feat(file): support lines arg to limit content (#46)

Author: HigherOrderLogic

src/generators/file.ts

@@ -13,6 +13,27 @@ export const file = defineGenerator({
       contents = contents.trim();
     }
 
+    if (args.lines) {
+      const groups = /^(?<startLine>\d+)?:(?<endLine>\d+)?$/.exec(
+        "args.lines",
+      )?.groups;
+
+      if (!groups) {
+        throw new Error("invalid lines format");
+      }
+
+      const lines = contents.split("\n");
+
+      const startLine = Number(groups.startLine) || 1;
+      const endLine = Number(groups.endLine) || lines.length;
+
+      if (startLine < 1) {
+        throw new Error("first line's index can not be smaller than 1");
+      }
+
+      contents = lines.slice(startLine - 1, endLine).join("\n");
+    }
+
     if (args.code) {
       contents = md.codeBlock(
         contents,

test/fixture/INPUT.md

@@ -37,7 +37,7 @@
 
 ## `file`
 
-<!-- automd:file src="./TEST.md" -->
+<!-- automd:file src="./TEST.md" lines=1:5 -->
 <!-- /automd -->
 
 ## `contributors`

test/fixture/OUTPUT.md

@@ -190,16 +190,14 @@ Why waste time solving problems when someone else has already done it for you? S
 
 ## `file`
 
-<!-- automd:file src="./TEST.md" -->
+<!-- automd:file src="./TEST.md" lines=1:5 -->
 
 ## The Lazy Coder's Guide to Programming
 
 Programming can be hard. But fear not! With the power of copy-paste, you can conquer any coding challenge without breaking a sweat. Just remember: if it works once, it'll work a thousand times. Who needs original code anyway?
 
 When your code doesn't work, don't blame yourself. It's clearly the compiler's fault for not understanding your genius. Remember, the more error messages you get, the closer you are to becoming a programming master.
 
-Why waste time solving problems when someone else has already done it for you? Stack Overflow is your best friend, your mentor, and your savior. Just make sure to upvote the answers that save your bacon.
-
 <!-- /automd -->
 
 ## `contributors`