Implements the download url builder.

Tasks.md

@@ -73,7 +73,7 @@ This document defines the complete project roadmap and task tracking system for
 | [NUT-002](#nut-002) | Implement Shared Rust Backend Library | Fixed | Foundation |
 | [NUT-003](#nut-003) | Implement WebDAV Upload Logic | Fixed | Feature |
 | [NUT-004](#nut-004) | Implement OCS Share Link Generation | Fixed | Feature |
-| [NUT-005](#nut-005) | Implement Direct Download URL Builder | Triage | Feature |
+| [NUT-005](#nut-005) | Implement Direct Download URL Builder | Fixed | Feature |
 | [NUT-006](#nut-006) | Implement Credential Storage System | Fixed | Feature |
 | [NUT-007](#nut-007) | Implement Multi-Account Support (Backend) | Triage | Feature |
 | [NUT-008](#nut-008) | Implement CLI Frontend | Triage | Feature |
@@ -174,19 +174,19 @@ Implement creation of public share links using the OCS Sharing API.
 - NUT-002
 
 
-<a id="nut-005" class="task" data-status="triage" data-task-type="feature"></a>
+<a id="nut-005" class="task" data-status="done" data-task-type="feature"></a>
 ### Implement Direct Download URL Builder  
 **ID:** NUT-005  
-**Status:** Triage  
+**Status:** Fixed  
 **Type:** Feature  
 
 **Description:**  
 Generate direct-download URLs from share tokens.
 
 **Requirements:**  
-- [ ] Build URL: `/index.php/s/<token>/download`  
-- [ ] Validate token format  
-- [ ] Provide helper API  
+- [x] Build URL: `/index.php/s/<token>/download`  
+- [x] Validate token format  
+- [x] Provide helper API  
 
 **Dependencies:**  
 - NUT-004
@@ -517,7 +517,7 @@ Tasks progress through defined statuses:
 1. `triage`: Under initial evaluation and specification. Missing requirements allowed.
 2. `pending`: Scope defined and ready for active work.
 3. `in_progress`: Active implementation in progress.
-4. `done`: Work complete, requirements checked, and verified.
+4. `done`: Fixed. Work complete, requirements checked, and verified.
 5. `blocked`: Blocked by an external obstacle or unmet dependency.
 6. `cancelled`: Deprecated or abandoned.
 

nextcloud_client/src/client.rs

@@ -109,17 +109,6 @@ impl NextcloudClient {
             .map_err(NextcloudError::from)
     }
 
-    /// Build the public download URL from a share token.
-    ///
-    /// Format: `https://<host>/index.php/s/<token>/download`
-    pub fn direct_download_url(&self, share_token: &str) -> Result<Url> {
-        let path_segment = format!("index.php/s/{share_token}/download");
-        self.config
-            .server_url
-            .join(&path_segment)
-            .map_err(NextcloudError::from)
-    }
-
     /// Check server reachability and retrieve server version info from `/status.php`.
     ///
     /// This endpoint does not require authentication.
@@ -218,18 +207,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn test_direct_download_url() {
-        let config = ClientConfig::new("https://nextcloud.example.com", None).unwrap();
-        let client = NextcloudClient::new(config).unwrap();
-        let download_url = client.direct_download_url("AbCdEf12345").unwrap();
-
-        assert_eq!(
-            download_url.as_str(),
-            "https://nextcloud.example.com/index.php/s/AbCdEf12345/download"
-        );
-    }
-
     #[test]
     fn test_status_deserialization() {
         let sample_json = r#"{

nextcloud_client/src/download.rs

@@ -0,0 +1,149 @@
+use url::Url;
+
+use crate::client::NextcloudClient;
+use crate::error::{NextcloudError, Result};
+
+/// Minimum permitted length for a Nextcloud share token.
+pub const MIN_SHARE_TOKEN_LENGTH: usize = 6;
+
+/// Maximum permitted length for a Nextcloud share token.
+pub const MAX_SHARE_TOKEN_LENGTH: usize = 64;
+
+/// Validates that a share token consists only of valid alphanumeric or safe characters (`[a-zA-Z0-9_-]`).
+///
+/// Returns `Ok(())` if valid, or a [`NextcloudError::Other`] describing the validation failure.
+pub fn validate_share_token(token: &str) -> Result<()> {
+    let trimmed = token.trim();
+
+    if trimmed.is_empty() {
+        return Err(NextcloudError::Other("Share token cannot be empty".into()));
+    }
+
+    if trimmed.len() < MIN_SHARE_TOKEN_LENGTH || trimmed.len() > MAX_SHARE_TOKEN_LENGTH {
+        return Err(NextcloudError::Other(format!(
+            "Invalid share token length ({}): expected between {} and {} characters",
+            trimmed.len(),
+            MIN_SHARE_TOKEN_LENGTH,
+            MAX_SHARE_TOKEN_LENGTH
+        )));
+    }
+
+    if !trimmed.chars().all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-') {
+        return Err(NextcloudError::Other(format!(
+            "Invalid characters in share token '{token}': tokens must only contain alphanumeric characters, hyphens, or underscores"
+        )));
+    }
+
+    Ok(())
+}
+
+/// Builds a direct download URL for a shared file given a base Nextcloud URL and share token.
+///
+/// Format: `https://<host>/index.php/s/<token>/download`
+pub fn build_direct_download_url(base_url: &Url, share_token: &str) -> Result<Url> {
+    validate_share_token(share_token)?;
+    let clean_token = share_token.trim();
+    let path_segment = format!("index.php/s/{clean_token}/download");
+    base_url.join(&path_segment).map_err(NextcloudError::from)
+}
+
+/// Builds a direct download URL for a specific file within a shared folder.
+///
+/// Nextcloud supports downloading an individual file from a shared directory via query parameters:
+/// `https://<host>/index.php/s/<token>/download?path=%2F&files=filename.ext`
+pub fn build_subfile_download_url(
+    base_url: &Url,
+    share_token: &str,
+    subfile_path: &str,
+) -> Result<Url> {
+    let mut url = build_direct_download_url(base_url, share_token)?;
+
+    let clean_path = subfile_path.trim_start_matches('/');
+    if let Some((dir, file)) = clean_path.rsplit_once('/') {
+        let root_dir = format!("/{dir}");
+        url.query_pairs_mut()
+            .append_pair("path", &root_dir)
+            .append_pair("files", file);
+    } else {
+        url.query_pairs_mut()
+            .append_pair("path", "/")
+            .append_pair("files", clean_path);
+    }
+
+    Ok(url)
+}
+
+impl NextcloudClient {
+    /// Generate a validated direct download URL from a share token.
+    pub fn direct_download_url(&self, share_token: &str) -> Result<Url> {
+        build_direct_download_url(&self.config.server_url, share_token)
+    }
+
+    /// Generate a validated direct download URL for a specific sub-file in a shared folder.
+    pub fn subfile_download_url(&self, share_token: &str, subfile_path: &str) -> Result<Url> {
+        build_subfile_download_url(&self.config.server_url, share_token, subfile_path)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_valid_tokens() {
+        assert!(validate_share_token("AbCdEf123456789").is_ok());
+        assert!(validate_share_token("aB1_2-3z").is_ok());
+        assert!(validate_share_token("kLx9Q2wP0vN4m1R").is_ok());
+    }
+
+    #[test]
+    fn test_invalid_tokens() {
+        // Empty
+        assert!(validate_share_token("").is_err());
+        // Too short (< 6 chars)
+        assert!(validate_share_token("abc").is_err());
+        // Too long (> 64 chars)
+        assert!(validate_share_token(&"a".repeat(65)).is_err());
+        // Path traversal / slashes
+        assert!(validate_share_token("../secret").is_err());
+        assert!(validate_share_token("abc/def").is_err());
+        // Spaces & query chars
+        assert!(validate_share_token("abc def").is_err());
+        assert!(validate_share_token("abc?download=1").is_err());
+        assert!(validate_share_token("abc#frag").is_err());
+    }
+
+    #[test]
+    fn test_build_direct_download_url() {
+        let base = Url::parse("https://cloud.example.com/").unwrap();
+        let download_url = build_direct_download_url(&base, "kLx9Q2wP0vN4m1R").unwrap();
+
+        assert_eq!(
+            download_url.as_str(),
+            "https://cloud.example.com/index.php/s/kLx9Q2wP0vN4m1R/download"
+        );
+    }
+
+    #[test]
+    fn test_build_subpath_installation() {
+        let base = Url::parse("https://example.com/nextcloud/").unwrap();
+        let download_url = build_direct_download_url(&base, "kLx9Q2wP0vN4m1R").unwrap();
+
+        assert_eq!(
+            download_url.as_str(),
+            "https://example.com/nextcloud/index.php/s/kLx9Q2wP0vN4m1R/download"
+        );
+    }
+
+    #[test]
+    fn test_build_subfile_download_url() {
+        let base = Url::parse("https://cloud.example.com/").unwrap();
+        let subfile_url =
+            build_subfile_download_url(&base, "kLx9Q2wP0vN4m1R", "archive/document.pdf").unwrap();
+
+        assert_eq!(
+            subfile_url.as_str(),
+            "https://cloud.example.com/index.php/s/kLx9Q2wP0vN4m1R/download?path=%2Farchive&files=document.pdf"
+        );
+    }
+}

nextcloud_client/src/lib.rs

@@ -7,6 +7,7 @@ pub mod auth;
 pub mod client;
 pub mod config;
 pub mod credentials;
+pub mod download;
 pub mod error;
 pub mod models;
 pub mod progress;
@@ -21,6 +22,10 @@ pub use auth::{
 pub use client::{NextcloudClient, ServerStatus};
 pub use config::{AccountCredentials, ClientConfig};
 pub use credentials::{CredentialStore, StoredAccount, KEYRING_SERVICE_NAME};
+pub use download::{
+    build_direct_download_url, build_subfile_download_url, validate_share_token,
+    MAX_SHARE_TOKEN_LENGTH, MIN_SHARE_TOKEN_LENGTH,
+};
 pub use error::{NextcloudError, Result};
 pub use models::{UploadOptions, UploadResult};
 pub use progress::{ProgressCallback, ProgressEvent};