package context

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/edgeai/gateway/pkg/api"
)

// SummaryGenerator 定义摘要生成接口，允许注入不同的实现。
type SummaryGenerator interface {
	// GenerateSummary 对给定消息生成对话摘要，返回摘要文本。
	GenerateSummary(ctx context.Context, messages []api.Message) (string, error)
}

// Summarizer 使用 LLM 对历史消息生成对话摘要。
type Summarizer struct {
	generator SummaryGenerator
	timeout   time.Duration
}

// NewSummarizer 创建一个新的摘要器。
func NewSummarizer(generator SummaryGenerator, timeout time.Duration) *Summarizer {
	return &Summarizer{
		generator: generator,
		timeout:   timeout,
	}
}

// Summarize 对被裁剪的老消息生成摘要。
// 如果摘要生成失败，回退到占位符文本。
func (s *Summarizer) Summarize(messages []api.Message) string {
	if s == nil || s.generator == nil || len(messages) == 0 {
		return "[Earlier conversation history has been summarized and omitted.]"
	}

	ctx, cancel := context.WithTimeout(context.Background(), s.timeout)
	defer cancel()

	summary, err := s.generator.GenerateSummary(ctx, messages)
	if err != nil || strings.TrimSpace(summary) == "" {
		return "[Earlier conversation history has been summarized and omitted.]"
	}

	return fmt.Sprintf("[Earlier conversation summary: %s]", strings.TrimSpace(summary))
}