From 5262710823ef08862fe264115a256abf79eca594 Mon Sep 17 00:00:00 2001
From: sviezypan <jaroslav.regec1@gmail.com>
Date: Tue, 6 Feb 2024 20:39:49 +0100
Subject: [PATCH] only rewrite file if content of module has changed

---
 auction_app.wit | 43 -------------------------------------------
 src/wit_gen.rs  | 45 +++++++++++++++++++++++++++++++++------------
 2 files changed, 33 insertions(+), 55 deletions(-)
 delete mode 100644 auction_app.wit

diff --git a/auction_app.wit b/auction_app.wit
deleted file mode 100644
index 6117a8d..0000000
--- a/auction_app.wit
+++ /dev/null
@@ -1,43 +0,0 @@
-package auction:app
-
-interface api {
-    
-    record bidder-id {
-        bidder-id: string,
-    }
-
-    record auction-id {
-        auction-id: string,
-    }
-
-    record auction {
-        auction-id: option<auction-id>, 
-		name: string, 
-		description: string, 
-		starting-price: float32, 
-		deadline: deadline,
-    }
-
-    variant bid-result {
-        failure(string), 
- 		success
-    }
-                
-    type deadline = u64
-
-    initialize: func(auction: auction)
-
-    bid: func(bidder-id: bidder-id, price: float32) -> bid-result
-
-    close-auction: func() -> option<bidder-id>
-
-    create-bidder: func(name: string, address: string) -> bidder-id
-
-    create-auction: func(name: string, description: string, starting-price: float32, deadline: u64) -> auction-id
-
-    get-auctions: func() -> list<auction>
-}
-
-world golem-service {
-    export api
-}
\ No newline at end of file
diff --git a/src/wit_gen.rs b/src/wit_gen.rs
index ba6acb5..79c1ed4 100644
--- a/src/wit_gen.rs
+++ b/src/wit_gen.rs
@@ -377,27 +377,48 @@ fn write_to_file(
     content: Vec<String>,
     ast_span: Span,
 ) -> Result<()> {
-    let mut file = File::create(file_name.clone())
-        .map_err(|e| syn::Error::new(ast_span, format!("Error while creating file {}", e)))?;
 
-    file.write_all(
+    let new_content = 
         format!(
-            "package {}
+        "package {}
 
 interface api {{
-    {}
+{}
 }}
 
 world golem-service {{
     export api
 }}",
-            package_name,
-            content.join("\n")
-        )
-        .trim()
-        .as_bytes(),
-    )
-    .map_err(|e| syn::Error::new(ast_span, format!("Error while writing to file {}", e)))?;
+        package_name,
+        content.join("\n"));
+
+    match File::open(file_name.clone()) {
+        Ok(mut file) => {
+            let mut old_content = String::new();
+
+            file.read_to_string(&mut old_content)
+                .map_err(|e| syn::Error::new(ast_span, format!("Error while reading from file {}", e)))?;
+
+            if old_content == new_content {
+                // do nothing
+                Ok(())
+            } else {
+                // recreate file
+                create_and_write_to_file(file_name, new_content, ast_span)
+            }
+        },
+        Err(_) =>  {
+            create_and_write_to_file(file_name, new_content, ast_span)
+        }
+    }    
+}
+
+fn create_and_write_to_file(file_name: String, new_content: String, ast_span: Span) -> Result<()> {
+    let mut file = File::create(file_name.clone())
+        .map_err(|e| syn::Error::new(ast_span, format!("Error while creating file {}", e)))?;
+
+    file.write_all(new_content.trim().as_bytes())
+        .map_err(|e| syn::Error::new(ast_span, format!("Error while writing to file {}", e)))?;
 
     Ok(())
 }