From 9bd0ffda30c0fa991a89920d01ec2cb12dbbf7bc Mon Sep 17 00:00:00 2001
From: Martin Ashby <martin@ashbysoft.com>
Date: Sat, 2 Dec 2023 00:14:41 +0000
Subject: Add arg parsing

---
 src/main.zig | 42 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 2 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 7425c6d..b47f48d 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -11,12 +11,34 @@ const trackproto = @import("tracker_protocol.zig");
 const peer_id = [20]u8{ 0x30, 0x30, 0x31, 0x31, 0x32, 0x32, 0x33, 0x33, 0x34, 0x34, 0x35, 0x35, 0x36, 0x36, 0x37, 0x37, 0x38, 0x38, 0x39, 0x39 };
 // To make this a practical torrent app...
 // Add some UI? or keep it a console app? I might keep it as a console app for now
-pub fn main() !void {
+const Args = struct {
+    torrent_file: []const u8,
+};
+
+fn read_args() !Args {
+    var args = std.process.args();
+    if (!args.skip()) return error.NotEnoughArgs;
+    const nxt = args.next() orelse return error.NotEnoughArgs;
+    if (std.mem.eql(u8, nxt, "-h") or std.mem.eql(u8, nxt, "--help")) {
+        try printUsage(false);
+        return error.Help;
+    }
+    return .{
+        .torrent_file = nxt,
+    };
+}
+
+fn do_main() !void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     defer _ = gpa.deinit();
     const a = gpa.allocator();
 
-    const f = try std.fs.cwd().openFile("src/sample.torrent", .{});
+    const args = read_args() catch |e| switch (e) {
+        error.Help => return,
+        else => |err| return err,
+    };
+
+    const f = try std.fs.cwd().openFile(args.torrent_file, .{});
     defer f.close();
     var fr = f.reader();
     var mib = try bencode.bdecode(a, fr);
@@ -120,6 +142,22 @@ pub fn main() !void {
     std.log.info("fin", .{});
 }
 
+pub fn main() !void {
+    do_main() catch |e| {
+        try printUsage(true);
+        return e;
+    };
+}
+
+fn printUsage(err: bool) !void {
+    var f = if (err) std.io.getStdErr() else std.io.getStdOut();
+    try f.writeAll(
+        \\ Usage: zbt TORRENTFILE 
+        \\ Download the data specfied by TORRENTFILE to the current directory
+        \\ 
+    );
+}
+
 test {
     _ = bencode;
     _ = MetaInfo;
-- 
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