From 41f619389ea6b74f629a680168e9263044613b9e Mon Sep 17 00:00:00 2001
From: Aleksei Malykh <49870662+ysomad@users.noreply.github.com>
Date: Mon, 14 Jul 2025 16:22:34 +0700
Subject: [PATCH] feat: alternate between go and test files

---
 lua/gopher/alternate.lua | 44 ++++++++++++++++++++++++++++++++++++++++
 plugin/gopher.lua        | 13 ++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 lua/gopher/alternate.lua

diff --git a/lua/gopher/alternate.lua b/lua/gopher/alternate.lua
new file mode 100644
index 0000000..f283c37
--- /dev/null
+++ b/lua/gopher/alternate.lua
@@ -0,0 +1,44 @@
+local M = {}
+
+function M.is_test_file()
+  local file = vim.fn.expand "%"
+  if #file <= 1 then
+    vim.notify("no buffer name", vim.log.levels.ERROR)
+    return nil, false, false
+  end
+  local is_test = string.find(file, "_test%.go$")
+  local is_source = string.find(file, "%.go$")
+  return file, (not is_test and is_source), is_test
+end
+
+function M.alternate()
+  local file, is_source, is_test = M.is_test_file()
+  if not file then
+    return nil
+  end
+  local alt_file = file
+  if is_test then
+    alt_file = string.gsub(file, "_test.go", ".go")
+  elseif is_source then
+    alt_file = vim.fn.expand "%:r" .. "_test.go"
+  else
+    vim.notify("not a go file", vim.log.levels.ERROR)
+  end
+  return alt_file
+end
+
+function M.switch(bang, cmd)
+  local alt_file = M.alternate()
+  if not vim.fn.filereadable(alt_file) and not vim.fn.bufexists(alt_file) and not bang then
+    vim.notify("couldn't find " .. alt_file, vim.log.levels.ERROR)
+    return
+  elseif #cmd <= 1 then
+    local ocmd = "e " .. alt_file
+    vim.cmd(ocmd)
+  else
+    local ocmd = cmd .. " " .. alt_file
+    vim.cmd(ocmd)
+  end
+end
+
+return M
diff --git a/plugin/gopher.lua b/plugin/gopher.lua
index 1ccc74e..d4bb682 100644
--- a/plugin/gopher.lua
+++ b/plugin/gopher.lua
@@ -85,3 +85,16 @@ end, "*")
 cmd("GoGenerate", function(opts)
   require("gopher").generate(opts.fargs or "")
 end, "?")
+
+-- :GoAlt
+cmd("GoAlt", function()
+  require("gopher.alternate").switch(true, "")
+end)
+
+cmd("GoAltV", function()
+  require("gopher.alternate").switch(true, "vsplit")
+end)
+
+cmd("GoAltS", function()
+  require("gopher.alternate").switch(true, "split")
+end)