From ee8a9a70d39944d26669104b9eb0a7a5e4bd98e1 Mon Sep 17 00:00:00 2001
From: Henry <henrysg88@gmail.com>
Date: Fri, 29 Mar 2024 10:16:53 -0400
Subject: [PATCH] Add Command GenConstructor

---
 README.md                      |  8 ++++++
 lua/gopher/api.lua             |  1 +
 lua/gopher/gen_constructor.lua | 51 ++++++++++++++++++++++++++++++++++
 plugin/gopher.vim              |  5 ++++
 4 files changed, 65 insertions(+)
 create mode 100644 lua/gopher/gen_constructor.lua

diff --git a/README.md b/README.md
index 88d6bfb..0171959 100644
--- a/README.md
+++ b/README.md
@@ -154,6 +154,14 @@ Notice: [nvim-dap](https://github.com/mfussenegger/nvim-dap) is required
 require"gopher.dap".setup()
 ```
 
+11. Generate `constructor` from a `struct`
+
+Set cursor on a struct name and execute:
+
+```vim
+:GenConstructor
+```
+
 ## Contributing
 
 PRs are always welcome. See [CONTRIBUTING.md](./CONTRIBUTING.md)
diff --git a/lua/gopher/api.lua b/lua/gopher/api.lua
index 6e854af..1d0c688 100644
--- a/lua/gopher/api.lua
+++ b/lua/gopher/api.lua
@@ -12,6 +12,7 @@ API.comment = require "gopher.comment"
 API.test_add = tests.func_test
 API.test_exported = tests.all_exported_tests
 API.tests_all = tests.all_tests
+API.gen_constructor = require "gopher.gen_constructor"
 
 API.get = function(...)
   cmd("get", ...)
diff --git a/lua/gopher/gen_constructor.lua b/lua/gopher/gen_constructor.lua
new file mode 100644
index 0000000..81ef477
--- /dev/null
+++ b/lua/gopher/gen_constructor.lua
@@ -0,0 +1,51 @@
+local u = require "gopher._utils"
+
+return function (cmd_args)
+    local parser = vim.treesitter.get_parser()
+    if not parser then
+        u.notify("no parser not available", "error")
+        return
+    end
+
+    -- When the command is runned on the 'struct name' the current node will be
+    -- the node referring directly to the 'struct name', therefore, to get the
+    -- node that refers to the entire struct we have to get the parent.
+    local current_node = vim.treesitter.get_node():parent()
+    if not current_node then
+        u.notify("no node found at cursor", "error")
+        return
+    end
+
+    if current_node:type() ~= 'type_spec' then
+        u.notify("not struct node under cursor","error")
+        return
+    end
+
+    -- TODO: allow to pass a funcName as an argument
+    -- local struct_name = (fn_args.args ~= nil and fn_args.args ~= "") and fn_args.args:gsub('"', '') or vim.treesitter.get_node_text(current_node:child(0), 1)
+    local struct_name = vim.treesitter.get_node_text(current_node:child(0), 1)
+    local struct_type_node = current_node:child(1):child(1)
+
+    local args = {}
+    local struct_initialization = {}
+    for field in struct_type_node:iter_children() do
+        if field:type() == 'field_declaration' then
+            local field_type_node = field:child(1)
+            local field_name_node = field:child(0)
+            if field_type_node and field_name_node then
+                local field_type = vim.treesitter.get_node_text(field_type_node, 1)
+                local field_name = vim.treesitter.get_node_text(field_name_node, 1)
+                local field_name_lower = string.lower(field_name)
+                table.insert(args, field_name_lower .. " " .. field_type)
+                table.insert(struct_initialization, field_name .. ": " .. field_name_lower)
+            end
+        end
+    end
+
+    local constructor_code = string.format(
+        "\nfunc New%s(%s) *%s {\n\treturn &%s{%s}\n}\n",
+        struct_name:gsub("^%l", string.upper), table.concat(args, ', '), struct_name, struct_name, table.concat(struct_initialization, ', ')
+    )
+
+    vim.fn.append(current_node:end_() + 1, vim.split(constructor_code, '\n'))
+end
diff --git a/plugin/gopher.vim b/plugin/gopher.vim
index e797966..c16206c 100644
--- a/plugin/gopher.vim
+++ b/plugin/gopher.vim
@@ -11,3 +11,8 @@ command! -nargs=* GoGenerate :lua require"gopher.api".generate(<f-args>)
 command! GoCmt :lua require"gopher.api".comment()
 command! GoIfErr :lua require"gopher.api".iferr()
 command! GoInstallDeps :lua require"gopher.api".install_deps()
+command! GoGenConstructor :lua require"gopher.api".gen_constructor(f-args)
+
+
+" TODO: Use this format to remove vimscript in the future"
+" vim.api.nvim_create_user_command('GenerateConstructor', generate_constructor, {})