> StdResult<PathBuf, DownloadFileError> {
+    trace!("downloading part: {:?}", part);
+    let (part, _duration) = part;
+
+    let part_url = format!("{}{}", base_url, part);
+    let part_url_unmuted = format!("{}{}", base_url, part.replace("-muted", ""));
+
+    let try_unmute = try_unmute && part.contains("-muted");
+    let target_path = folder_path.join(&part);
+
+    if try_unmute {
+        trace!("trying to download unmuted part: {}", part_url_unmuted);
+        match try_download_part(part_url_unmuted, &target_path, &client).await {
+            Ok(path) => Ok(path),
+            Err(_) => {
+                trace!("failed to download unmuted part. trying muted part");
+                try_download_part(part_url, folder_path, &client).await
+            }
+        }
+    } else {
+        trace!("not trying to unmute: {}", part_url);
+        try_download_part(part_url, &target_path, &client).await
+    }
+}
+async fn try_download_part(
+    url: String,
+    target_path: &Path,
+    client: &ReqwestClient,
+) -> StdResult<PathBuf, DownloadFileError> {
+    let request = client
+        .get(url)
+        .build()
+        .map_err(DownloadFileError::DownloadReqwest)?;
+    let mut response = client
+        .execute_with_backoff(request)
+        .await
+        .map_err(DownloadFileError::DownloadBackoff)?;
+
+    let mut file = fs::File::create(target_path)
+        .await
+        .map_err(DownloadFileError::FileCreation)?;
+
+    while let Some(chunk) = response
+        .chunk()
+        .await
+        .map_err(DownloadFileError::DownloadReqwest)?
+    {
+        file.write_all(&chunk)
+            .await
+            .map_err(DownloadFileError::Filesystem)?;
+    }
+    Ok(target_path.to_path_buf())
+}
+
+#[instrument]
+async fn convert_ts_to_mp4(ts_file: &Path, mp4_file: &Path) -> Result<()> {
+    info!("converting to mp4");
+    if mp4_file.exists() {
+        tokio::fs::remove_file(&mp4_file)
+            .await
+            .map_err(DownloadFileError::Filesystem)?;
+    }
+    debug!(
+        "running ffmpeg command: ffmpeg -i {} -c {}",
+        ts_file.display(),
+        mp4_file.display()
+    );
+    let mut cmd = Command::new("ffmpeg");
+    let start_time = Instant::now();
+    cmd.arg("-i")
+        .arg(ts_file)
+        .arg("-c")
+        .arg("copy")
+        .arg(mp4_file);
+    let result = cmd.output().await;
+    let duration = Instant::now().duration_since(start_time);
+    debug!("ffmpeg command finished after duration: {:?}", duration);
+    result.map_err(DownloadFileError::Ffmpeg)?;
+    Ok(())
+}
+
+fn parse_playlist(
+    playlist: String,
+) -> StdResult<(Option<usize>, HashMap<String, f32>), MalformedPlaylistError> {
+    info!("Parsing playlist");
+    const STREAMED_DATE_IDENT: &str = "#ID3-EQUIV-TDTG:";
+
+    let mut age = None;
+    let mut parts = HashMap::new();
+    dbg!(&playlist);
+    let mut lines = playlist.lines();
+    loop {
+        let line = lines.next();
+        trace!("line: {:?}", line);
+        if line.is_none() {
+            trace!("line is none. done parsing playlist");
+            break;
+        }
+        let line = line.unwrap();
+        if let Some(date) = line.strip_prefix(STREAMED_DATE_IDENT) {
+            let date = date.trim();
+            let date: chrono::DateTime<Utc> = convert_twitch_date(date)?;
+            let now = Utc::now();
+            let duration = now.signed_duration_since(date);
+            age = Some(duration.num_hours() as usize);
+            continue;
+        }
+        if let Some(part_duration) = line.strip_prefix("#EXTINF:") {
+            let mut line = lines.next().ok_or(PlaylistParseError::Eof)?;
+            if line.starts_with("#EXT-X-BYTERANGE:") {
+                warn!("Found byterange, ignoring the line and moving on");
+                line = lines.next().ok_or(PlaylistParseError::Eof)?;
+            }
+
+            let part_duration: f32 = part_duration.trim_matches(',').parse().unwrap_or(0.0);
+
+            parts.insert(line.trim().to_string(), part_duration);
+        } else {
+            //ignore everything but content lines
+            continue;
+        }
+    }
+    dbg!(&parts.len());
+    Ok((age, parts))
+}
+
+/// Converts a twitch date string to a chrono::DateTime<Utc>
+/// Example: 2021-05-01T18:00:00
+pub fn convert_twitch_date(date: &str) -> StdResult<chrono::DateTime<Utc>, PlaylistParseError> {
+    let date = date.trim();
+    let date = date.trim_matches('"');
+
+    //parse the date from a string like this: 2023-10-07T23:33:29
+    NaiveDateTime::parse_from_str(date, "%Y-%m-%dT%H:%M:%S")
+        .map(|e| e.and_utc())
+        .map_err(PlaylistParseError::InvalidTimeFormat)
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use chrono::{Datelike, Timelike};
+    #[test]
+    fn test_convert_twitch_date() {
+        let date = "2021-05-01T18:00:00";
+        let date = convert_twitch_date(date).unwrap();
+        assert_eq!(date.year(), 2021);
+        assert_eq!(date.month(), 5);
+        assert_eq!(date.day(), 1);
+        assert_eq!(date.hour(), 18);
+        assert_eq!(date.minute(), 0);
+        assert_eq!(date.second(), 0);
+    }
+}
+#[tracing::instrument(skip(playlist))]
+fn get_playlist_from_quality_list(playlist: String, quality: &str) -> Result<String> {
+    trace!("Parsing playlist:\n{}", playlist);
+
+    let mut qualties = HashMap::new();
+
+    let mut highest_quality = String::new();
+    let test: Vec<&str> = playlist.lines().collect();
+    for (i, line) in test.iter().enumerate() {
+        if !line.contains("#EXT-X-MEDIA") {
+            continue;
+        }
+
+        let found_quality = line.split("NAME=\"").collect::<Vec<&str>>()[1]
+            .split('"')
+            .collect::<Vec<&str>>()[0];
+
+        if qualties.get(found_quality).is_some() {
+            continue;
+        }
+        if qualties.is_empty() {
+            // the first one is the highest quality
+            highest_quality = found_quality.to_string();
+        }
+
+        let url = test[i + 2];
+        qualties.insert(found_quality, url);
+    }
+    if let Some(quality) = qualties.get(quality) {
+        Ok(quality.to_string())
+    } else {
+        warn!(
+            "Given quality not found ({}), using highest quality: {}",
+            quality, highest_quality
+        );
+        Ok(qualties
+            .get(highest_quality.as_str())
+            .ok_or(MalformedPlaylistError::NoQualities)?
+            .to_string())
+    }
+}
+#[derive(Debug, Clone)]
+struct DownloadInfo {
+    vod_age: Option<usize>,
+    parts: HashMap<String, f32>,
+    base_url: String,
+}
+#[cfg(test)]
+mod abc {
+    use futures_util::{StreamExt, TryStreamExt};
+    #[tokio::test]
+    async fn test1() {
+        let v = vec![1, 3, 5];
+        let x1 = run(v).await;
+        assert!(x1.is_err());
+        assert_eq!(x1.unwrap_err(), 5i64);
+    }
+    #[tokio::test]
+    async fn test2() {
+        let v = vec![1, 5, 1];
+        let x1 = run(v).await;
+        assert!(x1.is_err());
+        assert_eq!(x1.unwrap_err(), 5i64);
+    }
+    #[tokio::test]
+    async fn test3() {
+        let v = vec![1, 3, 2, 2];
+        let x1 = run(v).await;
+        assert!(x1.is_ok());
+        assert_eq!(x1.unwrap(), vec![1, 3, 2, 2]);
+    }
+    async fn run(v: Vec<i32>) -> Result<Vec<i16>, i64> {
+        async fn sample(part: i32) -> Result<i16, i64> {
+            dbg!(part);
+            if part <= 3 {
+                Ok(part as i16)
+            } else {
+                Err(part as i64)
+            }
+        }
+        let thread_count = 2;
+        let it = v.into_iter().map(sample);
+        let x = futures::stream::iter(it);
+        let x1: Result<Vec<i16>, i64> = x.buffer_unordered(thread_count).try_collect().await;
+        dbg!(&x1);
+        x1
+    }
+}
+
+fn sort_parts(files: &mut [PathBuf]) {
+    files.sort_by_key(|path| {
+        let number = path
+            .file_stem()
+            .map(|x| {
+                x.to_str()
+                    .unwrap_or("")
+                    .replace("-muted", "")
+                    .replace("-unmuted", "")
+            })
+            .unwrap_or(String::from("0"));
+        match number.parse::<u32>() {
+            Ok(n) => n,
+            Err(e) => {
+                warn!(
+                    "potentially catchable error while parsing the file number: {}\n{}",
+                    number, e
+                );
+                if !number.contains('-') {
+                    error!("Error while parsing the file number: {}", number);
+                    panic!("Error while parsing the file number: {}", number)
+                }
+                let number = number.split('-').collect::<Vec<&str>>()[1];
+                number
+                    .parse()
+                    .unwrap_or_else(|_| panic!("Error while parsing the file number: {}", number))
+            }
+        }
+    });
+}
+
+#[instrument(skip(files), fields(part_amount=files.len()))]
+async fn combine_parts_to_single_ts(files: &[PathBuf], target: &Path) -> Result<()> {
+    debug!("combining all parts of video");
+    debug!("part amount: {}", files.len());
+    let mut target = fs::File::create(target)
+        .await
+        .map_err(DownloadFileError::FileCreation)?;
+    for file_path in files {
+        trace!("{:?}", file_path.file_name());
+        let mut file = fs::File::open(&file_path)
+            .await
+            .map_err(DownloadFileError::Read)?;
+        tokio::io::copy(&mut file, &mut target)
+            .await
+            .map_err(DownloadFileError::Write)?;
+        tokio::fs::remove_file(&file_path)
+            .await
+            .map_err(DownloadFileError::Write)?;
+    }
+
+    Ok(())
+}
+
+async fn combine_parts_to_mp4(parts: &[PathBuf], folder_path: &Path) -> Result<PathBuf> {
+    let ts_file_path = folder_path.join("video.ts");
+    let mp4_file_path = folder_path.join("video.mp4");
+
+    combine_parts_to_single_ts(parts, &ts_file_path).await?;
+    convert_ts_to_mp4(&ts_file_path, &mp4_file_path).await?;
+    tokio::fs::remove_file(ts_file_path)
+        .await
+        .map_err(DownloadFileError::Filesystem)?;
+
+    Ok(mp4_file_path)
+}