feat!: Implement Prefix-First prompt structure for Gemini

- Add a new "Prefix-First" prompt structure for chat LLMs.
- Modified the Gemini provider's default prompt strategy to use this new
  structure.
- Other providers will continue to use their previous default prompt
  configurations.

Author: milanglacier

README.md

@@ -21,7 +21,6 @@
   - [Claude](#claude)
   - [Codestral](#codestral)
   - [Gemini](#gemini)
-    - [Experimental Configuration](#experimental-configuration)
   - [OpenAI-compatible](#openai-compatible)
   - [OpenAI-FIM-compatible](#openai-fim-compatible)
 - [Commands](#commands)
@@ -581,7 +580,13 @@ default_config = {
         -- see the documentation in each provider in the following part.
     },
     -- see the documentation in the `Prompt` section
-    default_template = {
+    default_system = {
+        template = '...',
+        prompt = '...',
+        guidelines = '...',
+        n_completion_template = '...',
+    },
+    default_system_prefix_first = {
         template = '...',
         prompt = '...',
         guidelines = '...',
@@ -593,6 +598,8 @@ default_config = {
     },
     default_few_shots = { '...' },
     default_chat_input = { '...' },
+    default_few_shots_prefix_first = { '...' },
+    default_chat_input_prefix_first = { '...' },
     -- Config options for `Minuet change_preset` command
     presets = {}
 }
@@ -814,14 +821,6 @@ provider_options = {
 
 </details>
 
-### Experimental Configuration
-
-Gemini appears to perform better with an alternative input structure, unlike
-other chat-based LLMs. This observation is currently experimental and requires
-further validation. For details on the experimental prompt setup currently in
-use by the maintainer, please refer to the [prompt
-documentation](./prompt.md#an-experimental-configuration-setup-for-gemini).
-
 ## OpenAI-compatible
 
 Use any providers compatible with OpenAI's chat completion API.

lua/minuet/config.lua

@@ -1,11 +1,15 @@
-local default_prompt = [[
+local default_prompt_prefix_first = [[
 You are the backend of an AI-powered code completion engine. Your task is to
 provide code suggestions based on the user's input. The user's code will be
 enclosed in markers:
 
 - `<contextAfterCursor>`: Code context after the cursor
 - `<cursorPosition>`: Current cursor location
 - `<contextBeforeCursor>`: Code context before the cursor
+]]
+
+local default_prompt = default_prompt_prefix_first
+    .. [[
 
 Note that the user's code will be prompted in reverse order: first the code
 after the cursor, then the code before the cursor.
@@ -57,6 +61,21 @@ def fibonacci(n):
     },
 }
 
+local default_few_shots_prefix_first = {
+    {
+        role = 'user',
+        content = [[
+# language: python
+<contextBeforeCursor>
+def fibonacci(n):
+    <cursorPosition>
+<contextAfterCursor>
+
+fib(5)]],
+    },
+    default_few_shots[2],
+}
+
 local n_completion_template = '8. Provide at most %d completion items.'
 
 -- use {{{ and }}} to wrap placeholders, which will be further processesed in other function
@@ -120,6 +139,10 @@ local default_chat_input = {
     end,
 }
 
+local default_chat_input_prefix_first = vim.deepcopy(default_chat_input)
+default_chat_input_prefix_first.template =
+    '{{{language}}}\n{{{tab}}}\n<contextBeforeCursor>\n{{{context_before_cursor}}}<cursorPosition>\n<contextAfterCursor>\n{{{context_after_cursor}}}'
+
 local M = {
     -- Enable or disable auto-completion. Note that you still need to add
     -- Minuet to your cmp/blink sources. This option controls whether cmp/blink
@@ -231,9 +254,18 @@ M.default_system = {
     n_completion_template = n_completion_template,
 }
 
+M.default_system_prefix_first = {
+    template = default_system_template,
+    prompt = default_prompt_prefix_first,
+    guidelines = default_guidelines,
+    n_completion_template = n_completion_template,
+}
+
 M.default_chat_input = default_chat_input
+M.default_chat_input_prefix_first = default_chat_input_prefix_first
 
 M.default_few_shots = default_few_shots
+M.default_few_shots_prefix_first = default_few_shots_prefix_first
 
 M.default_fim_template = {
     prompt = default_fim_prompt,
@@ -293,9 +325,9 @@ M.provider_options = {
     gemini = {
         model = 'gemini-2.0-flash',
         api_key = 'GEMINI_API_KEY',
-        system = M.default_system,
-        chat_input = M.default_chat_input,
-        few_shots = M.default_few_shots,
+        system = M.default_system_prefix_first,
+        chat_input = M.default_chat_input_prefix_first,
+        few_shots = M.default_few_shots_prefix_first,
         stream = true,
         optional = {},
     },

prompt.md

@@ -3,11 +3,11 @@
   - [Default Template](#default-template)
   - [Default Prompt](#default-prompt)
   - [Default Guidelines](#default-guidelines)
-  - [Default `n_completions` template](#default--n-completions--template)
+  - [Default `n_completions` template](#default-n_completions-template)
   - [Default Few Shots Examples](#default-few-shots-examples)
   - [Default Chat Input Example](#default-chat-input-example)
   - [Customization](#customization)
-  - [An Experimental Configuration Setup for Gemini](#an-experimental-configuration-setup-for-gemini)
+  - [A Practical Example](#a-practical-example)
 
 # FIM LLM Prompt Structure
 
@@ -42,12 +42,46 @@ tokens within the prompt function.
 
 # Chat LLM Prompt Structure
 
+We utilize two distinct strategies when constructing prompts:
+
+1. **Prefix First Style**: This involves including the code preceding the
+   cursor initially, followed by the code succeeding the cursor. This approach
+   is used only for the **Gemini** provider.
+
+2. **Suffix First Style**: This method involves including the code following
+   the cursor initially, and then the code preceding the cursor. It is employed
+   for **other** providers such as OpenAI, OpenAI-Compatible, and Claude.
+
+To access the **Suffix First Style** default prompt, use:
+
+1. `require('minuet.config').default_system`
+1. `require('minuet.config').default_few_shots`
+1. `require('minuet.config').default_chat_input`
+
+To access the **Prefix First Style** default prompt, use:
+
+1. `require('minuet.config').default_system_prefix_first`
+1. `require('minuet.config').default_few_shots_prefix_first`
+1. `require('minuet.config').default_chat_input_prefix_first`
+
 ## Default Template
 
 `{{{prompt}}}\n{{{guidelines}}}\n{{{n_completion_template}}}`
 
 ## Default Prompt
 
+**Prefix First Style**:
+
+You are the backend of an AI-powered code completion engine. Your task is to
+provide code suggestions based on the user's input. The user's code will be
+enclosed in markers:
+
+- `<contextAfterCursor>`: Code context after the cursor
+- `<cursorPosition>`: Current cursor location
+- `<contextBeforeCursor>`: Code context before the cursor
+
+**Suffix First Style**:
+
 You are the backend of an AI-powered code completion engine. Your task is to
 provide code suggestions based on the user's input. The user's code will be
 enclosed in markers:
@@ -81,6 +115,7 @@ Guidelines:
 ## Default Few Shots Examples
 
 ```lua
+-- suffix first style
 local default_few_shots = {
     {
         role = 'user',
@@ -114,6 +149,22 @@ def fibonacci(n):
 ]],
     },
 }
+
+-- prefix first style
+local default_few_shots_prefix_first = {
+    {
+        role = 'user',
+        content = [[
+# language: python
+<contextBeforeCursor>
+def fibonacci(n):
+    <cursorPosition>
+<contextAfterCursor>
+
+fib(5)]],
+    },
+    default_few_shots[2],
+}
 ```
 
 ## Default Chat Input Example
@@ -122,7 +173,27 @@ The chat input represents the final prompt delivered to the LLM for completion.
 Its template follows a structured format similar to the system prompt and can
 be customized as follows:
 
-`{{{language}}}\n{{{tab}}}\n<contextAfterCursor>\n{{{context_after_cursor}}}\n<contextBeforeCursor>\n{{{context_before_cursor}}}<cursorPosition>`
+**Suffix First Style**:
+
+```
+{{{language}}}
+{{{tab}}}
+<contextAfterCursor>
+{{{context_after_cursor}}}
+<contextBeforeCursor>
+{{{context_before_cursor}}}<cursorPosition>
+```
+
+**Prefix First Style**:
+
+```
+{{{language}}}
+{{{tab}}}
+<contextBeforeCursor>
+{{{context_before_cursor}}}<cursorPosition>
+<contextAfterCursor>
+{{{context_after_cursor}}}
+```
 
 Components:
 
@@ -207,17 +278,13 @@ require('minuet').setup {
 There's no need to replicate unchanged fields. The system will automatically
 merge modified fields with default values using the `tbl_deep_extend` function.
 
-## An Experimental Configuration Setup for Gemini
-
-Some observations suggest that Gemini might perform better with a `Prefix-Suffix`
-structured input format, specifically `Before-Cursor -> Cursor-Pos -> After-Cursor`.
-
-This contrasts with other chat-based LLMs, which may yield better results with
-the inverse structure: `After-Cursor -> Before-Cursor -> Cursor-Pos`.
+## A Practical Example
 
-This finding remains experimental and requires further validation.
+Here, we present a practical example for configuring the prompt for Gemini,
+aiming to reuse existing components of the default prompt wherever possible.
 
-Below is the current configuration used by the maintainer for Gemini:
+Please note that you should not copy-paste this into your configuration, as it
+represents the **default setting** applied to Gemini.
 
 ```lua
 local gemini_prompt = [[
@@ -251,6 +318,7 @@ local gemini_chat_input_template =
 gemini_few_shots[2] = require('minuet.config').default_few_shots[2]
 
 require('minuet').setup {
+    provider = 'gemini',
     provider_options = {
         gemini = {
             system = {