Validate container name

src/main.zig

@@ -1,16 +1,12 @@
 const std = @import("std");
+const validate = @import("validate.zig");
 const allocator = std.heap.page_allocator;
 var client: std.http.Client = .{ .allocator = allocator };
 const Command = enum { list, logs, create, delete, start };
 
 const ForwardedUser = "X-Forwarded-User";
 
-const PluginError = error{
-    InvalidUser,
-    InvalidCommand,
-    NoContainerName,
-    InvalidImage,
-};
+const PluginError = error{ InvalidUser, InvalidCommand, NoContainerName, InvalidImage, Unprocessable };
 
 const CodefirstAuth = struct {
     proxyScheme: []const u8,
@@ -104,7 +100,25 @@ pub fn run() !void {
         .proxyHost = std.os.getenv("PROXYHOST") orelse "dockerproxy:8080",
         .user = std.os.getenv("DRONE_REPO_OWNER") orelse return PluginError.InvalidUser,
     };
-    const containerName = std.os.getenv("PLUGIN_CONTAINER") orelse return PluginError.NoContainerName;
+    var containerNameEnv = std.os.getenv("PLUGIN_CONTAINER") orelse return PluginError.NoContainerName;
+    var shortUser = try std.mem.replaceOwned(u8, allocator, auth.user, ".", "");
+    defer allocator.free(shortUser);
+    var containerName = try std.fmt.allocPrint(allocator, "{s}-{s}", .{ shortUser, containerNameEnv });
+    defer allocator.free(containerName);
+
+    var idx: usize = 0;
+    validate.validateDockerContainerName(containerName, &idx) catch |err| {
+        switch (err) {
+            validate.NamingError.IllegalChar => {
+                std.log.err("Invalid container name at index {}: {}", .{ idx, err });
+            },
+            else => {
+                std.log.err("Invalid container name: {}", .{err});
+                return PluginError.Unprocessable;
+            },
+        }
+        return PluginError.Unprocessable;
+    };
 
     var envs = std.ArrayList([]const u8).init(allocator);
     defer envs.deinit();

src/validate.zig

@@ -0,0 +1,37 @@
+const std = @import("std");
+const ascii = std.ascii;
+
+pub const NamingError = error{ Empty, IllegalChar, TooLong };
+
+pub fn validateDockerContainerName(name: []const u8, error_index: *usize) !void {
+    // [a-zA-Z0-9][a-zA-Z0-9_.-]
+    if (name.len == 0) {
+        return NamingError.Empty;
+    }
+    if (name.len > 30) {
+        return NamingError.TooLong;
+    }
+
+    if (!ascii.isAlphanumeric(name[0])) {
+        error_index.* = 0;
+        return NamingError.IllegalChar;
+    }
+    for (name, 0..) |c, idx| {
+        if (!ascii.isAlphanumeric(c) and c != '.' and c != '_' and c != '-') {
+            error_index.* = idx;
+            return NamingError.IllegalChar;
+        }
+    }
+}
+
+test "valid name" {
+    var error_index: usize = 0;
+    try validateDockerContainerName("hello", &error_index);
+    try std.testing.expect(error_index == 0);
+}
+
+test "indicate non ascii letter" {
+    var error_index: usize = 0;
+    try std.testing.expectError(NamingError.IllegalChar, validateDockerContainerName("hello😀", &error_index));
+    try std.testing.expect(error_index == 5);
+}