feat: bootstrap goaichat CLI and config system

internal/chat/service.go

@@ -0,0 +1,111 @@
+package chat
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"strings"
+
+	"github.com/stig/goaichat/internal/config"
+	"github.com/stig/goaichat/internal/openai"
+)
+
+// CompletionClient defines the subset of the OpenAI client used by the chat service.
+type CompletionClient interface {
+	CreateChatCompletion(ctx context.Context, req openai.ChatCompletionRequest) (*openai.ChatCompletionResponse, error)
+}
+
+// Service coordinates chat requests with the OpenAI client and maintains session history.
+type Service struct {
+	logger      *slog.Logger
+	client      CompletionClient
+	model       string
+	temperature float64
+	stream      bool
+	history     []openai.ChatMessage
+}
+
+// NewService constructs a Service from configuration and an OpenAI-compatible client.
+func NewService(logger *slog.Logger, modelCfg config.ModelConfig, client CompletionClient) (*Service, error) {
+	if logger == nil {
+		return nil, errors.New("logger cannot be nil")
+	}
+	if client == nil {
+		return nil, errors.New("completion client cannot be nil")
+	}
+	if strings.TrimSpace(modelCfg.Name) == "" {
+		return nil, errors.New("model name cannot be empty")
+	}
+
+	return &Service{
+		logger:      logger,
+		client:      client,
+		model:       modelCfg.Name,
+		temperature: modelCfg.Temperature,
+		stream:      modelCfg.Stream,
+		history:     make([]openai.ChatMessage, 0, 16),
+	}, nil
+}
+
+// Send submits a user message and returns the assistant reply.
+func (s *Service) Send(ctx context.Context, input string) (string, error) {
+	if s == nil {
+		return "", errors.New("service is nil")
+	}
+	if ctx == nil {
+		return "", errors.New("context is nil")
+	}
+
+	content := strings.TrimSpace(input)
+	if content == "" {
+		return "", errors.New("input cannot be empty")
+	}
+
+	userMsg := openai.ChatMessage{Role: "user", Content: content}
+	s.history = append(s.history, userMsg)
+
+	messages := append([]openai.ChatMessage(nil), s.history...)
+	temperature := s.temperature
+
+	req := openai.ChatCompletionRequest{
+		Model:       s.model,
+		Messages:    messages,
+		Stream:      s.stream,
+		Temperature: &temperature,
+	}
+
+	s.logger.DebugContext(ctx, "sending chat completion", "model", s.model, "message_count", len(messages))
+
+	resp, err := s.client.CreateChatCompletion(ctx, req)
+	if err != nil {
+		return "", err
+	}
+
+	if len(resp.Choices) == 0 {
+		return "", errors.New("no choices returned from completion")
+	}
+
+	reply := resp.Choices[0].Message
+	s.history = append(s.history, reply)
+
+	return reply.Content, nil
+}
+
+// History returns a copy of the current conversation history.
+func (s *Service) History() []openai.ChatMessage {
+	if s == nil {
+		return nil
+	}
+
+	historyCopy := make([]openai.ChatMessage, len(s.history))
+	copy(historyCopy, s.history)
+	return historyCopy
+}
+
+// Reset clears the in-memory conversation history.
+func (s *Service) Reset() {
+	if s == nil {
+		return
+	}
+	s.history = s.history[:0]
+}