Add "merge" function

2 files changed, 36 insertions, 0 deletions

diff --git a/src/main.rs b/src/main.rs
index 2c53729..61c3baa 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@ use rss::Channel;
 use std::process::exit;
 
 mod fetch;
+mod merge;
 mod sort;
 mod take;
 mod filter;
@@ -19,6 +20,9 @@ enum Commands {
     /// Fetches a feed from a URL
     Fetch { url: String },
 
+    /// Merge merges the items of the feed contained in the given file with the feed in standard input
+    Merge { filename: String },
+
     /// Sorts a feed
     Sort {
         #[arg(short, long)] 
@@ -87,6 +91,24 @@ fn main() {
             }
         },
 
+        Commands::Merge { filename } => {
+            match Channel::read_from(std::io::stdin().lock()) {
+                Ok(c) => {
+                    match merge::run(c, filename) {
+                        Ok(c) => {
+                            c.pretty_write_to(std::io::stdout(), b' ', 2).unwrap();
+                        }, 
+                        Err(e) => {
+                            crash_and_burn(&e);
+                        }
+                    }
+                },
+                Err(e) => {
+                    crash_and_burn(&e);
+                }
+            }
+        },
+
         Commands::Sort { by, order } => {
             match Channel::read_from(std::io::stdin().lock()) {
                 Ok(c) => {
diff --git a/src/merge.rs b/src/merge.rs
new file mode 100644
index 0000000..5567d29
--- /dev/null
+++ b/src/merge.rs
@@ -0,0 +1,14 @@
+use std::str::FromStr;
+
+use rss::Channel;
+use anyhow::{Result, Context};
+
+pub fn run(c: Channel, filename: String) -> Result<Channel> {
+    let contents = std::fs::read_to_string(&filename)?;
+    let mut other_channel = rss::Channel::from_str(&contents).context(format!("error parsing {}", filename))?;
+
+    let mut c = c.clone();
+    c.items.append(&mut other_channel.items);
+
+    Ok(c)
+}
\ No newline at end of file