feat: Takeout CSV, Atom feed, yt-dlp progress, and SQLite layers

37 unit tests covering the three parsers and the database, including
that a feed refresh preserves download state and that a truncated
feed response fails rather than storing partial results.

src-tauri/src/takeout.rs

@@ -0,0 +1,116 @@
+//! Parsing of Google Takeout's `subscriptions.csv`.
+//!
+//! The export's real header is `Channel Id,Channel Url,Channel Title`, but the
+//! column order has varied across Takeout versions and locales, so we resolve
+//! columns by header name rather than by position.
+
+use crate::models::Channel;
+
+fn find_col(headers: &csv::StringRecord, name: &str) -> Option<usize> {
+    headers
+        .iter()
+        .position(|h| h.trim().eq_ignore_ascii_case(name))
+}
+
+pub fn parse_csv(input: &str) -> Result<Vec<Channel>, String> {
+    if input.trim().is_empty() {
+        return Err("The file is empty.".into());
+    }
+
+    let mut reader = csv::ReaderBuilder::new()
+        .flexible(true)
+        .from_reader(input.as_bytes());
+
+    let headers = reader
+        .headers()
+        .map_err(|e| format!("Could not read the CSV header: {e}"))?
+        .clone();
+
+    let id_col = find_col(&headers, "Channel Id")
+        .ok_or("This does not look like a Takeout subscriptions.csv: no 'Channel Id' column.")?;
+    let title_col = find_col(&headers, "Channel Title")
+        .ok_or("This does not look like a Takeout subscriptions.csv: no 'Channel Title' column.")?;
+    let url_col = find_col(&headers, "Channel Url");
+
+    let mut out = Vec::new();
+    for record in reader.records() {
+        let record = record.map_err(|e| format!("Malformed CSV row: {e}"))?;
+
+        let id = record.get(id_col).unwrap_or("").trim();
+        if id.is_empty() {
+            continue;
+        }
+
+        let title = record.get(title_col).unwrap_or("").trim();
+        let url = url_col
+            .and_then(|c| record.get(c))
+            .map(str::trim)
+            .filter(|u| !u.is_empty())
+            .map(str::to_string)
+            .unwrap_or_else(|| format!("https://www.youtube.com/channel/{id}"));
+
+        out.push(Channel {
+            id: id.to_string(),
+            title: if title.is_empty() {
+                id.to_string()
+            } else {
+                title.to_string()
+            },
+            url,
+        });
+    }
+
+    Ok(out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_standard_export() {
+        let csv = "Channel Id,Channel Url,Channel Title\n\
+                   UCabc,http://www.youtube.com/channel/UCabc,Linus Tech Tips\n";
+        let out = parse_csv(csv).unwrap();
+        assert_eq!(out.len(), 1);
+        assert_eq!(out[0].id, "UCabc");
+        assert_eq!(out[0].title, "Linus Tech Tips");
+        assert_eq!(out[0].url, "http://www.youtube.com/channel/UCabc");
+    }
+
+    #[test]
+    fn handles_commas_and_unicode_in_titles() {
+        let csv = "Channel Id,Channel Url,Channel Title\n\
+                   UCx,http://y.com/UCx,\"Kurzgesagt – In a Nutshell, Ltd\"\n";
+        let out = parse_csv(csv).unwrap();
+        assert_eq!(out[0].title, "Kurzgesagt – In a Nutshell, Ltd");
+    }
+
+    #[test]
+    fn tolerates_reordered_columns() {
+        let csv = "Channel Title,Channel Id,Channel Url\nVeritasium,UCz,http://y.com/UCz\n";
+        let out = parse_csv(csv).unwrap();
+        assert_eq!(out[0].id, "UCz");
+        assert_eq!(out[0].title, "Veritasium");
+    }
+
+    #[test]
+    fn derives_url_when_column_absent() {
+        let csv = "Channel Id,Channel Title\nUCq,Some Channel\n";
+        let out = parse_csv(csv).unwrap();
+        assert_eq!(out[0].url, "https://www.youtube.com/channel/UCq");
+    }
+
+    #[test]
+    fn skips_blank_lines_and_empty_file() {
+        assert!(parse_csv("Channel Id,Channel Url,Channel Title\n\n")
+            .unwrap()
+            .is_empty());
+        assert!(parse_csv("").is_err());
+    }
+
+    #[test]
+    fn errors_on_missing_required_column() {
+        assert!(parse_csv("Foo,Bar\n1,2\n").is_err());
+    }
+}