add --continue feature for download history

src/main.rs

@@ -30,6 +30,8 @@ struct Cli{
 	start_version:Option<u64>,
 	#[arg(long)]
 	end_version:Option<u64>,
+	#[arg(long)]
+	r#continue:bool,
 
 	//decompile options
 	#[arg(long)]
@@ -139,6 +141,7 @@ async fn main()->AResult<()>{
 
 	match cli.command{
 		Commands::DownloadHistory=>download_history(DownloadHistoryConfig{
+			continue_from_versions:cli.r#continue,
 			end_version:cli.end_version,
 			start_version:cli.start_version.unwrap_or(0),
 			output_folder:cli.output.unwrap(),
@@ -355,6 +358,7 @@ async fn download_asset_version(client:&reqwest::Client,cookie:&str,asset_id_str
 }
 
 struct DownloadHistoryConfig{
+	continue_from_versions:bool,
 	end_version:Option<u64>,
 	start_version:u64,
 	output_folder:std::path::PathBuf,
@@ -362,7 +366,46 @@ struct DownloadHistoryConfig{
 	asset_id:AssetID,
 }
 
-async fn download_history(config:DownloadHistoryConfig)->AResult<()>{
+async fn download_history(mut config:DownloadHistoryConfig)->AResult<()>{
+	let mut asset_list:Vec<AssetVersion>=Vec::new();
+	if config.end_version.is_none()&&config.continue_from_versions{
+		//load prexisting versions list
+		let mut versions_path=config.output_folder.clone();
+		versions_path.push("versions.json");
+		match std::fs::File::open(versions_path){
+			Ok(versions_file)=>asset_list.append(&mut serde_json::from_reader(versions_file)?),
+			Err(e)=>match e.kind(){
+				std::io::ErrorKind::NotFound=>return Err(anyhow::Error::msg("Cannot continue from versions.json - file does not exist")),
+				_=>Err(e)?,
+			}
+		}
+		//write down which versions are contained
+		let mut reference_hashmap=std::collections::HashSet::new();
+		for asset_version in &asset_list{
+			reference_hashmap.insert(asset_version.assetVersionNumber);
+		}
+		//find the highest number
+		match asset_list.iter().map(|asset_version|asset_version.assetVersionNumber).max(){
+			Some(max)=>{
+				//count down contiguously until a number is missing
+				for i in (1..=max).rev(){
+					if !reference_hashmap.contains(&i){
+						//that is end_version
+						config.end_version=Some(i);
+						break;
+					}
+				}
+				//if all versions are contained, set start_version to the max + 1
+				if config.end_version.is_none(){
+					config.start_version=max+1;
+				}
+			},
+			None=>Err(anyhow::Error::msg("Cannot continue from versions.json - there are no previous versions"))?,
+		}
+		//clear the asset list, I can't tell if roblox provides a way to start on a specific page
+		//so it just starts from the beginning every time
+		asset_list.clear();
+	}
 	let client=reqwest::Client::new();
 
 	let asset_id_string=config.asset_id.to_string();
@@ -372,7 +415,6 @@ async fn download_history(config:DownloadHistoryConfig)->AResult<()>{
 
 	//poll paged list of all asset versions
 	let mut cursor:Option<String>=None;
-	let mut asset_list=Vec::new();
 	loop{
 		let mut page=download_page(&client,config.cookie.as_str(),config.asset_id,cursor).await?;
 		let client=&client;
@@ -933,7 +975,7 @@ struct DecompileHistoryConfig{
 }
 
 async fn decompile_history_into_git(config:DecompileHistoryConfig)->AResult<()>{
-	//poll paged list of all asset versions
+	//use prexisting versions list
 	let mut versions_path=config.input_folder.clone();
 	versions_path.push("versions.json");
 	let asset_list:Vec<AssetVersion>=serde_json::from_reader(std::fs::File::open(versions_path)?)?;