Merge pull request #64 from cposture/fix-visual-selection

fix selection include extra content when the user is in visual mode

3 files changed, 33 insertions, 4 deletions

diff --git a/py/chat.py b/py/chat.py
index 6d88015..907e71a 100644
--- a/py/chat.py
+++ b/py/chat.py
@@ -52,6 +52,7 @@ initial_messages = parse_chat_messages(initial_prompt)
 
 chat_content = vim.eval('trim(join(getline(1, "$"), "\n"))')
 chat_messages = parse_chat_messages(chat_content)
+is_selection = vim.eval("l:is_selection")
 
 messages = initial_messages + chat_messages
 
@@ -75,7 +76,7 @@ try:
             printDebug("[chat] response: {}", resp)
             return resp['choices'][0]['delta'].get('content', '')
         text_chunks = map(map_chunk, response)
-        render_text_chunks(text_chunks)
+        render_text_chunks(text_chunks, is_selection)
 
         vim.command("normal! a\n\n>>> user\n\n")
         vim.command("redraw")
diff --git a/py/complete.py b/py/complete.py
index 8386c09..ede0aea 100644
--- a/py/complete.py
+++ b/py/complete.py
@@ -9,6 +9,7 @@ openai_options = make_openai_options(config_options)
 http_options = make_http_options(config_options)
 
 prompt = vim.eval("l:prompt").strip()
+is_selection = vim.eval("l:is_selection")
 
 def complete_engine(prompt):
     request = {
@@ -51,7 +52,7 @@ try:
         print('Completing...')
         vim.command("redraw")
         text_chunks = engines[engine](prompt)
-        render_text_chunks(text_chunks)
+        render_text_chunks(text_chunks, is_selection)
         clear_echo_message()
 except BaseException as error:
     handle_completion_error(error)
diff --git a/py/utils.py b/py/utils.py
index 4e638e2..b5ede7f 100644
--- a/py/utils.py
+++ b/py/utils.py
@@ -62,14 +62,41 @@ def make_http_options(options):
         'enable_auth': bool(int(options['enable_auth'])),
     }
 
-def render_text_chunks(chunks):
+# During text manipulation in Vim's visual mode, we utilize "normal! c" command. This command deletes the highlighted text,
+# immediately followed by entering insert mode where it generates desirable text.
+
+# Normally, Vim contemplates the position of the first character in selection to decide whether to place the entered text
+# before or after the cursor. For instance, if the given line is "abcd", and "abc" is selected for deletion and "1234" is
+# written in its place, the result is as expected "1234d" rather than "d1234". However, if "bc" is chosen for deletion, the
+# achieved output is "a1234d", whereas "1234ad" is not.
+
+# Despite this, post Vim script's execution of "normal! c", it takes an exit immediately returning to the normal mode. This
+# might trigger a potential misalignment issue especially when the most extreme left character is the line’s second character.
+
+# To avoid such pitfalls, the method "need_insert_before_cursor" checks not only the selection status, but also the character
+# at the first position of the highlighting. If the selection is off or the first position is not the second character in the line,
+# it determines no need for prefixing the cursor.
+def need_insert_before_cursor(is_selection):
+    if is_selection == False:
+        return False
+    pos = vim.eval("getpos(\"'<\")[1:2]")
+    if not isinstance(pos, list) or len(pos) != 2:
+        raise ValueError("Unexpected getpos value, it should be a list with two elements")
+    return pos[1] == "1"
+
+def render_text_chunks(chunks, is_selection):
     generating_text = False
     full_text = ''
+    insert_before_cursor = need_insert_before_cursor(is_selection)
     for text in chunks:
         if not text.strip() and not generating_text:
             continue # trim newlines from the beginning
         generating_text = True
-        vim.command("normal! a" + text)
+        if insert_before_cursor:
+            vim.command("normal! i" + text)
+            insert_before_cursor = False
+        else:
+            vim.command("normal! a" + text)
         vim.command("undojoin")
         vim.command("redraw")
         full_text += text