docs(pre-compute): add detailed Rustdoc comments for pre-compute app methods

Author: nabil-Tounarti

pre-compute/src/compute/pre_compute_app.rs

@@ -80,6 +80,13 @@ impl PreComputeAppTrait for PreComputeApp {
         Ok(())
     }
 
+    /// Checks whether the output folder specified in `pre_compute_args` exists.
+    ///
+    /// # Returns
+    ///
+    /// - `Ok(())` if the output directory (`output_dir`) exists.
+    /// - `Err(ReplicateStatusCause::PreComputeOutputFolderNotFound)` if the directory does not exist,
+    ///   or if `pre_compute_args` is missing.
     fn check_output_folder(&self) -> Result<(), ReplicateStatusCause> {
         let output_dir: &str = &self.pre_compute_args.output_dir;
         let chain_task_id: &str = &self.chain_task_id;
@@ -95,6 +102,21 @@ impl PreComputeAppTrait for PreComputeApp {
         Err(ReplicateStatusCause::PreComputeOutputFolderNotFound)
     }
 
+    /// Downloads the input files listed in `pre_compute_args.input_files` to the specified `output_dir`.
+    ///
+    /// Each URL is hashed (SHA-256) to generate a unique local filename.
+    /// If any download fails, the function returns an error.
+    ///
+    /// # Returns
+    ///
+    /// - `Ok(())` if all files are downloaded successfully.
+    /// - `Err(ReplicateStatusCause::PreComputeInputFileDownloadFailed)` if any file fails to download.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if:
+    /// - `pre_compute_args` is `None`.
+    /// - `chain_task_id` is `None`.
     fn download_input_files(&self) -> Result<(), ReplicateStatusCause> {
         let args = &self.pre_compute_args;
         let chain_task_id: &str = &self.chain_task_id;
@@ -110,6 +132,13 @@ impl PreComputeAppTrait for PreComputeApp {
         Ok(())
     }
 
+    /// Downloads the encrypted dataset file from a URL or IPFS multi-address, and verifies its checksum.
+    ///
+    /// # Returns
+    ///
+    /// * `Ok(Vec<u8>)` containing the dataset's encrypted content if download and verification succeed.
+    /// * `Err(ReplicateStatusCause::PreComputeDatasetDownloadFailed)` if the download fails or inputs are missing.
+    /// * `Err(ReplicateStatusCause::PreComputeInvalidDatasetChecksum)` if checksum validation fails.
     fn download_encrypted_dataset(&self) -> Result<Vec<u8>, ReplicateStatusCause> {
         let args = &self.pre_compute_args;
         let chain_task_id = &self.chain_task_id;
@@ -152,6 +181,19 @@ impl PreComputeAppTrait for PreComputeApp {
         Ok(encrypted_content)
     }
 
+    /// Decrypts the provided encrypted dataset bytes using AES-CBC.
+    ///
+    /// The first 16 bytes of `encrypted_content` are treated as the IV.
+    /// The rest is the ciphertext. The decryption key is decoded from a Base64 string.
+    ///
+    /// # Arguments
+    ///
+    /// * `encrypted_content` - Full encrypted dataset, including the IV prefix.
+    ///
+    /// # Returns
+    ///
+    /// * `Ok(Vec<u8>)` containing the plaintext dataset if decryption succeeds.
+    /// * `Err(ReplicateStatusCause::PreComputeDatasetDecryptionFailed)` if the key is missing, decoding fails, or decryption fails.
     fn decrypt_dataset(&self, encrypted_content: &[u8]) -> Result<Vec<u8>, ReplicateStatusCause> {
         let base64_key: &str = &self.pre_compute_args.encrypted_dataset_base64_key;
 
@@ -172,6 +214,18 @@ impl PreComputeAppTrait for PreComputeApp {
             .map_err(|_| ReplicateStatusCause::PreComputeDatasetDecryptionFailed)
     }
 
+    /// Saves the decrypted (plain) dataset to disk in the configured output directory.
+    ///
+    /// The output filename is taken from `pre_compute_args.plain_dataset_filename`.
+    ///
+    /// # Arguments
+    ///
+    /// * `plain_dataset` - The dataset content to write to a file.
+    ///
+    /// # Returns
+    ///
+    /// * `Ok(())` if the file is successfully saved.
+    /// * `Err(ReplicateStatusCause::PreComputeSavingPlainDatasetFailed)` if the path is invalid or write fails.
     fn save_plain_dataset_file(&self, plain_dataset: &[u8]) -> Result<(), ReplicateStatusCause> {
         let chain_task_id: &str = &self.chain_task_id;
         let args = &self.pre_compute_args;