add llm adapter interface and implementations

internal/llm/adapter_openai.go

@@ -0,0 +1,71 @@
+package llm
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/sashabaranov/go-openai"
+)
+
+// OpenAIAdapter implements Adapter using OpenAI's chat completions API
+type OpenAIAdapter struct {
+	client *openai.Client
+	config Config
+}
+
+// NewOpenAIAdapter creates a new OpenAI LLM adapter
+func NewOpenAIAdapter(cfg Config) *OpenAIAdapter {
+	return &OpenAIAdapter{
+		client: openai.NewClient(cfg.APIKey),
+		config: cfg,
+	}
+}
+
+func (a *OpenAIAdapter) Process(ctx context.Context, text string) (string, error) {
+	if text == "" {
+		return "", nil
+	}
+
+	opts := PostProcessingOptions{
+		RemoveStutters:    a.config.RemoveStutters,
+		AddPunctuation:    a.config.AddPunctuation,
+		FixGrammar:        a.config.FixGrammar,
+		RemoveFillerWords: a.config.RemoveFillerWords,
+	}
+
+	systemPrompt := BuildSystemPrompt(opts, a.config.Keywords)
+	userPrompt := BuildUserPrompt(text, a.config.CustomPrompt)
+
+	model := a.config.Model
+	if model == "" {
+		model = "gpt-4o-mini"
+	}
+
+	req := openai.ChatCompletionRequest{
+		Model: model,
+		Messages: []openai.ChatCompletionMessage{
+			{Role: openai.ChatMessageRoleSystem, Content: systemPrompt},
+			{Role: openai.ChatMessageRoleUser, Content: userPrompt},
+		},
+		Temperature: 0.3, // Low temperature for consistent cleanup
+	}
+
+	start := time.Now()
+	resp, err := a.client.CreateChatCompletion(ctx, req)
+	duration := time.Since(start)
+
+	if err != nil {
+		log.Printf("openai-llm-adapter: API call failed after %v: %v", duration, err)
+		return "", fmt.Errorf("openai chat completion: %w", err)
+	}
+
+	if len(resp.Choices) == 0 {
+		return "", fmt.Errorf("openai chat completion: no response choices")
+	}
+
+	result := resp.Choices[0].Message.Content
+	log.Printf("openai-llm-adapter: processed in %v: %q -> %q", duration, text, result)
+	return result, nil
+}