Enhance prompt processing with existing file content support (#43)

### Overview

This PR improves the prompt-based file generation functionality by
allowing the OpenAI-assisted file generation process to consider and
modify existing file content when applicable.

### Changes

- **Added** support for passing existing file content to the OpenAI
prompt within `file_item.py`.
- **Updated** default OpenAI model to `gpt-4.1` from `gpt-3.5-turbo`.
- **Modified** `generate.py` to read existing file content and pass it
to the `process_prompt()` method.
- **Created** a new example configuration file `example/gpt.yaml`
demonstrating usage with user prompts.

### Justification

This change provides more intelligent and context-aware file generation
by allowing existing content to be passed into the prompt. It helps to
enhance productivity and avoid overwriting relevant content
unintentionally.

### Impact

- Improves integration with OpenAI by enabling content-aware generation.
- Prevents accidental data loss when regenerating files.
- Demonstrates usage with an example YAML file, aiding users in
understanding configuration.

Author: httpdss

example/gpt.yaml

@@ -0,0 +1,5 @@
+files:
+  - .github/workflows/run_struct.yaml:
+      user_prompt: |
+        make sure that token is set on secrets and value is TOKEN
+        make sure that password is set on secrets and value is PASSWORD

struct_module/commands/generate.py

@@ -90,8 +90,19 @@ def _create_structure(self, args):
             }
           )
 
+        # Determine the full file path
+        file_path_to_create = os.path.join(args.base_path, name)
+        existing_content = None
+        if os.path.exists(file_path_to_create):
+          self.logger.info(f"File already exists: {file_path_to_create}")
+          with open(file_path_to_create, 'r') as existing_file:
+            existing_content = existing_file.read()
+
+        file_item.process_prompt(
+          args.dry_run,
+          existing_content=existing_content
+        )
         file_item.apply_template_variables(template_vars)
-        file_item.process_prompt(args.dry_run)
 
         file_item.create(
           args.base_path,

struct_module/file_item.py

@@ -47,18 +47,16 @@ def _configure_openai(self):
       self.openai_client = OpenAI(api_key=openai_api_key)
       if not openai_model:
         self.logger.debug("OpenAI model not found. Using default model.")
-        self.openai_model = "gpt-3.5-turbo"
+        self.openai_model = "gpt-4.1"
       else:
         self.logger.debug(f"Using OpenAI model: {openai_model}")
         self.openai_model = openai_model
 
     def _get_file_directory(self):
         return os.path.dirname(self.name)
 
-    def process_prompt(self, dry_run=False):
+    def process_prompt(self, dry_run=False, existing_content=None):
       if self.user_prompt:
-        self.logger.debug(f"Using user prompt: {self.user_prompt}")
-
         if not self.openai_client or not openai_api_key:
           self.logger.warning("Skipping processing prompt as OpenAI API key is not set.")
           return
@@ -68,17 +66,25 @@ def process_prompt(self, dry_run=False):
         else:
           system_prompt = self.system_prompt
 
+        # If existing_content is provided, append it to the user prompt
+        user_prompt = self.user_prompt
+        if existing_content:
+          user_prompt += f"\n\nCurrent file content (if any):\n```\n{existing_content}\n```\n\nPlease modify existing content so that it meets the new requirements. Your output should be plain text, without any code blocks or formatting. Do not include any explanations or comments. Just provide the final content of the file."
+
+        self.logger.debug(f"Using system prompt: {system_prompt}")
+        self.logger.debug(f"Using user prompt: {user_prompt}")
+
         if dry_run:
           self.logger.info("[DRY RUN] Would generate content using OpenAI API.")
           self.content = "[DRY RUN] Generating content using OpenAI"
           return
 
-        if not self.openai_client or not openai_api_key:
+        if self.openai_client and openai_api_key:
           completion = self.openai_client.chat.completions.create(
             model=self.openai_model,
             messages=[
               {"role": "system", "content": system_prompt},
-              {"role": "user", "content": self.user_prompt}
+              {"role": "user", "content": user_prompt}
             ]
           )